E-Letter responses to:

reports: Michel Desmurget, Karen T. Reilly, Nathalie Richard, Alexandru Szathmari, Carmine Mottolese, and Angela Sirigu Movement Intention After Parietal Cortex Stimulation in Humans Science 2009; 324: 811-813 [Abstract] [Full text] [PDF]

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Motor Neglect and Movement Intention

Paolo Bartolomeo   (25 June 2009)

Motor Neglect and Movement Intention 25 June 2009
Paolo Bartolomeo, Research scientist INSERM UMRS 975, Paris, France Respond to this E-Letter: Re: Motor Neglect and Movement Intention	Using direct cortical stimulation during neurosurgery ("Movement intention after parietal cortex stimulation in humans," Reports, 8 May 2009, p. 811), M. Desmurget and co-workers described peculiar sensations of intention or urge to move during stimulation of the inferior parietal lobule. Such sensations, when referred to limbs, emerged upon stimulation of the right hemisphere. Damage to the right inferior parietal lobule (1), or to parieto-frontal connections in the right hemisphere (2), often produces signs of visual neglect, whereby patients ignore events occurring on the left side of their personal or external space. But "nonsensory" forms of neglect have also been described (3). In one of these conditions, known as motor neglect (4), patients seem to "forget" to use their left limbs in everyday activities, even in the absence of elementary motor, sensory, or coordination deficit. For example, patients with motor neglect may use only their right hand to put on spectacles, thus leaving the left earpiece hanging (5). However, calling patients' attention on their left arm or leg can restore normal motility. Motor neglect typically occurs after parietal or frontal damage in the right hemisphere (4), and constitutes a source of disability for patients and a cause of concern for therapists. It is tempting to relate this condition to Desmurget et al.'s evocation of motor intentions for left limbs upon right parietal stimulation and to interpret motor neglect as a deficit of motor intention. In this view, parietal dysfunction or disconnection from frontal premotor circuits might lead to impaired intention for movements of left-sided limbs, thus resulting in limb underutilization. Paolo Bartolomeo INSERM UMRS 975, Paris, France. References 1. D. J. Mort et al., Brain 126, 1986 (2003). 2. M. Thiebaut de Schotten et al., Science 309, 2226 (2005). 3. E. Valenstein, K. M. Heilman, R. T. Watson, T. Van Den Abell, Neurology 32, 1198 (1982). 4. D. Laplane, J. D. Degos, J. Neurol. Neurosur. Ps. 46, 152 (1983). 5. F. Nicklason, P. Finucane, Lancet 336, 1380 (1990).