Neuroscience Midterm 2

Front 1

Chapter 12
The Somatic Sensory System

Back 1

.

Front 2

Sensation and Perception

Back 2

The function of each sensory system is to
provide the CNS with a representation of
the external world

Front 3

Sensation -

Back 3

detection of stimulus and
recognition that the event occurred.

Front 4

Perception -

Back 4

interpretation &
appreciation of that event.

Front 5

Sensory Systems

Back 5

Neurons in Sensory Systems signal
events by a combination of rate,
spatial and temporal codes.

Hint 5

– Intensity of stimulus - frequency (rate) of APs
– Spatial quality - location of activated neurons
(Braille)
– Temporal quality - music

Front 6

Sensory Systems:

Back 6

Chemical Senses (ch. 8):

Hint 6

• Smell (olfactory system)
• Taste (gustatory system)

Front 7

Sensory Systems:

Back 7

Auditory and Vestibular Systems (ch. 11)

Front 8

Sensory Systems:

Back 8

Visual System (ch. 9 & 10)

Front 9

Sensory Systems:

Back 9

Somatic Sensory System (ch. 12)

Front 10

Somatic Sensation

Back 10

Enables body to feel, ache, chill

Front 11

Somatic Sensation

Back 11

Sensitive to stimuli

Front 12

Somatic Sensation

Back 12

Responsible for feeling of touch and pain

Front 13

Somatic Sensation

Back 13

Somatic sensory system: Different from other systems in two ways

Hint 13

• Receptors: Distributed throughout the body instead of being concentrated in a small specialized location
• Responds to different kinds of stimuli

Front 14

Somatic Sensation

Back 14

We can think of it as a group of at least four senses which are?

Hint 14

touch, temperature, pain, and body position

Front 15

Somatic Sensation

Back 15

It is a collective category for all the sensations that are not seeing, hearing, tasting, smelling, and the vestibular sense of balance

Front 16

Touch

Back 16

Types and layers of skin

Hint 16

– The two types of skin: Hairy and glabrous (hairless)
– Epidermis (outer layer of skin) and dermis (inner layer of skin)

Front 17

Touch

Back 17

Functions of skin

Hint 17

– Protective function
– Prevents evaporation of body fluids
– Provides direct contact with world

Front 18

Touch

Back 18

Mechanoreceptors

Hint 18

– Most somatosensory receptors are mechanoreceptors

Front 19

Touch

Back 19

Look at figure on page 389

Front 20

Pacinian Corpuscle

Back 20

A mechanoreceptor that lies deep within the dermis, selective for high-frequency vibrations.

Hint 20

Rapidly adapting- Tend to respond quickly at first but then stop firing even thugh the stimulus continues

Front 21

Meissner's Corpuscle

Back 21

Meissner's corpuscles (or tactile corpuscles) are a type of mechanoreceptor. They are a type of nerve ending in the skin that is responsible for sensitivity to light touch.

-Lower frequencies than Pacinian corpuscle

Hint 21

Rapidly adapting- Tend to respond quickly at first but then stop firing even thugh the stimulus continues

Front 22

Merkel's disk

Back 22

the disklike expansion of the end of a nerve fiber together with a closely associated Merkel cell that has a presumed tactile function—called also Merkel's corpuscle

Hint 22

Slowly adapting- Generate a more sustained response during a long stimulus

Front 23

Ruffini's ending

Back 23

Found in both hairy and glabrous skin

Hint 23

Slowly adapting- Generate a more sustained response during a long stimulus

Front 24

Mechanosensitive ion channels

Back 24

Gating depends on stretching, or changes in tension, of the surrounding membrane

Front 25

Touch

Back 25

Look at figures on page 390

Front 26

Mechanoreceptors

Back 26

Receptive field size and adaptation rate
Look at figure on 390

Front 27

Mechanoreceptors

Back 27

Two-point discrimination- A simple measure of spatial resolution

-spatial resolution- is the minimum distance between two adjacent features

Ex. You can start with a paper clip bent into the shape of a U. Touch on finger, you should have no problem telling that there are two separate points touching your finger. Now bend the wire to bring the points closer together, and touch them to your finger again. When does it feel like one point?

Hint 27

the Importance between fingertips (highest resolution) and elbows

1. There is a much higher density of mechanoreceptors in the skin of the fingertip than on other parts of the body
2. The fingertips are enriched in receptor types that have small receptive fields
3. There is more brain tissure devoted to the sensory information of each square mm of fingertip than elsewhere
4. There may be special neural mechanisms devoted to high-resolution discriminations.

Look at figure on page 392

Front 28

Primary Afferent Axons- Axons bringing information from the somatic sensory receptors to the spinal cord or brain stem

Back 28

– Aα, Αβ, Αδ, C (These are in order of decresing sizes)- Axons from skin sensory receptors
– C fibers mediate pain and temperature and is unmyelinated and are the slowest because no myelin
– Aβ mediates touch sensations

Hint 28

Look at figure on page 393

Front 29

The Spinal cord

Back 29

Spinal segments (there are 30 of them)- spinal nerves divided into 4 groups in the spinal cord

-4 groups are called, Cervical, Thoracic, Lumbar, and Sacral

Hint 29

Look at figures on page 394, 395, and 396

Front 30

The Spinal cord

Back 30

Dermatomes- 1-to-1 correspondence with
segments and dermatomes

Dermatome- Area of the skin innervated by the right and left dorsal roots of a single spinal segment

Front 31

Touch: The Spinal cord

Back 31

Sensory Organization of the spinal cord

Hint 31

• Divisions
– Cervical (C)
– Thoracic (T)
– Lumbar (L)
– Sacral (S)

Front 32

Sensory Organization of the spinal cord

Back 32

Division of spinal gray matter: Dorsal horn; Intermediate zone; Ventral horn
– Myelinated Aβ axons (touch-sensitive)- enables us to form complex judgements about the stimuli touching the skin

Hint 32

Look at figure on page 397

Front 33

Dorsal Column–Medial Lemniscal Pathway

Back 33

– Touch information ascends through dorsal column, dorsal nuclei, medial lemniscus, and ventral posterior nucleus to primary somatosensory cortex

1.Dorsal column- Carry information about tactile sensation toward the brain
2.Dorsal column nuclei- Terminate the axons of the dorsal column
3.Medial lemniscus- Rises through the medulla, pons, and midbrain, and its axons synapse upon neurons of the Ventral Posterior nuclus of the thalamus.
4.Ventral Posterior nuclus- project to specific regions of primary somatosensory cortex

Hint 33

Look at figure on page 398

Front 34

The Trigeminal Touch Pathway

Back 34

– Trigeminal nerves
– Cranial nerves

Front 35

Second order sensory neurons

Back 35

The neurons that receive sensory input from primary afferents

Front 36

ipsilaterally

Back 36

Touch information from the left side of the body is represented in the activity of cells in the left dorsal column nuclei.

Front 37

Quick fact

Back 37

No sensory information goes directly into the neocortex without first synapsing in the thalamus

Front 43

The Trigeminal Touch Pathway

Back 43

– Trigeminal nerves
– Cranial nerves

Front 44

Second order sensory neurons

Back 44

The neurons that receive sensory input from primary afferents

Front 45

ipsilaterally

Back 45

Touch information from the left side of the body is represented in the activity of cells in the left dorsal column nuclei.

Front 46

drug form:
fluid

Back 46

inhalation, by nose
inhalation, by mouth
inhalation, by neblizer

Front 47

Somatosensory Cortex

Back 47

– Brodmann’s Area 3b (or S1): Primary somatosensory cortex

-Primary- area 3b is the PRIMARY somatic sensory cortex because
• Receives dense input from VP nucleus of the thalamus
• Neurons: Responsive to Somatosensory stimuli (not other sensory stimuli)
• Lesions impair somatic sensations
• Electrical stimulation evokes somatic sensory experiences

Hint 47

Look at figures on page 401

Front 48

Somatosensory Cortex

Back 48

Other areas

Hint 48

• Postcentral gyrus- Area 3a,1, and 2
Areas 1 and 2- receive dense inputs from area 3b.
-3b-->1 mainly texture information
-3b-->2 Mainly size and shape
• Posterior Parietal
Cortex- Areas 5 and 7

Front 49

Somatosensory Cortex

Back 49

Cortical Somatotopy

-Look at figure on page 402

Hint 49

Homunculus- sometimes called a somatotopic map which is the mapping of the body's surface sensations onto a sturcture in the brain
-Map is not always continuous but can be broken up
-Map is not scaled like the human body

Front 50

Somatosensory Cortex

Back 50

Cortical Somatotopy

Hint 50

Importance of mouth
– Tactile sensations: Important for speech
– Lips and tongue: Last line of defense when deciding if it is delicious or if it could break your tooth

Front 51

Somatosensory Cortex

Back 51

– Cortical Map Plasticity- What happens to the somatotopic map in cortex when an input, such as the finger, is removed?

Hint 51

Look at figure on page 403

Front 52

Somatosensory Cortex

Back 52

– Remove digits or overstimulate – examine
somatotopy before and after

Hint 52

• Conclusions of experiments
– Reorganization of cortical maps
» Dynamic
» Adjust depending on the amount of sensory
experience

Front 53

Somatosensory Cortex

Back 53

The Posterior Parietal Cortex

Hint 53

• Involved in perception, interpretation of
spatial relationship and movement planning

Front 54

Somatosensory Cortex

Back 54

Damage to The Posterior Parietal Cortex

Hint 54

• Agnosia- Inability to recognize objects even though simple sensory skills seem to be normal

Front 55

Somatosensory Cortex

Back 55

Damage to The Posterior Parietal Cortex

Hint 55

• Astereoagnosia- Cannot recognize common objects by feeling them

Front 56

Somatosensory Cortex

Back 56

Damage to The Posterior Parietal Cortex

Hint 56

• Neglect syndrome- Part of the body or a part of the world (the entire visual field left of the center of gaze) is ignored or suppressed, and its very existance is denied.

