International Meeting for Autism Research (London, May 15-17, 2008): NEURAL CORRELATES OF GREATER DUALTASKING COSTS IN AUTISM: AN fMRI STUDY OF TWO UNRELATED TASKS

Saturday, May 17, 2008

Champagne Terrace/Bordeaux (Novotel London West)

11:30 AM

S. R. Damarla , Psychology, Carnegie Mellon University, Pittsburgh, PA

T. A. Keller , Psychology, Center for Cognitive Brain Imaging, Carnegie Mellon University, Pittsburgh, PA

R. K. Kana , Psychology and Neurobiology, University of Alabama, Birmingham; Carnegie Mellon University, Birmingham, AL

D. L. Williams , Department of Speech Language Pathology, Duquesne University, Pittsburgh, PA

C. Prat , Psychology, Carnegie Mellon University, Pittsburgh

N. J. Minshew , Departments of Psychiatry and Neurology, University of Pittsburgh School of Medicine, Pittsburgh, PA

M. A. Just , Psychology, Center for Cognitive Brain Imaging, Carnegie Mellon University, Pittsburgh, PA

Background: People with high functioning autism (HFA) are impaired on most high-level cognitive tasks, but demonstrate intact/enhanced visuospatial performance. Concurrent performance of two tasks may require even more resources than doing a single high-level task. Previous studies have shown a greater dualtasking decrement in performance in autism (Garcia-Villamisar & Della Sala, 2002), however none have investigated the neural underpinnings of the psychological processes underlying these costs in autism.

Objectives: The goal of the current study was to investigate the neural correlates of greater dualtasking costs in autism than controls (performance was worse on both the tasks) from the perspective of two theoretical accounts: cortical underconnectivity (Just et al., 2004, 2007) and cortical capacity constraints (Just et al., 2001, 2007).

Methods: We used a combination of methodological tools: behavioral, fMRI, functional connectivity, and corpus callosum morphometry. Thirteen participants with HFA and 13 controls (age-, IQ-, and gender-matched) were scanned while performing a visuospatial task, an auditory sentence comprehension task, and both concurrently.

Results: The autism group demonstrated less cortical synchronization than controls between executive and language networks on the dual task. Also, the autism group reached their cortical capacity limit sooner by demonstrating A) Greater underadditivity than controls (the activation in the dual task was less than the sum of the activations in two single tasks), and B) Less new activation (regions that showed activation in the dual but not in the single tasks) than the control group. In addition, the corpus callosum (CC) was smaller in the autism group. Finally, a correlation between CC size and functional connectivity of language and executive networks was found in the autism group, but not in controls.

Conclusions: Reduced cortical connectivity and less availability of cortical resources may underlie greater impairment observed in dualtasking in autism.

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