Authors :
Presenting Author: Shigeta Fujitani, MD, PhD – Department of Neurosurgery, The University of Tokyo Hospital
Naoto Kunii, MD, PhD – Jichi Medical University
Anna Takeda, MD – the University of Tokyo
Ako Matsuhashi, MD – the University of Tokyo
Toshiya Aono, MD – the University of Tokyo
Seijiro Shimada, MD, PhD – the University of Tokyo
Nobuhito Saito, MD, PhD – the University of Tokyo
Rationale:
Auditory sensory processing is hierarchically organized, with predictions about incoming stimuli generated across cortical regions including the primary auditory cortex (A1), superior temporal gyrus (STG), and prefrontal cortex. Mismatch responses (MMRs) are elicited when a stimulus deviates from prior auditory patterns and are well-documented in the A1 and STG. However, the involvement of frontal and other higher-order cortical areas remains less well understood. The previously reported “cascade roving” (CR) paradigm (Fujitani S, et al. Cerebral Cortex. 2024;34(2):bhad508), which features five-tone sequences alternating in ascending or descending frequency, was able to evoke prediction-related activity across broad cortical areas, including the STG and inferior frontal gyrus (IFG). In this study, we focused on characterizing the progressive changes in prediction-related responses over time during this paradigm.
Methods:
Eight patients with refractory epilepsy underwent electrocorticographic (ECoG) recording as part of their presurgical evaluation. Subdural electrodes were placed based on clinical needs, over areas including the frontal and temporal regions. Participants passively listened to the CR paradigm, in which blocks of either three or seven five-tone trains were presented in either ascending or descending frequency order. The first train of each block, representing a directional change from the previous block, was defined as a deviant stimulus. High-gamma power (HGP; 70–150 Hz) was extracted using Hilbert transformation. Statistical comparisons were conducted to identify electrodes with significant deviant-related HGP responses. To assess temporal dynamics, the magnitude of these responses was compared between the first and second halves of the recording session.
Results:
The CR paradigm elicited clear deviant-related HGP responses, primarily in the STG and IFG. In a subset of electrodes, the amplitude of these responses changed significantly over time. Many electrodes in the STG and IFG showed stronger deviant-related activity in the latter half of the session, suggesting increasing sensitivity or adaptation of predictive mechanisms. Conversely, a small number of electrodes—particularly those located outside the STG—exhibited greater deviant-related responses in the earlier part of the task, which then declined as the session progressed.
Conclusions:
These results suggest that distinct cortical areas contribute differentially to auditory predictive processing over time. The progressive enhancement of deviant responses in the STG and IFG implies ongoing refinement of predictions about sound structure or context. In contrast, early-dominant responses outside the STG may reflect involvement in higher-order predictions or sensitivity to initial context shifts, such as the timing of cascade transitions. The CR paradigm thus provides a valuable framework for dissecting temporal and regional components of predictive coding in the human auditory system.
Funding: This work was supported by the Japan Agency for Medical Research and Development (grant numbers JP19dm0207069, JP18dm0307001, JP18dm0307004)