A longitudinal study of infant temperament and brain processing in childhood

In recent years, clear links have been shown between high and low reactive infant temperaments (defined by distinct behavioral responses to unfamiliar stimuli at four months) and subsequent behaviorally inhibited and uninhibited childhood profiles. These links include peripheral physiological features such as reactivity of the sympathetic nervous system. However, central physiological features associated with infant reactivity remain unknown. Such features are critical for identifying brain regions responsible for the physiological differences, for identifying physiological markers of temperamental disposition, and for guiding treatment of temperamentally related clinical disorders.; The following three studies explore the neurobiology associated with temperament by evaluating early brain processing in 10--12-year-olds. In Study I, auditory threshold and brainstem auditory evoked responses (BAERs) were evaluated in 56 children classified as high or low reactive at four months. High reactives had larger wave V components of the BAER, a finding possibly suggestive of greater excitability of limbic projections to the inferior colliculus. Study II was a developmental study of 10--12-year-old children ( N = 180) that evaluated the ERP response to stimuli of differing degrees of novelty in a visual oddball paradigm, prior to that paradigm being assessed for the temperamental groups only. The two types of novel stimuli included: photographs novel to the experimental paradigm, called "valid novel", and photographs that were ecologically invalid, and therefore novel to life experience, called "invalid novel". Children had larger Nc components to invalid novel pictures. Study III evaluated responses to the oddball paradigm as they related to temperament by analyzing only those children categorized as high or low reactive (N = 110). High reactives demonstrated larger Nc responses to the oddball and invalid novel stimuli types. These data suggest that high reactives have a lower cortical threshold to unfamiliar events. This finding is consistent with the reactive, reticent, and/or fearful behavioral responses to novel stimuli, people, and situations found in high reactive infants and behaviorally inhibited toddlers. As a whole, these studies provide the first evidence of central physiological differences between high and low reactive temperamental types by identifying features of brain processing in preadolescence that relate to infant behavioral patterns ten years earlier.