Biology subjects

Learmonth, G.

Publications and source records attributed to Learmonth, G..

10 recordsLinked to original sources

bioRxiv2026

No Evidence of tACS-Primed Enhancement of Alpha Neurofeedback

Neurofeedback shows promise as a clinical intervention, but its effectiveness is hindered by variability of response across individuals. One factor influencing neurofeedback success may be endogenous brain states, particularly the baseline power within target frequency bands. Transcranial alternating current stimulation (tACS) provides a potential mechanism to modulate these baseline frequency bands. This study explored whether tACS could effectively enhance participants' ability to gain neurofeedback control by increasing lateralised posterior alpha activity prior to engagement in a covert spatial attention-based neurofeedback task. Participants completed three counterbalanced sessions: 1) alpha tACS and active neurofeedback, 2) alpha tACS and sham neurofeedback, 3) gamma (40Hz) tACS and active neurofeedback. Neurofeedback performance was assessed via lateralised posterior alpha power shifts and Posner task reaction times. We identified no difference in reaction times or lateralised alpha power shifts across conditions. While participants reliably demonstrated lateralised posterior alpha patterns, consistent with the covert spatial attention neurofeedback protocol, no advantage of active neurofeedback over sham was observed. The lack of significant effects underscores the need for further rigorous tACS studies to identify the parameters essential for successful neural entrainment, and to evaluate its potential in enhancing neurofeedback efficacy.

neuroscience↗

bioRxiv2026

Environmental Demands Outweigh Age Effects in Cortical Dynamics During Walking

Reduced visibility is a common contributor to falls in older adults, but the neural processes that support safe locomotion under low lighting are not well established. In this study, 22 young (mean age = 22.5) and 20 older (mean age = 70.9) adults walked along a pathway under bright, ambient and dark lighting conditions while stepping over expected and unexpected obstacles projected on the floor. Mobile electroencephalography (EEG), combined with motion capture, was used to quantify spectral power changes during obstacle crossing preparation and the post-crossing phases, relative to a standing baseline. We identified that reduced lighting conditions elicited a widespread increase in cortical engagement, predominantly in the alpha band, during both preparation and reset phases. Obstacle negotiation recruited a distributed sensorimotor network, with reduced theta-alpha-beta desynchronisation during preparation and a robust post-movement beta rebound during the post-crossing reset phase. Expectation effects were modest, with unexpected obstacles inducing greater transient alpha-beta desynchronisation relative to expected obstacles, suggesting additional cortical resources are recruited under uncertainty. Age effects were minimal and limited to reduced frontal alpha desynchronisation in older adults compared to young adults during the preparation phase, possibly reflecting differences in walking speed rather than differences in neural control. In conclusion, environmental features such as low lighting and obstacle presence exert a stronger influence on cortical dynamics during walking than age and expectation effects alone. This provides a foundation for future work examining how these processes may differ in older adults at increased risk of falls.

neuroscience↗

bioRxiv2025

A meta-analysis of periodic and aperiodic M/EEG components in Parkinson's disease

Parkinsons disease is characterised by a range of motor and non-motor changes that can negatively impact quality of life. Many studies have identified potential clinical electrophysiological biomarkers of Parkinsons disease with an aim of developing new methods of identifying at-risk patients, and to form the basis of therapeutic interventions. However, these studies do not present consistent results, and a formal meta-analysis is warranted to identify reliable M/EEG characteristics across datasets. In this meta-(re-)analysis of open-access M/EEG datasets (n = 6; 4 EEG and 2 MEG), we compared periodic and aperiodic characteristics of resting-state recordings in 368 patients with Parkinsons disease and 570 age-matched healthy controls. Specifically, we compared the power and peak frequency of the aperiodic-adjusted alpha and beta oscillations, and the aperiodic exponent and offset across the two groups. Using spectral parametrisation, individuals with Parkinsons disease had higher alpha-band power and a slower alpha peak frequency compared to controls, however no group differences in beta-band power and peak frequency were identified in this resting state data. Parkinsons patients were furthermore found to have consistently higher aperiodic offset and exponent, possibly indicative of increased cortical inhibition. In conclusion, this large cohort meta-analysis points to a broadly consistent pattern of both periodic and aperiodic changes in Parkinsons patients in M/EEG signal that may be used to develop diagnostics and targeted interventions in the future.

neuroscience↗

bioRxiv2025

Age differences in motivation drive performance during the sustained attention to response task

