Bimanual non-congruent actions in motor neglect syndrome: a combined behavioral/fMRI study.
In Motor Neglect (MN) syndrome, a specific impairment in non-congruent bimanual movements has been described. In the present case-control study, we investigated the neuro-functional correlates of this behavioral deficit. Two right-brain-damaged (RBD) patients, one with (MN+) and one without (MN-) MN, were evaluated by means of functional Magnetic Resonance Imaging (fMRI) in a bimanual Circles-Lines (CL) paradigm. Patients were requested to perform right-hand movements (lines-drawing) and, simultaneously, congruent (lines-drawing) or non-congruent (circles-drawing) left-hand movements. In the behavioral task, MN- patient showed a bimanual-coupling-effect, while MN+ patient did not. The fMRI study showed that in MN-, a fronto-parietal network, mainly involving the pre-supplementary motor area (pre-SMA) and the posterior parietal cortex (PPC), was significantly more active in non-congruent than in congruent conditions, as previously shown in healthy subjects. On the contrary, MN+ patient showed an opposite pattern of activation both in pre-SMA and in PPC. Within this fronto-parietal network, the pre-SMA is supposed to exert an inhibitory influence on the default coupling of homologous muscles, thus allowing the execution of non-congruent movements. In MN syndrome, the described abnormal pre-SMA activity supports the hypothesis that a failure to inhibit ipsilesional motor programs might determine a specific impairment of non-congruent movements.
SAMBA (SpAtial, Motor and Bodily Awareness) Research Group, Department of Psychology, University of Turin Turin, Italy.
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Garbarini
Istituto Italiano di Tecnologia (IIT) Genova, Italy ; Center for Mind/Brain (CIMeC), University of Trento Trento, Italy.
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Turella
Biomedical Technology Department, IRCCS Don Carlo Gnocchi Foundation Milano, Italy.
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Rabuffetti
BrainCare Padova, Italy.
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Cantagallo
SAMBA (SpAtial, Motor and Bodily Awareness) Research Group, Department of Psychology, University of Turin Turin, Italy.
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Piedimonte
Department of Neuroradiology Unit, Neuroscience and Rehabilitation, Azienda Ospedaliera Universitaria Ferrara, Italy.
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Fainardi
SAMBA (SpAtial, Motor and Bodily Awareness) Research Group, Department of Psychology, University of Turin Turin, Italy.
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Berti
Istituto Italiano di Tecnologia (IIT) Genova, Italy ; Section of Human Physiology, University of Ferrara Ferrara, Italy.
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Fadiga
bimanual actions; bimanual coupling effect; fMRI; motor neglect; supplementary and pre-supplementary motor area (pre-SMA; SMA)