Biology subjects

Dowsett, J.

Publications and source records attributed to Dowsett, J..

5 recordsLinked to original sources

bioRxiv2026

Agency and Embodiment Provide Dissociable Benefits to Perception, Metacognition and Neural Processing During Active Sensing

Metacognition, judging how reliable our own perceptual decisions are, is central to adaptive behavior. Such judgments hinge on the reliability of the sensory evidence on which that decision is based, and active sensing through self-directed exploration is known to improve perception itself. Yet, how agency, the authorship over self-initiated actions, and the processing of the sensory consequences, which is implicit to active sensing, modulate metacognition and its calibration, remains unknown. Whether physical embodiment adds to this beyond virtual exploration is similarly unclear, yet relevant both for daily life and for self-monitoring in agentic AI. Here, we combined a naturalistic auditory search paradigm with mobile electroencephalography. Twenty participants performed a target-detection task under three conditions: active embodied exploration , active screen-based exploration, and passive listening to replays of their own trials, while we obtained steady-state auditory evoked potentials (SSAEPs) to characterize stimulus-locked neural responses. We find that both agency conditions improved accuracy, metacognitive sensitivity, and overall SSAEP amplitude relative to passive listening, indicating that agency, rather than whole-body movement, drives these enhancements. Crucially, however, embodiment uniquely grounded both the target-evoked neural response and the subjects' confidence to immediate sensory evidence. Thus, agency alone broadly enhances perceptual and neural processing, but embodiment specifically anchors confidence, neurally and behaviorally, to the present.

neuroscience↗

bioRxiv2026

Audiovisual stimulation using wearable shutter glasses robustly evokes 40 Hz neuronal activity but does not modulate associative memory

Audiovisual stimulation is a promising approach for studying and modulating human neuronal gamma (>30 Hz) oscillations and associated memory processes. Portable setups can increase ecological validity and therapeutic potential, but options remain limited. See-through shutter glasses are a new mobile technology that adds a visual flicker effect to what the user naturally sees. Here, we validated this method in a multisensory, cognitively relevant setting. We leveraged a previous experimental design from our lab, aiming to A) characterise the neuronal gamma activity evoked by shutter glasses, and B) conceptually replicate the previously reported effect of audiovisual gamma stimulation on memory accuracy, in line with a Spike Timing Dependent Plasticity model. We recorded high-density Electroencephalography (EEG) from 24 healthy participants during an associative memory task. Video-sound pairs were presented with the sound amplitude-modulated at 40 Hz and 40 Hz visual flicker elicited by the shutter glasses, with a phase offset between both modalities. The visual flicker preceded the auditory modulation by 90 or 270 degrees. Participants were asked to remember the video-sound associations. They also underwent a visual-only condition and an electrically equivalent control condition. EEG evoked power and phase coherence were reconstructed at source level and analysed along with behavioural accuracy. As expected, the shutter glasses robustly increased EEG evoked power and phase coherence at 40 Hz compared to the control condition. Effects were widespread and stronger than in a previous study not using shutter glasses. However, we did not replicate the previously reported effects of audiovisual phase offsets on memory accuracy. This could be due to reduced statistical power or methodological differences. Nonetheless, the validation of shutter glasses in a multisensory setting and the EEG analysis software, now improved and open source, enable important further investigations of audiovisual gamma stimulation in research and clinical settings.

neuroscience↗

bioRxiv2025

Decoding real world visual scenes from the human gamma band with flicker evoked oscillations.

