Abstract
Simple reaction times for visual targets are reduced for bi-lateral visual stimuli, compared to just one stimulus presented in one hemifield - the redundant target effect. The same reaction time pattern can be obtained for auditory targets: reaction times for targets presented to both ears are faster than for targets presented to only one ear. More interestingly, if two stimuli from different modalities are presented simultaneously, reaction times decrease even further relative to uni-modal bilateral stimuli. This reduction is larger than predicted based on statistical facilitation alone, and has been attributed to sensory cross-modal integration. The Superior Colliculus (SC) is thought to be crucial for integrating auditory and visual information. Here we tested a rare patient who suffered from a traumatic haemorrhagic avulsion of the dorsal midbrain resulting in a near-complete lesion of the left inferior colliclus, and damage to caudal part of the left SC. The patient's reaction times were prolonged for both auditory and visual targets in the contra visual field relative to her ipsilesional visual field. In addition, there was no benefit of RTs of presenting bilateral visual targets. Unlike healthy controls, the patient's reaction times to auditory targets were slower than to visual targets. However, the patient detected bilateral auditory targets faster than unilateral targets, suggesting an intact auditory redundant target effect. More interestingly, similar to healthy controls, the patient demonstrated a benefit in reaction times to cross-modal targets in both visual fields. When a visual stimulus was presented simultaneously with an auditory target, RT were faster than when only a visual, or only an auditory target was presented.