The role of pre-sleep arousal and frontoparietal circuitry in ADHD: a dimensional approach

Smullen, Daniel Justin (2025). The role of pre-sleep arousal and frontoparietal circuitry in ADHD: a dimensional approach. University of Birmingham. Ph.D.

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Abstract

Attention Deficit Hyperactivity Disorder (ADHD) is a neurodevelopmental disorder currently estimated to be diagnosed globally in around 3.1% in adults and 8% in children and adolescents (Ayano, Demelash, et al., 2023; Ayano, Tsegay, et al., 2023). The primary diagnostic trait of ADHD is impeded executive functioning, and symptoms negatively impact across multiple facets of day-to-day life including familally, socially, educationally and vocationally (Luo et al., 2019). One executive function which is impaired in ADHD is response inhibition (Penadés et al., 2007; Pievsky & McGrath, 2018; Willcutt et al., 2005; Wright et al., 2014). Response inhibition relies on recruitment of the left intraparietal sulcus (IPS), and its recruitment in ADHD is dictated on a specific frontoparietal functional circuitry between the inferior frontal gyrus (IFG) and the IPS (Kolodny et al., 2017, 2020). Chapter 2 investigates the role of white matter structure underpinning this frontoparietal circuitry in ADHD and its role in impaired response inhibition, finding that individual differences in the structural properties of the IPS-IFG circuit, including tract volume and diffusivity, were linked to IPS activation and even predicted response inhibition performance outside the scanner. These findings highlight the structural-functional coupling of the IFG-IPS circuit in response inhibition in ADHD and suggest a structural basis for maladaptive functional top-down control in deficient inhibition in ADHD. Building upon these findings, chapter 3 investigated the impact of lIPS inhibition via continuous theta-burst transcranial magnetic stimulation (cTBS) on response inhibition. I report that the disruption to response inhibition by lIPS inhibition is increased in individuals with greater ADHD traits, which may reflect individuals with greater ADHD traits may having reduced compensatory mechanisms or the complex relationship between TMS and activation state in the targeted region may also explain our these findings, such as ADHD-related differences in ongoing lIPS activity or increased cognitive load in the disorder.

Type of Work:

Thesis (Doctorates > Ph.D.)

Award Type:

Doctorates > Ph.D.

Supervisor(s):