Neural Plasticity and Intervention: Effects of the PEERS Program On EEG Activity and Respiratory Sinus Arrhythmia

Background: Few studies have examined neurophysiological plasticity due to intervention in autism spectrum disorders (ASD) despite the significant neural discrepancies identified in this population (Minshew, 2007). Here, we examine change in EEG power levels in the beta and gamma bands in those cortical areas of the brain associated with social behavior (Adolphs, 1999) in response to PEERS, a social skills intervention (Laugeson et al., 2009). Further, autonomic regulation via the vagus nerve, measured as Respiratory Sinus Arrhythmia (RSA), may serve as a biomarker of social behavior (Porges, 2001). RSA is therefore also assessed as a potential subcortical outcome measure. This study aims to explore the neurophysiological alterations associated with completion of an empirically supported behavioral treatment for ASD.

Objectives: Investigate changes in EEG beta and gamma activity and RSA as they relate to completion of a social skills intervention program in adolescents with ASD.

Methods: Forty adolescents (11-16 years old) were randomly assigned to an Experimental Group (EXP) or Waitlist Control Group (WL). Heart rate and neural activity, as measured by continuous EEG, were assessed pre- and post-intervention/delay during a 3-minute resting, eyes open condition. Average beta (13-30 Hz) and gamma (30-45Hz) band activity from left and right hemisphere electrodes was then calculated and compared across time (pre-/post-treatment) and group assignment (EXP/WL). Average beta band power was analyzed in the frontal, parietal, and temporal lobes. Average gamma power and coherence were analyzed in the frontal, frontal midline, parietal midline, and parietal-temporal regions. Beta and gamma findings were initially submitted as distinct projects but combined on request, explaining differences in data analysis choices. Final analyses would, however, be performed in a consistent manner. 

Results: Preliminary results indicate a group x time x location interaction for gamma power, F (5, 27) = 2.45, p <  .05, partial eta² = .31. Examination of data reveals midline frontal and parietal, and left parietal-temporal gamma power increases in the EXP group but not in the WL group. Gamma coherence measurements indicated an increase in left-right frontal coherence in the EXP group, t (16) = 2.33, p < .05. Beta power analysis reveals a time x group interaction in the left frontal lobe, F(1, 30)= 4.85, p < .05, partial eta²= .14, and left parietal lobe F(1, 29)= 4.641, p < .05, partial eta²= 14, again reflecting increases in the EXP group but not the WL group. No significant change in RSA was found.

Conclusions: Preliminary findings suggest that participation in the PEERS treatment program is associated with change in cortical brain regions but not in subcortical, cardiac regulatory systems. Beta band activity is associated with focused attention and brain activity synchronization, and gamma with higher-order information processing and neural synchronization, all of which are atypical in ASD (Dawson, 2008; Blinkowska, 2006; Minshew, 2007; Murias 2007). Further, atypical lateralization, specifically right asymmetry has been associated with increased symptom severity in the ASD population (Sutton et al., 2004). We suggest that the current results may be indicative of neural ‘correction’ in response to treatment.