Hemispheric differences in VEPs to lateralised stimuli are a marker of recovery from neglect

Visual-evoked potentials (VEPs) were recorded in seventeen patients with unilateral lesions of the right hemisphere (RH) and visuospatial neglect. Hemispheric differences were detected for VEP components in the time window from 130 to 280 msec; this result replicates data from a previous study using a larger group of patients (Di Russo et al., 2008). Three patients were tested twice; their hemispheric differences, i.e., the differences in latency and amplitude of VEPs to ipsilesional and contralesional stimuli, were evaluated at the beginning and end of visuospatial rehabilitation training for neglect. The hemispheric differences were limited to components anterior N1 (N1a), posterior N1 (N1p) and P2 (not C1 and P1) and showed a significant decrease after training; amelioration at the behavioural level was also observed. Fourteen patients were tested only once, at different steps of their training. For the overall group, we determined the correlation between VEP hemispheric differences and the number of sessions attended by the patients at the time of VEP recording. The correlation was negative, the higher the number of sessions, the lower the hemispheric asymmetry, and high, ranging from .45 to .64, for both the latency and amplitude of the N1p and P2 components, and for the amplitude of the N1a component. The correlation between VEP hemispheric differences and time from onset (TFO) of the pathological event was not significant. Overall, the hemispheric differences between specific components of the VEP responses to lateralised stimuli appear to be a good marker of recovery from neglect.