Multisensory Integration in ADHD: A Behavioral and EEG Investigation in Youth and Adults

In daily life, we are constantly bombarded with sensory information from multiple sources. Our ability to combine these cues into a single perceptual experience is known as multisensory integration. This process can be disrupted in neurodevelopmental conditions, such as autism spectrum disorder and dyslexia, affecting cognitive functions and language. Multisensory integration may be affected in attention-deficit/hyperactivity disorder (ADHD), though findings are conflicting. To explore these discrepancies, we conducted a meta-analysis to appraise the current state of the literature, elucidate observed inconsistent findings, and identify gaps in ADHD research. Then, we conducted studies to investigate multisensory integration in youth and adults with and without ADHD using behavioural tests and electroencephalography (EEG).\nIn the first study, youth (ages 6-17) with ADHD (n=53) and without ADHD (n=60) completed tasks such as the Sound-Induced Flash Illusion (SIFI), McGurk task, and a speech-in-noise task. No group differences were found in the SIFI, but ADHD youth showed reduced susceptibility to the McGurk illusion compared to neurotypical (NT) youth. The speech-in-noise task revealed no differences in multisensory gain, though hyperactive-impulsive traits were negatively related to phoneme accuracy.\nIn the second study, youth (ages 8-17) with ADHD (n=30) and without ADHD (n=23) performed a speeded-response time task while EEG recorded their responses to auditory, visual, or combined stimuli. No differences in multisensory gain were found, but ADHD youth showed delayed integration in occipital regions.\nIn the third study, adults (ages 18-59) with ADHD (n=32) and without ADHD (n=32) completed perception-matched and stimulus-matched detection tasks. ADHD adults showed higher response-time gain in the perception-matched task but no differences in the stimulus-matched task. EEG revealed differences in multisensory integration in frontal and occipital regions, more pronounced in the perception-matched task, possibly due to task difficulty or controlled unisensory perception.\nOverall, our findings suggest that ADHD affects multisensory integration, influenced by task demands and age. This is important because multisensory integration supports the development of higher-order cognitive functions and language, and challenges with multisensory integration may impact these processes. Future research in ADHD should investigate multisensory integration across development, the relationship between attention and integration, and multisensory integration and cognitive functioning.