The neural bases of semantic memory: A transcranial magnetic stimulation investigation. (360G-Wellcome-078734_Z_05_Z)

This project investigates the neural basis of semantic memory. We will use transcranial magnetic stimulation (TMS) to assess the specific contributions of various cortical regions to semantic tasks in healthy participants. TMS produces a magnetic field over the scalp that transiently disrupts processing in the underlying cortex. We have selected cortical sites for investigation primarily on the basis of neuropsychological studies. Diverse neural regions are implicated in semantic processing by different patient populations (e.g., dementia, herpes simplex encephalitis and stroke aphasia); our TMS investigations will allow an integration of these literatures with functional neuroimaging. Performance on semantic tasks will be examined before and after ten minutes of low frequency repetitive TMS. Coil location will be confirmed for each subject using structural MR imaging and the influence of TMS at different cortical sites will be compared over several sessions for each participant. We will manipulate (1) input modality (pictures vs. words), (2) output modality (comprehension vs. production of object names), (3) specificity of semantic judgement (e.g., knowledge of animals, dogs and Labradors), (4) category of knowledge (faces vs. animals vs. tools) and (5) the requirement for semantic control, in order to elucidate the neural organisation of semantic memory.