Low positive emotionality in young children: association with EEG asymmetry.

Low positive emotionality (PE; e.g., listlessness, anhedonia, and lack of enthusiasm) has been hypothesized to be a temperamental precursor or risk factor for depression. The present study sought to evaluate the validity of this hypothesis by testing whether low PE children have similar external correlates as individuals with depression. This paper focused on the external correlate of EEG asymmetry. Previous studies have reported that individuals at risk for depression exhibited a frontal EEG asymmetry (greater right than left activity). Others have reported an association with posterior asymmetries (greater left than right activity). In the present study, children classified as having low PE at age 3 exhibited an overall asymmetry at age 5-6 with less relative activity in the right hemisphere. This asymmetry appeared to be largely due to a difference in the posterior region because children with low PE exhibited decreased right posterior activity whereas high PE children exhibited no posterior asymmetry. These findings support the construct validity of the hypothesis that low PE may be a temperamental precursor or risk factor for depression.