Early-Stage Vision and Perceptual Imagery in Autism Spectrum Conditions

Abstract

Autism spectrum conditions (ASC) are characterized by multifaceted alterations in visual perception and mental imagery. However, the interaction between early-stage visual perception and imagery has not been explored. We recruited 40 individuals with ASC and 20 neurotypical control volunteers to participate in a lateral masking task. Participants detected a luminance-contrast target pattern (Gabor patch) flanked by two collinear masks. The flanking masks inhibit target detection at small target-mask distances and facilitate target detection at intermediate target-mask distances. In the perceptual task, the masks appeared adjacent to the target. In the imagery task, participants imagined the masks immediately after seeing them. Results revealed that individuals with ASC characterized by exceptional visuoconstructional abilities (enhanced Block Design performance; n = 20) showed weaker inhibition at small target-mask distances and stronger facilitation at intermediate target-mask distances relative to the controls. Visual imagery was markedly dampened in ASC regardless of the visuoconstructional abilities. At the behavioral level, these results indicate increased facilitation via lateral connections in the primary visual cortex (V1) of individuals with ASC who exhibit exceptional visuoconstructional abilities, together with less efficient mental imagery.

Keywords: autism; early vision; lateral masking; mental imagery; perception.

Figure 1

Illustration of experimental stimuli. A low-contrast, central Gabor patch (target) was flanked by two lateral masks at three different target-mask distances (1λ, 3λ, and 6λ). Contrast threshold was measured for the target. At short target-mask distances (1λ), masks inhibit target detection (higher contrast threshold is needed for detection), at intermediate target-mask distances (3λ) masks facilitate target detection (lower contrast threshold is needed for detection), whereas at long target-mask distances (6λ) masks have a negligible effect.

Figure 2

Mean log-contrast threshold (95% confidence intervals) in people with autism spectrum conditions (ASC) exhibiting a Block Design peak performance (ASC Peak), an average Block Design performance (ASC Non-Peak), and neurotypical (non-autistic) control volunteers. In this condition, a single Gabor stimulus was presented without masks. There were no statistically significant between-group differences (p > 0.5).

Figure 3

Mean log-contrast threshold changes (masks present minus isolated target stimuli). Error bars denote 95% confidence intervals. Negative values indicate facilitation by masks (lower contrast threshold for the target when the masks are presented relative to an isolated target). Perception: *Contrast threshold changes were significantly lower in the ASC Peak group (people with ASC exhibiting a Block Design peak performance) relative to the control individuals at 1λ and 3λ [Tukey’s Honestly Significant Difference (HSD) tests, ps < 0.01]. Imagery: ⁺The ASC Peak and ASC Non-Peak (people with autism spectrum disorders exhibiting an average Block Design performance) groups showed weaker inhibition at 1λ (lower contrast threshold changes) and weaker facilitation (higher contrast threshold changes) at 3λ relative to the controls (Tukey’s HSD tests, ps < 0.01).

Figure 4

Correlations between contrast threshold changes and Block Design Scores at different target-mask distances in the perception task in individuals with ASC exhibiting a Block Design peak performance (n = 20). A significant relationship was found at 3λ (partial r = −0.65, p < 0.01).