http://bura.brunel.ac.uk/handle/2438/256 2026-05-13T00:46:45Z 2026-05-13T00:46:45Z Pandya, Snehal P. http://bura.brunel.ac.uk/handle/2438/33206 2026-04-26T18:50:00Z 2025-01-01T00:00:00Z

Title: Effect of polygenic risk scores for Alzheimer's disease on brain structure, cerebrospinal fluid, and cognition Authors: Pandya, Snehal P. Abstract: Background: Apolipoprotein E (APOE) is the most studied gene in relation to, and has the strongest genetic association with, sporadic Alzheimer’s disease (AD). The APOE epsilon 4 (ɛ4) risk variant is found in approximately 14% of the general population and in approximately 37% of the AD population, globally. This indicates that the presence of ɛ4 is not required for the development of sporadic AD. In fact, sporadic AD is considered a polygenic disease with thousands of causative variants. Therefore, there is a need to investigate other genes and associated variants, and the concurrent effect of these on sporadic AD. Polygenic risk scores (PRSs) are ideal for this purpose as they consider multiple genetic variants/single nucleotide polymorphisms (SNPs) that have genome-wide significance, simultaneously. However, PRSs are difficult to calculate since numerous factors must be taken into consideration, and there is no optimal procedure. Nonetheless, PRSs can improve understanding of genotype-to-phenotype associations and risk predictions. Aim: The aim of the current research is to investigate whether PRSs for AD can predict cross-sectional regional grey matter volume (Experiment One), cross-sectional cerebrospinal fluid (CSF) biomarkers (Experiment Two Part A), cross-sectional cognitive markers (Experiment Two Part B), longitudinal CSF biomarkers (Experiment Three Part A), and/or longitudinal cognition (Experiment Three Part B) across the continuum of sporadic AD. Methodology: Participants from the Alzheimer's Disease Neuroimaging Initiative (n = 738; mean age in years: 73.94 ± 7.58) were analysed using various binomial hierarchical logistic regression models, and multiple hierarchical linear regression models, that controlled for numerous demographic and clinical variables. Participants were stratified by several variables to assess risk of AD in different groups. Three PRSs were constructed: PRSwithAPOE, PRSwithoutAPOE, and APOEonlyPRS. SNPs relating to APOE were from the entire APOE region, and three statistical thresholds were calculated for each of the three PRSs. Results: Overall, PRSwithAPOE and APOEonlyPRS were associated consistently with outcome measures. Generally, PRSwithAPOE and APOEonlyPRS were: associated negatively with bilateral hippocampus (right (R) > left (L)), bilateral amygdala (R > L), bilateral entorhinal area, and R middle occipital gyrus; associated positively with CSF amyloid-beta 42 (Aβ42) more than they were with CSF phosphorylated-tau181 (p-tau181), cross-sectionally; associated negatively with memory and visuospatial cognition, cross-sectionally; associated with CSF p-tau181 more than they were with CSF Aβ42, longitudinally; associated positively with longitudinal cognitive decline. Discussion: The results highlight that stratification by amyloid positivity improves risk prediction over stratification by clinical diagnosis. The findings also concur to previous literature indicating that CSF amyloid decreases early on in AD after which it reaches a plateau, whereas changes in tau continue throughout the disease. The current research presents a novel, systematic, and thorough approach to evaluate risk of sporadic AD, including: a multi-modal approach that assesses outcome measures that are used to diagnose individuals with AD clinically (i.e., brain structure, CSF biomarkers, and symptomology); the use of both cross-sectional and longitudinal study designs; a multi-stratification approach whereby participants are divided in several ways to assess risk in different groups – for some groups, findings have been reported for the first time (to knowledge). Conclusion: This work highlights the added value of non-ɛ4-APOE SNPs and non-APOE SNPs (i.e., both PRSwithAPOE and APOEonlyPRS) in detecting associations with AD-specific cross-sectional and longitudinal outcome measures. In parallel with existing literature, an ideal threshold has not been determined in the current research. However, it may be that certain thresholds identify associations better according to the outcome measure at hand. Additionally, the current research demonstrates the clinical relevance of PRSs for AD and that these may support diagnosis and prognosis of AD. It is recommended that future investigations assess PRSwithAPOE and APOEonlyPRS with longitudinal CSF biomarkers, in independent samples, and in ethnically diverse populations. Description: This thesis was submitted for the award of Doctor of Philosophy and was awarded by Brunel University London

2025-01-01T00:00:00Z Bennetts, RJ Butcher, N Lander, K http://bura.brunel.ac.uk/handle/2438/32717 2026-01-26T03:01:04Z 2025-10-30T00:00:00Z

