Robust perceptual-load-dependent audiovisual integration in adult ADHD

We perceive our daily-life surrounded by different senses (e.g., visual, and auditory). For a coherent percept, our brain binds those multiple streams of sensory stimulations, i.e., multisensory integration (MI). Dependent on stimulus complexity, early MI is triggered by bottom–up or late via top–down attentional deployment. Adult attention-deficit/hyperactivity disorder (ADHD) is associated with successful bottom–up MI and deficient top–down MI. In the current study, we investigated the robustness of the bottom–up MI by adding additional task demand varying the perceptual load. We hypothesized diminished bottom–up MI for high perceptual load for patients with ADHD. 18 adult patients with ADHD and 18 age- and gender-matched healthy controls participated in this study. In the visual search paradigm, a target letter was surrounded by uniform distractors (low load) or by different letters (high load). Additionally, either unimodal (visual flash, auditory beep) or multimodal (audiovisual) flanked the visual search. Linear-mixed modeling was used to investigate the influence of load on reaction times. Further, the race model inequality was calculated. Patients with ADHD showed a similar degree of MI performance like healthy controls, irrespective of perceptual load manipulation. ADHD patients violated the race model for the low load but not for the high-load condition. There seems to be robust bottom–up MI independent of perceptual load in ADHD patients. However, the sensory accumulation might be altered when attentional demands are high.