Biopsych Final 2

Front 1

Principles of sensorimotor function

Back 1

- Sensorimotor system is hierarchically organized
- Motor input is guided by sensory input
- Learning changes the nature and locus of sensorimotor control

Front 2

Posterior parietal association cortex

Back 2

- Inputs from visual, auditory, and somatosensory systems
- Outputs to motor cortex, frontal eye field
- Handles information about position of body in relation to objects and directs attention
- When damaged, apraxia and contralateral neglect

Front 3

Dorsolateral prefrontal association cortex

Back 3

- Inputs from posterior parietal cortex
- Outputs to primary and secondary motor cortices
- Evaluation of/reaction to external stimuli
- Gives ideas to SMC; SMC does the programming

Front 4

Secondary motor cortex: classic vs. newly discovered areas

Back 4

- Previously, a two-area concept: supplementary motor area and premotor cortex, both on the frontal lobe
- Newly discovered in monkeys: at least seven areas of SMC in each hemisphere
- Newly discovered in humans: similar to monkeys; at least two cingulate motor areas

Front 5

Secondary motor cortex: responsibilities

Back 5

- Programming specific movements according to instructions from dorsolateral prefrontal cortex

Front 6

Secondary motor cortex: inputs/outputs

Back 6

- Input information from dorsolateral prefrontal cortex
- Output information to each other; to primary motor cortex

Front 7

Secondary motor cortex: mirror neurons

Back 7

- Located in ventral premotor cortex, posterior parietal lobe
- Fire when an individual performs a particular goal-directed hand movement or observes it in others
- Provides evidence for social cognition

Front 8

Primary motor cortex: organization

Back 8

- Located in precentral gyrus of frontal lobe
- Receives input from receptors in muscles and joints

Front 9

Primary motor cortex: function

Back 9

- Grand Central Station: Point of convergence of cortical sensorimotor signals and point of departure of signals from cerebral cortex

Front 10

Stereognosis

Back 10

- Process of identifying objects by touch
- Facilitated by skin input to primary motor cortex

Front 11

Primary motor cortex: damage

Back 11

- Sites that move a particular body part overlap with parts that move other body parts; can't selectively disrupt movement of a single finger
- May disrupt ability to move finger independently of others, however
- Damage may produce deficits in stereognosis
- May reduce speed, accuracy, force of movements

Front 12

Hierarchy of sensorimotor system

Back 12

Association cortex
Secondary motor cortex
Primary motor cortex
Brain stem motor nuclei
Spinal motor circuits

Spinal motor circuits feedback to each other and on up the loop

Front 13

Cerebellum

Back 13

- 10% of mass of the brain but contains 50% of neurons
- Input from primary and secondary motor cortices, brain stem motor nuclei, motor responses
- Compares sources of input and corrects movement that isn't going where it's supposed to
- Damage to cerebellum means inability to control movements

Front 14

Basal ganglia

Back 14

- Neural loops that receive cortical input from different areas and transmit it back to the motor cortex via the thalamus
- Modulators rather than actioners

Front 15

Descending motor tracts

Back 15

- Two direct, two indirect
- Signals on these pathways act together in controlling voluntary movement

Front 16

Direct descending motor pathways

Back 16

Dorsolateral corticospinal tract
- Medullary pyramids
- Betz cells: large pyramidal primary motor cortex neurons
- Thought to be the means by which we exert voluntary control over legs

Ventromedial corticospinal tract
- Descend from primary motor cortex into spinal white matter

Front 17

Indirect descending motor pathways

Back 17

Dorsolateral corticurubrospinal tract
- Axons descend from red nucleus to cranial nerves that control facial muscles; others control muscles of arms and legs

Ventromedial cortico-brainstem-spinal tract
- Interacts with tectum, vestibular nucleus, reticular formation
- Controls proximal muscles of trunk and limbs

