Biology subjects

Chong, T. T.- J.

Publications and source records attributed to Chong, T. T.- J..

4 recordsLinked to original sources

bioRxiv2025

Generalisation between motor and declarative memory sequences: A conceptual replication of Mosha & Robertson (2016)

Motor and declarative memory systems have been traditionally considered distinct. However, a study by Mosha and Robertson (2016) reported striking evidence of generalisation between motor and declarative learning. Specifically, learning improved if the current task (e.g. motor sequence) shared the same high-level ordinal structure as an earlier task (e.g. word list), demonstrating cross-domain transfer of unstable memories. This finding has significant implications for our understanding and conceptualisation of memory taxonomies but has not been replicated. Here, healthy adult participants (N = 125) completed a word list and motor sequence task in counterbalanced order with either a shared or distinct sequence structure. In contrast to Mosha & Robertson (2016), we found that a shared ordinal structure between the declarative and motor sequence tasks did not facilitate performance. Overall, our results challenge the robustness of cross-domain generalisation, and underscore the complexity of cross-memory interactions.

neuroscience↗

bioRxiv2025

Factor Analysis of Multimodal MRI, Biofluid and Vascular Health Biomarkers Reveals Latent Constructs of Brain Health

Individual imaging and fluid biomarkers provide insights into specific components of brain health, but integrated multimodal approaches are necessary to capture the complex, interrelated biological systems that contribute to brain homeostasis and neurodegenerative disease. Using data from the Brain and Cognitive Health (BACH) cohort study (N=127; mean age=67 years, 68% women), we performed an exploratory factor analysis to identify latent constructs of brain health. We included multimodal neurovascular imaging markers, brain atrophy metrics, plasma Alzheimers disease (AD) biomarkers and cardiovascular risk factors. Five constructs emerged: "Brain & Vascular Health" (greater hippocampal volume, basal ganglia enlarged perivascular spaces [ePVS], cerebral blood flow and HDL cholesterol; lower ventricle volume and BMI); "Structural Integrity" (greater cortical thickness, fractional anisotropy and basal ganglia ePVS); "Fluid Transport" (greater white matter ePVS and Free Water); "AD Biomarkers" (higher phosphorylated tau [pTau]181 and pTau217; lower amyloid-beta 42/40 ratio); and "Neuronal Injury" (higher glial fibrillary acidic protein and neurofilament light chain). All constructs were associated with age ({beta}=-0.70-0.39, p[≤].014), except for Fluid Transport (p>.05). Brain & Vascular Health and Structural Integrity (partial r=.305, p<.001), and AD Biomarkers and Neuronal Injury (partial r=.248, p=.005) were positively correlated. Only Brain & Vascular Health was associated with global cognition ({beta}=0.27, SE=0.13, p=.043). These findings provide a data-driven framework for examining distinct constructs underlying vascular health, fluid regulation and neurodegenerative pathology. We demonstrate the utility of using multiple biomarkers to probe these biological systems, paving the way for future research to explore how these systems change across diverse neurodegenerative conditions.

neuroscience↗

bioRxiv2024

Supplementary motor area disinhibition during motor sequence learning: A TMS-EEG study

BackgroundIn primary motor cortex, changes in excitatory and inhibitory neurotransmission (E:I balance) accompany motor sequence learning. In particular, there is an early reduction in inhibition (i.e., disinhibition). The supplementary motor area (SMA) is a key brain region involved in the learning of sequences, however the neurophysiological mechanisms within SMA which support motor sequence learning remain poorly understood. Disinhibition may also occur in SMA, but this possibility remains unexamined. ObjectiveWe investigated disinhibition within SMA during motor sequence learning using combined transcranial magnetic stimulation (TMS) and electroencephalography (EEG). MethodsTwenty-nine healthy adults practiced a sequential motor task. TMS-evoked potentials (TEPs) resulting from SMA stimulation were measured with EEG before, during, and after practice. The N45 TEP peak was our primary measure of disinhibition. Furthermore, the slope of aperiodic EEG activity was included as an additional E:I balance measure. ResultsSignificant improvements in task performance (i.e., learning) occurred with practice. We observed smaller N45 amplitudes during early learning relative to baseline (both p < .01), indicative of disinhibition. Intriguingly, aperiodic exponents increased as learning progressed and were associated with greater sequence learning (p < .05). ConclusionOur results show disinhibition within SMA during the planning phase of motor sequence learning and thus provide novel understanding on the neurophysiological mechanisms within higher-order motor cortex that accompany new sequence learning.

neuroscience↗

bioRxiv2023

Neurophysiological mechanisms underlying post-stroke deficits in contralesional perceptual processing

Slowed responding to sensory inputs presented in contralesional space is pervasive following unilateral cerebral stroke, but the causal neurophysiological pathway by which this occurs remains unclear. To this end, here we leverage a perceptual decision-making framework to disambiguate information processing stages between sensation and action in 30 unilateral stroke patients (18 right hemisphere, 12 left hemisphere) and 27 neurologically healthy adults. By recording neural activity using electroencephalography (EEG) during task performance, we show that the relationship between strokes in either hemisphere and slowed contralesional response times is sequentially mediated by weaker target selection signals in the contralateral hemisphere (the N2c ERP), and subsequently delayed evidence accumulation signals (the centroparietal positivity). Notably, asymmetries in CPP and response times across hemispheres are associated with everyday functioning. Together, these data suggest a plausible neurophysiological pathway by which post-stroke contralesional slowing arises and highlight the utility of neurophysiological assessments for tracking clinically relevant behaviour.

neuroscience↗