Impulsivity in humans: neurobiology and pathology

Impulsivity refers to premature behaviours and rash, poorly considered decisions which are made in spite of negative consequences. It is not a singular entity, consisting of a number of sub-categories under the two broad headings of motor and decisional impulsivity. The subtypes of motor impulsivity are laid out first, discussing waiting impulsivity, also known as premature responding, which can be a predictor of addiction, and response inhibition impulsivity, which is the capacity to inhibit pre-potent response. The chapter then explores the forms of decisional impulsivity, such as delay discounting and reflection impulsivity, along with their relation to attention-deficit/hyperactivity disorder. Finally, the prevalence of impulsivity across disorders as wide-ranging as obsessive–compulsive disorder and Huntington’s disease is discussed, and a case study of Parkinson’s-related impulsivity is presented.