Increased functional activity, bottom-up and intrinsic effective connectivity in autism.

Researchers used brain scans to study how autistic and non-autistic people process information during decision-making tasks. While both groups performed equally well, autistic participants showed more brain activity in several areas and stronger connections flowing from visual processing regions upward to thinking areas. This supports the idea that autistic brains may process sensory information differently, with more emphasis on incoming sensory details rather than using existing expectations to filter information.

This fMRI study examined brain activity patterns in autistic individuals and neurotypical controls during a decision-making task under uncertainty. While task performance was similar between groups, autistic participants showed significantly greater brain activation in multiple regions including the precuneus, occipital areas, cuneus, and superior frontal gyrus. Dynamic causal modeling revealed increased bottom-up connectivity from visual processing areas to higher-order brain regions in the autism group. These findings support theories proposing that sensory differences in autism result from increased bottom-up information flow relative to top-down control mechanisms, providing neurobiological evidence for altered sensory-cognitive processing patterns.

Findings suggest autistic individuals may benefit from interventions that account for increased bottom-up sensory processing. Understanding these neural differences could inform sensory-based therapies and environmental modifications to support sensory regulation and reduce overwhelm in autism.

Sample size not reported, limiting assessment of statistical power. Single-task paradigm may not generalize to broader sensory processing differences. Cross-sectional design prevents causal inferences about developmental patterns or intervention responses.

Sensory perceptual alterations such as sensory sensitivities in autism have been proposed to be caused by differences in sensory observation (Likelihood) or in forming models of the environment (Prior), which result in an increase in bottom-up information flow relative to top-down control. To investigate this conjecture, we had autistic individuals (AS) and neurotypicals (NT) perform a decision-under-uncertainty paradigm while undergoing functional magnetic resonance imaging (fMRI). There were no group differences in task performance and in Prior and Likelihood representations in brain activity. However, there were significant group differences in overall task activity, with the AS group showing significantly greater activation in the bilateral precuneus, mid-occipital gyrus, cuneus, superior frontal gyrus (SFG) and left putamen relative to the NT group.

Further, when pooling the data across both groups, we found that those with higher AQ scores showed greater activity in the left cuneus and precuneus. Effective connectivity analysis using dynamic causal modelling (DCM) revealed that group differences in BOLD signals were underpinned by increased activity within sensory regions and a net increase in bottom-up connectivity from the occipital region to the precuneus and the left SFG. These findings support the hypothesis of increased bottom-up information flow in autism during sensory learning tasks.