alien hand syndrome

what is it

movements which the patient regards as foreign, involuntary (unwilled)

unwilled grasping behaviours mentioned in lecture but other behaviours have been recorded

understand the hand is theres but have lost voluntary control over it

neural correlates

lesions to the medial frontal lobes

lesions to the corpus callosum

increasingly reported in corticobasal degeneration/syndrom which affects the basal ganglia which is linked to movement

more recent reports of a small number of cases following posterior parietal stroke and posterior cerebral artery stroke

control/awaremess of action

forward model of motor control

when the outcome and prediction of the motor command match there is a low sensory discrepancy

if they don't match and there's a discrepancy then we may feel we don't have ownership of the movement

free will (libet et al., 1983)

asked p's to press red button and say clock position at the time of conscious intention

found brain activity occurred a whole second before p's felt they intended to press button

suggests conscious action is after the neural signals prepare the action

this would suggest unconscious processes in the brain are the true initiator of volitional acts and therefore free will plays no part in their initiation

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free won't (brass & haggard, 2007)

voluntary inhibition does seem to exist

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