Proactive Cortical Control in Spinal Cord Injury Subjects with Paraplegia

Preparatory cortical activities were investigated in subjects with paraplegia attributed to spinal cord injury (SCI). Electroencephalogram (EEG) and behavioral data were recorded simultaneously in a visual-motor discrimination go/no-go task performed with the right upper limb. Eighteen SCI subjects participated to one, two, or three experimental sessions (Go/No-Go task), according to their availability and willingness to participate. To evaluate the effects of SCI on cortical activities as a function of time, we considered three SCI groups (9 individuals each), based on different time from the injury onset (acute, 1-2 months; subacute, 3-5 months; chronic, 6-9 months), and a control group of 9 healthy participants matched for age and sex. Results indicate that response time (RT) was slower and percentage of omissions was higher in SCI subjects than healthy, independently from time from lesion (TFL). Also, the proactive motor preparation, indexed by the Bereitschafts potential (BP), and the pre-frontal cognitive control, indexed by the pre-frontal negativity component, showed reduced amplitude in SCI subjects, independently from TFL. Conversely, TFL effect was observed in the BP topography, which showed a more posterior focus in subacute and chronic groups than healthies. Interestingly, despite this posteriorization, BP amplitudes maintained the well-known correlation with RTs. Overall, SCI affects cortical reorganization independently from TFL, regarding proactive activities for action inhibition and reaction time; conversely, a TFL effect was observed in the topography changes related to the cortical areas involved in proactive motor activity. Present data are in line with growing evidence of brain changes after SCI, in particular focusing on cognitive effects and evidencing possible functional mechanisms related to motor and cognitive readiness processing, relevant for SCI rehabilitation programs.