Impaired formation and updating of internal predictive models in a rat model of Fragile X Syndrome

Male Fmr1 KO rats detect deviant stimuli at wildtype levels but show reduced anticipation of deviant occurrence from cross-trial statistics and fail to update behavior when those statistics change.

• Why it matters: Sensory abnormalities in autism spectrum disorders are theorized to arise from an imbalance between top-down predictions and bottom-up signals, but separating these contributions in animal models is difficult.
• What they did: The study built a probabilistic oddball task that separately requires tracking local within-trial statistics and global across-trial statistics, then fit computational models to behavior in Fmr1 KO versus wildtype rats.
• The result: Modeling indicates overweighting of immediate sensory evidence and temporal response pressure over learned predictive expectations, implying imprecise internal models skewed toward sensory immediacy.

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