Pivotal Response Treatment Improves Neural Efficiency for Social Perception in Children with Autism Spectrum Disorder

Background:  

Individuals with autism spectrum disorder (ASD) demonstrate reduced social motivation, resulting in diminished attention to people and consequent dysfunction in the specialization of neural mechanisms associated with social behavior. This dysfunction has been reliably associated with a deficit in the neural response to face stimuli, indexed both functional neuroimaging and electrophysiological techniques. Pivotal Response Treatment (PRT) is an empirically validated behavioral treatment for ASD that focuses on improving key social and communication abilities by enhancing social motivation. Prior research from our group demonstrated that a 16-week PRT intervention results in meaningful improvements in pragmatic language, social engagement, and adaptive functioning (Ventola et al., 2014), with accompanying changes in regional brain activation (Voos et al., 2012). Effects of treatment on neural efficiency have not yet been studied. The current study utilizes electroencephalography (EEG), an imaging method with excellent temporal resolution, to examine the temporal dynamics of brain responses associated with positive response to intervention.

Objectives:  

To identify temporal changes in neural mechanisms associated with social perception following PRT treatment.

Methods:  

Seven children with ASD between ages 4 and 6 years received PRT for 8 hours per week (child: 6 hours; parent: 2 hours) for 16 consecutive weeks. Participants completed an EEG session, recorded with a 128-channel Hydrocel Geodesic sensor net, both pre- and post-treatment. A waitlist control sample completed an EEG session 16 weeks prior to starting treatment to differentiate effects of treatment from those resulting from developmental changes over a four-month period. During the EEG sessions, participants viewed 73 distinct, computer-generated faces displaying neutral and fearful expressions. Data were segmented to onset of face stimuli and event-related potentials (ERPs) were extracted over the right occipitotemporal region. Changes in the amplitude and latency of early feature detection and face-sensitive ERP components (P100 and N170, respectively) were examined.

Results:  

Results revealed a main effect of treatment [F(1,6) = 11.34, p = .015], indicating a change in the efficiency of face processing, indexed by N170 latency. Post-hoc paired samples t-tests revealed that the reduction in N170 latency was significant for both neutral (p = .027) and fearful (p = .029) face stimuli from pre-treatment to post-treatment assessments. There were no significant changes in N170 amplitude or in either P100 latency or amplitude (p > .05). There was no significant change in N170 latency across the 4-month period prior to treatment when participants were enrolled as waitlist controls [F(1,2) = 2.45, p = .26].

Conclusions:  

A 4-month course of PRT for young children with ASD was associated with improved efficiency of neural indicators of social behavior. Effects of treatment were reflected in brain responses associated with social perception (N170), rather than low-level sensory processes (P100), suggesting focal treatment effects on social processing mechanisms. Preliminary data also revealed that a 4-month period of development without intervention does not result in similar changes in neural efficiency, indicating specific effects of treatment. These findings provide the first evidence of increased processing efficiency for social information resulting from PRT.