Emotional Processing in the First 2 Years of Life: A Review of Near‐Infrared Spectroscopy Studies

Abstract

Emotional stimuli processing during childhood helps us to detect salient cues in our environment and prepares us for our social life. In early childhood, the emotional valences of auditory and visual input are salient and relevant cues of social aspects of the environment, and it is of special interest to understand how exactly the processing of emotional stimuli develops. Near‐infrared spectroscopy (NIRS) is a noninvasive neuroimaging tool that has proven valuable in studying emotional processing in children. After conducting a systematic search of PubMed, Web of Science, and Embase databases, we examined 50 NIRS studies performed to study emotional stimuli processing in children in the first 2 years of age. We found that the majority of these studies are done in infants and the most commonly used stimuli are visual and auditory. Many of the reviewed studies suggest the involvement of bilateral temporal areas in emotional processing of visual and auditory stimuli. It is unclear which neural activation patterns reflect maturation and at what age the emotional encoding reaches those typically seen in adults. Our review provides an overview of the database on emotional processing in children up to 2 years of age. Furthermore, it demonstrates the need to include the less‐studied age range of 1 to 2 years, and suggests the use of combined audio‐visual stimuli and longitudinal studies for future research on emotional processing in children. Thus, NIRS might be a vital tool to study the associations between the early pattern of neural responses and socioemotional development later in life.

Brain activity, underlying mood and the environment: A systematic review

“…Further, NIRS is well suited to studies of emotion (Balconi & Molteni, 2016). For example, in the emotional processing of visual and auditory stimuli, where NIRS showed activation of temporal areas (Maria et al, 2018); activation in prefrontal areas when participants recall emotional events (Ohtani, Matsuo, Kasai, Kato, & Kato, 2005); improved mood following mindful breathing being associated with frontal activation (Matsubara et al, 2018). In summary, research has established the presence of different patterns of brain activity in response to different emotional responses.…”

Hemodynamic responses to emotional speech in two-month-old infants imaged using diffuse optical tomography

“…reported a statistically significant speech response at the group level only on the left hemisphere, although inter-subject differences were comparable in magnitude to inter-hemispheric differences 20 . Thus, altogether these findings indicate that the current literature does not show a clear hemispheric predominance to speech or emotion processing in infants 40 , although individual studies show aspects of speech and emotion processing in some cases statistically significant on one hemisphere but not in the other.…”

Cortical Activation to Social and Mechanical Stimuli in the Infant Brain

“…Not only does the superior temporal cortex respond to the socially-relevant behavior of hands and faces ( Lloyd-Fox et al, 2009 ; Biondi et al, 2016 ), but also to agentive, goal-directed behavior. We also know that temporal and/or frontal areas show specialized responses to the processing of faces, emotional vocalizations, and eye-gaze during the first 8 months (for reviews see Wilcox and Biondi, 2015a , b ; Maria et al, 2018 ; McDonald and Perdue, 2018 ). And activation has been reported in the right parietal-temporal junction (PTJ) in 7-month-olds during processing of true and false belief events ( Hyde et al, 2018 ).…”