Tunnel vision: sharper gradient of spatial attention in autism

Abstract

Enhanced perception of detail has long been regarded a hallmark of autism spectrum conditions (ASC), but its origins are unknown. Normal sensitivity on all fundamental perceptual measures-visual acuity, contrast discrimination, and flicker detection-is strongly established in the literature. If individuals with ASC do not have superior low-level vision, how is perception of detail enhanced? We argue that this apparent paradox can be resolved by considering visual attention, which is known to enhance basic visual sensitivity, resulting in greater acuity and lower contrast thresholds. Here, we demonstrate that the focus of attention and concomitant enhancement of perception are sharper in human individuals with ASC than in matched controls. Using a simple visual acuity task embedded in a standard cueing paradigm, we mapped the spatial and temporal gradients of attentional enhancement by varying the distance and onset time of visual targets relative to an exogenous cue, which obligatorily captures attention. Individuals with ASC demonstrated a greater fall-off in performance with distance from the cue than controls, indicating a sharper spatial gradient of attention. Further, this sharpness was highly correlated with the severity of autistic symptoms in ASC, as well as autistic traits across both ASC and control groups. These findings establish the presence of a form of "tunnel vision" in ASC, with far-reaching implications for our understanding of the social and neurobiological aspects of autism.

Figure 1.

Procedure used to map attentional gradients. A, Time course of one trial. Each trial began with a fixation cross followed by a brief cue that captured participants' attention to a discrete point on the horizontal meridian to the left or right of fixation. After a variable ISI (67, 135, or 210 ms), a target appeared briefly, on the same side of the screen as the cue. Simultaneously, a distractor circle was presented 180° from the target. Participants indicated whether the opening was on the top or bottom of the target. B, Stimulus locations and sizes. The numbers next to the possible target locations give their distances in degrees from the cue location.

Figure 2.

Sharper gradient of spatial attention in autism. A, Performance was measured as negative inverse efficiency scores [−1 × (reaction time/accuracy)]. To highlight the spatial gradient of attention for the purpose of the plot, performance scores were normalized by subtracting the mean performance for each combination of diagnosis and ISI. All statistics were calculated without this normalization being applied. In both groups, performance was better the closer the target was to the cue. This fall-off was much stronger in participants with ASC than controls, demonstrating a much sharper gradient of attentional enhancement. B, Sharpness of the gradient across ISIs. The slope of the attentional function increased with ISI in both groups. This effect was more pronounced in ASC, although the interaction between ISI and diagnosis did not reach significance. Error bar, SEM. *p < 0.05.

Figure 3.

Sharpness of the attentional gradient correlates with autistic symptoms and traits in both ASC and controls. A, ASC participants with higher ADOS scores (an interview-based measure of autistic traits) had sharper attentional gradients averaged across ISIs (p < 0.01). B, Across both groups (ASC, red; controls, blue), participants with higher AQ scores (a social survey-based measure of autistics traits) evidence sharper attentional gradients (p < 0.001).