lecture 17 - stuart baker

Question 1

motor system has to convert cartesian coordinates into…

Answer 1

joint angles

Question 2

it then has to work out how to get the arm into that configuration

Answer 2

have to plan in joint torques (dynamics) to over come the resistive forces of the external world

Question 3

such as…

Answer 3

gravity
inertia (accelerate mass)
friction
viscosity
centripetal (rotations)
coriolis (rotations)

Question 4

ballistic movement (fast movements)

Answer 4

desired behaviour –> inverse model –> motor command –> muscles –> movement

Question 5

sensory feedback (precise slow movement) from the movement and feeds back to the…

Answer 5

desired behaviour and provides a check

Question 6

problem with this model is that

Answer 6

feedback is slow meaning feedback is never up to date

Question 7

the nervous system adds in a forward model (just a prediction) which…

Answer 7

takes a copy of the mode of command (efference copy)
feeds it through the forward model which turns the command into a predicted movement and predicted sensory feedback
can be done without delay

Question 8

we also get parametric feedback which…

Answer 8

updates the forward model

Question 9

for example if you go to pick up a suitcase which is lighter than you think its going to be real sensory feedback comes in a says predictive sensory feedback is wrong and corrects the desired behaviour
parametric feedback updates the model and says that’s an empty empty suitcase so the next time you pick up the suitcase it is fine

Question 10

the motor cortex
motor areas of the cerebral cortex are…

Answer 10

parts of the brain that when stimulated at low threshold produce a movement

Question 11

where are the motor areas generally located

Answer 11

anterior to the central sulcus

Question 12

primary motor cortex (M1) is area 4 of brodmanns
what is anterior to this

Answer 12

we have the premotor areas (brodmanns area 6)

Question 13

corticospinal tract (from the cortex to the spinal cord)

Answer 13

corticospinal axons are long descending axons that come down through the internal capsule, through the cerebral peduncle, to the pyramid in the medulla where they decussate (cross over). they then pass down the spinal cord and enter the grey matter of the spinal cord and can activate motor neurones

Question 14

more ventral termination in the spinal cord pattern correlates with improved fine motor control, especially fine, independent finger movements. E.g in the cat the terminals are more dorsal and in chimpanzee theyre more ventral.

Answer 14

for the cat any control of movement via the corticospinal tract has to go via the interneurones in the spinal cord
however, in the monkey the terminals are directly controlling the motor neurones

Question 15

as monkeys get older there’s more corticospinal (CS) terminals amongst the motor neurones.

Question 16

recorded from CS neurone
the monkey had to move a handle
the CS neurone fires before the monkey moves the handle
when a weight is added the CS neurone fires even more before the movement
this suggests…

Answer 16

the motor cortex is representing force