Mesial temporal lobe and memory function in autism spectrum disorder: An exploration of volumetric findings

Abstract

Studies have shown that individuals with autism spectrum disorder (ASD) tend to perform significantly below typical developing individuals on standardized measures of memory, even when not significantly different on measures of IQ. The current study sought to examine within ASD whether anatomical correlates of memory performance differed between those with average-to-above-average IQ (AIQ group) and those with low-average to borderline ability (LIQ group) as well as in relations to typically developing comparisons (TDC). Using automated volumetric analyses, we examined regional volume of classic memory areas including the hippocampus, parahippocampal gyrus, entorhinal cortex, and amygdala in an all-male sample AIQ (n = 38) and LIQ (n = 18) individuals with ASD along with 30 typically developing comparisons (TDC). Memory performance was assessed using the Test of Memory and Learning (TOMAL) compared among the groups and then correlated with regional brain volumes. Analyses revealed group differences on almost all facets of memory and learning as assessed by the various subtests of the TOMAL. The three groups did not differ on any region of interest (ROI) memory-related brain volumes. However, significant size–memory function interactions were observed. Negative correlations were found between the volume of the amygdala and composite, verbal, and delayed memory indices for the LIQ ASD group, indicating larger volume related to poorer performance. Implications for general memory functioning and dysfunctional neural connectivity in ASD are discussed.

Keywords:

• Memory
• Autism spectrum disorders
• Neurodevelopmental disorders
• Magnetic resonance imaging

The authors report no conflicts of interest. The content is solely the responsibility of the authors and does not necessarily represent the official views of the National Institute of Mental Health, the National Institute of Child Health & Development, or the National Institutes of Health. We thank former members of the Utah Autism Collaborative Program of Excellence for their assistance during the early stages of this project. We sincerely thank the children, adolescents, and adults with autism and the individuals with typical development, who participated in this study, and their families. Although E. D. Bigler is the co-author of the Test of Memory and Learning (TOMAL), he receives no royalties and reports no conflict of interest. The assistance of Jo Ann Petrie with manuscript preparation is gratefully acknowledged.

Additional information

Funding

The project described was supported by the National Institute of Mental Health [grant number RO1 MH080826 (J.E.L., E.D.B., A.L.A., N.L.)], [grant number RO1 MH084795 (J.E.L., P.T.F., N.L.)], [grant number KO8 MH092697 (J.S.A.)]; the Eunice Kennedy Shriver National Institute of Child Health and Human Development [grant number T32 HD07489 (B.G.T.)], [grant number P30 HD003352-45 (Waisman Center Core Grant)]; The Hartwell Foundation (B.G.T.); and the Primary Children’s Foundation Early Career Development Award (B.A.Z.). Support from the Poelman Foundation to Brigham Young University for autism research is gratefully acknowledged.