pharm of parkinson's

Question 1

Feedback controller

Answer 1

system in which environment first change and then controller causes a change to compensate

slow and often overcompensate

Question 2

example of feedback controller

Answer 2

thermostat that can turn on heater or cooler to keep room at steady temp

decr temp –> turn on heater
but time and sense delay causes overshoot and turns on cooler

Question 3

feedforward controller

Answer 3

uses sensory data to calculate state coming at future time (predicted state)

cues to predict future system based on internal model

Question 4

feedforward controller example

Answer 4

thermostat turn on heter or cooler to keep room at steady temp
can sense window open, outside temp to predict change in room temp and act pre-emptive to counteract temp drop

therefore, controller has model of system and calculates how changes in one variable will affect output and how controlled variable will affect same output in opposite direction

Question 5

ddifference between feedback vs feedforward

Answer 5

feedback = react to a change
feed forward = plans ahead and make changes

if use feedback instead of feedforward –> you get oscillation or intention tremor

Question 6

role of parietal cortex in matching joint position sense with visual coordinates for reaching motion

map from occipital to parietal

how does parietal association cortex guide you to reach target

Answer 6

• stream of info for “where” advances dorsally from occipital cortex to parietal lobe

parietal association cortex = btwn visual “where pathway and joint position”, it senses info from somatosensory cortex

then integrates info about target and somatosensory info about limb position

fed into motor cortex in frontal lobe to guide movement of libm to target

Question 7

where are parietal association cortex located

Answer 7

located around intraparietal sulcus

can calculate difference btwn target and joint angles necessary and send to premotor cortex

Question 8

describe brodmann area 6

Answer 8

calculates difference btwn current location and desired location so command for proper joint angle changes to reach desired location

sent info to primary motor cortex

Question 9

what is meant by internal model of the system to match joint angles to visual coordinates

Answer 9

specifies predictions about what joint angles will achieve given location in visual coordinate

Question 10

purpose of cerebellum adapting cortical networks to change relationship btwn joint position sense and visual coordinates

Answer 10

to fix mismatch btwn visual coord of target and joint angles to get to the target that was different than expected

Question 11

how does cerebellum make corrections

Answer 11

connection btwn parietal and premotor cortices causes re-calibration so

if visual coord (like adding prism) and given set of joint angles differ, rain adapt (ADAPTATION DEPENDS ONLY ON CEREBELLUM)

Question 12

cellular mechanism of cerebellar correction for adaptation

pathway from parietal cortex to premotor for adaptation

Answer 12

parietal cortex sends cortico-pontine fibers thru internal capsule and synapse on ponto-cerebellar neurons

reach contralateral pontine gray that send out cerebro-cerebellum’s mossy fibers

mossy fibers synapse on granule cells whose paralell fibers synapse on purkinje

purkinje send output to dentate –> thalamus –> motor and premotor cortex

Question 13

what are mossy fiber input a reflection of ?

Answer 13

mossy fiber input = current state of parietal cortical mapping btwn visual and proprioceptive signals

Question 14

what else sends fibers to purkinje cells besides mossy fibers

Answer 14

1) inferior olivary nucleus sends climbing fibers

2) simultaneous climbing fibers + parallel fibers causes synaptic strength changes of parallel-purkinje synapses

Question 15

what drives inferior olivary activty

what is the purpose of this

Answer 15

1) GABA-ergic neurons from deep cerebellar nuclei

and
2) multiple sensory modalities (prop and visual feeback) which differ for subregions of ION and project to diff functional zones of cerebellum

therefore, also an additional reflection of parietal cortex mapping of visual and proprioceptive coordinates

Question 16

what happens if proprioceptive and visual feedback exactly what current parietal network would predict,

Answer 16

parietal network convey to ION would cancel out visual feedback so NO CHANGE IN ION ACTIVITY

Question 17

function of ION
what drives expected vs observed state

Answer 17

compares expected state = deep cerebellar nuclei as reflection of parietal network with

observed state = visual and prop feedback

Question 18

what happens if prop feedback and visual feedback different than what expect

describe LTD

Answer 18

signal generated by ION proportional to magnitude of difference

error signal carried by climbing fibers to cerebellar cortex to initatie complex spikes in purkinje cells

simult parallel + climbing fiber on purkinje undergo synaptic change (LTD) to decr efficacy of parallel fiber to fire Purkinje (deactivate error movement)

Question 19

How does ION contribute to adaptation

Answer 19

inferior olive fires when there is error/mismatch btwn observed and intended state

Question 20

describe VTA
where is it located
what is housed in it
important where

Answer 20

located in midline at floor of midbrain

contains DA cell bodies of mesocorticolimbic-DA system

important in cognition, motivation, drug addiction, emotion

Question 21

role of DA neurons in VTA/SNc to convey reward prediction errors to striatum

describe what happens first

Answer 21

1) push button on vending machine
2) what you want comes out and spike in AP by DA neurons
3) after few trials, you learn to associate symbol on machine with reward so fire DA AP each time button (reward predicting cue) seen
4) over more trials, after relation btwn cue and reward established and expected, DA release stops

Question 22

mechanism of how DA neurons in VTA/SNc to convey reward prediction errors to striatum

pathway of what happens

Answer 22

DA/basal ganglia function similar to ION
both convey predictions about rewards

1) DA neurons convey current predictions about rewards (present state of cortico-striatal network)
2) additional input to SNc/VTA convey info (efference copy directly to subst nigra) about actual reward experience
3) unexpected reward strongly activate DA neurons
4) DA releases into striatum to alter activity and plasticity of cortico-striatal network
5) networks that correctly predict error reinforced and those that don’t diminsihed

Question 23

how is DA/basal ganglia similar to ION

Answer 23

formation of action sequences via recalibration of direct and indirect paths to correctly predict rewarding behaviors

also state of revised network conveyed via striosome to VTA/SNc to now predict reward and VTA/SNc won’t discharge in response to discrepancy btwn expected and observed rewards so corticostriatal network intact until next unexpected reward

Question 24

compare ION in cerebellum vs VTA/SNc in corticostriatal

1) type of error signal
2) return projection
3) comparator?
4) what conveys prediction
5) critic of …

Answer 24

1) cerebellum = ION; basal ganglia = DA neurons
2) cerebellum = reach ION directly from deep cerebellar nuclei or indirect via red nucleus to find error btwn expect and actual

basal ganglia = reach DA from groups of stratal medium spiny neurons in striosomes to find error

3) both comparators

4) cerebellum = GABAergic inhib neurons via deep cerebellar nuclei to IO
basal ganglia = GABAergic inhib nurons via striosome to SNc

5) critic of parallel-purkinje vs critic of cortico-striatal