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136 Cards in this Set

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In order to "sense", we must be able to do what?
Convert stimuli in the environment into neural activity.
What is transduction?
The conversion of one form of energy to another.
Sensing is done through...
Transduction; during some point in the neural pathway, there has to be transduction.
What is the Law of Specific Nerve Energies by Muller?
The activity of a particular nerve always conveys the same kind of information to the brain
Our perception is an end result of what?
Which sensory nerves are activated by peripheral nerve receptors.
Details of perception are supplied by...
the pattern, timing, and strength of the activation.
Where does light travel once it hits the retina?
Retina sends it to the thalamus. Thalamus sends it to the occipital lobe.
Where is the retina?
In the back of your eyeball
What is the fovea?
Responsible for central sharpest vision; full of cones for color vision.
What is the blindspot?
Its where all the optic nerves exit together as a big bundle of axons.
Where does light go once it hits the eyeball?
All the way to the back of the eyeball first.
What is sound?
Periodic compressions of air, water and other media.
What is the role of the dorsal stream in simultanagnosia?
The dorsal stream is responsible for visually localizing objects in space.
What is functional segregation?
each level of the sensorimotor hierarchies tends to be composed of different neural structures (units), each of which perform a different function.
What is the main difference between the sensory systems and the sensorimotor system?
The primary direction of information flow: sensory, info flows up through hierarchy. sensorimotor: info mainly flows down
What are three principles of the sensorimotor?
1. The sensorimotor system is hierarchically organized
2. Motor output is guided by sensory input
3. Learning can change the nature and the locus of sensorimotor control.
The sensorimotor system is a parallel hierarchical system meaning..
they are hierarchical systems in which signals flow between levels over multiple paths
What role does sensory feedback play?
directing the continuation of the responses that produced it. (excluding ballistic movements)
What are ballistic movements?
Brief, all-or-none, high-speed movements, such as swatting a fly.
Many adjustments in motor output that occur in response to sensory feedback are controlled unconsciously by...
lower levels of the sensorimotor hierarchy without the involvement of the higher levels.
Sensorimotor system can be compared to...
a large company.
What is the hierarchical order of the sensorimotor system?
Association cortex-> secondary motor cortex-> primary motor cortex-> brain stem motor nuclei-> spinal motor cortex
What are the two major areas of the association cortex?
Posterior parietal and dorsolateral prefrontal association cortex
What is the role of the posterior parietal association cortex?
integrating information about the original position of the body parts that are to be moved and the positions of any external objects with which the body is going to interact; and directing attention
Why is the posterior parietal cortex classified as an association cortex?
because it receives input from more than one sensory system.
What three sensory systems play roles in the localization of the body and external objects in space?
Visual system, auditory system and the somatosensory system.
What three sensory systems does the posterior parietal cortex receive information from?
visual, auditory, somatosensory
Where does much of the ouput of the posterior parietal cortex go to?
areas of the motor cortex: dorsolateral prefrontal association cortex, areas of secondary motor cortex and frontal eye field.
Damage to the posterior parietal can produce a variety of...
sensorimotor deficits: perception and memory of spatial relationships, accurate reaching/grasping, eye movement, attention.

Most important: apraxia and contralateral neglect
How does the dorsolateral prefrontal association cortex work?
receives projections from posterior parietal cortex and sends projections to areas of secondary motor cortex, to primary motor cortex and to the frontal eye field.
What are the functions of the dorsolateral prefrontal association cortex?
evaluation of stimuli and the initiation of voluntary reactions to them
What serves a strategic role in gating of information flow to cortex?
Thalamus (LGN)
What cells in the visual system project to the brain?
Ganglion cells
What is photopic vision?
Vision of the eye under well-lit conditions
What is scotopic vision?
Scotopic vision is the monochromatic vision of the eye in low light
X cells:
near the fovea, receive input from cones; have small receptive fields: only a couple of cells will activate
What are the two types of ganglion cells?
X and Y
Y cells?
Found in periphery of retina so they get most input from rods. Not sensitive to color difference
Low convergence occurs with ___-fed circuits. High convergence occurs with ___-fed circuits.
Cone; rod

Cones:ganglion::1:1 (sometimes)
Rods:ganglion::Many:1
What are photopigments?
Photopigments are unstable pigments that undergo a chemical change when they absorb light
What is the important photopigment in retina?
Rhodopsin
Where is rhodopsin found?
Vitamin A
How does the photopigment work for visual transduction?
Works through a G-protein mediated process that causes a decrease in Na+ permeability.
What is cyclic GMP?
the second messenger system for the visual system.
What is the dark current?
