Brain Activation Changes In Autism During Learning In a Spatial Working Memory Task

Background: Impaired learning in autism has been studied behaviorally in several tasks (e.g. Mostofsky et al., 2000; Plaisted et al., 1998). Although numerous studies have examined learning-related changes in brain activation in neurotypical individuals (see Kelly and Garavan, 2005 for a review), few have examined learning-related brain activation changes in autism. Two studies have shown that the decreases in activation with learning are smaller or non-existent in autism, compared to neurotypical participants (Müller et al., 2004; Schipul et al., under review). These findings suggest that fundamental brain mechanisms of learning may be deficient in individuals with autism.

Objectives: This fMRI study investigated whether there are learning-related brain activation atypicalities in individuals with autism over the course of learning the locations of objects.

Methods: 13 high-functioning adult individuals with autism and 13 age and IQ matched neurotypical individuals learned the locations of 10 objects around the perimeter of a circle. The experiment began with a pretest, consisting of one block each of Passive Viewing and Recall. In the Passive Viewing block, participants viewed the objects as they were exposed at their locations, one at a time, for 2500 ms each. The Recall block followed to behaviorally assess the participants’ knowledge of the objects’ locations. Following the pretest was the training session, which consisted of 6 Training blocks of a working memory recall task. In each Training block participants decided whether or not the location of the currently-presented object was adjacent to the object shown on the previous trial, a working memory demand that recruits frontal regions which often have atypical activation in autism. Following the training session was the posttest, which consisted of one Passive Viewing block and one Recall block. The entire run of the pretest, training, and posttest was repeated later in the scanning session with a new set of 10 different objects. Behavioral performance and brain activation were compared before and after learning within and between experimental sessions.

Results: Both groups showed significant decreases in activation across 6 blocks of Training in frontal, temporal, parietal, and occipital regions. However, between the pretest and posttest Passive Viewing blocks, the autism group showed a significantly smaller decrease in activation in frontal, temporal, and parietal regions relative to the neurotypical group. The behavioral data showed that both groups improved at the task as they learned and the performance was comparable between the two groups throughout the experiment.

Conclusions: The autism participants showed the typical learning-related decreases in brain activation across Training blocks, but failed to do so during Passive Viewing blocks. These findings suggest that the learning-related brain activation of individuals with autism may be typical during the acquisition of a skill, but atypical during passive visual encoding in the context of new knowledge.