Attention-deficit disorder (attention-deficit/ hyperactivity disorder without hyperactivity): A neurobiologically and behaviorally distinct disorder from attention-deficit/hyperactivity disorder (with hyperactivity)

Abstract

Most studies of attention-deficit/hyperactivity disorder (ADHD) have focused on the combined type and emphasized a core problem in response inhibition. It is proposed here that the core problem in the truly inattentive type of ADHD (not simply the subthreshold combined type) is in working memory. It is further proposed that laboratory measures, such as complex-span and dual-task dichotic listening tasks, can detect this. Children with the truly inattentive type of ADHD, rather than being distractible, may instead be easily bored, their problem being more in motivation (under-arousal) than in inhibitory control. Much converging evidence points to a primary disturbance in the striatum (a frontal-striatal loop) in the combined type of ADHD. It is proposed here that the primary disturbance in truly inattentive-type ADHD (ADD) is in the cortex (a frontal-parietal loop). Finally, it is posited that these are not two different types of ADHD, but two different disorders with different cognitive and behavioral profiles, different patterns of comorbidities, different responses to medication, and different underlying neurobiologies.I join the growing chorus of those who argue that attention-deficit/hyperactivity disorder (ADHD) of the "truly" inattentive subtype (what I will call "attention-deficit disorder" [ADD]) is a different disorder from ADHD where hyperactivity is present (e.g

Neurocircuitry Underlying the Preferential Sensitivity of Prefrontal Catecholamines to Low-Dose Psychostimulants

“…Consistent with this, drugs used to treat ADHD, including psychostimulants, SNRIs and a 2 -receptor agonists, improve an array of PFCdependent processes (Chamberlain et al, 2007;Diamond, 2005;Mehta et al, 2001;Turner et al, 2005). Neurochemically, low and clinically relevant doses of MPH preferentially increase extracellular levels of NE and DA within the PFC relative to other cortical and subcortical regions (for review, Berridge and Devilbiss, 2011).…”

Testing Computational Models of Dopamine and Noradrenaline Dysfunction in Attention Deficit/Hyperactivity Disorder

“…Nevertheless, it is clear that ADHD is not a unitary disorder Nigg and Casey, 2005;Diamond, 2005), and other behavioral symptoms of ADHD are not easily explained by the reduced DA hypothesis. For example, ADHD participants typically show more withinsubject variability in their reaction times (Leth-Steensen et al, 2000;Lijffijt et al, 2005;Castellanos et al, 2005).…”

Attentional blink in children with attention deficit hyperactivity disorder

“…[5][6][7][8] However, major difficulties appear in tasks that require sustained attention, or attentional control and redirection of attention. 5,8,9,12 Most studies with groups of children, adolescents, and adults with ADHD which used the RSVP paradigm have shown that these participants exhibit a powerful AB effect as compared with controls.…”

“…4,5 However, they usually exhibit difficulties in voluntary processes, such as redirecting attention to new stimuli, sustaining their attentional level or, in some tasks, with persevering. [5][6][7][8] Many studies have investigated selective visual attention (i.e., the ability to focus on relevant stimuli while ignoring irrelevant distractors) in children, adolescents, and adults with ADHD. Some of this research indicates that, although ADHD children may be distracted by irrelevant stimuli, they are no more affected than are controls.…”