Unexpected sound omissions are signaled in human posterior superior temporal gyrus: an intracranial study

Abstract:

Context modulates sensory neural activations enhancing perceptual and behavioral performance and reducing prediction errors. However, the mechanism of when and where these high-level expectations act on sensory processing is unclear. Here, we isolate the effect of expectation absent of any auditory evoked activity by assessing the response to omitted expected sounds. Electrocorticographic signals were recorded directly from subdural electrode grids placed over the superior temporal gyrus (STG). Subjects listened to a predictable sequence of syllables, with some infrequently omitted. We found high-frequency band activity (HFA, 70–170 Hz) in response to omissions, which overlapped with a posterior subset of auditory-active electrodes in STG. Heard syllables could be distinguishable reliably from STG, but not the identity of the omitted stimulus. Both omission- and target-detection responses were also observed in the prefrontal cortex. We propose that the posterior STG is central for implementing predictions in the auditory environment. HFA omission responses in this region appear to index mismatch-signaling or salience detection processes.

Authors:

• Hohyun Cho

• Yvonne M Fonken

• Markus Adamek

• Richard Jimenez

• Jack J Lin

• Gerwin Schalk

• Robert T Knight

• Peter Brunner

Date: 2023

DOI: https://doi.org/10.1093/cercor/bhad155

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Intracranial recordings demonstrate medial temporal lobe engagement in visual search in humans

Abstract:

Visual search is a fundamental human behavior, which has been proposed to include two component processes: inefficient search (Search) and efficient search (Pop-out). According to extant research, these two processes map onto two separable neural systems located in the frontal and parietal association cortices. In the present study, we use intracranial recordings from 23 participants to delineate the neural correlates of Search and Pop-out with an unprecedented combination of spatiotemporal resolution and coverage across cortical and subcortical structures. First, we demonstrate a role for the medial temporal lobe in visual search, on par with engagement in frontal and parietal association cortex. Second, we show a gradient of increasing engagement over anatomical space from dorsal to ventral lateral frontal cortex. Third, we confirm previous work demonstrating nearly complete overlap in neural engagement across cortical regions in Search and Pop-out. We further demonstrate Pop-out selectivity manifesting as activity increase in Pop-out as compared to Search in a distributed set of sites including frontal cortex. This result is at odds with the view that Pop-out is implemented in low-level visual cortex or parietal cortex alone. Finally, we affirm a central role for the right lateral frontal cortex in Search.

Authors:

• S. J. Katarina Slama

• Richard Jimenez

• Sujayam Saha

• David King-Stephens

• Kenneth D Laxer

• Peter B Weber

• Tor Endestad

• Pål G Larsson

• Anne-Kristin Solbakk

• Jack J Lin

• Robert T Knight

Date: 2021

DOI: https://doi.org/10.1162/jocn_a_01739

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