Excessive contralateral motor overflow in schizophrenia measured by fMRI

Schizophrenia is characterized by significant problems in control of behavior; however, the disturbances in neural systems that control movement remain poorly characterized. We used functional magnetic resonance imaging (fMRI) to evaluate the origin of motor overflow in schizophrenia. Twenty-seven clinically stable medicated outpatients with Diagnostic and Statistical Manual, 4th edition, text revision (DSM-IV-TR)-defined schizophrenia (SZ), and 18 healthy control (HC) subjects, all right-handed, performed a dominant-handed, single-choice visual sensorimotor reaction time paradigm during fMRI. Voxel-wise analyses were conducted within sensorimotor cortical and striatal regions on general linear model (GLM)-derived measures of blood oxygen level-dependent (BOLD) signal change. The SZ group was not different from the HC group in reaction time, activation in somatosensory or motor cortices ipsilateral to the active (intended) descending corticospinal tract, nor visual cortex. However, in the right hemisphere (contralateral to the active M1), the SZ group showed significantly higher activation in primary motor cortex and adjacent premotor and somatosensory cortices (right Brodmann areas (BA) 1 through 4, and 6), and significantly lower activation in bilateral basal ganglia. Right BA 4 activation was strongly related to disorganization and poverty symptoms (and unrelated to medications) in the patient group. This study provides evidence in SZ of excessive neural activity in motor cortex contralateral to the intended primary motor cortex, which may form the basis for altered motor laterality and motor overflow previously observed, and disorganized behavior. This pathological motor overflow may be partly due to altered modulation of intended movement within the basal ganglia and premotor cortex.