Visual evoked fields in patients of unilateral spatial neglect

Purpose: To establish whether the visual evoked fields (VEFs) in patients of unilateral spatial neglect (USN) caused by cerebrovascular accident (CVA) are different from ones in subjects without USN. Method: In three patients of CVA with left USN and three controls (a healthy subject, a patient of CVA without USN and a patient of hemianopsia), the VEFs following pattern reversal stimulation on the left hemifield were measured. Magnetic recordings were conducted using a 160-channel helmet-type axial superconducting quantum interference device (SQUID) gradiometer system. The behavioural inattention test (BIT) was also scored in patients of USN. Results: Magnetic source imaging revealed two components (P100m and N145m) on the VEFs in the healthy subject and patient of CVA without USN, and no component in the patient of hemianopsia. The pattern of two components in patients with USN was various. Only P100m for patient 1, N145m for patient 2 and both components for patient 3 were detected. Concerning the BIT scores, line bisection and cancellation task for patient 1, coping, drawing and cancellation task for patient 2, and only cancellation task for patient 3 were impaired. Conclusion: Our results demonstrate that pattern of two components (P100m and N145m) on the VEFs does not reflect only hemianopsia, but also USN caused by deficits of the cortical process of attention.