Functional connectivity dynamics of the left midfusiform gyrus during single, printed word presentation

Abstract

The left temporal language network is largely understood in terms of various distinct brain regions with functions related to language processing, including those thought to support the process of transforming printed words into their phonological form and meaning. However, little is understood about how these regions communicate to accomplish these tasks. The aim of this study was to spatiotemporally characterize the functional connectivity between a core part of the network, the left midfusiform gyrus [lmFG] also known as the "visual word form area," and other regions of the brain during individual printed word presentation. By calculating phase locking values between intracranial electrodes and posterior probabilities derived from a 6-way Bayesian classifier, functional connectivity between electrodes and information content within electrodes could be visualized over time and space. The results of these analyses support the notion that two distinct stages exist in visual word form processing: an early stage (150-200 ms), characterized by long range connectivity from the lmFG to more anterior and superior regions of the left temporal lobe, and a later stage (250-400 ms) where word form information tends to be more distributed throughout the left midfusiform and neighboring gyri. Taken together, these results support recent findings of multi-stage orthographic processing in the lmFG and that the dynamic shift from gist-level to individual-level word representation occurs through network-level interactions among regions of the language network. More focused experimental paradigms and network-based statistics are necessary to determine how information flows among these regions to support these multiple stages of orthographic processing, and how this sub-network fits into the larger language network.

Meeting abstract presented at VSS 2017