Search bioRxiv⌕ Search
Home/Archive/bioRxiv

bioRxiv · 10.1101/190595

The hidden spatial dimension of alpha: 10 Hz perceptual echoes propagate as periodic travelling waves in the human brain.

VanRullen, R.·Lozano-Soldevilla, D.
View original source ↗Export metadata ↓

Abstract

Alpha oscillations play a special role in vision. During sensory processing, reverse-correlation techniques revealed that white-noise luminance sequences elicit a robust occipital [~]10 Hz response that periodically reverberates the input sequence for up to 1 s. These perceptual echoes constitute the impulse response function of the visual system. However, the spatial dimension of perceptual echoes remains unknown: do they reverberate across the cortex simultaneously? Does stimulation over multiple visual coordinates evoke multiple synchronized echoes, or do they show consistent phase differences? Here, we tested the spatial dimension of perceptual echoes in two electroencephalogram (EEG) experiments manipulating the location of the visual stimulation. When a single disc flickered a white-noise luminance sequence in the upper visual field, we observed a single \"echo wave\" originating in posterior sensors and spatially propagating towards frontal ones (i.e. periodic travelling wave). The presentation of two independent flickering discs in separate visual hemifields produced two simultaneous and superimposed echo waves propagating in opposite directions, one in response to each stimulus. Strikingly, at many electrode sites, the phase of the two echoes differed, with a phase advance for the contralateral stimulus location. EEG source reconstruction tentatively located the waves within contralateral parieto-occipital cortex. In conclusion, the alpha rhythm processes stimulus information as a travelling wave that propagates across the cortical representation of retinotopic space in the human brain. In line with the \"cortical scanning\" hypothesis (Pitts & McCulloch, 1947), these results suggest the existence of an additional spatial dimension embedded in the phase of the alpha rhythm.\n\nSignificance statementHow does the spatial dimension of sensory processing relate to the temporal dimension of brain rhythms? Using correlation techniques, we characterized perceptual echoes, the average electroencephalogram response induced by visual stimuli that change luminance randomly. We found that perceptual echoes are actually periodic waves that travel through human visual cortex. Strikingly these periodic waves show consistent phase differences across the visual field, processing screen locations sequentially across distinct phases of the cycle following basic retinotopy. These results suggest the existence of an additional \"hidden\" spatial dimension in sensory cortex, encoded in the phase of the alpha oscillatory cycle. This could mean that perceptual echoes behave like sweeps of a sonar, processing the visual field in cycles of [~]100 ms duration.

Source connections

Explore related subjects

neurosciencePreprint

Keep this discovery

BibTeXRIS

VanRullen, R., Lozano-Soldevilla, D.. 2017-09-19. The hidden spatial dimension of alpha: 10 Hz perceptual echoes propagate as periodic travelling waves in the human brain.. https://doi.org/10.1101/190595

Cite the original work for its findings. Save a collection to share your selection of sources.

KEEP EXPLORING

Related preprints

bioRxiv2026

The Unreasonable Effectiveness of Cell Types in Describing Neuronal Physiological Features

Single-cell RNA sequencing (scRNA-seq) captures detailed gene expression profiles at scale, while patch-clamp recordings measure intrinsic neuronal electrophysiological properties. Modeling the relations between these two modalities remains a challenge. Here, we compare how well electrophysiological features can be predicted by traditional transcriptomic cell type classification, representations derived from a foundational model (scGPT) pretrained on large-scale scRNA-seq datasets, ion channel-coding genes, and highly variable genes. Using paired transcriptomic and electrophysiological patch-sequencing data from 495 human neurons from neurosurgical tissue, we find that cluster-level cell type representations consistently outperform highly variable gene selection, ion channel gene selection, and context-enriched scGPT embeddings. Notably, performance varies across model architectures and initializations, and the best results are obtained by combining the outputs of separate cell type and scGPT-based models. Together, these findings suggest that traditional discrete cellular classification is highly effective in predicting physiological features. For maximum performance it can be complemented by pretrained transformer models.

neuroscience↗
bioRxiv2026

A nonlinear inhibition pathway underlying cortical responses to tuned holographic optogenetic perturbations

Optogenetics enables causal manipulation of cortical activity. Perturbation responses can be counterintuitive due to network interactions, making theory essential for predicting them. Existing approaches often rely on linear approximations, which fail for many biologically relevant perturbations. Here we develop a nonlinear theory of responses to holographic perturbations in cell-type-specific recurrent networks with structured connectivity. We fit a nonlinear model to mouse V1 data, which shows cotuned-ensemble suppression: perturbing spatially clustered neurons with similar preferred orientations yields markedly stronger short-range suppression than perturbing untuned ensembles. We show that cotuned-ensemble suppression arises from a feature-tuned, nonlinear inhibition pathway implicating somatostatin-positive (SST) interneurons. The theory predicts that cotuned ensembles suppress parvalbumin-positive (PV) neurons but facilitate SST neurons, and links the degree of cotuned-ensemble suppression or facilitation to the variance of the SST response. This framework identifies mechanisms by which nonlinear inhibition sculpts cortical dynamics and establishes a predictive basis for targeted optogenetic interventions.

neuroscience↗
bioRxiv2026

Proteomic signatures of APOE ε4 across human tissues and cell types in Alzheimers disease

The apolipoprotein E {varepsilon}4 (APOE {varepsilon}4) allele is the strongest genetic risk factor for late-onset Alzheimers disease (AD). However, the underlying molecular mechanisms remain unclear. This study included 1691 participants from the Religious Orders Study and Rush Memory and Aging Project (ROSMAP), 1226 participants from the Accelerating Medicines Partnership - Alzheimers Disease (AMP-AD) Diverse Cohorts Study, and 735 participants from the Alzheimers Disease Neuroimaging Initiative (ADNI). To characterise APOE {varepsilon}4 molecular effects, we analysed proteomic data from plasma, cerebrospinal fluid (CSF), and induced pluripotent stem cell (iPSC)-derived astrocytes and neurons, as well as transcriptomic and proteomic data from multiple brain regions. The association of APOE {varepsilon}4 with AD neuropathology was also examined. APOE {varepsilon}4 carriers shared a plasma proteomic signature enriched for immune processes, irrespective of AD diagnosis. A machine learning classifier trained on this signature discriminated APOE {varepsilon}4 carriers from non-carriers in an independent cohort using CSF proteomics. APOE {varepsilon}4 carriage was associated with higher Braak stages and Consortium to Establish a Registry for Alzheimers Disease (CERAD) score. However, only limited APOE {varepsilon}4-associated transcriptomic and proteomic changes were observed in bulk brain tissue, with poor cross-layer concordance. Proteomic analyses of iPSC-derived astrocytes and neurons further revealed cell-type-specific APOE {varepsilon}4-associated changes. APOE {varepsilon}4 is associated with a consistent proteomic signature across plasma and CSF. Its molecular effects in the brain differ across cell types, brain regions and molecular layers. These findings support the need for cell-type-resolved multi-omic studies to elucidate how APOE {varepsilon}4 confers AD risk.

neuroscience↗