Stimulus-driven and behavior-driving activity along the cortical auditory hierarchy

TL;DR

This study explores how auditory processing in the brain leads to speech perception and behavior using brain activity measurements in epilepsy patients.

Contribution

The study identifies distinct patterns of brain activity linked to stimulus processing and behavior in the auditory cortex using intracranial EEG.

Findings

Stimulus-related high gamma activity is widespread in the auditory and sensorimotor cortex.

Behavior-related activity is sparse, with the highest prevalence in the prefrontal cortex.

Faster responses correlate with stronger stimulus-locked activity in non-core auditory and prefrontal regions.

Abstract

Auditory areas on the superior temporal plane and lateral convexity are key initial stages of speech processing in the human cortex, representing acoustic and phonetic attributes in a temporally precise manner. More complex representations in auditory-related cortex along the ventral and dorsal processing streams and prefrontal cortex are associated with perception and action. In this study, we used intracranial electroencephalography (iEEG) to clarify where and how activity leading to perceptually driven behavioral events emerges. Participants were patients undergoing iEEG monitoring for medically intractable epilepsy. Stimuli were monosyllabic words, and participants pressed a button in response to a semantic target category. Significant high gamma activity after stimulus onset and immediately prior to motor response defined stimulus- and behavior-related activity patterns, respectively. The stimulus-related pattern was more common than behavior-related throughout the cortical auditory hierarchy as well as sensorimotor cortex. Behavior-related activity was sparsely represented, with the highest prevalence in the prefrontal cortex and a more limited representation in anterior temporal and parieto-occipital cortex. Hemispheric asymmetries included a higher prevalence of stimulus-related activity in the right sensorimotor cortex and a higher prevalence of the behavior-related pattern in the left prefrontal cortex. Faster behavioral responses were associated with greater stimulus-locked high gamma power in non-core auditory, prefrontal, and premotor cortex. Results reveal the cortical distribution of sensory stimulus-driven responses and activity time-locked to behavior and provide insights into neural substrates of speech perception.

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