Effects of Disrupted Neural Circuitry on Learning Processes in Autism

Background: Learning is a network process that requires the integration of several distinct brain regions. Therefore, it is unsurprising that studies have reported impaired behavior and atypical brain activation patterns during learning in autism, which has been characterized as a disorder of brain connectivity. For example, a recent fMRI study revealed that participants with autism did not show the same changes in brain activation with learning as did neurotypical participants (Schipul et al., in press). Furthermore, the participants with autism had lower functional connectivity than neurotypical participants throughout the learning process. These results suggest that neural processing during learning in autism may be affected by disrupted brain circuitry. To clarify the extent to which neural circuitry affects the learning process in autism, we sought to compare learning during two tasks that vary in their reliance on a distributed network of regions. Dot pattern prototype learning is a complex task requiring the integration of a distributed network of brain regions and has shown behavioral impairments in autism. Paired associate learning of words requires a limited network of areas and has shown intact performance in autism.

Objectives: This fMRI study examined the brain activation patterns after learning to determine whether neural learning processes are only atypical in autism in tasks recruiting a distributed network, thereby implicating disrupted neural circuitry.

Methods: Participants include adults with autism spectrum disorders and neurotypical participants matched on age and IQ. The study includes two learning paradigms: (1) Implicit learning of dot pattern prototypes and (2) Explicit paired associate learning of words. Participants were trained outside the scanner on one set of stimuli for each task. After training, brain activation was measured during task performance on the trained items they had practiced earlier, as well as on untrained items. Brain activation was compared between task performance on the trained and untrained items to determine if the neural learning process could extend to novel stimuli. This contrast was compared between the Implicit task and the Explicit task, and between the autism participants and the neurotypical participants.

Results: Preliminary results with 10 participants in each group suggest that the autism group showed increased activation for the untrained items relative to the trained items in the Implicit task, reflecting the recruitment of increased resources for the novel stimuli. The neurotypical participants did not show this effect. These findings suggest that the learning process was specific to the trained stimuli in the autism participants, while it extended to novel stimuli in the neurotypical participants. This effect occurred in the Implicit task, which required the integration of many distinct brain regions. However, in the Explicit task, both groups showed a similar neural response for the trained and untrained items, reflecting intact neural processing in autism during learning of a less distributed task.

Conclusions: These preliminary findings suggest that individuals with autism show restricted neural adaptations during learning of an Implicit task requiring the integration of several distinct brain regions, but not during an Explicit task relying on a limited network.