Biology subjects

Papai, M. S.

Publications and source records attributed to Papai, M. S..

3 recordsLinked to original sources

bioRxiv2024

Single trial characterization of frontal Theta and parietal Alpha oscillatory episodes during Spatial Navigation in humans

Theoretical proposals and empirical findings both highlight the relevance of theta brain oscillations in human Spatial Navigation. However, whilst the general assumption is that the relevant theta band activity is purely oscillatory, most empirical studies fail to disentangle oscillatory episodes from wide band activity. In addition, experimental approaches often rely on averaged activity across trials and subjects, disregarding moment-to-moment fluctuations in Theta activity, contingent on key aspects of the task. Here, we used novel oscillation detection approaches to investigate the dynamics of theta and alpha episodes in human subjects performing a spatial navigation task in a Virtual Reality environment, resolved at single-trial level. The results suggest that bouts of theta oscillatory activity are related to task difficulty and access to previously encoded information, across different timescales. alpha episodes, instead, seem to anticipate successful navigational decisions and could be related to shifts in internal attention.

neuroscience↗

bioRxiv2023

Behavioural and electrophysiological correlates of the cross-modal enhancement for unaware visual events

According to many reports, cross-modal interactions can lead to enhancement of visual perception, even when visual events appear below awareness. Yet, the mechanism underlying this cross-modal enhancement is still unclear. The present study addressed whether cross-modal integration based on bottom-up processing can break through the threshold of awareness. We used a binocular rivalry protocol, and measured ERP responses and perceptual switches time-locked to flashes, sounds or flash-sound co-occurrences. In behavior, perceptual switches happened the earliest when subthreshold flashes co-occurred with sounds. Yet, this cross-modal facilitation never surpassed the benchmark indicated by the probability summation, thus suggesting independence rather than integration of sensory signals. Likewise, the ERPs to audiovisual events did not differ from the summed unimodal ERPs, also suggesting that the cross-modal behavioural benefit for unaware visual events can be explained by the independent contribution of unisensory signals and suggest no need for a multisensory integration mechanism. Hence, even though cross-modal benefits appeared behaviourally, we suggest that this cross-modal facilitation might origin from well-known bottom-up attentional capture processes, contributed by each individual sensory stimulus.

neuroscience↗

bioRxiv2019

Neural evidence of cognitive conflict during binocular rivalry

To make sense of ambiguous and, at times, incomplete sensory input, the brain relies on a process of active interpretation. At any given moment, only one of several possible perceptual outcomes prevails in our conscious experience. Our hypothesis is that the competition between alternative representations induces cognitive conflict, eventually leading to fluctuations between different perceptual interpretations. We used binocular rivalry, a popular protocol to probe changes in perceptual awareness [1-3] and drew on the conflict monitoring theory, which holds that cognitive control is invoked by the detection of conflict during information processing. We looked for an increase in power of fronto-medial theta oscillations (5-7 Hz), an established EEG marker of conflict detection [4-7]. Our results show that fm-theta power increases right before perceptual alternations and decreases thereafter, suggesting that conflict monitoring is related to perceptual competition. Furthermore, to investigate conflict resolution via attentional engagement, as held by the conflict monitoring theory [8], we also looked for changes in parieto-occipital alpha oscillations (8-12 Hz) associated to perceptual switches. These oscillations have been associated to attention allocation via functional inhibition in sensory cortices [9-12]. The power of parieto-occipital alpha was inversely related to that of fm-theta, reflecting periods of high inter-ocular inhibition during stable perception, and low inhibition around moments of perceptual change. Our findings validate a prediction made 20 years ago in the seminal paper formulating the conflict monitoring theory, and establish a previously unknown link between conflict mechanisms and the processes leading to perceptual awareness. HighlightsO_LIBinocular rivalry induces conflict between competing perceptual representations C_LIO_LIMid-frontal theta power increases around the resolution of perceptual conflict C_LIO_LIPosterior alpha decreases reflect neural excitability around perceptual switches C_LIO_LIThe results link cognitive conflict theory with perceptual inference C_LI

neuroscience↗