Biology subjects

Williams, A. G.

Publications and source records attributed to Williams, A. G..

3 recordsLinked to original sources

bioRxiv2023

Comparison of online and offline applications of dual-site transcranial alternatingcurrent stimulation (tACS) on functional connectivity between pre-supplementarymotor area (preSMA) and right inferior frontal gyrus (rIFG) for improving responseinhibition

BackgroundThe efficacy of transcranial alternating current stimulation (tACS) is thought to be brain state-dependent, such that tACS during task performance would be hypothesised to offer greater potential for inducing beneficial electrophysiological changes in the brain and associated behavioural improvement compared to tACS at rest. However, to date, no empirical study has directly tested this postulation. ObjectiveHere we compared the effects of tACS applied during a stop signal task (online) to the effects of the same tACS protocol applied prior to the task (offline) and a sham control stimulation. MethodsA total of 53 young, healthy adults (32 female; 18-35 yrs) received dual-site beta tACS over the right inferior frontal gyrus (rIFG) and pre-supplementary motor area (preSMA), which are thought to play critical roles in action cancellation, with phase-synchronised stimulation for 15 min with the aim of increasing functional connectivity. ResultsEEG connectivity analysis revealed significantly increased task-related functional connectivity following online but not offline tACS. Correlation analyses suggested that an increase in functional connectivity in the beta band at rest following online tACS was associated with an improvement in response inhibition. Interestingly, despite the lack of changes in functional connectivity at the target frequency range following offline tACS, significant improvements in response inhibition were still observed, suggesting offline tACS may still be efficacious in inducing behavioural changes, likely via a post-stimulation early plasticity mechanism. ConclusionOverall, the results indicate that online and offline dual-site beta tACS are beneficial in improving inhibitory control via distinct underlying mechanisms.

neuroscience↗

bioRxiv2022

Spontaneous Variations in Arousal Modulate Subsequent Visual Processing and Local Field Potential Dynamics in the Ferret during Quiet Wakefulness

Behavioral states affect neuronal responses throughout the cortex and influence visual processing. Quiet wakefulness (QW) is a behavioral state during which subjects are quiescent, but awake and connected to the environment. Here, we examined the effects of pre-stimulus arousal variability on post-stimulus neural activity in primary visual cortex (V1) and posterior parietal cortex (PPc) in awake ferrets, using the pupil diameter as an indicator of arousal. We observed that during low arousal, low- frequency power increases during visual stimulation, and that the peak alpha frequency shifted depending on the arousal state. High arousal increased gamma power as well as low-frequency inter- and intra-areal coherence. Using a simplified model of laminar circuits, we show that this connectivity pattern is compatible with feedback signals targeting infragranular layers in area PPc and supragranular layers in V1. Neurons in V1 displayed higher firing rates at their preferred orientations on high-arousal trials. Broad-spiking cells in V1 entrained to high-frequency oscillations (>80 Hz), whereas narrow-spiking neurons phase-locked to low (12-18 Hz) and high-frequency (>80 Hz) rhythms. These results indicate that the variability and sensitivity of post-stimulus cortical responses and coherence depend on the pre-stimulus behavioral state and account for the neuronal response variability observed during repeated stimulation.

neuroscience↗

bioRxiv2021

Different underlying mechanisms for high and low arousal in probabilistic learning in humans

Humans are uniquely capable of adapting to highly changing environments by updating relevant information and adjusting ongoing behaviour accordingly. Here we show how this ability --termed cognitive flexibility-- is differentially modulated by high and low arousal fluctuations. We implemented a probabilistic reversal learning paradigm in healthy participants as they transitioned towards sleep or physical extenuation. The results revealed, in line with our pre-registered hypotheses, that low arousal leads to diminished behavioural performance through increased decision volatility, while performance decline under high arousal was attributed to increased perseverative behaviour. These findings provide evidence for distinct patterns of maladaptive decision-making on each side of the arousal inverted u-shaped curve, differentially affecting participants ability to generate stable evidence-based strategies, and introduces wake-sleep and physical exercise transitions as complementary experimental models for investigating neural and cognitive dynamics.

neuroscience↗