Anatomic dissociation of auditory and visual naming in the lateral temporal cortex

Background and Objective: Visual object naming traditionally has been used to identify cortical areas essential for naming (i.e., word retrieval), and investigators have found critical naming sites in the middle and posterior temporal region in most patients. Based. on clinical observation, empirica l findings, and the pathophysiology of temporal lobe epilepsy, the authors hypothesized that naming sites identified from auditory cues might also be relevant, and that within the temporal region, these sites would be anatomi cally distinct and located anterior to naming sites based on visual cues. M ethods: Twenty patients requiring resective surgery involving the left (lan guage dominant) temporal lobe underwent pre-resection language mapping usin g direct cortical stimulation. Visual and auditory naming were tested at la teral temporal sites extending from 1 cm from the anterior tip to the parie tal operculum. Results: Auditory naming was consistently disrupted by stimu lation in the anterior temporal lobe, whereas both auditory and visual nami ng were impaired by stimulation in the posterior temporal region. Conclusio ns: This pattern may explain why word finding difficulties sometimes arise or worsen following surgical procedures in which the anterior temporal regi on is resected without language mapping, or when resection is based on mapp ing that identifies language cortex exclusively using visual tasks. These r esults suggest that utilization of auditory based naming tasks might improv e pre-resection identification of essential language cortex during direct s timulation cortical mapping, as well as noninvasive localization of dysfunc tion during presurgical cognitive testing.