Poster E29, Thursday, August 22, 2019, 3:45 – 5:30 pm, Restaurant Hall
Visual and auditory semantic processing converges in the anterior temporal lobe
Akihiro Shimotake1, Riki Matsumoto1,2, Kiyohide Usami1, Takayuki Kikuchi1, Kazumichi Yoshida1, Masao Matsuhashi1, Takeharu Kunieda1,3, Ryosuke Takahashi1, Matthew Lambon-Ralph4, Akio Ikeda1;1Kyoto University, 2Kobe University, 3Ehime University, 4University of Cambridge
Introduction: There is growing evidence that the anterior temporal lobe (ATL) play a critical role in semantic processing, especially as a multimodal semantic hub. The implantation of intracranial electrodes provided us with a rare opportunity to explore the cortical function directly to investigate the multimodal semantic processing in the temporal lobe. We aimed to delineate that the ATL underpins a modality-invariant representational semantic hub by using the semantic judgement task with intracranial electrodes. Methods: We studied 4 patients with intractable epilepsy, who underwent presurgical evaluation with subdural grid implantation over the lateral and ventral ATL (Language dominant:3, non-dominant:1). Visual and auditory semantic judgement tasks were performed. The stimuli were presented visually or auditory by color photos or sounds every 2 seconds. The stimuli included 48 items: half living and half nonliving objects. They are randomly presented with 96 trials per session and 3 sessions were performed for visual and auditory stimuli respectively. Patients were asked to answer whether the stimulus is living or nonliving by pressing the button. As a control task, high-low judgement task was also performed by judging whether the location of the scrambled image is higher or lower for visual control, and whether the tone of noise sound is higher or lower for auditory control. Sampling rate of ECoG was 1000 or 2000 Hz and time-frequency representation of ECoG power was calculated using a short-time Fourier Transform (STFT) with a Hanning window of 100 points (frequency resolution of 10 or 20 Hz). ECoG data was averaged with the stimulus onset from -200 ms to 1800 ms across trials and converted to the logarithmic scale. Results: Compared with control tasks, a robust gamma activity (40-50 Hz) was observed in the electrodes along the anterior to middle fusiform gyrus and inferior temporal gyrus for visual semantic judgement task. For the auditory semantic judgement, gamma activity was observed in the anterior to middle part of the middle and inferior temporal gyri, and the high gamma activity (80-100 Hz) was also observed in the anterior to middle fusiform gyrus in the 2 patients. Gamma activity was partly overlapped between visual and auditory semantic judgement in the anterior to middle part of the inferior temporal gyrus. Conclusions: The visual and auditory semantic processing converged in the ATL, especially in the inferior temporal gyrus. The ATL can be the important area for a modality-invariant representational hub within the semantic system. For further analysis, comparison with the gamma activities related to other semantic tasks (expressive, receptive) will be needed.
Themes: Meaning: Combinatorial Semantics, Meaning: Lexical Semantics
Method: Electrophysiology (MEG/EEG/ECOG)