title: Infants' neural responses to facial emotion in the prefrontal cortex are correlated with temperament: a functional near-infrared spectroscopy study.
abstract: Accurate decoding of facial expressions is critical for human communication, particularly during infancy, before formal language has developed. Different facial emotions elicit distinct neural responses within the first months of life. However, there are broad individual differences in such responses, so that the same emotional expression can elicit different brain responses in different infants. In this study, we sought to investigate such differences in the processing of emotional faces by analyzing infants's cortical metabolic responses to face stimuli and examining whether individual differences in these responses might vary as a function of infant temperament. Seven-month-old infants (N = 24) were shown photographs of women portraying happy expressions, and neural activity was recorded using functional near-infrared spectroscopy (fNIRS). Temperament data were collected using the Revised Infant Behavior Questionnaire Short Form, which assesses the broad temperament factors of Surgency/Extraversion (S/E), Negative Emotionality (NE), and Orienting/Regulation (O/R). We observed that oxyhemoglobin (oxyHb) responses to happy face stimuli were negatively correlated with infant temperament factors in channels over the left prefrontal cortex (uncorrected for multiple comparisons). To investigate the brain activity underlying this association, and to explore the use of fNIRS in measuring cortical asymmetry, we analyzed hemispheric asymmetry with respect to temperament groups. Results showed preferential activation of the left hemisphere in low-NE infants in response to smiling faces. These results suggest that individual differences in temperament are associated with differential prefrontal oxyHb responses to faces. Overall, these analyses contribute to our current understanding of face processing during infancy, demonstrate the use of fNIRS in measuring prefrontal asymmetry, and illuminate the neural correlates of face processing as modulated by temperament.
authors.affiliation: Laboratories of Cognitive Neuroscience, Division of Developmental Medicine, Boston Children's Hospital, Boston MA, USA.
authors.forename: Miranda M
authors.initials: MM
authors.lastname: Ravicz
authors.affiliation: Laboratories of Cognitive Neuroscience, Division of Developmental Medicine, Boston Children's Hospital, Boston MA, USA ; Department of Pediatrics, Harvard Medical School, Boston MA, USA.
authors.forename: Katherine L
authors.initials: KL
authors.lastname: Perdue
authors.affiliation: Laboratories of Cognitive Neuroscience, Division of Developmental Medicine, Boston Children's Hospital, Boston MA, USA.
authors.forename: Alissa
authors.initials: A
authors.lastname: Westerlund
authors.affiliation: Laboratories of Cognitive Neuroscience, Division of Developmental Medicine, Boston Children's Hospital, Boston MA, USA ; Department of Pediatrics, Harvard Medical School, Boston MA, USA.
authors.forename: Ross E
authors.initials: RE
authors.lastname: Vanderwert
authors.affiliation: Laboratories of Cognitive Neuroscience, Division of Developmental Medicine, Boston Children's Hospital, Boston MA, USA ; Department of Pediatrics, Harvard Medical School, Boston MA, USA ; Harvard Graduate School of Education, Cambridge MA, USA.
authors.forename: Charles A
authors.initials: CA
authors.lastname: Nelson
keywords: emotion; face processing; functional near-infrared spectroscopy; infancy; negative emotionality; prefrontal cortex; temperament