Front 57

Pain- Dont study tooo much on this portion till slide 73

Back 57

Nociceptors- Besides mechanoreceptors, somatic sensation depends strongly on nociceptors, the free, branching, unmyelinated nerve endings that signal that body tissue is being damaged or is at risk of being damaged.

-The membrans of nociceptors contain ion channels that are activated by these types of stimuli

-Normally respond only when stimuli are strong enough to damage tissue

Front 58

Pain

Back 58

Pain and nociception are not the same thing

Hint 58

– Pain - feeling of sore, aching, throbbing
– Nociception - sensory process that provides the
signals that trigger pain

Front 59

Pain

Back 59

Nociception and the Transduction of Painful Stimuli

Hint 59

Types of Nociceptors

-Polymodal nocireceptors- The majority of nociceptors respond to mechanical, thermal, and chemical stimuli and are therefore called polymodal nociceptors

-Mechanical nocireceptors- Showing selective responses to strong pressure

-Thermal nocireceptors- Showing selective responses to burning heat or extreme cold.

Front 60

Pain

Back 60

Nociception and the Transduction of Painful Stimuli

Hint 60

Hyperalgeia - Our body's ability to control its own pain
• Primary (occurs within the area of damaged tissue) and secondary hyperalgesia (Tissues surrounding a damaged area may become supersensitive by the process of secondary hyperalgesia)
• Bradykinin (binds to specific receptor molecules that activate ionic conductances in some nociceptors), prostaglandins, and substance P (these three makes it more sensitive to thermal or mechanical stimuli

Front 61

Pain

Back 61

Primary Afferents and Spinal mechanisms

Hint 61

– First pain (fast and sharp) and second pain (duller, longer-lasting)
– Referred pain: Angina

Look at figure on page 412

Front 62

IMMUNOLOGY

Back 62

study of the molecules, cells, organs,
and systems responsible for the
recognition of foreign material

Front 63

Ascending Pain Pathways

Back 63

Spinothalamic Pain Pathway
-Information about pain in the body is conveyed from the spinal cord to the brain by the Spinothalamic Pain Pathway

Hint 63

Brown-Séquard Syndrome- The constellation of sensory and motor signs following damage to one side of the spinal cord is called Brown-Séquard Syndrome

Front 64

Ascending Pain Pathways

Back 64

The Trigeminal Pain Pathway

Hint 64

Pain information from the face and head takes a path to the thalamus that is analogous to the spinal path

Front 65

Ascending Pain Pathways

Back 65

The Thalamus and the Cortex

Hint 65

• Touch and pain systems remain segregated
• Pain and temperature information sent to various
cortical areas

Front 66

Ascending Pain Pathways

Back 66

Look at figure on page 414

Front 67

Ascending Pain Pathways

Back 67

Look at figure on page 415

Front 68

The Regulation of Pain

Back 68

– Afferent Regulation- Pain evoked by activity in nociceptors can also be reduced , for ex. rubbing on shin when you bruise it.
– Descending Regulation- pain suppression (feel no pain)
– The endogenuos opiates
• Opioids and endorphins- act by binding tightly and specifically to several types of opioid receptors in the brain and that the brain itself manufactures endogenous morphin-like substances, collectivly called endorphines.

Hint 68

Look at figure on page 417

Front 69

The Regulation of Pain

Back 69

– Descending regulation
– PAG = pariaqueductal gray matter of the midbrain
– PAG can influnce the raphe nuclei of the medulla- depress the activity of nociceptive neurons.

Front 70

Thermoreceptors

Back 70

– “Hot” and “cold” receptors
– Varying sensitivities

Hint 70

Look at figure on page 419

Front 71

Thermoreceptors

Back 71

Hot and cold receptors

Hint 71

Look at figure on page 420

Front 72

The Temperature Pathway

Back 72

– Organization of temperature pathway
• Identical to pain pathway
– Cold receptors coupled to Aδ and C
– Hot receptors coupled to C

Front 73

Concluding Remarks

Back 73

• Sensory systems exhibit similar organization
and function
• Sensory types are segregated within the
spinal cord and cerebral cortex
• Repeated theme
– Parallel processing of information
• Perception of object involves the seamless
coordination of somatic sensory information

Hint 73

Dont study too much up to here, next ones studyy!!!

Front 74

Lecture 9: Cortical and Descending Motor Systems.

Back 74

Chapter 13 & 14

Hint 74

We will turn our attention to the system that actually gives rise to behavior

Front 75

Look at slide 2!!

Back 75

helpful

Front 76

Motor Programs

Back 76

Motor system: All of our Muscles and neurons that control muscles

Front 77

Motor Programs

Back 77

Role: Generation of coordinated movements

Front 78

Motor Programs

Back 78

Motor control can be divided into two parts which are:

Hint 78

• Spinal cord's command and control of coordinated muscle contraction
• Brain's control and command motor programs in spinal cord

Front 79

The Somatic Motor System

Back 79

Types of Muscles

Hint 79

Two types of Striated muscle:
• skeletal (bulk of
body muscle mass) and functions to move bones around joints
• Cardiac (heart)

Front 80

The Somatic Motor System

Back 80

Types of Muscles

Hint 80

Smooth muscle lines the digestive tract, arteries, and related structures and is innervated by nerve fibers from the autonomic nervous system
-Plays a role in peristalsis (movement of material through the intestines) and the control of blood pressure and blood flow.

Front 81

The Somatic Motor System

Back 81

Look at figures on page 425

Front 82

Somatic Musculature

Back 82

– Axial muscles are responsible for movement of the Trunk
– Proximal muscles move Shoulder, elbow, pelvis,
knee movement
– Distal muscles move Hands, feet, digits (fingers and
toes) movement

Front 83

The Lower Motor Neuron

Back 83

– Lower motor neuron: Innervated (stimulate through nerves.) by ventral horn of
spinal cord

Hint 83

Look at figure on page 427

Front 84

The Lower Motor Neuron

Back 84

– Upper motor neuron: Supplies input to the spinal cord

Front 85

Somatic musculature is innervated (stimulate through nerves.) by somatic motor neurons

Back 85

.

Front 86

The Motor Unit- One alpha motor neuron and all the muscle fibers it innervates collectively make up the elementary component of motor control called the motor unit

Back 86

Look figure on page 429

Front 87

Two lower motor neurons

Back 87

• Alpha neurons- directly trigger the generation of force by muscles
• Gamma neurons

Front 88

-Muscle contraction results from the individual and combined actions of those motor units

Back 88

.

Front 89

Motor neuron pool

Back 89

collection of alpha motor neurons the innervates a single muscle.

Front 90

Graded Control of Muscle Contraction by Alpha Motor Neurons

Back 90

– Varying firing rate of motor neurons

Front 91

Graded Control of Muscle Contraction by Alpha Motor Neurons

Back 91

– Recruit additional synergistic motor units
-depends on how many muscle fibers are in that unit
- motor units are recruited in the order of smallest first, largest last.

Front 92

Inputs to Alpha Motor Neurons
-Has three sources of input

Back 92

• ALS (Amyotrophic Lateral Sclerosis) = Lou Gehrig’s Desease
– Selective degeneration of alpha motor neurons

3 sources:
1. The dorsal root ganglion cells with axons that innervate a specialized sensory apparatus embedded within the muscle known as a muscle spindle.
2. Derives from upper motor neurons in the motor cortex and brain stem
3.Is the largest input to an alpha motor neuron derives from interneurons in the spinal cord

Hint 92

Look at figure on page 430

Front 93

Neuromuscular Matchmaking

Back 93

• Alternate nerve input

Hint 93

– Switch in muscle phenotype (physical
characteristics) as a consequence of increased or
decreased activity.

Front 94

Neuromuscular Matchmaking

Back 94

Increased in activity leads to Hypertrophy: Exaggerated growth of muscle fibers as seen in body builders

Front 95

Neuromuscular Matchmaking

Back 95

Prolonged inactivity leads to Atrophy: Degeneration of muscle fibers
ex. Joints in a cast is immobilized

Front 96

Excitation-Contraction Coupling

Back 96

Muscle contraction

Hint 96

Alpha motor neurons release Ach
• Innervate muscle fibers

Front 97

Excitation-Contraction Coupling

Back 97

Muscle contraction

Hint 97

ACh produces large EPSP in muscle fibers (via nicotinic Ach
receptors

Front 98

Excitation-Contraction Coupling

Back 98

Muscle contraction

Hint 98

EPSP evokes action potential

Front 99

Excitation-Contraction Coupling

Back 99

Muscle contraction

Hint 99

Action potential (excitation) triggers Ca2+ release, leads to
fiber contraction

Front 100

Excitation-Contraction Coupling

Back 100

Muscle contraction

Hint 100

Relaxation, Ca2+ levels lowered by organelle reuptake

Front 101

Muscle contraction is initiated by the release of ACh (actylcoline) from the axon terminals of alpha motor neurons

Back 101

.

