We are in the final stage of a prospective longitudinal study of infants at familial risk for attentional deficit hyperactivity disorder (ADHD), originally designed and conducted with Judy Auerbach, Rivka Landau, Shoshana Arbelle, and Naama Atzaba-Poria. The present phase is done in collaboration with Ilan Disntein and Christopher Klein.

We will invite all the subjects that still remain in the study to the event-related potentials (ERP) lab for the purpose of studying different plausible neural sources of intrasubject variability (ISV) in reaction times at adolescence. ISV in reaction times is a promising endophenotype for ADHD and among the most robust hallmarks of the disorder. ISV, also known as increased response time variability (RTV) refers to inconsistency in an individual’s speed of responding to a task, including periodic instances of longer reaction times. Increased ISV is a stable and reliable feature of ADHD that correlates with ADHD symptom severity. A variety of accounts have been suggested regarding the brain mechanisms reflected in ADHD’s ISV. The ERP is an especially suitable methodology for studying the neural sources of ISV thanks to its excellent time resolution, especially when a trial-by-trial analysis strategy is adopted, which allows for continuous, millisecond-accurate tracking of the participant’s brain activity and behavioral performance. However, recent attempts in this direction have led to apparent contradictory findings. Some ERP findings suggest that ISV in ADHD is caused by dysfunctions in high-order brain areas, which fail to govern low-order sensory and motor brain areas. However, other research suggests that RT variability is related to more variable (noisier) ongoing neural fluctuations in ADHD at the more basic perceptual stages of processing. These findings are not necessarily mutually exclusive because they have been tested in separate samples and different tasks. Therefore, we will study these different plausible neural sources of ISV in the same sample of participants. Moreover, we will relate the behavioral and neural ISV to plausible genetic risk, based on specific dopamine polymorphisms that have been related to behavioral ISV as well as the interaction with environmental risk based on parents’ own ADHD symptoms, which might be reflected in parenting practices and household routines. The uniqueness of the present research lies in its ability to examine, in a prospective longitudinal design, the stability and developmental course of one of the most characteristic ADHD phenotypes.