Biology subjects

Leon-Correa, E.

Publications and source records attributed to Leon-Correa, E..

3 recordsLinked to original sources

bioRxiv2026

Causal Evidence for Left DLPFC Contributions to Working Memory, Attention, and Cognitive Control in Ageing: A cTBS/ERP Study

Ageing is characterised by progressive neurodegeneration and marked declines in working memory (WM), a domain critically dependent on the integrity of the dorsolateral prefrontal cortex (DLPFC). Although non-invasive brain stimulation is widely used to target this region, the causal contribution of the DLPFC to WM performance in older adults remains insufficiently understood. Here, we applied continuous theta burst stimulation (cTBS) to transiently inhibit the left DLPFC in twenty healthy older adults and assessed the behavioural and neurophysiological consequences during verbal and visuospatial N-back tasks. Behaviourally, moderate learning effects emerged exclusively in the verbal task following vertex stimulation, whereas learning after DLPFC stimulation remained inconclusive. Performance in the visuospatial task showed no reliable evidence of learning across conditions, consistent with greater interindividual variability and age-related decline in spatial WM. Neurophysiologically, ERP amplitudes were stable across conditions; however, marked latency perturbations were observed. In the verbal task, P200 and N200 latencies robustly predicted performance, with P200 latency significantly prolonged after DLPFC inhibition, indicating disrupted early attentional gating. N200 and P300 latency modulations further suggested load-dependent compensatory strategies, reflecting adaptive slowing of cognitive control processes. In contrast, visuospatial performance was not reliably predicted by P200 latency, although N200 and P300 latencies remained informative, indicating domain-specific differences in DLPFC involvement. Taken together, these findings provide causal evidence that left DLPFC disruption selectively interferes with the temporal coordination of verbal WM, emphasising the central role of processing speed and compensatory dynamics in cognitive ageing. ERP latency markers emerge as sensitive indices of subtle stimulation-induced perturbations in older adults.

neuroscience↗

bioRxiv2025

Balancing Efficiency and Compensation: Age-related Theta and Alpha Dynamics in High-load Working Memory

Working memory (WM) declines with age, yet older adults often preserve performance through compensatory mechanisms. Oscillatory dynamics in the theta and alpha bands are central to these adaptations, but their distinct roles across maintenance, manipulation, and recall remain unclear. We examined behavioural and neural differences in WM using electroencephalography (EEG) during verbal (Letter Span) and visuospatial (Corsi Block) tasks under retention and manipulation conditions. Behaviourally, older adults preserved performance in the Letter Span but showed deficits in the Corsi Test, suggesting domain-specific declines, while higher task demands reduced accuracy across both groups. At the neural level, younger adults exhibited stronger mid-frontal and temporal theta activity, supporting more efficient recruitment of WM processes and stronger performance associations. Older adults showed attenuated theta power, indicative of neural saturation, and appeared to compensate through alpha-mediated mechanisms during the delay period (maintenance / manipulation): reduced alpha suppression in the Letter Span facilitated rehearsal and updating, whereas increased upper alpha in the Corsi Test protected stored visuospatial information. These findings suggest theta oscillations underpin core WM functions, whereas alpha oscillations flexibly support compensatory strategies in ageing.

neuroscience↗

bioRxiv2025

Boosting Brainpower in Ageing: Task-Specific and Transfer Effects of tDCS-Enhanced Working Memory Training

Ageing is associated with neural alterations that impair cognitive abilities, particularly working memory (WM)--the capacity to temporarily store and manipulate information essential for daily functioning. Transcranial Direct Current Stimulation (tDCS) has shown promise in enhancing WM in older adults by modulating cortical excitability and promoting neuroplasticity. However, findings on the combined effects of tDCS and WM training remain inconsistent, particularly regarding transfer effects to non-trained WM tasks (near transfer) or other cognitive domains (far transfer). This study examined the behavioural and neural effects of tDCS on distinct WM phases (encoding, retention/manipulation, recall) in older adults. Over three weeks, participants underwent six sessions of adaptive WM training paired with tDCS targeting the left dorsolateral prefrontal cortex (DLPFC). Neural activity was assessed via EEG, focusing on theta and alpha bands. Participants were divided into tDCS and placebo groups and completed two WM tests, the Letter Span and Corsi Test, with retention and manipulation conditions. Results showed no additional behavioural or neural benefits of tDCS. However, both groups exhibited near-transfer effects that persisted one-month post-training. Neural changes varied by task: the Letter Span showed increased alpha power during manipulation, indicating enhanced maintenance of information during that phase, while the Corsi Test showed reduced left-hemisphere theta power during recall, reflecting reduced hemispheric asymmetry. Inter-individual variability likely contributed to inconsistencies and a lack of correlations between outcomes. These findings highlight the importance of personalised tDCS protocols and suggest adaptive WM training can yield enduring cognitive and neural benefits in older adults.

neuroscience↗