Front 102

Excitation-Contraction Coupling

Back 102

• Myasthenia Gravis

Hint 102

– NMJ Disease

Front 103

Excitation-Contraction Coupling

Back 103

• Myasthenia Gravis

Hint 103

– autoimmune disease; nicotinic ACh Receptors dysfunction

Front 104

Excitation-Contraction Coupling

Back 104

• Myasthenia Gravis

Hint 104

– Drugs: AChE blockers

Front 105

Muscle Fiber
Structure

Back 105

Look at figure on page 434 &435

Front 106

The Molecular Basis of Muscle Contraction

Back 106

Z lines: Division of myofibril into segments by disks

Front 107

The Molecular Basis of Muscle Contraction

Back 107

Sarcomere: segment comprised of Two Z lines and myofibril in between

Front 108

The Molecular Basis of Muscle Contraction

Back 108

Thin filaments: Series of bristles- on each side of the Z lines

Front 109

The Molecular Basis of Muscle Contraction

Back 109

Thick filaments: Between and among thin filaments

Front 110

The Molecular Basis of Muscle Contraction

Back 110

Sliding-filament model:

Hint 110

• Binding of Ca2+ to troponin causes myosin to bind to
actin
• Myosin heads pivot, cause filaments to slide

Front 111

Part of the muscle fiber- Sarcolemma

Back 111

Muscle fibers are enclosed by an excitable cell membrane called the Sarcolemma

Front 112

Part of the muscle fiber- Myofibrils

Back 112

Within the muscle fiber are a number of cylindrical structures called Myofibrils

Front 113

Part of the muscle fiber- Sarcoplamic

Back 113

Surrounds the myofibrils and is an extensive intracellular sac that stores Ca

Front 114

Part of the muscle fiber- T tubules

Back 114

Action potentials sweeping along the sarcolemma gain access to the sarcoplamic reticulum deep inside the fiber by way of netweork of tunnels called T tubules

Front 115

Summarization of EXCITATION of the excitation-contraction coupling

Back 115

1. An action potential occurs in an alpha motor neuron axon

Front 116

Summarization of EXCITATION of the excitation-contraction coupling

Back 116

2. ACh is released by the axon terminal of the alphamotor neuron at the neuromuscular junction

Front 117

Summarization of EXCITATION of the excitation-contraction coupling

Back 117

3. Nicotinic receptor channels in the sarcolemma open, and the postsynaptic sarcolemma depolarizzes (EPSP)

Front 118

Summarization of EXCITATION of the excitation-contraction coupling

Back 118

4. Voltage-gated sodium channels open, and an action potential is generated in the muscle fiber, which sweeps down the sarcolemma and into the T tubules

Front 119

Summarization of EXCITATION of the excitation-contraction coupling

Back 119

5. Depolarization of the T tubules causes Ca release from the sarcoplasmic reticulum

Front 120

Summarization of CONTRACTION of the excitation-contraction coupling

Back 120

1. Ca binds to troponin

Hint 120

Look at figure on page 436

Front 121

Summarization of CONTRACTION of the excitation-contraction coupling

Back 121

2. Myosin binding sites on actin are exposed

Front 122

Summarization of CONTRACTION of the excitation-contraction coupling

Back 122

3. Myosin heads bind actin

Front 123

Summarization of CONTRACTION of the excitation-contraction coupling

Back 123

4. Myosin heads pivot

Front 124

Summarization of CONTRACTION of the excitation-contraction coupling

Back 124

5. Myosin heads disengage at the expense of ATP

Front 125

Summarization of CONTRACTION of the excitation-contraction coupling

Back 125

6. The cycle continues as long as CA and ATP are present

Front 126

Summarization of RELAXATION of the excitation-contraction coupling

Back 126

1. As EPSPs end, the sarcolemma and T tubules return to their resting potentials

Front 127

Summarization of RELAXATION of the excitation-contraction coupling

Back 127

2. Ca is sequestered by the sarcoplasmic reticulum by an ATP-driven pump

Front 128

Summarization of RELAXATION of the excitation-contraction coupling

Back 128

3. Myosin binding sites on actin are covered by troponin

Front 129

• Steps in Excitation-

Back 129

Contraction Coupling
– Excitation: Action potential, ACh release,
EPSP, action potential in muscle fiber,
depolarization
– Contraction: Ca2+, myosin binds actin, myosin
pivots and disengages, cycle continues until
Ca2+ and ATP present
– Relaxation: EPSP end, resting potential, Ca2+ by
ATP driven pump, myosin binding actin covered

Front 130

Spinal Control of Motor Units

Back 130

First source: Sensory feedback from muscle

Hint 130

Look at figure on page 438

Front 131

The Myotatic Reflex

Back 131

Stretch reflex: Muscle pulled--> tendency to pull back

Front 132

The Myotatic Reflex

Back 132

Feedback loop-
ex. When a weight is placed on a muscle and the muscle starts to lengthen, the muscle spindles are streched. The stretching of the spindle leads to depolarization of the Ia axon endings due to the opening of mechanosensitive ion channels. Therefore it synaptically depolarizaes the alpha motor neurons, which respond by incresing their action potential frequency. This causes the muscle to contract, thereby shortening it.

Hint 132

Principles of the feedback control systems are that a set point is determined (in this case, the desired muscle length), deviations from the set point are detected by a sensor (the Ia axon endings), and deviations are compensated for by an effector system (alpha motor neurons and extrafusal muscle fibers), returning the system to the set point of the myotatic feedback loop

Front 133

The Myotatic Reflex

Back 133

Discharge rate of sensory axons: Related to muscle length
-As the muscle is streched, the discharge rate goes up
-As the muscle is shortened and goes slack, the discharge rate goes down.

Front 134

The Myotatic Reflex

Back 134

Monosynaptic (monosynaptic myotatic reflex arc)- because only one synapse separates the primary sensory input from the motor neuron output.
Example: knee-jerk reflex

Front 135

The Myotatic Reflex

Back 135

Look at figure on page 441

Front 136

Gamma Motor Neurons

Back 136

Muscle spindle- contains modified skeletal muscle fibers within its fiberous capsule

Hint 136

Intrafusal fibers: gamma- modified skeletal muscle fibers within its fiberous capsule

Front 137

Gamma Motor Neurons

Back 137

Muscle spindle

Hint 137

Extrafusal fibers: alpha -
more numerous than intrafusal fibers and lie outside the spindle and form the bulk of the muscle

Front 138

An important difference between extrafusal and intrafusal fibers is that..

Back 138

-Extrafusal fibers are innervated by alpha motor neurons
-Intrafusal fibers receive their motor innervation by gamma motor neurons.

Front 139

An important difference between extrafusal and intrafusal fibers is that..

Back 139

-Alpha and Gamma motor neurons have the opposite effects on Ia axon output.
-Alpha activation alone decreases Ia activity, while gamma activation alone increases Ia activity

Front 140

What happens when there is an Activation of alpha motor neurons?

Back 140

It causes the extrafusal muscle fibers to shorten.

Front 141

What happens when there is an Activation of Gamma motor neurons?

Back 141

It causes the poles of the spindle to contract, keeping it "on-the-air"

Front 142

Gamma Loop

Back 142

Changing the activity of the gamma motor neurons changes the set point of the myotatic feedback loop

Front 143

Gamma Loop

Back 143

Provides additional control of alpha motor neurons and muscle contraction

Front 144

Gamma Loop

Back 144

Circuit

Hint 144

• Gamma motor neuron--> intrafusal muscle fiber
--> Ia afferent axon --> alpha motor neuron --> extrafusal muscle fibers

Front 145

Proprioception from Golgi Tendon Organs

Back 145

Reverse myotatic reflex function: Regulate muscle tension within optimal range

-Ib axons enter the spinal cord, branch repeatedly, and synapse on interneurons in the ventral horn. Some of these interneurons form inhibitory connections with alpha motor neurons innervating the same muscle.

-This reflex arc protects the muscle from being overloaded

-As muscle tension increases, the inhibition of the alpha motor neuron slows muscle contraction; as muscle tension falls, the inhibition of the alpha motor neuron is reduced, and muscle contraction increases.

Hint 145

Look at figure on page 443

Front 146

Proprioception

Back 146

Awareness of the position of one's body.

Front 147

Golgi Tendon Organs

Back 147

-Monitors force of contraction and muscle tension
Location: junction of the muscle and the tendon and are innervated by group Ib sensory axons, which are slightly smaller than the Ia axons innervating the muscle spindles

Front 148

Important

Back 148

-Spindle fibers are situated in parallel with muscle fibers
-golgi tendon organs are situated in series
--This is what distinguishes the types of information these two sensors provide the spinal cord: Ia activity from the spindle encodes muscle length information, while Ib activity from the golgi tendon organ encodes muscle tension information.

Front 149

Proprioception from the joints

Back 149

Proprioceptive axons in connective joint tissues

Front 150

Proprioception from the joints

Back 150

Respond to angle, direction and velocity of movement in a joint

Front 151

Spinal Interneurons

Back 151

Synaptic inputs

Hint 151

Actions of Ib inputs from golgi tendon organs on alpha motor neurons are entirely polysynaptic

Spinal interneurons receive synaptic input from
1.Primary sensory axons 2.Descending axons from brain
3.Collaterals of lower motor neuron axons

Front 152

Inhibitory Input

Back 152

Reciprocal inhibition: Contraction of one muscle set accompanied by relaxation of antagonist muscle, the extensors

Hint 152

Example: Myotatic reflex

Look at figure on page 445

Front 153

The Generation of Spinal Motor
Programs for Walking

Back 153

Central pattern generators
-Circuits that give rise to rhythmic motor activity

Hint 153

Look at figure on page 448

Front 154

Spinal control of movement

Back 154

Different levels of analysis

Front 155

Spinal control of movement

Back 155

Sensation and movement linked

Hint 155

Direct feedback
- The normal function of the alpha motor neuron depends on direct feedback from the muscles themselves and indirect information from the tendons, joints, and skin.

