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TASK 1 - Cortical Voluntary Motor Control (Passingham et al.…
TASK 1 - Cortical Voluntary Motor Control
Wong et.al
movement generation
What
environment observation
object selection
FEF - specifying motor goals
task rules
PFC - task rules
Motor Goal
How
action selection
Medial motor cortex - selection of an appropriate action
movement specification
Dorsal premotor & Primary Motor cortex = action modulation witch changes in posture
Parietal cortex - movement specification of trajectory
Ventral PMC - action modulation unrelated to posture
abstract kinematics
left parietal cortex
drift diffusion model (accumulation of evidence for given action)
Optimal feedback control (OFC) (
null space
feedback control policy
action selection+movement specification = contrl policy (determine the movement)
Binkofski et. al.
dorsal (where/how ) pathway
dorso-dorsal pathway (Grasp) (online control of the pathway)
LESION = optic ataxia
V6->PMd
ventro-dorsal (Use) (action understanding)
LESION = limb apraxia
MT->PMv
Ventral (what) pathway
object affordances
structure vs object based actions
Passingham et al.
Supplementary motor area + ACC
(generation of voluntary actions, self-reflection, balance of parietal [external] and medial-prefrontal [internal] action control)
OFC
(association between stimuli and outcomes)
ACC
(association between action and outcomes) (also error detection - switching actions when no external stimuli forces that)
pre-SMA & SMA
(voluntary, self-generated action)
generation of action and self -refection paper
default system
dorsal paracingulate cortex = reflection over ones performence
Sumner et al.
STUDY 1
H: determine whether
SMA/SEF
contribute to voluntary controll of action through inhibition of unwanted motor plans (activated unconsciously condition-action associations)
paradigm -
masked-prime task
facilitatory priming
= when prime and stimuli were separated by shorter than 100ms
negative compatibility effect (NCE)
- when delay between target and prime was greater than 100ms (responses slower for compatible primes than incompatable)
sub-threshold activation caused by prime gets dumpen by inhibitory mechanisms, causing the effect
STUDY 2 (Lesion study)
H: inhibition happening in
effector-specific manner
, for example:
SMA
= inhibition of manual movements &
SEF
=inhibition of eye movements
Results:
Controll + pre-SMA +Premotor = all showing expected NCE
SMA = positive compatibility effect - inhibition o longer exist and therefore prime activation facilitates the movement
SEF = affects NCE of eyes but not of the hand movement (normal priming for manual responses)
STUDY 3
paradigm=
masked-prime task for the eye movements
(left/right saccades rather than pressing the button)
Results:
Control = normal NCE
SMA = positive comatibility effect for manual+saccadic responses
SEF = positive comaptibility effect for saccades
Discussion:
SMA & SEF
= automatic inhibition of primed actions
SMA
= voluntary actions unsupervised by visual input
SEF
= control of self-paced eye movements and saccade sequences