Residual information processing in the neglected visual half-field.

A patient with neglect of visual half-field without hemianopia performed "same/different" interfield comparisons and named stimuli presented either unilaterally or bilaterally in the visual half-fields. With unilateral presentation he could name all stimuli in both fields, whereas with simultaneous bilateral stimulation his performance decreased to about 50% correct naming of left visual field (LVF) stimuli. This performance was not improved by cueing for the presence of LVF stimuli. Interfield comparisons were 100% correct in all conditions. It is concluded that inattention for the left hemispace in patients with visual neglect occurs whenever information in the right hemi-space attracts attention or must be consciously processed. Simple "same/different" judgements are presumably performed on a pre-attentional level and are not affected by neglect.