EARLY VISUAL PROCESSING IN NEGLECT PATIENTS - A STUDY WITH STEADY-STATE VEPS

Reliable steady-state visual evoked potentials (VEPs) were recorded in a group of 19 right brain-damaged patients with visuospatial heminegl ect (Neglect), and two control groups: 15 left brain-damaged (LED) pat ients and 12 right brain-damaged (RED) patients without neglect. Moreo ver, VEPs were recorded in two rare cases of left brain damage and rig ht visuospatial hemineglect. Stimuli were gratings phase-reversed at v arious temporal frequencies presented in the left and right visual hel d. In the Neglect group, VEPs to stimuli displayed in the left visual field (contralesional stimuli) had longer latencies. The delay was not present for the two control groups. As regards the VEP amplitudes, th e Neglect group data showed a less distinctive pattern than in the cas e of latency. VEPs to stimuli contralateral to the lesion were smaller than those recorded for stimuli ipsilateral to the lesion in both Neg lect and RED groups. On the contrary, the VEP amplitudes for the two h emifields were comparable in the LED group. In the case of left brain damage and neglect, VEPs to right visual field stimuli had longer late ncies and lower amplitudes compared to the ipsilesional responses in b oth patients. Overall, the data support the view that, in most cases, early visual processing is not intact in the neglected hemifield. Copy right (C) 1966 Elsevier Science Ltd