Excessive audio–visual stimulation leads to impaired social behaviour with an effect on amygdala: Early life excessive exposure to digital devices in male rats

Today, the effect of extreme early‐life exposure to digital devices is suggested as a risk factor for neurodevelopmental disorders. However, the multitude of factors that influence brain development with subsequent behavioural abnormalities have not been fully elucidated. Herein, we simulated extreme early‐life exposure to digital devices in rats by audio and visual stimulation and investigated its effects on autism‐related behaviours and brain structural alteration. Male rat pups were exposed to excessive audio–visual stimulation (EAVS) from PND (post‐natal day) 12 to PND 35, with and without maternal separation (MS). Autism‐related behaviours including abnormal sociability, stereotype behaviours, anxiety and locomotor dysfunction were tested at PND 42. Brain structural alternation was examined by considering the amygdala, mPFC (medial prefrontal cortex) and hippocampal regions while performing 3D quantitative stereological analysis. We found that EAVS led to social behaviour deficit and higher locomotion in rats, which were associated with increases in the number of neurons and volume of the amygdala. We also showed that MS did not exaggerate the effect of extreme sensory stimulation on behaviour and the structure of the brain. This study proposed EAVS in rats as an animal model of early exposure to digital devices for investigating possible neurobiological alternations underlying autistic‐like behaviours with an emphasis on the amygdala area. In this study, we showed that rat pups exposed to excessive audio–visual stimulation (6 h/day) from PND 12 to PND 35 have abnormalities in brain structure in the volume of the region and number of the neurons in the amygdala and social behaviour deficits along with higher locomotor behaviour at adolescence, which are characteristic of autism spectrum disorders.