Fear perception as a function of hemisphere- and time-specific dynamics in the medial temporal lobes

TL;DR

The right medial temporal lobe enhances early fear perception, while the left down-regulates it, based on electrophysiology data from patients.

Contribution

This study identifies lateralized and time-specific roles of the medial temporal lobes in fear processing using ERP and GBA data from resection patients.

Findings

Right medial temporal lobe resection patients lack fear-neutral differentiation in early P1 amplitudes.

Right hemisphere supports rapid attentional shifts toward fear and coordinates fear-neutral differentiation in gamma-band activity.

Left medial temporal lobe appears to down-regulate fear responses continuously.

Abstract

The medial temporal lobes (mTL) are thought to enhance visual processing of fearful faces, yet the underlying mechanisms remain underspecified. To fill this gap, we recorded and compared event-related potentials (ERPs) and stimulus-induced gamma-band activity (GBA) from 36 patients with left- or right-hemispheric antero-medial temporal lobe resections including the amygdala (lTLR/rTLR) and 18 healthy controls. Only rTLR patients were found to lack fear-neutral differentiation in early P1 amplitudes (~100 ms) and exhibited heightened GBA for neutral faces over ipsi-resectional occipito-temporal areas (95–300 ms). lTLR patients showed strongest emotion differentiation in ERP components beyond the P1. Therefore, the right mTL, potentially particularly the amygdala, appears to support rapid attentional shifts toward fear and to coordinate fear-neutral differentiation in GBA. Conversely, the left mTL seems to down-regulate fear responses. These results reveal complementary, lateralized, and time-specific roles of the medial temporal lobes in fear processing, thereby refining models of emotional vision.

Electrophysiology from resection patients reveals lateralized, temporally specific functions of the medial temporal lobes in fear perception: the right enhances early fear perception, while the left down-regulates it continuously.

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