Monday, 22 February 2016

Atypical Spatial Attention in Those with a High Level of Self-reported Autistic Traits

Dunn, S., Freeth, M., Milne, E. (in press). Electrophysiological Evidence of Atypical Spatial Attention in Those with a High Level of Self-reported Autistic Traits. Journal of Autism and Developmental disorders, doi: 10.1007/s10803-016-2751-3

 by Stephanie Dunn

Article Summary:

Atypical attention is one of the earliest identifiable characteristics of autism spectrum conditions (ASC) and work has shown that differences in attention also correlate with autistic traits in the general population.  The current project was driven by a motivation to understand the brain basis of attention in ASC and to describe neural characteristics associated with autistic traits.  

We carried out studies to see whether those who report high levels of autistic traits, but no clinical diagnosis of ASC, demonstrate atypical neural correlates of attention. Autistic traits can be measured with an existing questionnaire which asks the participants a series of questions about different social and communication preferences (Autism Quotient - AQ). The AQ gives a score on a scale from 0-50, with everybody showing a certain level of autistic traits, extending from the existing idea of an ASC spectrum. 

The typical visual scene is cluttered with goal relevant objects and irrelevant distracting objects; we can access the mechanisms underlying efficient performance in this situation by using a visual search task. Work has shown that those with an ASC perform well on tasks of visual search; better than their typically developing peers. If those with high levels of autistic traits are also processing a visual scene in a different way, we might expect to see altered correlates of attention; specifically in this case, spatial attention and the processing of targets and distracters. 

We used a task in which participants had to tell whether a letter T was upright or inverted. This task was specifically designed to elicit the brain signal of interest; a component recorded using electroencephalography (EEG), termed the N2pc. The N2pc reflects processes that occur to select a target in space and complete a visual search task. In a second study we also recorded the two subcomponents of the N2pc; the NT and PD, which reflect the actual selection of the target (NT) and the suppression of distracters (PD).

We found a significantly larger N2pc in those with high levels of autistic traits. There was no difference in the amplitude of the NT, but PD amplitude was significantly reduced in the participants with high levels of autistic traits. These results suggest that the allocation of spatial attention differs in those with high levels of autistic traits compared to those with fewer autistic traits; and those with high levels of autistic traits do not appear to suppress irrelevant distracters in a visual array.   

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