The fate of global information in dorsal simultanagnosia

We report a patient with simultanagnosia and Balint-Holmes syndrome, follow ing bilateral parieto-occipital lesions, who exhibits a selective disturban ce of global processing in everyday situations and in clinical tasks. For h ierarchical Navon stimuli, where global letters are formed by the layout of smaller local letters, she could report only local shapes. She could ident ify the global form via proprioceptive input, when her finger was passively moved to trace the global shape, provided her eyes were closed. However, w ith her eyes open, the local visible form dominated once again even when th e global shape was traced. This demonstrates dominance of pathological visi on over intact proprioception, and shows that local capture persists even w hen the global information can still be processed by the patient, through a nother modality. This raises the possibility that some visual global proces sing might likewise still take place despite the local capture. In accordan ce with this notion, additional experiments showed that the patient was fas ter at naming local shapes if the global shape had the same identity rather than an incongruent identity. Moreover, a visual-search task found that pa rallel searching for unique features was preserved across the visual field. Taken together, our experiments suggest that the dominance of the local sc ale for KB is not due to a total inability to code any global information, but rather to an attentional bias towards salient local details following h er brain damage.