Multisensory Selective Attention: Evidence of Enhanced Performance Facilitation in ASD with the Introduction of Distractor-Target Intervals

Background: The temporal coincidence of two stimulus events in two different modalities is automatically integrated by the brain of typically developing individuals (TD) even if one of the stimuli is irrelevant to the task at hand. This multisensory integration leads to patterns of behavioral performance (reaction time: RT) that are relatively predictable and related to temporal characteristics of the stimuli to be integrated (e.g. the temporal window of integration). In contrast, individuals with autism spectrum diagnoses (ASD) may show temporal binding deficits (e.g. Brock, et al., 2002; Molholm, et al, IMFAR 2008) and greater performance benefits when provided with more time to process stimuli (e.g. Landry et al., in press; Russo et al., IMFAR, 2008). Here we assay multisensory selective attention abilities in ASD and TD individuals in cases where the target (e.g. visual) and distractors (e.g. auditory) could occur simultaneously or at a delay of 450m.

Objectives: To examine the ability of ASD individuals to selectively attend to one modality (e.g. visual) in the presence of distractors from a different modality (e.g. auditory) and to test the effects of a 450ms delay between the distractor and the target on performance.

Methods: 13 ASD and 13 IQ, gender, and handedness matched TD persons completed a RT multisensory selective attention task.  Participants had to detect the spatial location (left or right) of targets in one modality (e.g. visual) in the presence of distractors from a different modality (e.g. auditory). The distractors and target could either be spatially congruent (both were presented on the same side) or incongruent (presented to opposite sides). Targets and distractors could occur either simultaneously or with a 450ms delay between the presentation of the distractors and the subsequent presentation of the target. Distractors were presented on 90% of trials, whereas 10% of trials included no distractor so that comparisons could be made to unisensory attention. The dependent measure was reaction time (RT).

Results: When targets and distractors were presented simultaneously, performance was similar between the groups. However, significant group differences emerged in the delay conditions. When targets were visual, the presentation of an auditory distractor 450ms prior to the target slowed the performance of TD participants by approximately 120ms, but facilitated the performance of the ASD group by 75ms.  When targets were auditory, the presentation of a visual distractor 450ms prior to the target improved the performance of both groups but the improvements in the ASD group were greater by 150ms than in the TD group.

Conclusions: The pattern of performance between participants with ASD and TD persons were similar when targets and distractors were presented simultaneously, but ASD individuals demonstrated greater performance gains in delay conditions than TD participants. These findings support the notion of a longer temporal window of multisensory integration in ASD and will be discussed with respect to theories of cognitive and perceptual processing in ASD.