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, empirical 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 anatomically distinct and located anterior to naming sites based on visual cues. METHODS: Twenty patients requiring resective surgery involving the left (language dominant) temporal lobe underwent pre-resection language mapping using direct cortical stimulation. Visual and auditory naming were tested at lateral temporal sites extending from 1 cm from the anterior tip to the parietal operculum. RESULTS: Auditory naming was consistently disrupted by stimulation in the anterior temporal lobe, whereas both auditory and visual naming were impaired by stimulation in the posterior temporal region. CONCLUSIONS: This pattern may explain why word finding difficulties sometimes arise or worsen following surgical procedures in which the anterior temporal region is resected without language mapping, or when resection is based on mapping that identifies language cortex exclusively using visual tasks. These results suggest that utilization of auditory based naming tasks might improve pre-resection identification of essential language cortex during direct stimulation cortical mapping, as well as noninvasive localization of dysfunction during presurgical cognitive testing.

Auditory naming and temporal lobe epilepsy.

Patients with left (i.e. language-dominant) temporal lobe epilepsy (TLE) typically report word finding difficulties. However, these deficits are not reliably detected with traditional visual object naming tests. We administered both visual and auditory naming tests to left and right TLE patients and normal controls. We hypothesized that an auditory naming test might be more sensitive since it better simulates the conditions under which word finding problems occur in daily living. The left TLE group obtained significantly lower scores than other groups on auditory naming, whereas their performance on visual naming was indistinguishable from that of right TLE patients and normals. Furthermore, whereas cut-off scores on the auditory naming task predicted seizure focus laterality in 85% of patients, performance on the visual naming task predicted laterality in only 60% of patients. These findings suggest that compared with visual naming, as assessed in the present study, auditory naming may more accurately characterize and lateralize TLE-associated language dysfunction. These results also propose a more complex understanding of word retrieval that incorporates modality and contextual information.