International Meeting for Autism Research: Beta-Adrenergic Modulation of Context Processing in Individuals with An Autism Spectrum Disorder

Beta-Adrenergic Modulation of Context Processing in Individuals with An Autism Spectrum Disorder

Thursday, May 20, 2010
Franklin Hall B Level 4 (Philadelphia Marriott Downtown)
1:00 PM
K. E. Bodner , Psychological Sciences, University of Missouri, Columbia, MO
S. S. Saklayen , Interdisciplinary Graduate Studies Program, The Ohio State University, Columbia, MO
D. Q. Beversdorf , Radiology, Neurology and Psychology, University of Missouri, Columbia, MO
S. E. Christ , Psychological Sciences, University of Missouri, Columbia, MO
Background: Previous studies have shown improvements in cognitive flexibility and verbal problem solving following administration of a beta adrenergic antagonist to individuals with an autism spectrum disorder (ASD).  The observed effect is presumed to be related to the adrenergic projections to the prefrontal cortex and related brain regions. It remains unclear, however, to what extent this benefit may extend to other prefrontally-mediated aspects of executive function.

Objectives: To evaluate the potential effect of propranolol, a beta-adrenergic antagonist, on additional aspects of executive function (i.e., working memory and inhibitory control) using a context processing task in individuals with and without an ASD.

Methods: An AX continuous performance test (AX-CPT) was used to assess context processing in 14 individuals with an ASD (mean age = 18.8 yrs; mean FSIQ = 103) and a demographically-matched comparison group of 13 typically developing individuals (mean age = 19.2 yrs; mean FSIQ = 108). In the AX-CPT, participants were shown a series of cue-probe letter pairs, with each cue letter being followed shortly by a probe letter.  They were instructed to press a target button when the probe letter X followed the cue letter A.  For all other cue-probe combinations, they were to press a non-target button.  AX cue-probe stimuli were presented on 70% of the task trials. The remaining 30% of trials were split evenly across 3 additional conditions: (1) the AY condition in which the cue letter A was followed by a letter other than X, (2) the BX condition in which the cue was a letter other than A but the probe was still X, and (3) the BY condition in which neither the cue nor probe were A or X. Performance in the AY condition is taken as a measure of inhibitory control in that participants must inhibit the prepotent tendency to respond to a probe following the cue letter A.  Also, good working memory can aid in performance in the BX condition.  (Participants may press the target button in response to a probe letter X if they cannot remember what preceded it.)

Results: Overall the groups performed comparably in the AY condition of the task, suggesting intact inhibitory control for the ASD group [Main effect of group: F(1, 24)=1.64, p>.2].  In contrast, individuals with ASD made more errors in the BX and BY conditions of the task, consistent with working memory difficulties [Main effect of group: Fs(1, 24)>8.90, p<.05].  Importantly, administration of propranolol was associated with improvements in working memory (i.e., decreased number of BX errors) for the ASD group but had no effect on performance in the control group [Group by Rx Interaction: F(1, 24)=5.53, p<.05].  Other aspects of task performance (e.g., inhibitory control as reflected by AY errors) were unaffected [p>.05 in all instances].

Conclusions: The present findings suggest that pharmacological treatment with propranolol may help individuals with ASD to overcome difficulties with executive control and context processing.  Additional research, however, is needed to better understand the neurophysiological mechanisms underlying this observed effect.

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