Front 156

Spinal control of movement

Back 156

Spinal cord contains an Intricate network of circuits for the control of movement

Front 157

Brain Control of Movement
Chapter 14

Back 157

.

Front 158

The brain influences activity of the spinal cord for what?

Back 158

Voluntary movements

Front 159

Hierarchy of controls

Back 159

– Highest level: Strategy
-Represented by the association areas of neocortex and basal ganglia of the forebrain: the goal of the movement and the movement strategy that best achieves the goal

– Middle level: Tactics
-Represented by the motor cortex and cerebellum: the sequences of muscle contractions, arranged in space and time, required to smoothly and accurately achieve the strategic goal.

– Lowest level: Execution
-Represented by the brain stem and spinal cord: activation of the motor neuron and interneuron pools that generate the goal-directed movement and make any necessary adjustments of posture

Front 160

Sensorimotor system

Back 160

Sensory information: Used by motor system
-The proper functioning of each level of the motor control hierarchy relies so heavily on sensory information that the motor system of the brain might properly be considered a sensorimotor system.

-At the highest level, sensory information generates a mental image of the body and its relationship to the environment

-At the middle level, tachtical decisions are based on the memory of sensory information from past movements.

-At the lowest level, sensory feedback is used to maintain posture, muscle length, and tension before and after each voluntary movement.

Front 161

Principles of Motor Systems organization:

Back 161

A. There is a hierarchy of motor subsystems.

Front 162

Principles of Motor Systems organization:

Back 162

B. Whenever possible a subsystems of the hierarchy
accomplishes movements through control of automatic and reflex behaviors organized at lower levels.

Front 163

Principles of Motor Systems organization:

Back 163

C. Almost all components of the motor system contain somatotopic maps.

Front 164

Principles of Motor Systems organization:

Back 164

D. Each subsystems receives somatosensory info.

Front 165

Principles of Motor Systems organization:

Back 165

E. Movements can be accomplished by means of the spinal cord (or brain stem) lower motor neurons, which innervate muscles.

Front 166

Principles of Motor Systems organization:

Back 166

F. The lower motor neurons may be reflexly activated at the
segmental level or may be voluntarily activated by a higher
subsystem in the hierarchy

Front 167

Principles of Motor Systems organization:

Back 167

G. The cerebellum and basal ganglia have some control over the subsystems of the motor hierarchy but not project to the
lower motor neurons.

Hint 167

Look at figure on page 455

Front 168

Descending Spinal Tracts

Back 168

Axons from brain descend along two major pathways:

Hint 168

Lateral Pathways
• Involved in voluntary movement of the distal musculature and are under direct cortical control

Front 169

Descending Spinal Tracts

Back 169

Axons from brain descend along two major pathways:

Hint 169

Ventromedial Pathways
• Control of posture and locomotion are under brain stem control

Front 170

The Lateral Pathways

Back 170

Voluntary movement --> under direct cortical control

Hint 170

Look at figure on page 453

Front 171

The Lateral Pathways

Back 171

Components

Hint 171

• Corticospinal tract- most important component
-Originating in the neocortex
-regulate the flow of somatosensory information to the brain

• Pyramidal tract
-At the junction of the medulla and spinal cord, the pyramidal tract crosses, this means that the right motor cortex directly commands the movement of the left side of the body and the left motor cortex controls the muscles on the right side.

• Rubrospinal tract
-originates in the "red nucleus" of the midbrain, named for its distinctive pinkish hue
-A major source of input to the red nucleus is the very region of frontal cortex that also contributes to the corticospinal tract.

Front 172

The Lateral Pathways

Back 172

The Effects of Lateral Pathway Lesions

Hint 172

Partial lesions in corticospinal and rubrospinal tracts
– Fractionated movement of arms and hands; they could not move their shoulders, elbows, wrists, and fingers independently

Front 173

The Lateral Pathways

Back 173

The Effects of Lateral Pathway Lesions

Hint 173

Damage of corticospinal tract
» Paralysis on contralateral side

Front 174

The Ventromedial Pathways

Back 174

Posture and locomotion --> under brain stem control

Hint 174

The Ventromedial Pathways use sensory information about balance, body position, and the visual environment to reflexively maintain balance and body posture

Front 175

The Ventromedial Pathways

Back 175

The Vestibulospinal tract
-Keeps head balanced on the shoulders as the body moves, and turn the head in response to new sensory stimuli.

-Originate in the vestibular nuclei of the medulla, which relay sensory information from the vestibular labyrinth in the inner ear. The vestibular labyrinth consists of fluid-filled canals and cavities in the temporal bone that are closely associated with the cochlea.

-Proojects bilaterally down the spinal cord and activates the cervial spinal circuits that control the neck and back muscles

Front 176

The Ventromedial Pathways

Back 176

The Tectospinal tract
-Originates in the superior colliculus of the midbrain, which receives direct input from the retina

Front 177

The Ventromedial Pathways

Back 177

The Pontine and Medullary Recticulospinal tract.

-The Pontine Recticulospinal tract enhances the antigravity reflexes of the spinal cord

-Helps maintain gravity by facilitating the extensors of the lower limbs

-The Medullary Recticulospinal tract has the opposite effect; it liberates the antigravity muscles from reflex control

-Activity in both reticulospinal tracts is controlled by descending signals from the cortex

Front 178

The Ventromedial Pathways

Back 178

Contains four descending tracts that originate in the brain stem and terminate among the spinal interneurons controlling proximal and axial muscles

Front 179

The four tracts are?

Back 179

1. Vestibulospinal tract,
2. Tectospinal tract,
3. The pontine reticulospinal tract,
4. The Medullary reticulospinal tract.

Front 180

The Planning of Movement by
the Cerebral Cortex

Back 180

Motor Cortex
– Area 4 and area 6 of the frontal lobe is called the motor cortex
-The control of voluntary movement engages almost all of the neocortex

Hint 180

Look at figure on page 460

Front 181

What is Area 4 now referred to?

Back 181

Primary motor cortex or M1

Front 182

Somatotopic map of primary motor Cortex

Back 182

Compare the Somatosensory Cortex and Motor Cortex

Hint 182

Figures on page 460 and page 402

Front 183

Motor Cortex (Penfield)

Back 183

Area 4 = “Primary motor cortex” or “M1”

Front 184

Motor Cortex (Penfield)

Back 184

Area 6 = “Higher motor area” (Penfield)

Hint 184

Lateral region --> Premotor area (PMA)
-The PMA connects primarily with reticulospinal neurons that innervate proximal motor units

Front 185

Motor Cortex (Penfield)

Back 185

Area 6 = “Higher motor area” (Penfield)

Hint 185

Medial region --> Supplementary motor area (SMA)
-The SMA sends axons that innervate distal motor units directly

Front 186

Motor Cortex (Penfield)

Back 186

Area 6 = “Higher motor area” (Penfield)

Hint 186

Motor maps in PMA and SMA
– Similar functions; different groups of muscles innervated

Front 187

The Contributions of Posterior Parietal and Prefrontal Cortex

Back 187

Represent highest levels of motor control

Hint 187

Decisions made about actions and their outcome

Front 188

The Contributions of Posterior Parietal and Prefrontal Cortex

Back 188

Area 5:
-Target of inputs from the primary somatosensory cortical areas 3,1,and 2

Front 189

The Contributions of Posterior Parietal and Prefrontal Cortex

Back 189

Area 7: Inputs from higher-order visual cortical areas such as MT

Front 190

The Contributions of Posterior Parietal and Prefrontal Cortex

Back 190

The parietal lobes are extensively interconnected with regions in the Anterior frontal lobes:
-Anterior frontal lobes (prefrontal): Abstract thought, decision making and anticipating consequences of action

Hint 190

These "prefrontal areas" along with the posterior parietal cortex, represent the highest levels of the motor control hierarchy, where decisions are made about what actions to take and their likely outcome.

Front 191

The Contributions of Posterior Parietal and Prefrontal Cortex

Back 191

-Prefrontal and parietal cortex both send axons that converge on cortical area 6

Area 6: Actions converted into signals specifying how actions will be performed

Front 192

The Contributions of Posterior Parietal and Prefrontal Cortex

Back 192

Per Roland --> Monitored cortical activation
accompanying voluntary movement by (PET)

Hint 192

• Results supported view of higher order motor planning

Front 193

Neuronal Correlates of Motor Planning

Back 193

Evarts: Recorded activity in motor areas of awake, behaving animals

Hint 193

Demonstrated importance of area 6 in planning movement (Where SMA and PMA are located)

Front 194

Neuronal Correlates of Motor Planning

Back 194

Evarts: Recorded activity in motor areas of awake, behaving animals
(ready,set, go!)

Hint 194

“ready”- readiness depends on activity in the Parietal and frontal lobes

Front 195

Neuronal Correlates of Motor Planning

Back 195

Evarts: Recorded activity in motor areas of awake, behaving animals
(ready,set, go!)

Hint 195

“set”- Supplementary and premotor areas (SMA and PMA)
-Where movement strategies are devised and held until they are executed

Front 196

Neuronal Correlates of Motor Planning

Back 196

Evarts: Recorded activity in motor areas of awake, behaving animals
(ready,set, go!)

Hint 196

“go”- Area 6

Front 197

The Basal Ganglia

Back 197

The major subcortical input to area 6 arises in a nucleus of the dorsal thalamus, called the ventral lateral (VLo) nucleus

-The input to this part of VLo, arises from the basal ganglia buried deep within the telencephalon.

