Maternal odor shapes rapid face categorization in the infant brain

Abstract

To successfully interact with a rich and ambiguous visual environment, the human brain learns to differentiate visual stimuli and to produce the same response to subsets of these stimuli despite their physical difference. Although this visual categorization function is traditionally investigated from a unisensory perspective, its early development is inherently constrained by multisensory inputs. In particular, an early‐maturing sensory system such as olfaction is ideally suited to support the immature visual system in infancy by providing stability and familiarity to a rapidly changing visual environment. Here, we test the hypothesis that rapid visual categorization of salient visual signals for the young infant brain, human faces, is shaped by another highly relevant human‐related input from the olfactory system, the mother's body odor. We observe that a right‐hemispheric neural signature of single‐glance face categorization from natural images is significantly enhanced in the maternal versus a control odor context in individual 4‐month‐old infant brains. A lack of difference between odor conditions for the common brain response elicited by both face and non‐face images rules out a mere enhancement of arousal or visual attention in the maternal odor context. These observations show that face‐selective neural activity in infancy is mediated by the presence of a (maternal) body odor, providing strong support for multisensory inputs driving category acquisition in the developing human brain and having important implications for our understanding of human perceptual development.

Does any mother’s body odor stimulate interest in mother’s face in 4‐month‐old infants?

“…In conclusion, the present results indicate that olfaction plays an important role in young infants’ perception of their social partners and they are consistent with findings showing that the mother's body odor can also shape face categorization by enhancing a face‐selective electro‐encephalographic response in the infant brain (Leleu et al, ). Findings such as these add to a growing body of evidence indicating that multisensory interaction has a pervasive influence on behavior in early human development (Lewkowicz, ).…”

Maternal Odor Reduces the Neural Response to Fearful Faces in Human Infants

“…Bayet et al, 2017;Heck, Hock, White, Jubran, & Bhatt, 2016;Safar & Moulson, 2020). Furthermore, prior studies showing an impact of maternal odor on face processing investigated infants at 4 months of age (Durand et al, 2013(Durand et al, , 2020Leleu et al, 2019), showing that maternal odor influences face processing per se already at an earlier age than investigated here.…”

“…Three recent studies have suggested a modulation of infant face processing in general by the presence of maternal odor (Durand et al, 2013(Durand et al, , 2020Leleu et al, 2019). Most importantly, Leleu et al (2019) found an enhanced neural response to faces in the presence of maternal odor. While their work thereby shows a modulation by maternal odor of face processing per se, the present result suggest that maternal odor can furthermore impact neural responses to specific aspects of face processing.…”

“…Four-month-old infants tend to look longer at faces, and in particular the eye region of faces, in the presence of maternal odor (Durand et al, 2013). In a recent study, Leleu and colleagues (Leleu et al, 2019) furthermore investigated the influence of maternal odor on the neural response to faces in 4-month-old infants, and found an enhanced facerelated neural response in the presence of maternal odor. In sum, maternal odor therefore appears to impact face processing in infancy both on a neural and a behavioral level.…”

Hemispheric Organization for Visual Object Recognition: A Theoretical Account and Empirical Evidence

“…In a further challenge, in experiments conducted with 4-to 6-month-old infants, natural images of faces were displayed embedded among a stream of common objects, and in a second experiment, phase scrambled versions of the faces and objects were displayed (de Heering & Rossion, 2015). A clear response at the base stimulation frequency was observed for faces but not for the phase-scrambled versions, and this response was present to a greater degree over the RH than LH (see also Leleu et al, 2019). These findings led to the conclusion that selective processes for face processing are present well before word recognition is acquired and hence cannot possibly be the outcome of the hemispheric competition and cooperation that ensues over development.…”