Abstracts

Rationale: The left temporal pole (TP) plays a critical role in proper naming, especially the retrieval of names for familiar people. An intriguing open question is whether the role of the left TP in proper name retrieval is sensory modality-specific. We evaluated this question using electrocorticographic (ECoG) recordings from left TP while participants named American presidents from either visual (pictures) or auditory (voices) stimuli. Methods: Experimental subjects were two adult male neurosurgery patients undergoing chronic ECoG monitoring for diagnosis and treatment of medically intractable epilepsy. The subjects were asked to name pictures or voice recordings of Bill Clinton, George W. Bush, and Barack Obama. Voice naming and picture naming were performed in separate blocks. Fifty unique stimuli for each president and each modality were randomized and presented in each block. ECoG data were obtained from subdural electrode grids, designed in-house and implanted on the convexity of left TP for the purpose of seizure localization. Recorded data were segmented and analyzed offline. Event-related band power (ERBP) was measured for all trials in each block (pictures, voices) for each recording site (Fig. 1).Results: Both picture and voice naming resulted in significant (p < 0.05) increases in ERBP, maximal in the low ECoG frequency range (4-50 Hz). The two modalities typically elicited comparable responses at individual sites on the TP, resulting in spatially overlapping response patterns across the TP (Fig. 2). Increases in low frequency ERBP typically peaked at around 500-1000 ms after stimulus onset. Voice naming responses often featured a second peak at around 1500 ms. Conclusions: Using ECoG recording in human participants, we found that regions of the left TP demonstrated significant increases in low frequency power when participants were naming American presidents from either visual (pictures) or auditory (voices) stimuli. These results provide important convergent evidence in support of the hypothesis that the left TP has a critical role in proper name retrieval, and that this role is multimodal. Peak activation for voice naming occurred later than picture naming, consistent with the obligatory temporal processing requirements of auditory versus visual stimuli.