Biology subjects

van Boxtel, J. J. A.

Publications and source records attributed to van Boxtel, J. J. A..

3 recordsLinked to original sources

bioRxiv2022

Characterising modulatory effects of transcranial random noise stimulation using the perceptual template model.

Neural noise is an inherent property of all nervous systems. However, the mechanisms by which such random and fluctuating neural activity influences perception are still unclear. To elucidate the relationship between neural noise and perceptual performance we require techniques that can safely manipulate neural noise in humans. Transcranial random noise stimulation (tRNS), a form of electrical brain stimulation, has been proposed to increase neural noise according to principles of stochastic resonance (SR); where small to moderate intensities of tRNS improve performance, while higher intensities are detrimental. To date, high intensity (i.e., >2mA) tRNS effects on neural noise levels have not been directly quantified, nor have the detrimental effects proposed by SR been demonstrated in early visual processing. For this purpose, we applied a maximum current intensity of 3mA high-frequency tRNS to the visual cortex (V1) during an orientation discrimination task across increasing external visual noise levels, and fit the perceptual template model to contrast thresholds to quantify intrinsic mechanisms related to noise underlying changes in perceptual performance. We found that tRNS generally worsened perceptual performance by increasing observers internal noise and reducing the ability to filter external noise compared to sham. While most observers experienced detrimental effects, others demonstrated improved perceptual performance (i.e., reduced internal noise and better noise filtering). Preliminary evidence suggests that individual baseline internal noise levels may drive the observed beneficial or detrimental observer responses to tRNS. These findings have important implications for the application of tRNS to investigate the impact of internal noise and noise filtering processes on perception.

neuroscience↗

bioRxiv2018

Frequency-tagging visual background information enables multi-target perceptual filling-in to be distinguished from phenomenally matched replay

Perceptual filling-in (PFI) occurs when a physically-present visual target disappears from conscious perception, with its location filled in by the surrounding visual background. Compared to other visual illusions, these perceptual changes are crisp and simple, and can occur for multiple spatially-separated targets simultaneously. Contrasting neural activity during the presence or absence of PFI may complement other multistable phenomena to reveal the neural correlates of consciousness (NCC). We presented four peripheral targets over a background dynamically updating at 20 Hz. While participants reported on target disappearances/reappearances via button press/release, we tracked neural activity entrained by the background during PFI using steady-state visually evoked potentials (SSVEPs) recorded in the electroencephalogram. We found background SSVEPs closely correlated with subjective report, and increased with an increasing amount of PFI. Unexpectedly, we found that as the number of filled-in targets increased, the duration of target disappearances also increased, suggesting facilitatory interactions exist between targets in separate visual quadrants. We also found distinct spatiotemporal correlates for the background SSVEP harmonics. Prior to genuine PFI, the response at the second harmonic (40 Hz) increased before the first (20 Hz), which we tentatively link to an attentional effect. There was no difference between harmonics for physically removed stimuli. These results demonstrate that PFI can be used to study multi-object perceptual suppression when frequency-tagging the background of a visual display, and because there are distinct neural correlates for endogenously and exogenously induced changes in consciousness, that it is ideally suited to study the NCC.\n\nHighlightsO_LIPerceptual filling-in (PFI) has distinct advantages for investigating the neural correlates of consciousness.\nC_LIO_LIParticipants can accurately report graded changes in consciousness using four simultaneous buttons.\nC_LIO_LIFrequency-tagging of visual background information tracks changes in visual perception.\nC_LIO_LISpatiotemporal EEG responses differentiate PFI from phenomenally matched physical disappearances.\nC_LI

neuroscience↗

bioRxiv2018

Attention periodically samples competing stimuli during binocular rivalry

The attentional sampling hypothesis suggests that attention rhythmically enhances sensory processing when attending to a single (~8 Hz), or multiple (~4 Hz) objects. Here we investigated using binocular rivalry whether attention samples sensory representations that are not part of the conscious percept, during competition for perceptual dominance. When crossmodally cued toward a conscious image, subsequent changes in consciousness occurred at ~8 Hz, consistent with rates of undivided attentional sampling. However, when attention was cued toward the suppressed image, changes in consciousness slowed to ~3.5 Hz, indicating the division of attention away from the conscious visual image. In the electroencephalogram, we found that at 3.5 and 8 Hz, the strength of inter-trial phase coherence over fronto-temporal and parieto-occipital regions correlated with behavioral measures of changes in perception. When cues were not task-relevant, these effects disappeared, confirming that perceptual changes were dependent upon the allocation of attention, and that attention can flexibly sample away from a conscious image in a task-dependent manner.

neuroscience↗