An exploration of the role of the superior temporal gyrus in visual search and spatial perception using TMS

This study sought to investigate the recent claim by H.-O. Karnath and his colleagues that the crucial locus of neurological damage in neglect patients lies in the right superior temporal gyrus (STG), and not in the right posterior parietal cortex (PPC) as conventionally thought. Using transcranial magnetic stimulation (TMS), we first tested the involvement of the right STG in a task commonly used in the diagnosis of neglect, the landmark task. No evidence was found for a critical involvement of the right STG in the processing of this task, though evidence was found for the involvement of the right PPC. In contrast, however, when we examined the effects of TMS on exploratory search, a double dissociation between right STG and right PPC was found. When the processing of conjunction items was required, involvement of the right PPC (and not STG) was found in accordance with our previous research. When a difficult exploratory search through feature items was required, however, the right STG (not PPC) was found to be involved. A hitherto unknown role for right STG in visual search tasks was thus uncovered. These data suggest that conclusions about the area of brain damage resulting in neglect-like symptoms are highly dependent on the task used to diagnose them, with lesions in right PPC leading to deficits on the landmark task and conjunction visual search, and lesions in right STG resulting in deficits in feature based serial exploratory search tasks.