Interlimb coupling due to illusory movements: evidence from anosognosia for hemiplegia

In anosognosia for hemiplegia, patients affected by a complete paresis of the side of the body opposite to the brain lesion may claim having performed willed actions with the paralyzed limb despite unambiguous evidence to the contrary. Does this false belief of being able to move reflects the functioning of the mechanisms that govern normal motor performance? By examining in anosognosic patients the temporal coupling effects known to exist during bimanual movements in normal subjects, we demonstrated that the illusory movements of the plegic arm impose to the healthy arm the same constraints that emerge during actual movements. Our findings strongly suggest that the same neurocognitive processes subserving movement execution underpin the ‘nonveridical’ experience of willed movements in anosognosic patients. Additionally, these data support the view that coupling effects depend on information already within the brain (i.e., a motor representation), rather than on on-line information from the periphery.