Self-initiated movements in chronic prefrontal traumatic brain injury: an event-related functional MRI study.

Electrophysiological studies found traumatic lesions of the prefrontal cortex (PFC) to affect the preparation of self-initiated movements. However, a precise localization of the observed effects has not been reported yet. Moreover, previous reports did not account for effects of lesion location. Therefore, the present study utilized functional MRI to investigate the influence of predominantly left or right hemispheric PFC lesions on movement preparation in chronic traumatic brain injury (TBI) patients. 18 TBI patients with MRI-defined contusions of the PFC as well as 18 healthy control subjects matched for age and gender were examined. Patients were divided into subgroups of predominantly left or right hemispheric lesions. During functional image acquisition, subjects performed self-initiated abductions of their right index finger. Neuropsychological tests of attention and working memory, which are supposed to modulate preparatory processes, were conducted. Patients with predominantly left contusions demonstrated enhanced activity of the dorsal lateral premotor cortex in comparison to healthy control subjects. In predominantly right lesioned patients, reduced activity within the right caudate head was observed. Compared to predominantly left lesioned patients, neuropsychological tests yielded reduced task performances in the right lesion subgroup. In line with previous electrophysiological research, imaging results of the present study are interpreted to represent altered preparatory networks in chronic prefrontal TBI patients. Since attentional and working memory functions are supposed to modulate preparatory processes, differences between the patient subgroups are suggested to result from the more pronounced cognitive impairments in the right-lesioned group.