The dark current is the Na+ flowing into the cell when its dark. The Na+ flows in because the cyclic GMP (2nd messenger system) is attached to the Na+ channel and makes it stay open. It depolarizes the cell.
What is different about the resting membrane potential when its dark?
It isn't hyperpolarized when its not activated because of cyclic GMP and Na+ channels.
What happens in the light?
Light strikes rhodopsin, which then splits. Retinal binds with and activates transducin (G-protein). When it is activated, it activates phosphodiesterase, which comes and destroys cyclic GMP. This closes the Na+ channel that was being held open for Na+ in the dark.
What is transducin?
The G-protein that is activated by retinal when it is light.
In the dark the cell is ____polarized. In the light, the cell is ____polarized.
Depolarized (dark); hyperpolarized (light). most important thing to know.
What triggers action potential in the visual system in the dark?
ganglion cells; photoreceptors and bipolar cells can't.
The membrane in the dark is depolarized so it can release _____.
a NT; glutamate.
When glutamate is released, bipolar cells can't release glutamate because _____.
They are hyperpolarized, so there can be no action potential. Even though it is depolarized, the final result is no action potential.
How does glutamate cause hyperpolarization?
It has an inhibitory effect on the next cell. Some of the G-protein receptors are considered inhibitory, so the net output at the synaptic level is hyperpolarization.
Inhibiting the release of glutamate in the light has a _______ effect on the ________.
Inhibitory; postsynaptic cell.
Because you inhibit the release of glutamate in the light, you end up with ______.
Action potential.
What are horizontal cells and amacrine cells important for?
Lateral communication in the retina.
What is lateral inhibition?
The stimulated receptor connects to bipolar cell and excites it; it also activates the horizontal cell. The horizontal cell inhibits the bipolar cell and several nearby. Because the neighbor cells aren't receiving stimulus, they are inhibited.
What is a scotoma?
an area of blindness; the blind spot produces a natural scotoma
What is completion?
The way of filling in gaps in our vision; its how we make up for the blindspot. We constantly move our eyes so we can perceive everything.
What are saccades?
very quick eye movements connecting fixations.
What are the types of cones for color perception?
Short (blue), medium (green), long (red): colors basically represent their sensitivity to that color spectrum. Their responsiveness depends on the wavelength of the color system.
What is the trichromatic theory?
All of our color perception is based on selective sensitivity of cones to one of three wavelengths.
The trichromatic theory is like...
blending different colors together to come up with what you want. Using the cones and their three sensitivities, you can create all the color you need in your brain.
What is the opponent process theory?
We perceive color in terms of paired opposites.
What explains the after image of (example:) the green heart?
The trichromatic theory cannot. Its a rebound effect after you saturated the green cones, which cannot adapt as quickly as the screen switch.
What is the basis of the opponent process theory?
There are three types of ganglion cells.
Red-green cells
Yellow-blue cells
Brightness-coding cells.
If you are looking at green, you still...
activate red.
Why is there a rebound effect when looking at an image that is only green?
The cells were suppressed for a long time so they rebound and overshoot and we see red.
What is a negative afterimage?
Adaptation in the rate of firing of retinal ganglion cells (rebound effect).
What and for what is the lateral geniculate nucleus important?
A sub nuclei in the thalamus; important for processing visual information!!!
What and for what is the lateral geniculate nucleus important?
A sub nuclei in the thalamus; important for processing visual information!!!
What is the striate cortex?
The primary cortex in the visual cortex where info from thalamus gets to first?
Where is AP triggered in the eye and where does it travel?
The ganglion cells; travel the axons of the ganglion cells out of the retina to the thalamus.
Where does transduction occur in the visual system?
photoreceptors.
Ganglion cells leave the retina by traveling along...
optic nerves.
When optic nerves pass the ______ ____, they are called ____ ____.
Optic chiasm; optic tracts.
The nerves coming from the ____ part of the retina don't cross.
Temporal.
The nerves coming from the ____ cross once they reach the optic chiasma
nasal halves of the retina
Where is the visual field of the temporal part of the right eye retina is?
The left visual field.
The majority of information in the visual system ends up in the....
Lateral geniculate nucleus.
The majority of information in the visual system ends up in the....
Lateral geniculate nucleus.
How many layers does the lateral geniculate nucleus have?
6:
4 outer layers: parvocellular: P pathways
2 inner layers form magnocellular: M pathways.
What are cells in the parvocellular layer important for?
color perception?
What are magnocellular layers responsive to?
movements rather than details or colors of objects.
What are five characteristics of the parvocellular layer?
Outer 4 layers of LGN
Small cell bodies
Responsive to color and fine detail
Stationary or slow moving objects
Primarily cone input
What are four characteristics of the magnocellular layer?