Young and older adults prioritise speed and accuracy differently during sustained attention tasks. While older adults generally show a preference of accuracy over speed, this is not always the case. The underlying factor behind this inconsistency may be motivational differences, with older participants compensating for a speed disadvantage with increased intrinsic motivation to perform well. We investigated this in a pre-registered study, using the Sustained aAttention to Response Task (SART) in young (n = 25, mean age = 19) and older adults (n = 25, mean age = 69.5). We matched participant accuracy by titrating response window length. Both groups achieved similar performance and strategy during the titration, enabling a comparison without confounds resulting from differences in default age-specific strategies. All participants were then monetarily encouraged to perform better in terms of accuracy. Both groups responded with an adaptive strategy of slowed reaction times and enhanced accuracy, but the young participants improved much more, outperforming older adults, and reversing the speed-accuracy strategies that are typically observed. In addition, older participants reported higher baseline levels of motivation alongside a reduced motivation to alter performance for money. So, while the older participants could match young participant performance in titration due to their higher baseline motivational levels, the young participants improved much more than older adults in response to the monetary incentive. From these findings we argue that older adults are intrinsically motivated to do well on tasks whereas younger age groups perform optimally only after incentivisation.

neuroscience↗

bioRxiv2024

EEG markers of vigilance, task-induced fatigue and motivation during sustained attention: Evidence for decoupled alpha- and beta-signatures

Reduced vigilance can be captured in measures of attentional lapses in sustained attention tasks, but just how these lapses relate to task-induced fatigue and motivation to maintain optimal performance is unclear. We used the sustained attention to response task (SART) to induce fatigue, and manipulated motivation levels for the last block of the task in young and older participants (N = 34), while recording EEG to track electrophysiological markers of vigilance change, fatigue and motivation. Despite significant increases in subjective fatigue and mind wandering over 45 minutes, no vigilance decline was observed. However, the age groups differed markedly in their response strategies from the outset (adopting distinct speed-accuracy trade-off strategies) with faster/more erroneous responses in the younger and slower/more accurate responses in the older participants. The subjective rises in fatigue/mind wandering were coupled with an increase in pre-stimulus alpha-power, whereas the post-stimulus activity revealed two distinguishable beta signatures: a fronto-central topography as a marker of response strategy and a fronto-parietal distribution modulated by motivation per se. Our results thus show three distinct neural patterns underpinning the effects of fatigue, response strategy and motivation and suggest a (motivational) cognitive control mechanism behind resetting of performance decrement, independent of persistent fatigue.

neuroscience↗

bioRxiv2024

Proximity to Visual Stimuli Reduces Post-Saccadic Alpha Lateralisation

Posterior alpha lateralisation is a well-established marker of visual spatial attention, with growing evidence suggesting that it may also be linked to oculomotor planning and execution. However, saccades also result in a change in visual input to the fovea, which could be linked to lateralised posterior alpha. In this study, we investigate the interplay between saccade-induced foveal input changes and lateralised posterior alpha by analysing saccades from the cue period of a Posner task and the active feedback period of a neurofeedback task, where visual stimuli were present on screen. Specifically, we examine the impact of saccade landing proximity to visual stimuli and saccade amplitude on post-saccade alpha lateralisation. Consistent with previous research, we observe a general post-saccade alpha lateralisation across both tasks. Importantly, we find that alpha lateralisation is reduced in the neurofeedback task when saccades land close to visual stimuli compared to those landing further away, while saccade amplitude has no significant effect. This investigation highlights the importance of controlling for both eye movements and visual stimuli when investigating alpha lateralisation in fixational tasks. Moreover, it shows how both oculomotor and afferent processing mechanisms affect posterior alpha lateralisation.

neuroscience↗

bioRxiv2023

Probing sustained attention and fatigue across the lifespan

Trait fatigues reflects tiredness that persists throughout a prolonged period, whereas state fatigue is defined to be short term after "intense and/or prolonged effort". We investigated the impact of prolonged sustained attention (using the SART task) on both trait and state fatigue levels in the general population. A JsPsych online version of the SART task was undertaken by 115 participants, stratified across the whole adult lifespan. While pre-task trait fatigue was a strong indicator of the initial state fatigue levels, undergoing the task itself induced an increase in reported subjective state fatigue, as well as reduced energy. Consistent with this finding, greater subjective state fatigue levels were associated with reduced accuracy. In addition, age was the best predictor of inter-participant accuracy (the older the participants, the greater the accuracy), and learning (i.e., task duration reducing reaction times). Moreover, a ceiling effect occurred where participants with higher trait fatigue did not experience greater state fatigue changes relative to those with low trait scores. In summary, we found improved accuracy in older adults, as well as a tight coupling between state fatigue and SART performance decline (in an online environment). The findings warrant further investigation into fatigue as a dynamic, task-dependent state and into SART task performance as an objective measure and inducer of fatigue.

