Effects of Multiple-Session Transcranial Direct Current Stimulation (tDCS) on Behavioral, Physiological, and Electrophysiological Measures With Adults With Autism Spectrum Disorder (ASD)

Our long-term goal is to develop safe and effective treatments to reduce negative symptoms of social communication impairments to improve overall quality of life. Our central hypotheses are (1) active, anodal tDCS over the right temporoparietal junction (rTPJ) paired with social learning activities will result in improved performance on behavioral and physiological measures, when compared to sham stimulation, (2) these improvements in performance will be correlated with changes in electrophysiological measures that contribute to successful participant social alignment after receipt of anodal tDCS, such as reductions in spectral alpha power (8-12Hz), which has been robustly associated with accurate internal modeling of sensorimotor activity during action comprehension and speech perception, and (3) improvements in performance on social measures will be accompanied by power reductions in theta oscillations (4-8Hz), which arise from prefrontal cortices and support context-specific cognitive control.

Specific Aim 1: Determine the effects of multiple sessions of active compared to sham tDCS. This aim will employ a within-subject, cross-over randomized controlled trial (RCT) design to explore the effects of 5 sessions of active vs. 5 sessions of sham tDCS on behavioral, physiological, and electrophysiological measures with autistic adults or adults with high traits of autism.

Objective 1: The development of improved stimulation protocols

While even a single session of tDCS has been shown to improve performance on social measures with adults diagnosed with autism spectrum disorder (ASD), recent work with children with ASD has shown that increasing the number of sessions from one to even five produces positive effects that are retained for up to one year, even when tDCS was not paired with a task. Importantly, it has been shown that pairing a task with the receipt of tDCS improves results when compared to delivering tDCS without a task. However, the majority of literature on the use of tDCS with adults with ASD has been restricted to studies examining a low number of sessions and/or tDCS paired with no task or tasks that are unrelated to treating the core diagnostic social impairments of ASD. This reinforces the need for research examining multiple sessions of tDCS paired with social interventions that are relevant to core diagnostic social impairments in autistic adults or adults with high traits of autism.

Objective 2: The improvement of social communication and social alignment in autistic adults or adults with high traits of autism

Successful social communication is a complex social process that not only requires the expression and reception of verbal speech, but also the modification and coordination of many behaviors to achieve social alignment. Social alignment is a mostly unconscious phenomenon in which people become more similar to a conversation partner by adjusting communication features such as vocal speech prosody (patterns of voice stress or intonation), facial expressions, and gestures.It is also suggested that social alignment reduces the burden placed on the cognitive system, thus making social interactions easier, and possibly less anxiety filled. Autistic individuals have significantly lower social alignment when compared to their neurotypical peers.

Of great interest is also capitalizing on the rTPJ's role in social alignment because of the rTPJ's participation in using sensory information (including visual and auditory) to evaluate self against others and in mediating embodied processes relevant to perspective taking (such as facial expression and gesture). Consequently, the proposed project has significance in its approach for investigating tDCS applied over the rTPJ that is paired with social learning to target processes of social communication and social alignment in autistic adults or adults with high traits of autism.