Presentation
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Intracranial neural dynamics of cognitive control in rapid word recognition.
Poster E45 in Poster Session E, Saturday, October 8, 3:15 - 5:00 pm EDT, Millennium Hall
Also presenting in Poster Slam E, Saturday, October 8, 3:00 - 3:15 pm EDT, Regency Ballroom
Meredith McCarty1,2, Oscar Woolnough1,2, Xavier Scherschligt1,2, Patrick Rollo1,2, Nitin Tandon1,2,3; 1Vivian L. Smith Department of Neurosurgery, McGovern Medical School at UT Health Houston, 2Texas Institute for Restorative Neurotechnologies, University of Texas Health Science Center at Houston, 3Memorial Hermann Hospital, Texas Medical Center
The ability to select important information from the environment and flexibly adapt this process based on behavioral goals is an essential feature of human cognition. Within human visual processing, flexible cognitive control enables rapid directed attention to salient stimuli. In a visually crowded environment, in a matter of milliseconds, humans are able to recognize a familiar face in a crowd of people or the words on a street sign. This process is hypothesized to involve a distributed top-down cognitive control network that modulates earlier bottom-up visual processing within the ventral visual stream. fMRI work has revealed that task-based attentional conditions can modulate category selective regions of ventral occipitotemporal cortex (vOTC), such as the visual word form area. In this study, we utilize the robust spatial and temporal resolution of intracranial EEG recordings to characterize the modulation of visual word regions in vOTC by changing task demands. Data was collected from 21 patients undergoing electrode implantation for seizure localization of intractable epilepsy. We utilized a rapid visual recognition task, with visual stimuli of different categories (Words, Faces, Scenes, Animals). For the same stimulus set, patients performed multiple tasks with varying cognitive demands: for example, tracking color changes of a fixation point, performing a one back task, or making semantic decisions (e.g., finding names of fruits).We used broadband gamma activity (BGA; 70-150 Hz) as an index of local neural activity. Within the vOTC, we isolated regions selective for words relative to other stimulus categories. Consistent with previous intracranial findings, this region extended much more anteriorly than the fMRI-derived visual word form area. Word selective regions of vOTC showed distinct scaling of BGA responses with selectivity increasing as attentional task demand increased, suggesting a task-driven recruitment of distinct cortical substrates. We quantified inter-areal dynamics within patients with concurrent vOTC and inferior frontal gyrus (IFG) coverage. The onset of peak BGA was earliest for vOTC relative to IFG across attentional conditions. Within IFG, we found a greater and more sustained increase in BGA in IFG for semantic trials in which words were selectively attended to. This suggests that distinct changes in local neural activity within word-selective regions of the vOTC are scaled by attentional task conditions. These findings point to a complex interplay beyond a bottom-up feedforward model of visual word form recognition, illustrating that attentional task demands and behavioral state play a critical modulatory top-down role in this process.
Topic Areas: Reading, Control, Selection, and Executive Processes