Relations between Frontal Gamma Power, Socioeconomic Status, and IQ Among Adolescents with and without ASD

Background: Research suggests that socioeconomic status (SES) has implications for cognitive development (e.g., executive functioning and IQ) among typically developing (TYP) children (Farah et al., 2006), namely that children from lower SES backgrounds experience difficulties in these cognitive domains. Studies have found that the cognitive impact of SES can be observed on a neurological level through electroencephalogram (EEG) in the frontal gamma band (Tomalski et al., 2013); this area has been linked with higher-order cognitive processes (Gou, Choudhury, & Benasich, 2011). Lower gamma power has been examined in individuals with ASD (Maxwell et al., 2015), however, the relation of SES, frontal gamma power, and IQ among a sample of youth with ASD has not been examined.

Objectives: The objective of the present study was to evaluate the relations between SES, EEG frontal gamma power, and IQ among adolescents with and without ASD. It was hypothesized that frontal gamma power and IQ would be positively related to SES.

Methods: Fifty-nine adolescents with ASD and 18 without ASD (TYP), aged 11-17, participated. Participants were from a social skills intervention study; data here was from the pretest (before intervention) time point. Participants completed a three-minute resting state EEG paradigm from which frontal gamma power was calculated and the KBIT-2 (Kaufman & Kaufman, 2004) to obtain IQ. Parents/primary caregivers completed a demographic form that asked about their own education and household income, which were used as separate indicators of SES.

Results: No significant differences in demographic variables were found between groups. Spearman correlations revealed no significant associations between SES and frontal gamma power within either group for income (ASD: r_s(57)=-.020, p=.880; TYP: r_s(18)=-.202, p=.421) or education (ASD: r_s(59)=-.203, p=.124; TYP: r_s(18)=.045, p=.860). There was a significant association between SES and IQ for education in both groups (ASD: r_s(59)=.259, p=.047; TYP: r_s(18)=.614, p=.007) and income in the TYP (ASD: r_s(57)=.122, p=.366; TYP: r_s(18)=.488, p=.040). Pearson’s correlations were conducted to examine the association between frontal gamma power and IQ within each group; a negative link was found in the ASD (r_s(59)=-.266, p=.042), but not the TYP, group.

Conclusions: Contrary to hypotheses, results showed no relation between frontal gamma power and SES among adolescents with or without ASD. This is in contrast to previous work that identified association between brain development and SES among typically developing children (Noble, Houston, Kan, & Sowell, 2012). Additionally, there was a negative link between IQ and frontal gamma power in the ASD group but no relation in the control group. This finding could be from the atypical gamma power found in individuals with ASD. Paradoxically, IQ was related to education among both groups which suggests that SES might influence certain cognitive processes in ASD. Of note, the current sample was comprised of participants from relatively high SES and, thus, links between SES and neurological functioning may have been undetectable due to the small number of participants in the lower SES categories.