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Visual System

開催日 2014/9/11
時間 16:00 - 17:00
会場 Poster / Exhibition(Event Hall B)

Frequency-dependent spatiotemporal profiles of visual responses in ECoG signals recorded from awake monkeys

  • P1-180
  • 高浦 加奈 / Kana Takaura:1 土谷 尚嗣 / Naotsugu Tsuchiya:2,3 藤井 直敬 / Naotaka Fujii:1 
  • 1:独立行政法人理化学研究所・脳科学総合研究センター / RIKEN BSI, Saitama, Japan 2:Monash University, Melbourne, Australia / Monash University, Melbourne, Australia 3:JST / JST, Tokyo, Japan 

Electrocorticography (ECoG) constitutes a promising neural recording modality both in humans and animals, and often decomposed in to several frequency bands. The activity in high-gamma band [80-250 Hz] has been proposed as a reliable measure of the local cortical activity, but the differences across the bands have not been systematically investigated. To address this issue, we recorded ECoG from two awake monkeys in a retinotopic mapping task. We defined the preferred spatial position, receptive field (RF) and the response latencies in each electrode and each frequency band (i.e., alpha [8-16 Hz], beta [16-30 Hz], low- [30-80 Hz] and high- gamma), and compared them across the bands. As a whole, spatial preferences were comparable across the bands. We observed topographic structure representing the contralateral visual field in all the bands. The high-gamma activity showed smaller RF than the other bands. The response latencies in the alpha band were always longer than the other bands. Comparison of spatiotemporal response profiles within each region (V1, V4 and TEO/TE) revealed that the relationships between the frequency bands and the spatiotemporal profiles were dependent on the regions. While in V1 and V4, the response latencies in the beta, low- and high-gamma bands were almost identical, in TEO/TE, the responses in the beta and low-gamma bands preceded those in the high-gamma band by 15 ms. The spatial profiles in TEO/TE also differentiated the beta and low-gamma responses from those in the high-gamma. The initially-arriving beta and low-gamma tend to prefer more peripheral visual fields and show larger RF compared to the late-coming alpha and high-gamma, which suggest that TEO/TE first receives the less spatially selective information from the wide extent of the visual field, and later, the spatially fine-tuned information from the parafoveal space. These results demonstrate that the high-gamma and the lower-frequency bands can be informative independently of each other, and indicate that close examination on the across-bands differences enables us to infer the dynamic aspects of the local cortical processing.

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