Auditory processing in the human cortex: An intracranial electrophysiology perspective

Abstract

ObjectiveDirect electrophysiological recordings in epilepsy patients offer an opportunity to study human auditory cortical processing with unprecedented spatiotemporal resolution. This review highlights recent intracranial studies of human auditory cortex and focuses on its basic response properties as well as modulation of cortical activity during the performance of active behavioral tasks. Data Sources: Literature review. Review Methods: A review of the literature was conducted to summarize the functional organization of human auditory and auditory‐related cortex as revealed using intracranial recordings.ResultsThe tonotopically organized core auditory cortex within the posteromedial portion of Heschl's gyrus represents spectrotemporal features of sounds with high temporal precision and short response latencies. At this level of processing, high gamma (70–150 Hz) activity is minimally modulated by task demands. Non‐core cortex on the lateral surface of the superior temporal gyrus also maintains representation of stimulus acoustic features and, for speech, subserves transformation of acoustic inputs into phonemic representations. High gamma responses in this region are modulated by task requirements. Prefrontal cortex exhibits complex response patterns, related to stimulus intelligibility and task relevance. At this level of auditory processing, activity is strongly modulated by task requirements and reflects behavioral performance.ConclusionsDirect recordings from the human brain reveal hierarchical organization of sound processing within auditory and auditory‐related cortex.Level of EvidenceLevel V

Joint Representation of Spatial and Phonetic Features in the Human Core Auditory Cortex

“…Figure 3A shows the STRFs of five neighboring electrodes for all five directions (E1, most medial, to E5, most lateral electrode). We observe a gradual decrease in frequency tuning across the 5 electrodes (see a comparison of the excitatory peak of the STRFs across rows in Figure 3A), consistent with the reported tonotopy in Heschl’s gyrus (Formisano et al, 2003; Humphries et al, 2010; Nourski, 2017). However, STRFs from different directions at a single electrode are very similar (see a comparison of columns in Figure 3A).…”

Audio–visual and olfactory–visual integration in healthy participants and subjects with autism spectrum disorder

“…Our study not only shows commonalities among the brain networks linked to MSI, but it also demonstrates sensory‐specific integration effects. Consistent with the fMRI literature with respect to unisensory processing, we observed activation in the amygdala during olfactory processing (e.g., Seubert et al, ), activation of the STG as well as the IFG and the dorsomedial prefrontal cortex (dmPFC) during auditory stimulation, and activation of the striate/extrastriate visual areas, the dmPFC and the insula/IFG during visual stimulation (e.g., Costafreda, Brammer, David, & Fu, ; Nourski, ; Salomon et al, ). Examining the network linked to the integration of visual and olfactory information (OV > O + V), we observed activation in the amygdala, the putamen and the caudate, which dropped out at the conjunction with the respective contrast for audio–visual integration.…”

Cortical functional connectivity indexes arousal state during sleep and anesthesia

“…Finally, all subjects participated in multiple additional research protocols over the course of their hospitalization, including a range of behavioral tasks. Behavioral and neural data obtained in these other experiments were examined for consistency with a corpus of published human intracranial electrophysiology data (reviewed in Nourski, 2017). None of the subjects exhibited aberrant responses that could be interpreted as grounds for caution in inclusion in this study.…”