ebook_ADHD2019

The World Federation of ADHD Guide 23 validity in distinguishing subjects with ADHD from controls. Stimulation of neu- ronal nicotinic acetylcholine receptors by nicotine may be mediated directly via changes of cholinergic neurotransmission and/or by modulating activity of other neurotransmitters including dopamine, which in turn has a recognized role in the neurobiology of ADHD (see section on dopamine above). Trials of nicotinic drugs demonstrated beneficial effects in adults with ADHD, with evidence for also posi- tive effects on cognitive and emotional domains, although there are no approved medications for ADHD that target nicotinic acetylcholine receptor function. 32 COGNITION For many years, cognitive research in ADHD has been dominated by theories about primary key cognitive impairment that would be causal to the development of the disorders (see Box 2.1). This was followed by theories about dual- and triple pathways models (see Box 2.1). Currently, there is consensus that ADHD is cha- racterized by a fragmented pattern of deficits in relatively independent cognitive domains. The classification of these cognitive domains varies by paper, but include inhibition, working memory, arousal, activation, response variability, temporal in- formation processing, memory span, processing speed, decision making and delay aversion. 33,34 We will review executive function and reward processing deficits in particular in more detail below (Box 2.1). EXECUTIVE FUNCTIONS  Executive functions (referred to as executive function and cognitive control) is a umbrella term for a set of cognitive processes that are necessary for the cognitive control of behaviour. Executive functions include basic cognitive processes such as attentional control, cognitive inhibition, inhibitory control, working memory, and cognitive flexibility. Higher order executive functions require the simulta- neous use of multiple basic executive functions and include planning and fluid in- telligence (i.e., reasoning and problem solving). Executive functioning deficits in ADHD are seen in inhibitory control, visuo-spatial and verbal working memory, vigilance, and planning. 41 RESPONSE INHIBITION Response inhibition is one aspect of cognitive control. Attention, behaviour, thou- ghts, and emotions are regulated through inhibition processes executing top-down cognitive control. Response inhibition specifically is the ability to control oneself