C-46Episodic Memory Deficits in Autism Spectrum Disorder: A Meta-Analysis

Abstract

Introduction.- Episodic memory is a complex memory system implicating some abilities that are affected in autism spectrum disorder (ASD). Studies conducted on this topic report contrasting results. Hence, we conducted a meta-analysis of episodic memory impairments in ASD and evaluated possible moderators of these impairments, such as the type of material (visual vs. verbal), items (semantically related vs. semantically unrelated items), and retrieval task (free recall vs. recognition). Methods.- Twenty-nine case-control studies published from 1997 to February 2017 comparing groups of children, adolescents and adults with ASD to typically developing controls (TD) were included, corresponding to a total of 1057 participants (548 with ASD and 509 TD). Results.- Results showed that ASD participants demonstrated significantly reduced episodic memory (Cohen's d =-0.28 [-0.40; -0.16]; P < 0.001) particularly in the visual domain (d =-0.38 [-0.66; -0.09]; P = 0.01), with no difference in memory for verbal material (d =-0.12 [-0.27; 0.03]; P = 0.11). However, subgroup analysis revealed a verbal free recall difficulty for semantically related items (d =-0.51 [-0.86; -0.17]; P = 0.004), but not for semantically unrelated items (d = 0.21 [-0.23; 0.65]; P = 0.36). Discussion.- This meta-analysis confirmed the presence of episodic memory difficulties in ASD for verbal material when ASD people are provided unsupported retrieval tasks after on semantically related items. This profile confirms difficulties in ASD in processing complex information implicating binding with semantic knowledge when no support is provided. Our results extend the scope of this difficulty to non-verbal material as has recently been observed in a meta-analysis of working memory tasks (Wang et al., 2017, Neuropsychol Rev 27:46-61).