Individuals with pediatric bipolar disorder (pBD) had a larger late positive potential (LPP) for happy faces compared with healthy controls, according to a study published in the Journal of Affective Disorders.
Alessio Simonetti, MD, Clinical Assistant Professor, Baylor College of Medicine, Houston, Texas, and colleagues set out to compare the LPP between children with pBD and age- and sex-matched healthy controls while the participants viewed faces with neutral, fearful, or happy emotional expressions. An additional objective was to compare P1 amplitude and latency between children with pBD and controls to determine the modulating effects of P1 on LPP. P1 is a measure of bottom-up visual sensory processing and LPP is a neural marker that reflects facilitated attention to emotional content.
The study included 20 participants between ages 6 and 17 years with pBD and 26 healthy controls. The investigators observed an emotion by group interaction for LPP, revealing a significantly larger amplitude for happy facial expression among participants with pBD than among healthy controls, with a difference of moderate size (Cohen’s d = 0.72). Although they did not find a significant group effect on P1 amplitude, P1 was delayed in those with pBD as compared with healthy controls. The delayed P1 peaking time showed a large effect (Cohen’s d = 0.99).
The larger LPP for happy faces suggests a higher sensitivity to positive stimuli that has been previously observed in pediatric mania and in those at-risk for BD. Other studies in individuals with pBD have found consistently greater activation of the amygdala during tasks involving positive words or happy faces. The researchers suggested that amygdala hyperactivity combined with prefrontal dysfunction may be a central mechanism underlying mood dysregulation in pBD.
The groups, although matched for sex and age, were a mixture of children and adolescents, which could have introduced neurodevelopmental heterogeneity. The researchers called for a replication of the current findings in a larger sample population.
Simonetti A, Lijffijt M, Kahlon RS, et al. Early and late cortical reactivity to passively viewed emotional faces in pediatric bipolar disorder. J Affect Disord. 2019;253:240-247.