Hint 197

Look at figure on page 465
-important both figures

Front 198

The Basal Ganglia

Back 198

Cortex

Hint 198

Projects back to basal ganglia

Front 199

The Basal Ganglia

Back 199

Cortex

Hint 199

Forms a “loop”

Front 200

The Basal Ganglia

Back 200

Function of the loop: Selection and initiation of willed movements

Front 201

Anatomy of the Basal Ganglia

Back 201

Caudate nucleus, putamen, globus pallidus, subthalamic nucleus

-Caudate and putamen together are called the striatum, which is the target of the cortical input to the basal ganglia.
-The globus pallidus is the source of the output to the thalamus.
-The other structures participate in various side loops that modulate the direct path:

Hint 201

Cortex-->striatum-->globus pallidus-->VLo--> cortex(SMA)

Front 202

Anatomy of the Basal Ganglia

Back 202

Substantia nigra: Connected to basal ganglia

Front 203

The Motor Loop: Selection and initiation of willed movements

Back 203

Origin of the most direct path in the motor loop through the basal ganglia originates with an Excitatory connection from the cortex to cells in putamen

Hint 203

Cortical activation of the putamen is excitation of the SMA by VL

Front 204

The Motor Loop: Selection and initiation of willed movements

Back 204

Cortical activation

Hint 204

1.Excites putamen neurons

Front 205

The Motor Loop: Selection and initiation of willed movements

Back 205

Cortical activation

Hint 205

2. Inhibits globus pallidus neurons

Front 206

The Motor Loop: Selection and initiation of willed movements

Back 206

Cortical activation

Hint 206

3. Release cells in VLo from inhibition

Front 207

The Motor Loop: Selection and initiation of willed movements

Back 207

Activity in VLo boosts the activity in SMA

Front 208

The Motor Loop

Back 208

Basal Ganglia Disorders:
Hypokinesia (increased inhibition of the thalamus by the basal ganglia, little movement) and hyperkinesia (a decreased in basal ganglia output leads to hyperkinesia, an excess of movement)

Front 209

The Motor Loop

Back 209

Basal Ganglia Disorders:
Parkinson’s disease
(characterized by hypokinesia)

Hint 209

Symptoms: Bradykinesia (slowness of movements), akinesia (difficulty in initiating willed movements), rigidity (increased muscle tone) and
tremors of hand and jaw

Front 210

The Motor Loop

Back 210

Basal Ganglia Disorders:
Parkinson’s disease
(characterized by hypokinesia)

Hint 210

Organic basis: Degeneration of substantia nigra inputs to striatum

Front 211

The Motor Loop

Back 211

Basal Ganglia Disorders:
Parkinson’s disease
(characterized by hypokinesia)

Hint 211

Dopamine treatment: Facilitates production of dopamine
to increase SMA activity

Front 212

The Motor Loop

Back 212

Basal Ganglia Disorders:
Huntington’s disease
(characterized by hyperkinesia)

Hint 212

Symptoms: Hyperkinesia, dyskinesia, dementia,
impaired cognitive disability, personality disorder

Front 213

The Motor Loop

Back 213

Basal Ganglia Disorders:
Hemiballismus (ballism
(characterized by hyperkinesia)

Hint 213

Violent, flinging movement on one side of the body

Front 214

Initiation of Movement by the Primary Motor Cortex

Back 214

Electrical stimulation of area 4

Hint 214

Contraction of small group of muscles

Front 215

Initiation of Movement by the Primary Motor Cortex

Back 215

The Input-Output Organization of M1

Hint 215

Betz cells: Pyramidal cells in cortical layer 5 (V)

Front 216

Initiation of Movement by the Primary Motor Cortex

Back 216

The Input-Output Organization of M1

Hint 216

Two sources of input to Betz cells
• Cortical areas
• Thalamus

Front 217

Initiation of Movement by the Primary Motor Cortex

Back 217

The Coding of Movement in M1

Hint 217

Activity from several neurons in M1 encodes force and direction of movement

Front 218

Initiation of Movement by the Primary Motor Cortex

Back 218

The Coding of Movement in M1

Hint 218

Look at figure on page 470

Front 219

Initiation of Movement by the Primary Motor Cortex

Back 219

The Coding of Movement in M1
-There are 3 important conclusions about how M1 commands voluntary movement which are,

Hint 219

1. Motor cortex: Active for every movement

Front 220

Initiation of Movement by the Primary Motor Cortex

Back 220

The Coding of Movement in M1
--There are 3 important conclusions about how M1 commands voluntary movement which are,

Hint 220

2. Activity of each cell: Represents a single “vote”

Front 221

Initiation of Movement by the Primary Motor Cortex

Back 221

The Coding of Movement in M1
--There are 3 important conclusions about how M1 commands voluntary movement which are,

Hint 221

3. Direction of movement: Determined by a tally (and averaging)

Front 222

The Coding of Movement in M1(

Back 222

The Malleable Motor Map

Hint 222

Experimental evidence from rats
– Microstimulation of M1 cortex normally elicits
whisker movement--> cut nerve that supplies
whisker muscles--> Microstimulation now causes
forelimb movement

Front 223

The Coding of Movement in M1(

Back 223

The Malleable Motor Map

Hint 223

Decoding M1 activity
– Helps patients with severe damage to their motor
pathways

Front 224

The Coding of Movement in M1(

Back 224

The Malleable Motor Map

Hint 224

The larger the population of neurons representing a type of movement, the finer the possible control

Front 225

The Cerebellum

Back 225

Function: Sequence of muscle contractions

Hint 225

Ataxia
• Uncoordinated and inaccurate movements

Front 226

The Cerebellum

Back 226

Function: Sequence of muscle contractions

Hint 226

Ataxia
• Caused by cerebellar lesions

Front 227

The Cerebellum

Back 227

Function: Sequence of muscle contractions

Hint 227

Ataxia
• Symptoms
– Dysynergia (decomposition of synergistic multijoint movement), dysmetric

Front 228

The Cerebellum

Back 228

The Motor Loop Through the Lateral Cerebellum

Hint 228

-- Pontine nuclei
• Axons from layer V pyramidal cells in the sensorimotor
cortex form massive projections to pons

Front 229

The Cerebellum

Back 229

The Motor Loop Through the Lateral Cerebellum

Hint 229

– Corticopontocerebellar projection
• 20 times larger than pyramidal tract

Front 230

The Cerebellum

Back 230

The Motor Loop Through the Lateral Cerebellum

Hint 230

– Function
• Execution of planned, voluntary, multijoint movements

Front 231

The Cerebellum

Back 231

The Motor Loop Through the Lateral Cerebellum

Hint 231

Look at figure on page 476

Front 232

Concluding Remarks

Back 232

Example of the baseball pitcher

Hint 232

Walking: Ventromedial pathways

Front 233

Concluding Remarks

Back 233

Example of the baseball pitcher

Hint 233

Ready to pitch
• Neocortex, ventromedial pathways

Front 234

Concluding Remarks

Back 234

Example of the baseball pitcher

Hint 234

Pitch signs and strategy
• Sensory information engages parietal and prefrontal cortex and area 6

Front 235

Concluding Remarks

Back 235

Example of the baseball pitcher

Hint 235

– Winds and throws
• Increased basal ganglia activity (initiation)

Front 236

Concluding Remarks

Back 236

Example of the baseball pitcher

Hint 236

– Winds and throws
• SMA activity --> M1 activation

Front 237

Concluding Remarks

Back 237

Example of the baseball pitcher

Hint 237

– Winds and throws
• Corticopontocerebellar pathways --> Cerebellum

Front 238

Concluding Remarks

Back 238

Example of the baseball pitcher

Hint 238

– Winds and throws
Cortical input to reticular formation --> Release of
antigravity muscles

Front 239

Concluding Remarks

Back 239

Example of the baseball pitcher

Hint 239

– Winds and throws
Lateral pathway --> engages motor neurons --> action

Front 240

Look at concluding remarks in chapter 14

Back 240

IMPORTANT SUMMARY

Front 241

Chapter 9
The eye

Back 241

.

Front 242

Overview of the Visual System

Back 242

Visual information is projected the following pathway:

Hint 242

• Retina
• Optic nerve
• Optic chiasm
• Optic tract
• Lateral geniculate nucleus (LGN)
• Visual radiations
• Primary visual cortex
• Higher visual cortex

Front 243

Overview of the Visual System

Back 243

The visual world is represented throughout the visual pathway in a map that basically is “upside down and backwards”

Front 244

Retina

Back 244

A thin layer of cells at the back of the eye that transduces light energy into neural activity by photoreceptors
-specialized to detect differences in the intensity of light falling on different parts of it.
• Photoreceptors: Converts light energy into
neural activity
• Detects differences in intensity of light

Front 245

Optic nerve

Back 245

The bundle of ganglion cell axons that passes from the eye to the optic chiasm.
-distributes visual information in the form of action potentials.

Front 246

Optic chiasm

Back 246

The structure in which the right and left optic nerves converge and partially decussate (cross) to form the optic tracts.

Front 247

Optic tract

Back 247

A collection of retinal ganglion cell axons stretching from the optic chiasm to the brain stem.
Important targets of the optic tract are the lateral geniculate nucleus and superior colliculus.

Front 248

Lateral geniculate nucleus (LGN)

Back 248

A thalamic nucleus that relays information from the retina to
the primary visual cortex.
• First synaptic relay in the primary visual pathway
• Visual information ascends to cortex --> interpreted and remembered

Front 249

Visual radiations

Back 249

a charted band of wavelengths of electromagnetic radiation obtained by refraction or diffraction.

