Behavioral Relevance of Early Neural Coding of Low-Level Odor Features in Humans

Area of Science:

• Neuroscience
• Sensory Neuroscience
• Olfactory Neuroscience

Background:

• The temporal dynamics of neural odor coding and their link to olfactory perception and behavior are not well understood, particularly in early sensory processing.
• Characterizing early neural responses to odors is key to understanding how the brain processes olfactory information.

Purpose of the Study:

• To investigate which odor features are encoded in early neural responses.
• To determine the functional significance of these early neural codes for olfactory perception and behavior.

Main Methods:

• Electroencephalography (EEG) was used to record brain activity in participants exposed to various odors.
• Participants underwent olfactory tests (detection, discrimination, identification) and completed questionnaires.
• Time- and frequency-resolved decoding and representational similarity analysis were applied to EEG data.

Main Results:

• Early theta-band activity (peaking at 370 ms) encoded low-level physicochemical odor properties.
• The fidelity of theta coding to odor features correlated with odor discrimination ability.
• Later delta-band activity (peaking at 980 ms) encoded pleasantness and correlated with affective reactivity.
• Theta decoding accuracy was higher on correct odor discrimination trials.

Conclusions:

• Early theta-band representations of physicochemical odor features are functionally relevant to olfactory performance.
• These early neural codes precede perceptual representations and contribute to odor-guided behavior.
• Distinct temporal dynamics exist for encoding of odor features versus pleasantness.