Biological sex and age as key biological factors in sensory processes in persons with ASD.
Autism is a neurodevelopmental disorder characterized by atypical social behaviors and restricted and repetitive interests. A central feature is divergent sensory processing, which conditions perception and response to the environment depending on the context.
These manifestations vary throughout development and differ according to biological sex, which in females may mask symptoms and delay diagnosis:
The theory of predictive coding helps to understand these differences. Our brain generates predictions about the environment and corrects its models when something does not match what is expected. In this framework, we distinguish three key processes:
- iRS: repetition suppression, when regular stimuli reduce the neuronal response.
- iPE: prediction error, additional activation in the face of unexpected stimuli
- iMM: global index combining both mechanisms.
In autism, it has been proposed that these mechanisms are less flexible, leading to atypical perception, increased sensitivity to the unexpected, and a preference for stable routines.
In our laboratory we use a model of prenatal exposure to valproic acid, a drug associated with increased risk of autism in humans. With it we studied how male and female rats, in adolescence and adulthood, process regular and unexpected sounds.
The results show that valproic acid alters the neuronal response in the inferior colliculus, the first brain region that encodes environmental regularity. Moreover, these alterations are sex- and age-dependent: adolescent males and females showed a reduced iMM, whereas adult females exhibited an increased iMM.
These findings highlight the importance of subcortical mechanisms of predictive coding in autism-like conditions, and reveal that gender and age are key factors in understanding clinical and sensory heterogeneity within the autism spectrum.