Inner layers of the LGN
Large cell bodies
Particularly responsive to movement
Primarily rod input
P pathways receive their input from...
X cells (97%)
The P pathway is the best for....
high acuity, detail and color information
M pathways input is from?
40% Y cells
60% X cells
P pathway receives most of their input from ____ cells which receive most of their input from ___
X; cones: so they're best for high acuity, color, detail
M pathway is best for...
broad outlines of shapes, depth and movement detection
Each level of the visual pathway is organized like....
a map of the retina
Images get projected onto the retina in a very...
organized manner
What are the four visual areas of the human neocortex
Primary visual cortex
Prestriate cortex
Posterior parietal cortex
Inferotemporal cortex
The primary visual (striate) cortex is...
the first area that receives input from the thalamus
The prestriate cortex is
in front of the primary cortex
The posterior parietal cortex
does more complicated things.
The primary visual cortex (V1) receives direct input from...
P and M pathways of LGN
What makes up the secondary visual cortical area?
Prestriate cortex (V2)
Inferotemporal cortex
The posterior parietal cortex contains other _____ regions, thought of as ______ cortex.
"higher" regions; association
What is the hierarchical response property of the visual cortex?
As you move from the LGN to the primary visual cortex and then to higher cortical areas, the response properties of neurons tend to become more complex.
Primary-->Secondary-->postparietal
Cells in the post parietal cortex respond to _____ visual stimuli
more complex
The dorsal pathway of the visual cortex is the ____ pathway; its important for _____ and _____.
"Where" pathway; location and movement
The ventral pathway of the visual cortex is the ____ pathway; its important for _______ and _______.
"what" object recognition; knowing what you're looking at.
Where is area V4? What is it important for?
Just in front of the secondary visual cortex; ventral pathway; important for color perception and orientation of certain objects
Cells in the inferior temporal cortex respond to _______ shapes than the V4
More complex
Area IT is responsive to....
a wide variety of colors and abstract shapes.
What pathway are Area V4 and Area IT in?
ventral
What pathway are Area MT and Area MST in?
Dorsal
Area MT (medial temporal) and Area MST (medial superior temporal) are important for
motor perception
Area MT cells are ________ and respond to types of ______
direction-selective; motion
Area MST cells are selective for _____, ______, and ______ motions
linear, radial and circular;
Area MST is important for ________, _________ _________ and _______ _______
navigation, directing eye movement, motion perception
The receptive field is _____ because it is a part of the visual field.
external
There is a receptive field for every neuron at the level of the _____, _____, and ____.
Retina, thalamus, cortex
Retina-geniculate-striate
What did Hubel and Weisel do?
Recording of neurons in the primary visual cortex.
What are the three types of cells for the visual fields?
on/off center, simple, complex
The primary visual cortex is known for having what kind of cells?
simple and complex
What are the two types of on and off center cells
retinal ganglion cells
lateral geniculate nucleus cells
On center cells are found mainly in the...
ganglion cells in the thalamus, but some in visual cortex
An on center cell has an off area but that does not make it an off-center cell
Not a question card.
What shape are on and off center cell receptive fields?
circular
On center cells are involved in shape recognition and edge detection
Not a question card.
Where are simple cells mainly found?
Primary visual cortex
What are they most responsive to?
bars of light or dark in a particular orientation and position
Most simple cells are a) monocular or b) binocular?
monocular

sensitive to ORIENTATION
What shape are simple cell receptive fields?
Rectangular: very sensitive to ORIENTATION.
What are complex cells most responsive to?
most strongly excited or inhibited by bars of light in a particular orientation that are moving in a particular direction (usually perpendicular to the axis on the bar)
What shape is the receptive field of complex cells?
There is no on and off regions. If it is in the receptive field, the cell will show some activation no matter where.
What are complex cells important for?
Movement!!!!!!!
What are unique characteristics of complex cells?
Larger receptive fields
No on-off zones
Binocular
Some responsiveness to retinal disparity (greatest response when stimulation is simultaneously presented to both eyes but in slightly different retinal positions---a basis of depth perception.
How are visual fields organized?
Cortical columns: input from the same visual fields of the left and right eyes are arranged in adjacent columns. If one cell receives info from the left eye, chances are the other cells in that column will also; they alternate: left, right, left, right
What are color blobs?
Cytochrome oxidase blobs
^ Mitochondria enzyme
The cells in the inferior temporal cortex are....
maximally excited by complex visual stimuli such as faces or hands; even a single cell can respond to a complicated visual stimulus
What is the columnar organization of the inferior temporal cortex?
Cells form columns that respond to categories of shapes
Motor system starts from the ___ and goes to the ____; the sensory system goes from ______ to ___
top to bottom
bottom to top