Front 18

Difference between dorsolateral and ventromedial pathways

Back 18

- Ventromedial tracts more diffuse- innervate many more neurons than do dorsolateral tracts
- Ventromedial tracts project to proximal muscles of trunk and limbs (shoulders) rather than distal muscles (fingers) as in dorsolateral tracts

Front 19

Lawrence and Kuypers: descending motor tracts experiments

Back 19

- Transection of dorsolateral corticospinal tracts: monkeys could stand, walk, and climb, but other limb movements (e.g. reaching) impaired
*** Same response performed in different contexts can be controlled by different parts of the CNS

- Transection of dorsolateral corticorubrospinal tract led to monkeys unable to use arms unless while standing, walking, climbing

- Transection of ventromedial tracts led to severe postural problems with problems walking or sitting

Front 20

Functions of descending motor tracts

Back 20

- Dorsolateral: control movements of the limbs
- Ventromedial: control of posture and whole-body movements

Front 21

Synergistic muscles

Back 21

Any two muscles whose contraction produces the same movement

Front 22

Antagonistic muscles

Back 22

Any two muscles whose contraction acts in opposition

Front 23

Isometric muscle contraction

Back 23

Activating a muscle increases tension that it exerts on two bones without pulling them together

Front 24

Dynamic muscle contraction

Back 24

Activating a muscle increases tension and pulls two bones together

Front 25

Motor units

Back 25

Smallest units of motor activity; a single motor neuron and all of its skeletal muscle fibers

Front 26

Motor pol

Back 26

All of motor neurons innervating fibers of a single muscle

Front 27

Reciprocal innervation

Back 27

Antagonistic muscles have a smooth, unimpeded motor response- one contracts, the other relaxes

Front 28

Recurrent collateral inhibition

Back 28

Inhibition produced by local feedback circuits around a motor neuron; makes sure that muscle fibers receive an R&R break

Front 29

H.M.'s surgery and amnesia

Back 29

- Had medial portions of temporal lobes removed to treat epilepsy
- Reduced seizures
- Mild retrograde amnesia
- Severe anterograde amnesia
** Ability to hold information in short term storage is normal
** Difficulty forming new LT memories

Front 30

Tests of memory

Back 30

- Digit span + 1 test: repeat a series of numbers
- Block-tapping memory span test: test sequence of tapping blocks; shows amnesia for information presented in tactile form
- Mirror-drawing test: draw a shape by watching hand in a mirror; performance should improve over time
- Rotary pursuit test
- Incomplete pictures test

Front 31

Scientific implications of H.M.'s case

Back 31

- Bilateral medial temporal lobectomy causes LT memory deficits without disrupting ST memory
- Ergo: different modes of storage for LT vs ST memory

Front 32

Korsakoff's syndrome

Back 32

- Characterized by extreme confusion and retrograde amnesia
- Damage to mediodorsal nuclei of the thalamus- seems this is implicated in memory

Front 33

Alzheimer's- neurotransmitter deficiency

Back 33

- Deficiency in acetylcholine
- Brain damage to medial temporal lobe, prefrontal cortex

Front 34

Sources of amnesia

Back 34

Posttraumatic amnesia- follows head blow (concussion)
- Anterograde and retrograde memory deficits

Electroconvulsive shock

Front 35

Memory consolidation

Back 35

- Storage of older memories strengthened
- Demonstrated in ECS patients: by disrupting neural activity ECS would only disrupt memories that had not consolidated

Front 36

Reconsolidation

Back 36

- Each time a mmeory is retrieved from LT memory it is held in labile ST memory, where it is susceptible to posttraumatic amnesia before reconsolidation

Front 37

Hippocampal lesions in animal models

Back 37

- Rats on morris water maze- very difficult for rats with lesions
- Rats with lesions major deficits in reference and working memories

Front 38

Object recognition amnesia in animal models

Back 38

- Delayed nonmatching-to-sample test
- Select unfamiliar object to obtain food
- Monkeys with bilateral medial temporal lbe lesions had major object-recognition deficits (like HM)
- problems due to hippocampal damage