the sensorimotor system: cortex (2.6)

Question 1

principles of sensorimotor function (3)

Answer 1

hierarchical organization (association cortex highest; muscles lowest); motor output is guided by sensory input (sensory feedback); learning changes the nature and locus of sensorimotor control

Question 2

association cortex

Answer 2

where sensory ends and motor begins; where things come together

Question 3

major areas of association cortex (2)

Answer 3

posterior parietal, dorsolateral prefrontal

Question 4

posterior parietal association cortex (PPAC)

Answer 4

where processing starts; need to know current position of body parts and location of external objects of interest; receives input from dorsal streams

Question 5

apraxia

Answer 5

results from damage to the PPAC; inability to make a requested movement (inability to form the intent)

Question 6

contralateral neglect

Answer 6

results from damage to the PPAC; inability to respond to stimuli contralateral to the lesion

Question 7

dorsolateral prefrontal association cortex (DLPFAC)

Answer 7

receives input from the PPAC; forms a plan of action; outputs to secondary motor cortex

Question 8

ventrolateral prefrontal association cortex (VLPFAC)

Answer 8

knows what’s going on; knows flavor; target of all ventral streams; anticipates consequences (?)

Question 9

major areas of M2 (3)

Answer 9

premotor, supplementary, cingulate

Question 10

secondary motor (function)

Answer 10

converts general plans of action into specific sets of instructions; active during planning or imagining movements; tells you how to do it (specifics); outputs to M1

Question 11

primary motor cortex

Answer 11

controls the execution of movement; major point of convergence of cortical sensorimotor signals; major, but not only, point of departure of signals from cortex

Question 12

motor homunculus

Answer 12

motor cortex is organized in a somatotopic manner (according to body map); hands and face overrepresented

Question 13

mirror neurons

Answer 13

active not only when performing a specific action, but are also active when observing the same action; possible neural basis of learning by imitation

Question 14

cerebellum

Answer 14

going to do it well; helps primary motor; knows both the plan (pontine nuclei) and how it’s going (inferior olive); informed of motor commands (M1) and performance (somatosensory and vestibular systems); involved in coordination, precision, and timing of execution commands from M1; motor learning

Question 15

basal ganglia

Answer 15

important for motor selection; collection of cells located right outside of the thalamus; helps M2 decide which specific set of instructions to use; striatum and globus padillus (and subthalamic nucleus, substantia nigra)

Question 16

yes vs no decision in striatum

Answer 16

yes (direct/excitation): globus padillus inhibition (GPi) -> VA thalamus (“yes”) -> M2
no (indirect/hyper-direct/inhibition): globus padillus inhibition (GPe) -> GPi

Question 17

Parkinson’s disease

Answer 17

characterized by slowness or absence of movement (bradykinesia or akinesia), rigidity, and a resting tremor (hands, fingers); loss of dopaminergic neurons in the substantial nigra; allows K+ to flow; vote “no”

Question 18

Huntington’s disease

Answer 18

characterized by choreiform movements (involuntary, jerky movements of the body, especially of the extremities and face); vote “yes”