Title: Consistent Eye Movement Patterns in Static and Dynamic Face Recognition: A Hidden Markov Model Study Authors: Bennetts, RJ; Butcher, N; Lander, K Abstract: Background/Objectives: Eye movements provide important insights into face processing. Hidden Markov models of eye movements (EMHMMs) are a relatively new approach that identifies common patterns across observers, moving beyond region-of-interest analyses. Prior EMHMM studies with static faces have typically revealed two strategies: a central “holistic” style and a feature-based “analytical” style. However, it is unknown whether such patterns extend to dynamic faces, which more closely reflect real-world viewing. This study is the first to apply EMHMMs to dynamic face recognition. Methods: Participants completed a face learning task in which half of the identities were presented as static images and half as dynamic videos. Eye movements were analysed using EMHMMs during both learning and recognition phases. Results: Two consistent patterns emerged across conditions: Central-focused and Eye-focused. A small subgroup displayed a third, central-plus-right-eye pattern when learning static faces. Eye movement patterns were largely stable across static and dynamic conditions, with only 16–27% of participants switching between them. Patterns were generally unrelated to recognition accuracy; however, participants adopting Eye-focused patterns during static learning performed better on static recognition. Conclusions: EMHMM-identified patterns generalise from static to dynamic faces, indicating strong stability in face-viewing behaviour across stimulus types. This finding contrasts with previous region-of-interest analyses suggesting greater differences between static and dynamic faces. By extending EMHMMs to dynamic faces, this study underscores the value of diverse analytical approaches for capturing eye movement behaviour and advancing understanding in face processing. Description: Data Availability Statement: The individual participant data on which study conclusions are based and a list of all the stimulus materials have been made publicly available on the Open Science Framework (see https://osf.io/xz2hr/).

2025-10-30T00:00:00Z King, Tavis Ryan http://bura.brunel.ac.uk/handle/2438/32397 2025-11-25T03:01:08Z 2025-01-01T00:00:00Z

Title: Taking pride from cultures of shame: The influence of cultural values on the development of internalised attitudes towards same-sex attraction in gay men across cultures Authors: King, Tavis Ryan Abstract: Theoretically, internalised homonegativity (IH-) has been studied by mainstream and lesbian, gay, bisexual, trans and queer (LGBTQ) psychology as an ill-defined individual difference investigated over several paradigms. Historically, psychology’s heterosexist bias has focussed on IH- as a pathologising construct for gay men, without considering how homopositive attitudes could be internalised. Moreover, cross-cultural research investigating gay men’s IH- is scant, and these few studies have not controlled for cultural values. Therefore, this thesis aims to address psychology’s heterosexism by introducing internalised homopositivity (IH+) alongside IH-, within a psycho-socio-cognitive theory of internalised attitudes towards samesex attraction (IASSA). Over three studies with multinational samples, crosssectional designs utilising hierarchical linear regressions (HLR) investigated the relationships between cultural values systems, parental acceptance-rejection, attachment styles and IASSA. 2,276 men sexually attracted to men were volunteer sampled via social media from Brazil, Ireland, Mexico, the United Kingdom and the United States. Each study’s participants completed questionnaire batteries. Study 1 found that conservatism was positively associated with IH- while egalitarianism was negatively associated. Study 2 revealed maternal acceptance was positively associated with IH-, while maternal rejection and paternal acceptance/rejection were not. Study 3 initially found English-speaking cross-cultural validity via exploratory factor analysis for IH+. Subsequent HLR analyses then evidenced high paternal religiosity moderated a negative association between avoidant attachment and IH+; avoidant attachment to mothers was negatively associated with IH+; and cultural masculinity was negatively associated with IH- for both parents across anxious/avoidant attachments. These unexpected results warrant further investigation, particularly the positive association between maternal acceptance and IH- and the negative association between cultural masculinity and IH-. Additionally, the IASSAQ supports future research with a greater unified and less pathologising psycho-social-cognitive IASSA model. Moreover, cross-cultural psychology can be reconciled with LGBTQ psychology. When applied, the IASSA model could help psychological practitioners support ashamed gay men to discover pride. Description: This thesis was submitted for the award of Doctor of Philosophy and was awarded by Brunel University London

2025-01-01T00:00:00Z Saifullah, Anam Hamid http://bura.brunel.ac.uk/handle/2438/31490 2025-06-25T02:01:10Z 2025-01-01T00:00:00Z

