Aims: In individuals with Autism Spectrum Disorder (ASD), behavioral findings are indicating episodic memory deficits, while ERP studies show an atypical, but controversial, pattern for successfully retrieved target images in comparison to new ones (old-new effect). It is possible that atypical retrieval processes in ASDs may be associated with functionally distinct retrieval pathways. Episodic retrieval success is reflected in increased theta oscillatory activity in typically-developed individuals (TD), although retrieval in ASD remains unexplored. The present study aims to examine supposed episodic retrieval deficits in ASDs and the associated atypical theta activity. Methods: Oscillatory activity in the EEG was analyzed during a recognition memory task in TD contrasted to ASD. For OLD versus NEW images from the real-world, induced oscillatory activity in the theta band was compared at frontal, temporo-parietal and midline areas. Results: As expected, TDs showed memory-related change in theta synchronicity for the oscillatory old-new effect in a time-window of the late parietal P3 component (LPC, 375-800ms) with a temporo-parietal and frontal distribution. Importantly, in ASD it was observed that the significant lower recognition memory performance was associated with an atypical theta activity, in line with the observed ERP results. Conclusions: The present study provides evidence for anomalies of theta oscillations during recognition memory retrieval. This is consistent with previous neural evidence of atypical hippocampus-cortical connectivity as well as with hippocampal structural differences in this clinical group. Our findings may clarify neural mechanisms involved in learning processing.

--