Olfactory-to-visual facilitation in the infant brain declines gradually from 4 to 12 months

Area of Science:

• Developmental psychology
• Neuroscience
• Sensory processing

Background:

• Intersensory facilitation, where information from one sense aids another, typically declines in infancy as unisensory perception sharpens.
• Previous research primarily used audiovisual stimuli to study this developmental trade-off.

Purpose of the Study:

• To investigate the age-related changes in the facilitating effect of maternal body odor on neural face categorization in infants.
• To determine if the previously observed effect at 4 months decreases by 12 months of age.

Main Methods:

• Fifty infants (4–12 months old) were tested using electroencephalography (EEG).
• Neural responses to faces were measured in a baseline odor context and with the addition of maternal body odor.
• EEG data analyzed for face-selective responses and the impact of maternal odor across different ages.

Main Results:

• A face-selective electroencephalographic response indicating improved face categorization increased and qualitatively changed from 4 to 12 months.
• The beneficial effect of maternal body odor on face categorization significantly decreased with age (R² = .31).
• This fading benefit showed an inverse relationship with the amplitude of the visual response, mirroring findings in audiovisual interactions.

Conclusions:

• The study demonstrates a developmental decline in the olfactory-visual intersensory facilitation for face processing in infants.
• This decline is linked to the maturation of unisensory visual perception, supporting a trade-off model of sensory development.
• Findings extend the understanding of intersensory interactions beyond the audiovisual domain into olfactory-visual pairings.