Irrelevant stimulus processing in ADHD: catecholamine dynamics and attentional networks

Abstract

A cardinal symptom of attention deficit and hyperactivity disorder (ADHD) is a general distractibility where children and adults shift their attentional focus to stimuli that are irrelevant to the ongoing behavior. This has been attributed to a deficit in dopaminergic signaling in cortico-striatal networks that regulate goal-directed behavior. Furthermore, recent imaging evidence points to an impairment of large scale, antagonistic brain networks that normally contribute to attentional engagement and disengagement, such as the task-positive networks and the default mode network (DMN). Related networks are the ventral attentional network (VAN) involved in attentional shifting, and the salience network (SN) related to task expectancy. Here we discuss the tonic–phasic dynamics of catecholaminergic signaling in the brain, and attempt to provide a link between this and the activities of the large-scale cortical networks that regulate behavior. More specifically, we propose that a disbalance of tonic catecholamine levels during task performance produces an emphasis of phasic signaling and increased excitability of the VAN, yielding distractibility symptoms. Likewise, immaturity of the SN may relate to abnormal tonic signaling and an incapacity to build up a proper executive system during task performance. We discuss different lines of evidence including pharmacology, brain imaging and electrophysiology, that are consistent with our proposal. Finally, restoring the pharmacodynamics of catecholaminergic signaling seems crucial to alleviate ADHD symptoms; however, the possibility is open to explore cognitive rehabilitation strategies to top-down modulate network dynamics compensating the pharmacological deficits.

Aberrant neural networks for the recognition memory of socially relevant information in patients with schizophrenia

“…Among the 36 independent components, 13 were found to be artifacts or noises upon visual inspection. Thus, 23 components were identified as anatomically and functionally meaningful networks, which was in accordance with previously reported networks (Aboitiz, Ossandon, Zamorano, Palma, & Carrasco, 2014; Green, Kraemer, Fugelsang, Gray, & Dunbar, 2010; Kahnt, Chang, Park, Heinzle, & Haynes, 2012; Kotz, Cappa, von Cramon, & Friederici, 2002; Mohanty et al., 2007; Nekovarova, Fajnerova, Horacek, & Spaniel, 2014; Nocchi et al., 2012; Rosazza et al., 2014; Spreng, Sepulcre, Turner, Stevens, & Schacter, 2012; Turken & Dronkers, 2011; Uddin, Clare Kelly, Biswal, Xavier Castellanos, & Milham, 2009; Wu, Liu, Hallett, Zheng, & Chan, 2013). …”

Altered intrinsic organisation of brain networks implicated in attentional processes in adult attention-deficit/hyperactivity disorder: a resting-state study of attention, default mode and salience network connectivity

“…We based our analyses on the model of the SN as a between-network switching hub, as proposed by Menon and Uddin [15], which is differentiated from the attentional networks. Hence, we separated the SN, comprised of bilateral insula and anterior cingulate cortex (ACC), from the VAN-DAN system [53,64]. The finding of a stronger SN-DAN anti-correlation in the control group, as well as a trend towards SN-VAN hyperconnectivity in the ADHD group, suggests a decreased brain network functional differentiation and adds to the frameworks where deficits in between brain networks balance are proposed to underlie ADHD.…”

Salience network coupling is linked to both tobacco smoking and symptoms of attention deficit hyperactivity disorder (ADHD)

“…Relative to healthy adolescents, those with ADHD show reduced RAI scores and decreased SN-ECN connectivity (Cai et al, 2015; von Rhein et al, 2017). One hypotheses suggests that individuals with ADHD have an immature SN which may contribute to both a lack of proper task preparation and over-activation of the SN resulting in impulsivity (Aboitiz et al, 2014), which is a common trait noted in those with a substance abuse disorder (Belin et al, 2008). Further, adults with ADHD have been found to have enhanced SN connectivity with other brain regions such as the putamen, which the author interprets as contributing to enhanced sensitivity to external stimuli (Dongchuan, 2013).…”