Frontal Asymmetry and Temperament In Young High Functioning Children with Autism Spectrum Disorders

Background: Studies of temperament in autism spectrum disorders (ASD) strongly suggest deficits in effortful control, lower positive affect, and higher negative affect compared to typically developing children. Among typically developing children, frontal EEG asymmetry has been related to temperamental factors. For instance, individuals with relatively greater right frontal activity tend to be more withdrawn and express negative affect whereas individuals with relatively greater left frontal activity tend to be more approach oriented and express positive affect (Baving et al., 2002; Hane et al., 2008). Frontal asymmetry may also serve as a bio-behavioral marker of individual differences in social motivation and emotional development in ASD (Sutton, et al., 2005).   

Objectives: To further examine temperament and its relation to frontal asymmetry in individuals with ASD.

Methods: Subjects were 14 6 and 7-year-olds with ASD with usable EEG data and 15 age and IQ-matched controls. Diagnosis was confirmed with the ADOS, ADI-R and DSM-IV-TR. All children in both groups had cognitive ability in the average to above average range. EEG was collected with a high-density (128 channel EGI) montage and referenced to the common average. Frontal asymmetry was calculated by taking the natural log of the mean alpha power for the 8-10 Hz frequency band and subtracting the value of left from right (F4 – F3). Temperament was assessed via parent report on the Children’s Behavior Questionnaire.   

Results: Children with ASD had lower CBQ scores for Attention Shifting (t(26) = -3.6, p < .01), Inhibitory control (t(26) = -4.86, p < .001), High Pleasure (t(26) = -2.08, p < .05), Smiling/Laughter (t(26) = -2.19, p < .05), and higher scores for Discomfort (t(26) = 2.65, p < .05), Fear (t(26) = 2.24, p < .05), Sadness (t(26)=2.45, p < .05), and Shyness (t(26)=2.08, p < .05).  
Groups differed in mean EEG alpha power in the right hemisphere (t(27) = 2.11, p < .05; ASD>TD), but not in the left hemisphere or in asymmetry scores. Within the ASD group, lower alpha power in the right hemisphere corresponded with increased scores on the High Pleasure scale (r(13) = -.56, p < .05). Greater left alpha power was related to increased Approach/Anticipation (r(13) = .63, p < .05) and increased Smiling/Laughter (r(13) = .56, p < .05).

Conclusions: Results support findings of temperamental differences in children with ASD including difficulties with attention shifting and inhibitory control as well as decreased expression of positive affect and higher rates of negative affect. Preliminary EEG results do not reveal differences in frontal asymmetry scores between groups, although the ASD group did have significantly greater right alpha power. Within the ASD group, alpha power in the right hemisphere was inversely related to pleasure while in the left hemisphere alpha power was positively related to approach and smiling.