Browsing by Subject "attention"

Attention-deficit/hyperactivity disorder (ADHD) is a pervasive neurodevelopmental disorder of executive functions, which affects the social, occupational, educational, and personal life of the individuals concerned. The main characteristics of this disorder are age inappropriate inattention, impulsivity and hyperactivity. The research on adult ADHD is still scarce, especially concerning the neural networks of attention. Childhood ADHD has been associated with impairment in two of the attentional network subsystems alerting and executive control, leaving the third subsystem, orienting of attention, intact. Research on adult ADHD and the subsystems of attentional network is contradicting. The aim of this study was to investigate neural activation of these attentional networks during highly demanding attentional tasks in adults with ADHD. The first hypothesis was that the ADHD group have decreased activity in the frontoparietal network during orienting of attention in contrast to the control group. The second hypothesis was that the ADHD group have decreased activity in the dorsolateral prefrontal cortex, anterior cingulate gyrus, and precuneus during divided attention in contrast to the control group. Both the ADHD group and the control group included 16 participants, aged 25 – 56 across all participants, whose brain activation was measured with functional magnetic resonance imaging during the attentional tasks. The tasks included divided and selective attention. Both conditions included task-irrelevant novel distractors. The results supported both hypotheses. The ADHD group had decreased brain activity in the frontoparietal network during top-down controlled and bottom-up triggered attention. Decreased activation in the dorsolateral prefrontal cortex, anterior cingulate gyrus and precuneus was observed during divided attention in the ADHD group. Furthermore, the default-mode network was hyperactivated in the ADHD group. Activation of this network has been related to increasing task demands and failure of maintaining an alert state. Thus, adult ADHD seems to associate with abnormally functioning attention networks. Moreover, the results indicated that in addition to dysfunctional alerting and executive control, adults with ADHD have also impaired orienting of attention. These dysfunctional attentional networks may have a connection with the inattentive symptoms of adult ADHD.