Current approaches to investigate the role of neural oscillations in natural scene processing have been limited to artificial stimuli and long data collection. We present a new way to decode real-world scenes participants are viewing from the steady-state visual evoked potentials (SSVEPs) evoked while wearing flickering LCD glasses. We discovered that SSVEP responses from real world scenes are surprisingly complex and have distinct waveform shapes: they differ markedly across scenes and participants but are consistent within individuals, even across multiple days. SSVEP shape varies greatly between stimuli, but is reliable, meaning that decoding works even with a single electrode. Decoding is highly accurate with 5-10 seconds of data and was still above chance level with less than a second of data. Decomposing the SSVEPs into frequency bands showed that the information about the visual scene is present across all of the harmonics of the flicker frequency, but with 40 Hz (gamma band) showing the highest amount of information across the different flicker frequencies tested. These findings implicate a broad range of oscillations in encoding real-world scenes, with a particular importance for 40 Hz. The SSVEPs temporal profile is a rich source of information for decoding.

neuroscience↗

bioRxiv2024

Visually Evoked 40 Hz Gamma Activity Enhanced by Transcranial Electrical Stimulation

ObjectiveTranscranial Electrical Stimulation and Visual Stimulation in the gamma band (30-100 Hz, especially 40 Hz) are increasingly used to study and even enhance human cognition. Combining both techniques would be of scientific and clinical value, provided that Steady-State Visually Evoked Potentials (SSVEPs) are measured concurrently to determine any neuronal effects of the electrical brain stimulation. This poses a substantial methodological challenge. We aimed to demonstrate that recording visually evoked 40 Hz activity with EEG during electrical brain stimulation is possible and to explore potential interactions. ApproachWe tested if electrical and visual stimulation might interact depending on which brain areas are electrically stimulated (Experiment 1; N=25) and how closely the respective frequencies match (Experiment 2; N=25). Experiment 3 (N=25) assessed how effectively the data processing pipeline can mitigate electrical artefacts and recover real evoked neuronal activity. SSVEPs were processed and analysed in the time domain using an optimised adaptive template subtraction approach. Main Results40 Hz SSVEPs were successfully recorded during frequency-matched electrical stimulation applied between central and occipital regions. Waveform correlations revealed that SSVEPs from combined visual and electrical stimulation were more similar in shape to baseline SSVEPs from visual stimulation alone than to control data from electrical stimulation alone. Accordingly, during combined stimulation, the recovered signals were stronger in amplitude than the electrical control data. We found no evidence of interactions between electrical and visual stimulation. SignificanceWe demonstrated that 40 Hz SSVEPs can be reliably measured with EEG during frequency-matched electrical brain stimulation, distinguishing neuronal activity from electrical or physiological confounds. This method enables fundamental and clinical researchers to combine rhythmic sensory and electrical stimulation in the gamma band and concurrently quantify neuronal electrophysiological effects.

neuroscience↗

bioRxiv2019

Mobile steady-state evoked potential recording: dissociable neural effects of real-world navigation and visual stimulation

BackgroundThe ability to record brain activity in humans during movement, and in real world environments, is an important step towards understanding cognition. Electroencephalography (EEG) is well suited to mobile applications but suffers from the problem of artefacts introduced into the signal during movement. Steady state visually evoked potentials (SSVEPs) give an excellent signal-to-noise ratio and averaging a sufficient number of trials will eventually remove any noise not phase locked to the visual flicker.\n\nNew MethodHere we present a method for producing SSVEPs of real world environments using modified LCD shutter glasses, which are commonly used for 3D TV, by adapting the lens to flicker at neurophysiologically relevant frequencies, in this case the alpha band. Participants viewed a room whilst standing and walking. Either the left or right side of the room was illuminated, to test if it is possible to recover the resulting SSVEPs when walking, as well as to probe the effect of walking on neural activity. Additionally, by using a signal generator to produce \"simulated SSVEPs\" on the scalp we can demonstrate that this method is able to accurately recover evoked neural responses during walking.\n\nResultsThe amplitude of SSVEPs over right parietal cortex was reduced by walking. This finding is in line with converging evidence that visual-vestibular integration involves cortical lateralization with the right hemisphere being dominant in right handers. Furthermore, the waveform and phase of the SSVEPs is highly preserved between walking and standing, but was nevertheless sensitive to whether visual stimulation was presented to the left or right visual hemifield.\n\nConclusionsThis method allows probing neural responses at a wide range of frequencies, during natural movements within real environments.

neuroscience↗