How do we empathize with others? A mechanism according to which action representation modulates emotional activity may provide an essential functional architecture for empathy. The superior temporal and inferior frontal cortices are critical areas for action representation and are connected to the limbic system via the insula. Thus, the insula may be a critical relay from action representation to emotion. We used functional MRI while subjects were either imitating or simply observing emotional facial expressions. Imitation and observation of emotions activated a largely similar network of brain areas. Within this network, there was greater activity during imitation, compared with observation of emotions, in premotor areas including the inferior frontal cortex, as well as in the superior temporal cortex, insula, and amygdala. We understand what others feel by a mechanism of action representation that allows empathy and modulates our emotional content. The insula plays a fundamental role in this mechanism.

Faulty inhibition is theorized to be a central feature in attention-deficit/hyperactivity disorder (ADHD), but it remains unclear whether inhibitory impairments encompass both motoric and attentional domains. Further, characterization of inhibitory deficits in adults with ADHD is needed. We experimentally assessed adults who met diagnostic criteria for ADHD and a subgroup who had partially remitted. Diagnostic and Statistical Manual of Mental Disorders (4th ed.; American Psychiatric Association, 1994) subtype effects were also examined. Motoric inhibition was assessed with the antisaccade task, and attentional inhibition was assessed with the attentional blink (AB) task. Antisaccade results replicated prior findings of extended latencies and increased anticipatory saccades in ADHD. Errors, however, appeared to be epiphenomenal to ADHD as they were absent when symptoms had partially remitted. Anticipatory saccades appeared as potential core problems that remained even when symptoms had improved. Differential response patterns were found for predominantly inattentive and combined subtypes, with the latter showing increasing anticipatory movements with increasing fixation time. In the AB task, ADHD groups committed more errors but showed no convincing evidence of an abnormal blink. These results demonstrate clear effects on motoric inhibition but not attentional inhibition in adults with ADHD.

Studies of cognitive control in attention-deficit/hyperactivity disorder (ADHD) have emphasized the ability to suppress motor responses (i.e., behavioral inhibition) rather than the ability to actively suppress prepotent mental representations (i.e., cognitive inhibition). Further, working memory deficits are suspected in ADHD, yet their distinction from cognitive inhibition is unclear. Two hundred and eighty-eight adolescent and adult participants, 115 of whom met criteria for ADHD and 173 of whom were for non-ADHD comparison, completed a sentence processing task that required the suppression of an incorrect interpretation and a working memory task. The results failed to support cognitive inhibition problems in ADHD. Moreover, the ability to reanalyze sentences with a temporary misinterpretation was at least partially related to working memory performance. The results challenge a unitary inhibition problem in ADHD and suggest inhibition problems do not extend to cognitive suppression in this age range.

An important research question is whether Attention Deficit Hyperactivity Disorder (ADHD) is related to early or late stage attentional control mechanisms and whether this differentiates a nonhyperactive subtype ("ADD"). This question was addressed in a sample of 145 ADD/ADHD and typically developing comparison adolescents (aged 13-17). Attentional blink and antisaccade tasks were used to assay early and late stage control, respectively. ADD was defined using normative cutoffs to assure low activity level in children who otherwise met full criteria for ADHD. The ADD group had an attenuated attentional blink versus controls and ADHD-combined (ADHD-C). The effect was not produced using DSM-IV definition of ADHD-primarily inattentive type nor DSM symptom counts. ADHD-C showed greater weakness in response inhibition, as manifest in the antisaccade task. Combining tasks yielded an interaction differentiating group performance on the two tasks. KeywordsADHD; ADD; ADHD subtypes; response inhibition; attentional blink; antisaccade; adolescence In considering the nosology of ADHD subtypes, it may be informative to consider the adolescent period of development. Whereas ADHD often persists into adolescence (Barkley, Fischer, Smallish, & Fletcher, 2002;Mannuzza, Klein, & Moulton, 2003), developmental maturation tends to result in normative reductions in hyperactivity (and perhaps also impulsivity) in adolescence (Hart et al., 1994). Therefore, the profile of subtypes (if subtypes exist) would be expected to modify in adolescence. In adolescence, enduring cases of ADHD with marked hyperactivity/impulsivity may be more easily discriminated from cases marked by only transient hyperactivity/impulsivity during childhood. This may assist the effort to identify a refined non-hyperactive ADHD subtype (referred to herein as "ADD" for simplicity to distinguish it from DSM-IV's ADHD primarily inattentive type or ADHD-PI). Note that in DSM-III, "ADD without hyperactivity" was allowed to have impulsivity. In contrast, as operationalized in the present study the "ADD" group will be low on hyperactivity/impulsivity as a unitary dimension.Adolescence is a particularly important developmental context in which to consider neural networks and related cognitive problems involved in ADHD and/or ADD. Maturation and myelination of brain regions involved in cognitive control, particularly prefrontal cortex and frontal-subcortical networks, continues into late adolescence and beyond (Benes, 2001). This may be reflected in important anatomical differences between children and adolescents NIH Public Access (Krain & Castellanos, 2006; Shaw et al, 2006). Thus, adolescents may differ from both adults and children with regard to their neuropsychological profile of cognitive control (Casey, Jones, & Hare, 2008) and (Halperin & Schulz, 2006).This matters for assessing subtypes, because it has been unclear whether the DSM-IV captures a conceptual non-hyperactive ADHD type or "ADD". Some researchers have argued that ADD is a distinct disorder from A...

In this chapter, we review the body of work performed in our laboratory and reviewed in the literature that attempts to isolate different kinds of putative inhibitory control in relation to attention-deficit/hyperactivity disorder (ADHD) and, to a lesser extent, other forms of impulsive psychopathology. ADHD is a disorder usually identified in childhood but that is now known to also occur in adults. It is described clinically by two highly correlated but partially distinct symptom domains: inattention-disorganization (e.g., losing things, not paying attention, having difficulty staying on task) and hyperactivity-impulsivity. These domains in turn are used to define a primarily inattentive subtype (ADHD-PI), a primarily hyperactive-impulsive subtype (ADHD-PH), and a combined subtype that involves both inattention and hyperactivity-impulsivity (ADHD-CT). Another type of psychopathology that we discuss is borderline personality disorder, a syndrome marked by unstable and intense interpersonal relationships, extreme anger, fear of abandonment, and self-destructive and impulsive behavior. We also mention conduct disorder (extreme rule breaking and aggressive behavior in childhood) and antisocial personality disorder (extreme rule breaking, aggression, and indifference to the rights of others in adulthood). Finally, we mention substance use disorders (out-of-control use of alcohol or illicit drugs).We present convergent evidence using multiple approaches to suggest that in parsing psychopathology, it is important to distinguish several kinds of inhibitory control, in particular effortful versus reactive control and motor response suppression versus interference control. We come to the following four conclusions:1. ADHD is related to problems in the effortful suppression of motor responses independently of a wide range of co-occurring symptoms and disorders.

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