ADHD phenotypes and hindbrain function: an exploratory study using smartphone-based neurometric testing

Abstract

Attention deficit hyperactivity disorder (ADHD) affects approximately 1 in 23 adults nationwide. ADHD is characterized by impulsivity, hyperactivity, and inattention — symptoms which can impair social, academic, or occupational functioning. These symptoms are alleviated by lisdexamfetamine, also known as Vyvanse, one of many stimulant drugs used to treat ADHD in children and adults. Cerebellar and brainstem atypicalities have been associated with ADHD, but tasks probing cerebellar learning in individuals with ADHD, such as eyeblink conditioning, remain unexplored. In addition, prepulse inhibition of the startle reflex, a sensorimotor gating function, and startle habituation, which measures the ability for the intrinsic damping of repetitive stimuli, have also been relatively underexplored in individuals with ADHD. This study aims to probe the potential existence of an ADHD phenotype in neurobehavioral testing paradigms, including eyeblink conditioning, prepulse inhibition of the startle response, and startle habituation, and investigate possible effects of Vyvanse on ADHD subjects’ performance in neurobehavioral tests, all while using a smartphone-based neurobehavioral testing platform. The results of this study reveal statistically significant differences in CR amplitude and percentage of CRs, as well as a lack of startle habituation, between ADHD and neurotypical groups, suggesting the potential existence of an ADHD phenotype in eyeblink conditioning and startle habituation. These results support the use of mobile technology to perform reliable neurobehavioral testing for ADHD symptoms that is reliable, ecologically valid, and nonverbal.