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Flashcards in Motor Control II Deck (34):
1

how is the overall movement direction encoded?

Each neurone has a preferred direction but responses of all neurons are combined to produce a population vector

2

what adjustments are made before movements begin?

anticipatory feedforward adjustments

3

what initiates feedforward anticipatory adjustments to stabilize posture?

brainstem reticular formation nuclei (controlled by the cortex)

4

what does cortical damage cause?

causes immediate flaccidity of contralateral muscles. Lift limb and release-drops passively

5

what is the babinski sign?

(normal adult, plantar flexion)
baby and cortical damage, extension – both indicate incomplete upper control of spinal circuits

6

describe Spasticity

increased muscle tone, hyperactive stretch reflex – due to removal of cortical suppressive influences

7

where does Major subcortical input to area 6 come from?

ventral lateral nucleus(VLo) in dorsal thalamus

8

what does the Basal ganglia motor loop do?

selects and initiates willed movements

9

describe the Basal ganglia motor loop

cycles via - cortex through basal ganglia and thalamus(VLo) - back to SMA in cortex

10

what is the input zone of the basal ganglia?

Corpus striatum - includes 2 principal nuclei the caudate and the putamen

11

what is the corticostriatal pathway?

multiple parallel pathways with different functions

12

when do the caudate and the putamen fire?

putamen fires before limb/trunk movements

caudate fires before eye movements

both are predictive of movements

13

what is glutamatergic?

excitatory axons

14

what is gabaergic?

axons are inhibitory

15

where do putamen and caudate project?

globus pallidus and to substantia nigra pars reticulata

16

what type of neurones go from Cortex to putamen?

excitatory

17

what type of neurones go from Putamen to Globus pallidus ?

inhibitory

18

what type of neurones go from Globus pallidus to VLo neurones?

inhibitory

19

what type of neurones go from VLo to SMA?

excitatory

20

so what is the functional consequence of cortical activation of putamen?

excitation

21

Why does cortical activation of putamen boost cortical excitation?

At rest globus pallidus neurones are spontaneously active and inhibit VL
So Cortical excitation excites putamen, which
inhibits the inhibitory Globus pallidus. Which therefore releases cells in VLo from inhibition so activity in VLo boosts SMA activity

22

describe the Cortical input flow by direct pathway

acts as a positive feedback loop, a “GO” signal to the SMA in cortex

it enhances the initiation of movements by the SMA

input from cortex releases Globus pallidus inhibition

23

describe the Cortical input flow by indirect pathway

antagonizes the direct route

Striatum inhibits GPe (globus pallidus external) which then inhibits both GPi (GPinternal) and STN (subthalamic nuclei)

Cortex excites STN; this excites Gpi; which inhibits thalamus

24

what is the role of the direct and indirect pathways?

Direct pathway selects specific motor actions
indirect pathway suppresses competing/inappropriate action

25

what is Parkinson’s disease?

type of hypokinesia
slowness, difficult to make voluntary movements, increased muscle tone (rigidity), tremors of hand and jaw.

26

what causes Parkinson’s disease?

caused by degeneration of neurones in substrantia nigra (SN) and their dopaminergic (excitatory) inputs to the striatum

27

describe Huntington’s disease

involves hyperkinesia with dementia and personality disorders

spontaneous, uncontrolled, rapid flicks and major movements with no purpose

28

what causes Huntington’s disease?

profound loss of caudate, putamen and globus pallidus

so loss of the ongoing inhibitory effects of the basal ganglia

29

what do lesions to cerebellum produce?

uncoordinated inaccurate movements
eg ataxia : fail to touch nose with eyes shut

30

what makes up the huge cortico-ponto-cerebellar projection?

Layer 5, areas 4 & 6, somatosensory cortex

31

what is the cortico-ponto-cerebellar projection?

connects cortex, pontine nuclei and cerebellum

32

what connects the cerebellum back to cortex?

via ventrolateral thalamus

33

what is the role of the cerebellum?

instructs direction, timing and force

34

describe the feedback motor loop through lateral cerebellum

through pons, cerebellum, thalamus and back to cortex