Biology subjects

Petras, K.

Publications and source records attributed to Petras, K..

5 recordsLinked to original sources

bioRxiv2026

Traveling waves in attention networks inherit the rhythms of sensory systems

Attention emerges from coordinated activity across distributed brain regions, each with their own intrinsic rhythm: alpha (7-12Hz) in visual cortex and theta (3-7Hz) in auditory cortex. When attention is sustained on a visual location, alpha power increases over the corresponding ipsilateral hemisphere, a robust neurophysiological marker of sustained visuospatial attention named alpha lateralization. Hemispheric asymmetry during sustained attention was recently also reported for anterior-to-posterior alpha traveling waves -smooth phase shifts across the cortex. This finding suggests that traveling waves support top-down inter-areal communication within the attention network. Here we asked whether traveling waves indeed reflect top-down attention signals or are merely a byproduct of sustained visuospatial attention. We manipulated attention through different sensory modalities (auditory cueing and visual stimulation), thus engaging different sensory cortices, while maintaining the task as visual discrimination. Using electroencephalography, we tested the hypothesis that if traveling waves reflect attention signals within the network, their frequency should follow the intrinsic rhythm of the engaged sensory system: theta for auditory cueing and alpha for visual stimulation. If instead they are a byproduct of attention allocated to visual information, their frequency should remain in alpha. Our results support the former: auditory cueing led to lateralized theta traveling waves, while visual stimulation produced lateralized alpha traveling waves. Crucially, traveling-wave lateralization in both frequencies correlated with trial-by-trial alpha power lateralization. Together, attention signals appear to propagate as waves at the intrinsic rhythm of the engaged sensory system and locally modulate alpha power lateralization in task-relevant visual regions.

neuroscience↗

bioRxiv2026

Traveling waves support rhythmic attentional search

Brain activity unfolds across space and time, giving rise to spatiotemporal dynamics that can manifest as cortical traveling waves -smooth phase shifts propagating across the cortex. Although traveling waves have been observed across species and measurement scales, their functional role in human cognition remains largely inferred from correlational evidence. In healthy humans, large-scale neural dynamics must be studied non-invasively, which provides limited access to their neural origins. Here, we tested whether global traveling waves causally contribute to inter-areal communication during attention. Using transcranial magnetic stimulation (TMS), we induced long-range traveling waves detectable with electroencephalography and assessed their neural and behavioral consequences during an attentional search task. Double-pulse TMS applied over the right frontal eye field transiently disrupted ongoing global waves and selectively induced direction- and frequency-specific traveling waves propagating toward the occipital visual cortex. These TMS-induced anterior-to-posterior theta traveling waves were rhythmically modulated by stimulation latency relative to search-trial onset. Critically, behavioral performance exhibited the same rhythmic pattern, with improved attentional search performance when TMS-induced traveling waves were more prominent. Together, these findings provide causal evidence that large-scale traveling waves support inter-areal communication during rhythmic visual attention.

neuroscience↗

bioRxiv2025

Locally induced traveling waves generate globally observable traveling waves

Cortical traveling waves have been proposed as a fundamental mechanism for neural communication and computation. Methodological uncertainties currently limit the interpretability of non-invasive, extracranial traveling wave data, sparking debates about their cortical origin. Studies using EEG or MEG typically report waves that cover large portions of the sensor array which are often interpreted as reflecting long range cortical waves. Meanwhile, invasive, intracranial recordings in humans and animals routinely find both local, mesoscopic waves and large scale, macroscopic waves in cortex. Whether the global sensor-array waves found with EEG/MEG necessarily correspond to macroscopic cortical waves or whether they are merely projections of local dynamics remains unclear. In this study, we made use of the well-established retinotopic organization of early visual cortex to generate traveling waves with known properties in human participants (N=19, m/f) via targeted visual stimulation, while simultaneously recording MEG and EEG. The inducer stimuli were designed to elicit waves whose traveling direction in mesoscopic retinotopic visual areas depends on stimulus direction, while leaving macroscopic activation patterns along the visual hierarchy largely unchanged. We observed that the preferred direction of traveling waves across the sensor array was influenced by that of the visual stimulus, but only at the stimulation frequency. Comparison between single-trial and trial-averaged responses further showed considerable temporal variation in traveling wave patterns across trials. Our results highlight that under tight experimental control, non-invasive, extracranial recordings can recover mesoscopic traveling wave activity, thus making them viable tools for the investigation of spatially constrained wave dynamics. Significant statementNon-invasively obtained time-resolved neuroimaging data is often thought to primarily reflect neural dynamics on the largest spatial scales. In the context of cortical traveling waves, this assumption can lead to a misinterpretation of spatio-temporal patterns observed in the sensor array. We here show that it is in principle possible that the global sensor array data is dominated by spatially constrained, local cortical traveling wave activity. Our findings crucially inform the ongoing discussion about the origin of traveling waves observed in surface recordings.

neuroscience↗

bioRxiv2023

Backward masking reveals coarse-to-fine dynamics in human V1

Natural images exhibit luminance variations aligned across a broad spectrum of spatial frequencies (SFs). It has been proposed that, at early stages of processing, the coarse signals carried by the low SF (LSF) of the visual input are sent rapidly from primary visual cortex (V1) to ventral, dorsal and frontal regions to form a coarse representation of the input, which is later sent back to V1 to guide the processing of fine-grained high SFs (i.e., HSF). We used functional resonance imaging (fMRI) to investigate the role of human V1 in the coarse-to-fine integration of visual input. We disrupted the processing of the coarse and fine content of full-spectrum human face stimuli via backward masking of selective SF ranges (LSFs: <1.75cpd and HSFs: >1.75cpd) at specific times (50, 83, 100 or 150ms). In line with coarse-to-fine proposals, we found that (1) the selective masking of stimulus LSF disrupted V1 activity in the earliest time window, and progressively decreased in influence, while (2) an opposite trend was observed for the masking of a stimulus HSF. This pattern of activity was found in V1, as well as in ventral (i.e. the Fusiform Face area, FFA), dorsal and orbitofrontal regions. We additionally presented participants with contrast negated stimuli. While contrast negation significantly reduced response amplitudes in the FFA, as well as coupling between FFA and V1, coarse-to-fine dynamics were not affected by this manipulation. The fact that V1 response dynamics to strictly identical stimulus sets differed depending on the masked scale adds to growing evidence that V1 role goes beyond the early and quasi-passive transmission of visual information to the rest of the brain. It instead indicates that V1 may yield a spatially registered common forum or blackboard that integrates top-down inferences with incoming visual signals through its recurrent interaction with high-level regions located in the inferotemporal, dorsal and frontal regions.

neuroscience↗

bioRxiv2021

Information redundancy across spatial scales modulates early visual cortical processing

Visual images contain redundant information across spatial scales where low spatial frequency contrast is informative towards the location and likely content of high spatial frequency detail. Previous research suggests that the visual system makes use of those redundancies to facilitate efficient processing. In this framework, a fast, initial analysis of low-spatial frequency (LSF) information guides the slower and later processing of high spatial frequency (HSF) detail. Here, we used multivariate classification as well as time-frequency analysis of MEG responses to the viewing of intact and phase scrambled images of human faces to demonstrate that the availability of redundant LSF information, as found in broadband intact images, correlates with a reduction in HSF representational dominance in both early and higher-level visual areas as well as a reduction of gamma-band power in early visual cortex. Our results indicate that the cross spatial frequency information redundancy that can be found in all natural images might be a driving factor in the efficient integration of fine image details.

neuroscience↗