EXTINCTION: POSSIBLE INTERFERENCE OF TOP-DOWN INFORMATION. A CASE STUDY

Background: Brain-damaged patients showing extinction are able to pro cess stimuli presented on either hemispace, but fail to report contralesional stimuli when simultaneously presented with an ipsilesional stimulus. Extinction may occur between stimuli of the same modality or between stimuli of different modalities (such as visual and tactile). This phenomenon has been inter preted as supramodal imbalance in stimulus competition for attention selection. However, recent studies have reported the existence of a complex interaction of competition-facilitation between visual and tactile information. Case study: We describe a patient (RP) who suffered from a brain damage on the right occipito-temporal cortical area. RP showed severe visual neglect associated with a rare case of extinction. He performed at ceiling on tactile extinction tasks when his eyes were closed, but showed dramatic tactile extinction when he looked directly at the hand being touched. Conclusions: The results as reflecting the existence of top-down mechanisms whereby the "absence" of visual information caused by visual neglect might have exacerbated underlying latent attentional biases.