Neural substrates of numerosity estimation in autism

Abstract

Visual skills, including numerosity estimation are reported to be superior in autism spectrum disorders (ASD). This phenomenon is attributed to individuals with ASD processing local features, rather than the Gestalt. We examined the neural correlates of numerosity estimation in adults with and without ASD, to disentangle perceptual atypicalities from numerosity processing. Fourteen adults with ASD and matched typically developed (TD) controls estimated the number of dots (80-150) arranged either randomly (local information) or in meaningful patterns (global information) while brain activity was recorded with magnetoencephalography (MEG). Behavioral results showed no significant group difference in the errors of estimation. However, numerical estimation in ASD was more variable across numerosities than TD and was not affected by the global arrangement of the dots. At 80-120 ms, MEG analyses revealed early significant differences (TD > ASD) in source amplitudes in visual areas, followed from 120 to 400 ms by group differences in temporal, and then parietal regions. After 400 ms, a source was found in the superior frontal gyrus in TD only. Activation in temporal areas was differently sensitive to the global arrangement of dots in TD and ASD. MEG data show that individuals with autism exhibit widespread functional abnormalities. Differences in temporal regions could be linked to atypical global perception. Occipital followed by parietal and frontal differences might be driven by abnormalities in the processing and conversion of visual input into a number-selective neural code and complex cognitive decisional stages. These results suggest overlapping atypicalities in sensory, perceptual and number-related processing during numerosity estimation in ASD.

Distinctive Role of Symbolic Number Sense in Mediating the Mathematical Abilities of Children with Autism

“…Instead, we found that children with ASD were significantly impaired on a non-symbolic comparison task relative to their TD peers. This pattern is broadly consistent with previous studies on non-symbolic number sense in ASD which also failed to find superior quantity estimation in individuals with ASD (Meaux et al 2014; Titeca et al 2014; Turi et al 2015). While attention to local features may be beneficial in tasks requiring identification of individual items, such as the Navon Task (Muth et al 2014; Navon 1977), our results suggest that this skill does not translate to enhanced non-symbolic quantity processing in children with ASD.…”

Atypicalities in Perceptual Adaptation in Autism Do Not Extend to Perceptual Causality

“…This possibility can be tested using paradigms that tap non-social processes of high-level vision, for example, numerosity. Numerosity is supported by a composite of different processes, including basic perceptual and high-level brain networks (e.g., temporal and parietal regions; [ 49 , 50 ]). Findings that numerosity is subject to adaptation [ 51 ] are suggestive of a primary visual process, which is independent of mechanisms related to visual features, such as texture perception [ 52 ].…”

“…Findings that numerosity is subject to adaptation [ 51 ] are suggestive of a primary visual process, which is independent of mechanisms related to visual features, such as texture perception [ 52 ]. The ability to estimate numerosity in visual scenes is less likely to contribute to social abilities, and indeed anecdotal reports have suggested superior number sense abilities in autism (though see [ 50 ], for poorer abilities for large numerosity estimation in adults with autism). Preliminary results from our laboratory [ 53 ] suggest that adaptation to number is reduced with autism.…”

Numerical Estimation in Children With Autism

“…Only one other study has investigated nonsymbolic (numerosity) perception in autism [Meaux, Taylor, Pang, Vara, & Batty, ]. In the context of a magnetoencephalography (MEG) study, autistic ( n = 14) and typical ( n = 14) adults were asked to estimate verbally the number of dots in stimuli arranged in either a nonmeaningful or a meaningful (e.g., animal) way, presented for 1,000 ms each.…”