Impaired perception of temporal order in auditory extinction.

It has been proposed that patients with extinction show a chronic bias of spatial attention towards the ipsilesional side. In this case, the law of 'prior entry' predicts that ipsilesional events should be perceived earlier than physically synchronous contralesional stimuli. In line with this prediction, previous studies have revealed substantial delays of awareness for contralesional visual and tactile events in patients with visual and with tactile extinction. The present study provides evidence that a 'prior entry' bias also occurs in the auditory modality. Patients with auditory extinction perceived two acoustic events (one presented to the left ear, the other to the right ear) as being 'simultaneous' when the contralesional sound was leading by 270 ms. The magnitude of this asynchrony was quite similar to that measured previously in the visual modality. Thus, the pathological delay of awareness for contralesional events may be independent of the sensory modality of the stimuli.