neuroscience↗

bioRxiv2023

Developmental changes in individual alpha frequency: Recording EEG data during public engagement events

Statistical power in cognitive neuroimaging experiments is often very low. Low sample size can reduce the likelihood of detecting real effects (false negatives) and increase the risk of detecting non-existing effects by chance (false positives). Here we document our experience of leveraging a relatively unexplored method of collecting a large sample size for simple electroencephalography (EEG) studies: by recording EEG in the community during public engagement and outreach events. We collected data from 346 participants (189 females, age range 6-76 years) over 6 days, totalling 29 hours, at local science festivals. Alpha activity (6-15 Hz) was filtered from 30 seconds of signal, recorded from a single electrode placed between the occipital midline (Oz) and inion (Iz) while participants rested with their eyes closed. A total of 289 good quality datasets were obtained. Using this community-based approach, we were able to replicate controlled, lab-based findings: IAF increased during childhood, reaching a peak frequency of 10.28 Hz at 28.1 years old, and slowed again in middle and older age. Total alpha power decreased linearly, but the aperiodic-adjusted alpha power did not change over the lifespan. Aperiodic slopes and intercepts were highest in the youngest participants. There were no associations between these EEG indexes and self-reported fatigue, measured by the Multidimensional Fatigue Inventory. Finally, we present a set of important considerations for researchers who wish to collect EEG data within public engagement and outreach environments.

neuroscience↗

bioRxiv2020

Mobile EEG reveals functionally dissociable dynamic processes supporting real-world ambulatory obstacle avoidance: Evidence for early proactive control

The ability to safely negotiate the world on foot takes years to develop in human infants, reflecting the huge cognitive demands associated with real-time dynamic planning and control of walking. Despite the importance of walking, surprisingly little is known about the neural and cognitive processes that support ambulatory motor control in humans. In particular, methodological limitations have, to date, largely prevented study of the neural processes involved in detecting and avoiding obstacles during walking. Here, using mobile EEG during real-world ambulatory obstacle avoidance, we captured the dynamic oscillatory response to changes in the environment. Time-frequency analysis of EEG data revealed clear neural markers of proactive and reactive forms of movement control (occurring before and after crossing an obstacle), visible as increases in frontal theta and centro-parietal beta power respectively. Critically, the temporal profile of changes in frontal theta allowed us to arbitrate between early selection and late correction mechanisms of proactive control: our data show that motor plans are updated as soon as an upcoming obstacle appears, rather than when the obstacle is reached, as previously thought. In addition, regardless of whether motor plans required updating, a clear beta rebound was present after obstacles were crossed, reflecting the resetting of the motor system. Overall, our use of mobile EEG during real-world walking provides novel insight into the cognitive and neural basis of dynamic motor control in humans, suggesting new routes to the monitoring and rehabilitation of motor disorders such as dyspraxia and Parkinsons disease.

neuroscience↗

bioRxiv2018

The Time Course of Ineffective Sham Blinding During 1mA tDCS

BackgroundStudies using transcranial direct current stimulation (tDCS) typically compare the effects of an active (10-30min) relative to a shorter sham (placebo) protocol. Both active and sham tDCS are presumed to be perceptually identical on the scalp, and thus represent an effective method of delivering double-blinded experimental designs. However, participants often show above-chance accuracy when asked which condition involved active/sham retrospectively.\n\nObjective/HypothesisWe aimed to assess the time course of sham-blinding during active and sham tDCS. We predicted that 1) Participants will be aware that the current is switched on for a longer duration in the active versus the sham protocol, 2) Active anodal tDCS will reduce reaction times more effectively than sham.\n\nMethods32 adults were tested in a pre-registered, double-blinded, within-subjects design. A forced-choice reaction time task was undertaken before, during and after active (10min 1mA) and sham (20s 1mA) tDCS. The anode was placed over the left primary motor cortex (C3) to target the right hand, and the cathode on the right forehead. Two probe questions were asked every 30s: \"Is the stimulation on? \"and \"How sure are you?\".\n\nResultsDistinct periods of non-overlapping confidence intervals were identified between the active and sham conditions, totalling 5min (57.1% of the total difference in stimulation time). These began immediately after sham ramp-down and lasted until the active protocol had ended. Active tDCS had no effect on reaction times compared to sham ({Delta}RT active vs sham p>0.38 in all blocks).\n\nConclusionsWe show a failure of placebo control during low-intensity tDCS.

neuroscience↗