Social and Non-Social Memory in Children and Adolescents with ASD

Background: Studies of memory abilities in ASD have consistently shown a discrepancy between difficulties in episodic memory for personally experienced events, relative to a preserved semantic memory for facts (Boucher and Bowler, 2008). How may we explain these findings? Are autobiographical memory deficits simply the extreme of a graded scale of information-processing deficits, or do they present a qualitatively independent impairment? This question relates more broadly to the search for a core deficit in autism, split between those arguing for a specific impairment in self and social abilities (Baron-Cohen et al., 2000, Hobson et al., 2006) and those arguing for a broader cognitive information-processing impairment (Happe and Frith, 2006; Minshew and Williams, 2007). Previous studies of memory in autism have generally compared simple semantic recall (such as word-generation, narrative memory) with complex episodic recall (Crane and Goddard, 2008; Losh and Capps, 2003; Klein et al., 1999), thus precluding the possibility of directly testing each alternative hypothesis. The present study aims to disentangle the underlying components of episodic and semantic memory, extending previous studies through carefully controlled behavioral measures, and through detailed phenotyping of social and cognitive skills.

Objectives: (1) To disentangle the relative importance of information-processing deficits from self- and social-processing deficits in ASD using episodic and semantic memory tasks matched for level of complexity. (2) To determine the neuropsychological co-variates of memory patterns in ASD, using in-depth clinical tests of social and cognitive processing.

Methods: Participants included 40 8-18 year-old subjects with ASD and 40 age, sex and IQ-matched controls. Autism diagnoses were confirmed using ADOS (Lord et al., 1999) and ADI-R assessments (Lord et al., 2003), and all subjects completed the Social Responsivity Scale (SRS) (Constantino, 2000) and Social Communication Questionnaire (SCQ) (Berument et al., 1999). Sub-tests from the NEPSY-II (Korkman et al., 2007) were used to obtain standardized measures of social and non-social semantic memory and organizational ability. The experimental tasks included a Levels-of-Processing task (based on Toichi et al., 2002) and a narrative recall task (based on Crane and Goddard, 2008) comparing memory for self, mother and favorite fictional character.

Results: Preliminary results, based on 15 ASD participants, support a self-reference effect (p = 0.018), with memory for self greater than memory for mother (p=0.056) and favorite fictional character (p=0.012) (contrary to Toichi et al., 2002 but in line with Lombardo et al., 2009; Henderson et al., 2009), thus providing support for the social-impairment hypothesis of autism. Further data collection, between-group and regressional analyses are underway to provide a more detailed picture of the underlying social and cognitive skills shaping the discrepant memory patterns in ASD.

Conclusions: By determining whether deficits in episodic memory in ASD arise from a particular impairment in organizing events in the world around their sense of self, or whether they are driven by broader information-processing deficits, our study aims to advance our understanding of the social communication deficit seen in autism as it unfolds over time, and to further specify targeted interventions.