Frequency-Dependent Cortical Interactions during Semantic Processing: An Electrocorticogram Cross-spectrum Analysis Using a Semantic Space Model
Naoyuki Sato, Riki Matsumoto, Akihiro Shimotake, Masao Matsuhashi, Mayumi Otani, Takayuki Kikuchi, Takeharu Kunieda, Hiroaki Mizuhara, Susumu Miyamoto, Ryōsuke Takahashi, Akio Ikeda
Abstract
Convergent evidence has demonstrated that semantics are represented by the interaction between a multimodal semantic hub at the anterior temporal lobe (ATL) and other modality-specific association cortical areas. Electrocorticogram (ECoG) recording with high spatiotemporal resolutions is efficient in evaluating such cortical interactions; however, this has not been a focus of preceding studies. The present study evaluated cortical interactions during picture naming using a novel ECoG cross-spectrum analysis, which was formulated from a computational simulation of neuronal networks and combined with a vector space model of semantics. The results clarified three types of frequency-dependent cortical networks: 1) an earlier-period (0.2-0.8 s from stimulus onset) high-gamma-band (90-150 Hz) network with a hub at the posterior fusiform gyrus, 2) a later-period (0.4-1.0 s) beta-band (15-40 Hz) network with multiple hubs at the ventral ATL and posterior middle temporal gyrus, and 3) a pre-articulation theta-band (4-7 Hz) network distributed over widely located cortical regions. These results suggest that frequency-dependent cortical interactions can characterize the underlying processes of semantic cognition, and the beta-band network with a hub at the ventral ATL is especially associated with the formation of semantic representation.