Front 250

Primary visual cortex

Back 250

Brodmann’s area 17, located
at the pole of the occipital lobe; also called striate
cortex and V1.

Front 251

Significance of vision

Back 251

Relationship between human eye & camera

-Like the camera, the eye automatically adjusts to differences in illumination and automatically focuses itself on objects of interest.

Front 252

Properties of Light

Back 252

Look at figure on page 279

Front 253

Light

Back 253

Light and electromagnetic radiation (wave of energy) - it is all around us

-Light is the electromagnetic radiation that is visible to our eyes.

Front 254

Light

Back 254

Electromagnetic radiation
• Wavelength, frequency, amplitude
Hot colors: Orange, red;
Cool colors: blue, violet

Front 255

Optics

Back 255

Study of light rays and their
interactions

Hint 255

Reflection
– Bouncing of light rays off a
surface

Front 256

Optics

Back 256

Study of light rays and their
interactions

Hint 256

Absorption
– Transfer of light energy to a
particle or surface

Front 257

Optics

Back 257

Study of light rays and their
interactions

Hint 257

Refraction
– Bending of light rays from one
medium to another
-Images are formed in the eye by refraction
-reflection and absorption determine what light enters the eye

Front 258

Optics

Back 258

Study of light rays and their
interactions

Hint 258

Look at figure on page 280

Front 259

The Structure of the Eye

Back 259

Gross Anatomy of the Eye

Hint 259

Pupil: Opening where light enters the eye and reach the retina

Front 260

The Structure of the Eye

Back 260

Gross Anatomy of the Eye

Hint 260

Sclera: "White of the eye" which forms the tough wall of the eyeball

Front 261

The Structure of the Eye

Back 261

Gross Anatomy of the Eye

Hint 261

Iris: Gives color to eyes surrounds the pupil

Front 262

The Structure of the Eye

Back 262

Gross Anatomy of the Eye

Hint 262

Cornea: Glassy transparent external surface of the eye covers the pupil and iris

Front 263

The Structure of the Eye

Back 263

Gross Anatomy of the Eye

Hint 263

Optic nerve: Carries Bundles of axons from the retina and reaches the base of the brain near the pituitary gland

Front 264

The Structure of the Eye

Back 264

Gross Anatomy of the Eye

Hint 264

Look at figure on page 280

Front 265

The Structure of the Eye

Back 265

Ophthalmoscopic Appearance of the Eye
-Optic disk-retinal vessels originate from a pale circular region called the optic disk, where the optic nerve fibers exit the retina

Hint 265

Look at figure on page 281

Front 266

Cross-Sectional Anatomy of the Eye

Back 266

Aqueous Humor: Because the cornea lacks blood vessels it is nourished by the fluid behind it, the aqueous humor

Front 267

Cross-Sectional Anatomy of the Eye

Back 267

Ciliary muscles: Ligaments that suspend lens

Front 268

Cross-Sectional Anatomy of the Eye

Back 268

Lens: Change shape to adjust focus

Hint 268

Divides eyes into two compartments
– Aqueous humor in anterior chamber- watery fluid that lies between the cornea and the lens
– Jelly-like vitreous humor in posterior chamber- Lies between the lens and the retina; its pressure serves to keep the eyeball spherical

Front 269

Image Formation by the Eye

Back 269

Introduction

Hint 269

– Eye collects light reflected off objects in the environment, focuses onto retina to form images
-Bringing objects into focus involves the combined refractive powers of the cornea and lens

Front 270

Image Formation by the Eye

Back 270

Refraction of light by the cornea
-The cornea, rather than the lens, is the site of most of the refractive power of the eyes.

Hint 270

Look at figures on page 284

Front 271

Image Formation by the Eye

Back 271

Focal distance = refractive surface to the point where parallel light rays converge
-focal distance depends on the curvature of the cornea
-----The tighter the curve, the shorter the focal distance

Front 272

Image Formation by the Eye

Back 272

Accommodation by the Lens

Hint 272

Changing shape of lens allows for extra focusing power a process called accommodation

Front 273

The Pupillary Light Reflex

Back 273

The pupillary light reflex involves Connections between retina and brain stem neurons that control the muscles that constirct the pupils

Front 274

The Pupillary Light Reflex

Back 274

Continuously adjusting to different ambient light levels

Front 275

The Pupillary Light Reflex

Back 275

Consensual- Shining light into one eye causes the constriction of the pupils of both eyes

Front 276

The Pupillary Light Reflex

Back 276

Pupil similar to the aperture (hole) of a camera
-Constriction of the pupil has the effect of increasing the depth of focus, just like decreasing the aperture size on a camera lens

Front 277

The Visual Field

Back 277

Amount of space viewed by the
retina when the eye is fixated
straight ahead
-space in front of you without moving head just eyes.

Front 278

Visual Acuity

Back 278

– Ability to distinguish two
nearby points

Hint 278

look at figure on page 288, 9.10

Front 279

Visual Acuity

Back 279

– Visual Angle: Distances across
the retina described in degrees

Front 280

Microscopic Anatomy of the Retina

Back 280

Photoreceptors:

Hint 280

– Cells that convert light energy into neural activity

Look at figures on page 289

Front 281

Microscopic Anatomy of the Retina

Back 281

Direct (vertical) pathway:
-visual information to exit the eye

Hint 281

Photoreceptors--> bipolar cells--> ganglion cells

Front 282

Microscopic Anatomy of the Retina

Back 282

Direct (vertical) pathway
-visual information to exit the eye

Hint 282

– Horizontal cells
-Influences retinal processing
-receives input from the photoreceptors and project neurites laterally to influence surrounding bipolar cells and photoreceptors

Front 283

Microscopic Anatomy of the Retina

Back 283

Direct (vertical) pathway
-visual information to exit the eye

Hint 283

– Amacrine cells
-Influences retinal processing
-receive input from the bipolar cells and project laterally to influence surrounding ganglion cells, bipolar cells, and other amacrine cells.

Front 284

Microscopic Anatomy of the Retina

Back 284

Direct (vertical) pathway
-visual information to exit the eye

Hint 284

– Ganglion cells
-fire action potentials in response to light, and these impulses propagate down the optic nerve to the rest of the brain

Front 285

2 important points

Back 285

1. The light-sensitive cells in the retina are the photoreceptors. All other cells are influenced by light only by direct or indirect synaptic interactions with the photoreceptors

Front 286

2 important points

Back 286

2. The ganglion cells are the only source of output from the retina. No other retinal cell type projects an axon through the optic nerve.

Front 287

The Laminar Organization
of the Retina

Back 287

Cells organized in layers

Hint 287

The layers are Inside-out; light must pass from the vitreous humor through the ganglion cells and bipolar cells before it reaches the photoreceptors

Front 288

Photoreceptor Structure

Back 288

Conversion of Electromagnetic radiation into neural signals

Front 289

Photoreceptor Structure

Back 289

Every photoreceptor has Four main regions

Hint 289

1. Outer segment

Front 290

Photoreceptor Structure

Back 290

Every photoreceptor has Four main regions

Hint 290

2. Inner segment

Front 291

Photoreceptor Structure

Back 291

Every photoreceptor has Four main regions

Hint 291

3. Cell body

Front 292

Photoreceptor Structure

Back 292

Every photoreceptor has Four main regions

Hint 292

4. Synaptic terminal

Front 293

Photoreceptor Structure

Back 293

Types of photoreceptors

Hint 293

• Rods (longer) and cones (shorter)

Front 294

Photoreceptor Structure

Back 294

Types of photoreceptors

Hint 294

• Rods are 1000x more sensitive to light than cones
-Under nighttime lighting, only rods contribute to vision
-Conversely, under day-time lighting cones do the bulk of the work.

Front 295

Photoreceptor Structure

Back 295

Types of photoreceptors

Hint 295

• All rods contain the same
photopigment
-There are three types of cones, each containing a different photopigment, variations among pigments make the different cones sensitive to different wavelengths of light
-cones are responsible for our ability to see color

Front 296

Photoreceptor Structure

Back 296

Look at figure on page 290

Front 297

Regional Differences in Retinal Structure

Back 297

Varies from fovea to retinal periphery

Front 298

Regional Differences in Retinal Structure

Back 298

Peripheral retina

Hint 298

• Peripheral retina has a Higher ratio of rods to cones

Front 299

Regional Differences in Retinal Structure

Back 299

Peripheral retina

Hint 299

• Peripheral retina has a Higher ratio of photoreceptors to ganglion cells

Front 300

Regional Differences in Retinal Structure

Back 300

Peripheral retina

Hint 300

• The combined effect of this arrangement is that the peripheral retina is more sensitive to light

1.Rods are specialized in low light
2. There are more photoreceptors feeding information to each ganglion cell

Front 301

Regional Differences in Retinal Structure

Back 301

Look at figure on page 291

Front 302

Regional Differences in Retinal Structure:

Back 302

Cross-section of fovea: Pit in retina

Hint 302

Look at figure on page 292

Front 303

Regional Differences in Retinal Structure:

Back 303

Structure: Maximizes visual acuity

Front 304

Regional Differences in Retinal Structure:

Back 304

Central fovea: All cones (no rods)

Hint 304

• 1:1 ratio with ganglion cells

Front 305

Regional Differences in Retinal Structure:

Back 305

Central fovea: All cones (no rods)

Hint 305

• Area of high visual acuity

Front 306

Phototransduction

Back 306

Phototransduction in Rods

Hint 306

Depolarization (movement of positive charge across the membrane) occurs in the dark: “Dark current”

Front 307

Phototransduction

Back 307

Phototransduction in Rods

Hint 307

Hyperpolarization in the light

Front 308

Phototransduction

Back 308

Phototransduction in Rods

Hint 308

One opsin in rods: Rhodopsin
• Receptor protein that is activated by light
-rebound agonist is called retinal, absorption of light causes a change in the conformation of retinal so that it activates the opsin, this process is called bleaching because it changes the wavelengths absorbed by the rhodopsin.

