Deficits of attention in acute and recovered visual hemi-neglect.

Three patients with right-sided lesions and, in two cases, clinically manifest neglect had to compare and to name stimuli presented tachistoscopically either bilateral-simultaneously or unilaterally in the LVF and/or RVF. Whereas there was no difference between unilateral LVF and RVF presentation, "extinction" of the LVF on bilateral stimulation occurred in both the acute and recovered stages. This deficit could be compensated by reducing information analysis in the RVF, thereby provoking covert shifting of attention to the LVF. The results suggest a common mechanism underlying visual neglect and "extinction" with three components--two affecting the directionally specific covert orienting and shifting of attention and one affecting the directionally non-specific processing of information by sequential analysis. The course of recovery is determined by improvement in the directionally specific shifting of attention.