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Human Brain Splits Smell Into Early Identity Code and Later Pleasantness Signal

EEG in healthy adults shows a temporal split in smell processing.

Overview

  • A University of Tokyo team reports in the Journal of Neuroscience that odor identity and affect are processed at different times in the brain.
  • Early theta-band activity beginning around 80 milliseconds and peaking near 370 milliseconds encodes low-level molecular features of odors.
  • The fidelity of this theta coding correlates with individuals’ odor discrimination ability and is stronger on correct versus incorrect discrimination trials.
  • A later delta-band response emerging from about 720 milliseconds reflects perceived pleasantness and aligns with self-reported affective reactivity to smells.
  • Researchers propose these frequency-specific signals as potential biomarkers for olfactory assessment, though any clinical use remains preliminary.