Front 309

Phototransduction

Back 309

Phototransduction in Rods

Hint 309

Look at figure on page 295

Front 310

Phototransduction in Cones

Back 310

Similar to rod phototransduction

Hint 310

-Vision during the day depends entirely on the cones, whose photopigments require more energy to become bleached

Front 311

Phototransduction in Cones

Back 311

Different opsins

Hint 311

• Red, green, blue

Front 312

Phototransduction in Cones

Back 312

Look at figures on page 296

Front 313

Color detection

Back 313

Contributions of blue, green,
and red cones to retinal signal

Front 314

Color detection

Back 314

Spectral sensitivity

Front 315

Color detection

Back 315

Young-Helmholtz trichromacy
theory of color vision
-The brain assigns colors based on a comparison of the readout of the three cone types, when all cones are active then we perceive "white"

Front 316

Dark and Light Adaptation

Back 316

Dark adaptation: All-cone daytime vision ---20-25mins-->All-rod nighttime vision this is the process of Dark adaptation

Front 317

Dark and Light Adaptation

Back 317

Dark adaptation—factors

Hint 317

• Dilation of pupils

Front 318

Dark and Light Adaptation

Back 318

Dark adaptation—factors

Hint 318

• Regeneration of unbleached rhodopsin

Front 319

Dark and Light Adaptation

Back 319

Dark adaptation—factors

Hint 319

• Adjustment of functional circuitry

Front 320

Dark and Light Adaptation

Back 320

Calcium’s Role in Light Adaptation

Hint 320

The ability of the eye to adapt to changes in light level relies on Calcium concentration changes within the cones.
-When you step out into bright light, the cones are hyperpolarized as much as possible.
-Reason that this happens is because it stems from the fact that the cGMP-gated sodium channels we discussed previously also admit calcium

-When the channels close, a process is initiated that gradually reopens them even if the light level does not change (Ca channels)

Front 321

Dark and Light Adaptation

Back 321

Calcium’s Role in Light Adaptation

Hint 321

Indirectly regulates levels of cGMP--> Ca channels

Front 322

Retinal Processing

Back 322

Research by

Hint 322

Keffer Hartline, Stephen Kuffler, and Horace Barlow

Front 323

Retinal Processing

Back 323

Research study

Hint 323

Action potential discharges retinal
ganglion cells
• Retina: Stimulated with light

Front 324

Retinal Processing

Back 324

Transformations in the Outer Plexiform Layer

Hint 324

Photoreceptors
• Release neurons when depolarized
-The transmitter released by photoreceptors is the amino acid glutamate
-Look at figure on page 300

Front 325

Retinal Processing

Back 325

Bipolar Cell Receptive Fields
-Categorized into two classes, based on their responses to glutamate

Hint 325

1. In OFF bipolar cells, glutamate- gated cation channels mediate a classical depolarizing EPSP from the influx of Na

Front 326

Retinal Processing

Back 326

Bipolar Cell Receptive Fields
-Categorized into two classes, based on their responses to glutamate

Hint 326

2. ON biopolar cells have G-protein-coupled receptors and respond to glutamate by hyperpolarizing

Front 327

NOTICE

Back 327

notice that the names OFF and ON refer to whether these cells depolarize in response to light off (more glutamate) or to light on (less glutamate)

Front 328

Retinal Output

Back 328

Ganglion Cell Receptive Fields

Hint 328

On-Center (will be depolarized and respond with a barrage of action potentials when a small spot of light is projected onto the middle of its receptive field) and Off-Center cells (Respond to a small dark spot presented to the middle of its receptive field.
-However in both types of cells, the response to stimulation of the center is canceled by the response to stimulation of the surround

Front 329

Retinal Output

Back 329

Ganglion Cell Receptive Fields

Hint 329

Responsive to differences in illumination that occur within their receptive fields

-Look at figure on page 302 and 303

Front 330

Retinal Output

Back 330

OFF-center cell

Hint 330

Dark in center causes cell to depolarize, whereas dark in the surround causes the cell to hyperpolarize
-In uniform illumination, the center and surround cancel to yield some low level of response.

Front 331

Types of Ganglion Cells

Back 331

– Categories based on appearance, connectivity,
and electrophysiological properties

Front 332

Two types of ganglion cells in monkey and human retina

Back 332

M-type (Magno=large)(5% of ganglion cells) and P-type (90% of ganglion cells) (Parvo=small)

Front 333

Color-Opponent Ganglion Cells

Back 333

Color-opponent cells- Majority of these color-sensitive neurons
-reflecting the fact that the response to one wavelength in the receptive field center is canceled by showing another wavelength in the receptive field surround.

Hint 333

Look at figure on page 305

Front 334

Parallel Processing

Back 334

Simultaneous input from two eyes

Hint 334

Information from two streams is compared in
the central visual system
– Depth and the distance of object

Front 335

Parallel Processing

Back 335

Simultaneous input from two eyes

Hint 335

Information about light and dark: ON-center and OFF-center ganglion cells

Front 336

Parallel Processing

Back 336

Different receptive fields and response properties of retinal ganglion cells: M- and P- cells, and nonM-nonP cells

Front 337

Concluding Remarks

Back 337

Light emitted by or reflected off
objects in space --> imaged onto the retina

Front 338

Concluding Remarks

Back 338

Transduction

Hint 338

Light energy converted into membrane potentials

Front 339

Concluding Remarks

Back 339

Transduction

Hint 339

Phototransduction parallels olfactory transduction
• Electrical-to-chemical-electrical signal

Front 340

Concluding Remarks

Back 340

Mapping of visual space onto retinal ganglion cells not uniform

Front 341

Chapter 10
Visual System II. The Central Visual System

Back 341

.

Front 342

Introduction

Back 342

Neurons in the visual system

Hint 342

Neural processing resulting in perception

Front 343

Parallel pathway serving conscious visual perception originate in the retina

Back 343

The pathway serving conscious visual perception includes the lateral geniculate nucleus, primary visual cortex & higher order visual areas in temporal and parietal lobes (aka. area 17, V1, or striate cortex)

Front 344

The Retinofugal Projection (neural pathway that leaves the eye)

Back 344

The Optic Nerve- exit the left and right eyes at the optic disks, travel through the fatty tissue behind the eyes in their bony orbits, then pass through holes in the floor of the skull

Optic Chiasm- The optic nerves from both eyes combine to form the optic chiasm, which lies at the base of the brain. The axons originating in the nasal retinas cross from one side to the other. Because only the axons originating in the nasal retinas cross, we say that a partial decussation of the retinofugal projection occurs at the optic chiasm

Optic Tract- Following the partial decussation of at the optic chiasm, the axons of the retinofugal projections form the optic tracts

Hint 344

Decussation- The crossing of a fiber bundle from one side of the brain to the other is called decussation.
Look at figure on page 311

Front 345

The Retinofugal Projection

Back 345

Right and Left Visual Hemifields

Hint 345

Optic nerve fibers cross in the optic chiasm so that the left visual hemifield is "viewed" by the right hemisphere and the right visual hemifield is :viewed" by the left hemisphere
Look at figure on page 312

Front 346

The Retinofugal Projection

Back 346

Look at figure on page 313

Front 347

The Retinofugal Projection

Back 347

Targets of the Optic Tract
-Most of them innervate the lateral geniculate nucleus (LGN) of the dorsal thalamus
-The neurongs in the LGN give rise to axons that project to the primary visual cortex, this projection is called the optic radiation.

Hint 347

Look at figure on page 313

Front 348

The Retinofugal Projection

Back 348

While cutting the left optic nerve would render a person blind in the left eye only, a cut of the left optic tract would lead to blindness in the right visual field

Hint 348

Look at figures on page 314

Front 349

The Retinofugal Projection

Back 349

Nonthalamic Targets of the Optic Tract:

Hint 349

Hypothalamus: Biological rhythms, including sleep and wakefulness

Front 350

The Retinofugal Projection

Back 350

Nonthalamic Targets of the Optic Tract:

Hint 350

Pretectum: Size of the pupil; certain types of eye movement

Front 351

The Retinofugal Projection

Back 351

Nonthalamic Targets of the Optic Tract:

Hint 351

Superior colliculus (optic tectum): Orients the eyes in response to new stimuli (saccadic eye movements)

Front 352

The Lateral Geniculate Nucleus (LGN)
-arranged in 6 layers for each eye and bent around the optic tract like a knee joint.
-segregation of the LGN neurons into layers suggests that different types of retinal information are being kept separate at this synaptic relay, and indeed this is the case: axons arising from M-type, P-type, and nonM-nonP ganglion cells in the two retinas synapse on cells in different LGN layers

Back 352

Look at figure on page 317

Front 353

The Lateral Geniculate Nucleus (LGN)

Back 353

-LGN neurons receive synaptic input from the retinal ganglion cells, and most geniculate neurons project an axon to primary visual cortex by the optic radiation
The Segregation of Input by Eye and by Ganglion Cell Type