Title: The effects of meditation on attentional capacity, emotion regulation, and sensory information processing Authors: Saifullah, Anam Hamid Abstract: Emerging evidence suggests beneficial effects of meditation generally, and mindfulness meditation specifically, on mental health and well-being via improved cognitive functioning and emotion regulation. The exact mechanisms underlying these effects, however, are yet to be fully understood, which is an overarching aim of three related studies reported in the thesis. One possible mechanism facilitating both more efficient attentional processing and emotion regulation in meditators is reduced attentional capture by salient stimuli, quantified in the present research using Attentional Blink (AB) phenomenon - a temporary inability to consciously perceive an attended stimulus when it is shortly preceded by another. Previous research using AB paradigms with neutral and emotional stimuli (referred to as Neutral Attention Blink (NAB) and Emotional Attentional Blink (EAB) paradigms, respectively) has shown that meditation practice (particularly mindfulness as secularly defined) attenuates NAB. Lower NAB has also been associated with higher trait non-reactivity (an aspect of mindfulness), both dispositional (innate) and trained through meditation practice. Study 1 (online behavioural study) investigated the effects of meditation on AB using both the NAB and EAB paradigms in meditators (n = 75) and non-meditators (n = 54), as well as the relationships of NAB and EAB magnitude with each other and with trait non-reactivity and equanimity (non-attachment), with the latter being another aspect of mindful awareness that should attenuate attentional capture by salient (emotional) stimuli. There were no significant NAB or EAB differences between meditators and non-meditators. However, lower EAB was significantly associated with higher trait non-reactivity and equanimity in meditators as a group and in the meditator practicing mindfulness as secularly defined, suggesting that non-reactivity and equanimity might be attenuating EAB via reduced attentional capture by emotional stimuli. Another mechanism that has been proposed to underlie AB is ‘gating’ or filtering of the sensory stimuli as a way to protect the processing of the first stimulus, given limited attentional capacity resources. Sensory gating is a fundamental mechanism protecting limited attentional processing capacity by an automatic inhibition of subsequent stimuli whilst the current stimulus is being processed and has been extensively studied using Prepulse Inhibition (PPI) – a modulation of the startle reflex when a startling stimulus (pulse) is preceded by a stimulus of less intensity (prepulse). Study 2 (lab-based study) explored the relationships of PPI with AB (with the focus on NAB) as well as with trait non-reactivity and equanimity in a separate sample of meditators (n = 23) and non-meditators (n = 21). There were no significant PPI differences between meditators and non-meditators and no significant associations of PPI with trait non-reactivity or equanimity. However, higher PPI was significantly associated with slower reaction times during NAB paradigm performance. The implications of this finding for the shared (or similar) mechanisms underlying AB and PPI are not clear, but given that PPI is an index of sensorimotor gating, they point to the relationship between automated (PPI) and voluntary (NAB) motor aspects engaged by the two paradigms. Yet another mechanism by which non-reactivity and equanimity might exert their attenuating effect on AB is the reduced activation of associative semantic memory networks in response to conceptually meaningful and/or emotionally salient stimuli, which has been observed in meditators in previous research. Associative semantic memory networks activation, alongside attentional capture, has been proposed as one of the mechanisms underlying the Affective Priming (AP) phenomenon – an impact that a first stimulus (prime) has on the speed and evaluation of the subsequent stimulus (target). Study 3 (online behavioural study) investigated the effects of meditation on AP and its relationship with EAB as well as trait non-reactivity and equanimity in meditators (n = 49) and non-meditators (n = 55) (a subsample of Study 1 participants). Congruent (same valence of primes and targets) and incongruent (opposite valence of primes and targets) were used in the AP paradigm. As expected, meditators were less impacted by the emotional valence of the primes or their congruity/incongruity with the targets, whereas non-meditators (particularly females) showed a strong priming effect. The correlation pattern between AP and EAB was somewhat inconsistent. Lower AP was associated with higher trait non-reactivity and equanimity in meditators for incongruent condition, suggesting that smaller AP in meditators may be due to reduced activation by the primes of associative semantic networks. Together, the findings highlight trait non-reactivity and equanimity as the mechanisms underlying the effects of meditation generally, and mindfulness meditation specifically, on attentional capacity and emotion regulation via reduced attentional capture and semantic associative network activation by affective stimuli. Longitudinal studies using the AB, PPI, and AP paradigms are required to further investigate where the observed cross-sectional and correlational findings are the effects of meditation rather than pre-existing individual differences between meditators and non-meditations (and within meditators) with the view of developing particularly AB and AP paradigms as objective tools of meditation practice on attentional capacity and emotion regulation. Description: This thesis was submitted for the award of Doctor of Philosophy and was awarded by Brunel University London

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