Hint 353

Look at figure on page 318

Front 354

Magnocellular LGN layers

Back 354

the ventral layers of LGN.
-layers 1 and 2 contain larger neurons

Front 355

Parvocellular LGN layers

Back 355

the dorsal layers of LGN
-layers 3-6 contain smaller neurons

Front 356

Receptive Fields

Back 356

Receptive fields of LGN neurons: Identical to the ganglion cells that feed them

Front 357

Receptive Fields

Back 357

Magnocellular LGN neurons: Large, monocular receptive fields with transient response

Front 358

Receptive Fields

Back 358

Parvocellular LGN cells: Small,monocular receptive fields with sustained response

Front 359

Nonretinal Inputs to the LGN

Back 359

Retinal ganglion cells axons: Not the main source of synaptic input to the LGN

Hint 359

Look at figure on page 319

Front 360

Nonretinal Inputs to the LGN

Back 360

Primary visual cortex: 80% of the synaptic inputs to the LGN

Front 361

Nonretinal Inputs to the LGN

Back 361

Neurons in the brain stem: regulate the influence on neuronal activity

Front 362

Anatomy of the Striate Cortex

Back 362

-LGN has a single major synaptic target: primary visual cortex
Look at figure on page 321

Front 363

Anatomy of the Striate Cortex

Back 363

Retinotopy- an organization whereby neighboring cells in the retina feed information to neighboring places in their target structures

Hint 363

Map of the visual field onto a target structure
(retina, LGN, superior colliculus, striate cortex) -
overrepresentation of central visual field

Front 364

Anatomy of the Striate Cortex

Back 364

Retinotopy

Hint 364

Discrete point of light: Activates many cells in the retina, and other target structures

Front 365

Anatomy of the Striate Cortex

Back 365

Retinotopy

Hint 365

Perception: Based on the brain’s interpretation of distributed patterns of activity

Front 366

Anatomy of the Striate Cortex

Back 366

Look at figure on page 320

Front 367

Anatomy of the Striate Cortex

Back 367

Lamination of the
Striate Cortex

Hint 367

Layers I - VI

Front 368

Anatomy of the Striate Cortex

Back 368

Lamination of the
Striate Cortex

Hint 368

Spiny stellate cells: Spinecovered
dendrites; seen in layer IVC
-Make local connections only within the cortex

Front 369

Anatomy of the Striate Cortex

Back 369

Lamination of the
Striate Cortex

Hint 369

Pyramidal cells: Spines; thick
apical dendrite; layers III, IVβ, V, VI
-only pyramidal cells send axons out of striate cortex to form connections with other parts of the brain.

Front 370

Anatomy of the Striate Cortex

Back 370

Lamination of the
Striate Cortex

Hint 370

Inhibitory neurons: Lack
spines; All cortical layers;
Forms local connections

Front 371

Anatomy of the Striate Cortex

Back 371

Lamination of the
Striate Cortex

Hint 371

Look at figure on page 321

Front 372

Anatomy of the Striate Cortex

Back 372

Inputs to the Striate Cortex

Hint 372

Magnocellular LGN neurons project to layer IVCα

Front 373

Anatomy of the Striate Cortex

Back 373

Inputs to the Striate Cortex

Hint 373

Parvocellular LGN neurons Project to layer IVCβ

Front 374

Anatomy of the Striate Cortex

Back 374

Inputs to the Striate Cortex

Hint 374

Koniocellular LGN axons: Bypasses layer IV to make synapses in layers II and III

Front 375

Anatomy of the Striate Cortex

Back 375

Ocular Dominance Columns

Hint 375

Look at figure on page 322

Front 376

Layer IVC innervates superficial layers

Back 376

Look at figure on page 323, 10.17

Front 377

Outputs of the Striate Cortex:

Back 377

Layers II, III, and IVB:
Projects to other cortical
areas

Hint 377

Look at figure on page 323, 10.18

Front 378

Outputs of the Striate Cortex:

Back 378

Layer V: Projects to the
superior colliculus and pons

Front 379

Outputs of the Striate Cortex:

Back 379

Layer VI: Projects back to
the LGN

Front 380

Cytochrome Oxidase
Blobs

Back 380

Cytochrome oxidase is a
mitochondrial enzyme
used for cell metabolism

Front 381

Cytochrome Oxidase
Blobs

Back 381

Blobs: Cytochrome oxidase
staining in cross sections
of the striate cortex

Front 382

Receptive Fields

Back 382

Layer IVC: Monocular; center-surround

Front 383

Receptive Fields

Back 383

Layer IVCα: Insensitive to the wavelength

Front 384

Receptive Fields

Back 384

Layer IVCβ: Center-surround color
opponency

Front 385

Binocularity

Back 385

Layers superficial to IVC: First binocular receptive fields in the visual pathway

Front 386

Receptive Fields

Back 386

Orientation Selectivity

Hint 386

Look at figure on page 325

Front 387

Receptive Fields

Back 387

Direction Selectivity

Hint 387

Neuron fires action potentials in response to moving bar of light

Look at figures on page 327

Front 388

Receptive Fields

Back 388

Simple cells: Binocular; Orientationselective;
Elongated on-off region with
antagonistic flanks responds to optimally oriented bar of light (location in the field)

Front 389

Receptive Fields

Back 389

Possibly composed of three LGN cell axons with center-surround receptive fields

Front 390

Receptive Fields

Back 390

Complex cells: Binocular; Orientationselective;
ON and OFF responses to the bar of light but unlike simple cells, no distinct on-off regions

Hint 390

Look at figure on page 329

Front 391

Physiology of the Striate Cortex

Back 391

Receptive Fields

Hint 391

Blob Receptive Fields
• Blob cells: Wavelength-sensitive; Monocular; No
orientation; direction selectivity

Front 392

Physiology of the Striate Cortex

Back 392

Receptive Fields

Hint 392

Parallel Pathways: Magnocellular;
Koniocellular; Parvocellular

-Look at figure on page 330

Front 393

Physiology of the Striate Cortex

Back 393

Receptive Fields

Hint 393

Cortical Module
-Look at figure on page 332

Front 394

Beyond Striate Cortex

Back 394

Dorsal stream

Hint 394

Analysis of visual
motion and the visual
control of action

Front 395

Beyond Striate Cortex

Back 395

Ventral stream

Hint 395

Perception of the
visual world and the
recognition of objects
-Look at figure on page 333

Front 396

Beyond Striate Cortex

Back 396

The Dorsal Stream (V1, V2, V3, MT, MST, Other dorsal areas)

Hint 396

Area MT (temporal lobe)
• Most cells: Direction-selective; Respond more
to the motion of objects than their shape

Front 397

Beyond Striate Cortex

Back 397

The Dorsal Stream (V1, V2, V3, MT, MST, Other dorsal areas)

Hint 397

Beyond area MT - Three roles of cells in area MST (parietal lobe)
– Navigation

Front 398

Beyond Striate Cortex

Back 398

The Dorsal Stream (V1, V2, V3, MT, MST, Other dorsal areas)

Hint 398

Beyond area MT - Three roles of cells in area MST (parietal lobe)
– Directing eye movements

Front 399

Beyond Striate Cortex

Back 399

The Dorsal Stream (V1, V2, V3, MT, MST, Other dorsal areas)

Hint 399

Beyond area MT - Three roles of cells in area MST (parietal lobe)
– Motion perception

Front 400

The Ventral Stream (V1, V2, V3, V4, IT, Other ventral areas)

Back 400

Area V4

Hint 400

Achromatopsia: Clinical syndrome in humans-caused by damage to area V4; Partial or complete loss of color
vision

Front 401

The Ventral Stream (V1, V2, V3, V4, IT, Other ventral areas)

Back 401

Area IT

Hint 401

Major output of V4

Front 402

The Ventral Stream (V1, V2, V3, V4, IT, Other ventral areas)

Back 402

Area IT

Hint 402

Receptive fields respond to a wide variety of colors and
abstract shapes

Front 403

The Ventral Stream (V1, V2, V3, V4, IT, Other ventral areas)

Back 403

Area IT

Hint 403

prosopagnosia

Front 404

From Single Neurons to Perception

Back 404

Visual perception

Hint 404

– Identifying & assigning meaning to objects

Front 405

From Single Neurons to Perception

Back 405

Hierarchy of complex receptive fields

Hint 405

Retinal ganglion cells: Center-surround structure, Sensitive to contrast, and wavelength of light

Front 406

From Single Neurons to Perception

Back 406

Hierarchy of complex receptive fields

Hint 406

Striate cortex: Orientation selectivity, direction selectivity, and binocularity

Front 407

From Single Neurons to Perception

Back 407

Hierarchy of complex receptive fields

Hint 407

Extrastriate cortical areas: Selective responsive to complex shapes; e.g., Faces

Front 408

From Single Neurons to Perception

Back 408

From Photoreceptors to Grandmother Cells

Hint 408

Grandmother cells: Face-selective neurons in area IT?

Front 409

From Single Neurons to Perception

Back 409

From Photoreceptors to Grandmother Cells

Hint 409

Probably not: Perception is not based on the activity of individual, higher order cells

Front 410

From Single Neurons to Perception

Back 410

Parallel Processing and Perception

Hint 410

Groups of cortical areas contribute to the perception of color,motion, and identifying
object meaning

Front 411

Concluding Remarks

Back 411

Vision

Hint 411

Perception combines individually
identified properties of visual objects

Front 412

Concluding Remarks

Back 412

Vision

Hint 412

Achieved by simultaneous, parallel
processing of several visual pathways

Front 413

Concluding Remarks

Back 413

Parallel processing

Hint 413

Like the sound produced by an orchestra of visual areas rather than the end product of an assembly line