Biology subjects

Morton, M. P.

Publications and source records attributed to Morton, M. P..

6 recordsLinked to original sources

bioRxiv2026

State-Dependent Dissociation of Shared Input and Directed Information Flow in the Visual Cortex

Understanding how brain state and sensory input shape inter-laminar communication is essential for interpreting cortical population dynamics. Using laminar recordings in macaque V1, we apply reduced-rank regression to quantify low-dimensional predictive subspaces linking Input and Superficial layers. We find that both visual stimulation and internal state (eyes open vs. closed) modulate the structure and efficacy of these subspaces, but through distinct mechanisms. Visual input induces a directional, feedforward pattern from input to superficial layers, while wakefulness-related modulation enhances coordination more symmetrically. Delay analysis and network simulations confirm that structured, layer-specific inputs produce directional prediction, whereas global fluctuations yield undirected co-activation. Importantly, differential structure across layers predicts the emergence of communication asymmetry. These findings dissociate communication from shared modulation, providing a principled framework for interpreting inter-population correlations. Our results generalize to broader cortical circuits, offering insights into when population coupling reflects genuine information flow versus global state dynamics.

neuroscience↗

bioRxiv2026

Uncovering Dynamic Neural Information Flow with Continuous-Time Weighted Dynamic Bayesian Networks

Understanding how information dynamically flows within neural systems is a crucial problem in neuroscience. Traditional approaches often assume stationary or quasi-stationary functional networks, which fail to capture the time-varying dynamics of interactions among neural variables. To address this limitation, we introduce Continuous-Time weighted Dynamic Bayesian Networks (CTwDBN), a non-stationary graphical modeling framework for uncovering smoothly time-varying conditional dependencies. Validation on synthetic datasets demonstrated that CTwDBN reliably recovers the structure and dynamics of ground-truth information flow. Application to electrophysiological recordings during a guided saccade task revealed temporal fluctuations in conditional dependencies in the cortical network that persisted an order of magnitude longer than the receptive field dynamics. In the resting-state cortex, CTwDBN revealed persistent fluctuations within a low-dimensional dependency space reflecting canonical anatomical motifs. These results highlight CTwDBN as a versatile analytical framework for capturing dynamic information flow in neural systems with broad applicability to complex biological and artificial systems.

neuroscience↗

bioRxiv2024

Spatial context non-uniformly modulates inter-laminar communication in the primary visual cortex

Our visual experience is a result of the concerted activity of neuronal ensembles in the sensory hierarchy. Yet how the spatial organization of objects influences neural activity in this hierarchy remains poorly understood. We investigate how the inter-laminar interactions in the primary visual cortex (V1) are affected by visual stimuli in isolation or with flanking stimuli at various spatial configurations that are known to cause non-uniform degradation of perception. By employing dimensionality reduction approaches to simultaneous layer-specific population recordings, we establish that cortical layers interact through a structurally stable communication subspace. Spatial configuration of contextual stimuli differentially modulates inter-laminar communication efficacy, the balance between feedforward and feedback signaling, and contextual signaling in the superficial layers. Remarkably, these modulations mirror the spatially non-uniform aspects of perceptual degradation. Our results suggest a model of retinotopically non-uniform cortical connectivity in the output layers of V1 that influences communication in the sensory hierarchy.

neuroscience↗

bioRxiv2023

Geometry of anisotropic contextual interactions in the visual cortex places fundamental limits on spatial vision

A prevailing assumption in our understanding of how neurons in the primary visual cortex (V1) integrate contextual information is that such processes are spatially uniform. Conversely, perceptual phenomena such as visual crowding, the impaired ability to accurately recognize a target stimulus among distractors, suggest that interactions among stimuli are distinctly non-uniform. Prior studies have shown flankers at specific spatial geometries exert differential effects on target perception. To resolve this discrepancy, we investigated how flanker geometry impacted the representation of a target stimulus in the laminar microcircuits of V1. Our study reveals flanker location differentially impairs stimulus representation in excitatory neurons in the superficial and input layers of V1 by tuned suppression and untuned facilitation of orientation responses. Mechanistically, this effect can be explained by asymmetrical spatial kernels in a normalization model of cortical activity. Strikingly, these non-uniform modulations of neural representation mirror perceptual anisotropies. These results establish the non-uniform spatial integration of information in the earliest stages of cortical processing as a fundamental limitation of spatial vision.

neuroscience↗

bioRxiv2023

Widespread Receptive Field Remapping in Early Visual Cortex

Our eyes are in constant motion, yet we perceive the visual world as stable. Predictive remapping of receptive fields is thought to be one of the critical mechanisms for enforcing perceptual stability during eye movements. While receptive field remapping has been identified in several cortical areas, the spatiotemporal dynamics of remapping, and its consequences on the tuning properties of neurons, remain poorly understood. Here, we tracked remapping receptive fields in hundreds of neurons from visual Area V2 while subjects performed a cued saccade task. We found that remapping was far more widespread in Area V2 than previously reported and can be found in neurons from all recorded cortical layers and cell types. Surprisingly, neurons undergoing remapping exhibit sensitivity to two punctate locations in visual space. Furthermore, we found that feature selectivity is not only maintained during remapping but transiently increases due to untuned suppression. Taken together, these results shed light on the spatiotemporal dynamics of remapping and its ubiquitous prevalence in the early visual cortex, and force us to revise current models of perceptual stability.

neuroscience↗

bioRxiv2021

Brain state and cortical layer-specific mechanisms underlying perception at threshold

Identical stimuli can be perceived or go unnoticed across successive presentations, producing divergent behavioral outcomes despite similarities in sensory input. We sought to understand how fluctuations in behavioral state and cortical layer and cell-class specific neural activity underlie this perceptual variability. We analyzed physiological measurements of state and laminar electrophysiological activity in visual area V4 while monkeys were rewarded for correctly reporting a stimulus change at perceptual threshold. Hit trials were characterized by a behavioral state with heightened arousal, greater eye position stability, and enhanced decoding performance of stimulus identity from neural activity. Target stimuli evoked stronger responses in V4 in hit trials, and excitatory neurons in the superficial layers, the primary feed-forward output of the cortical column, exhibited lower variability. Feed-forward interlaminar population correlations were stronger in hits. Hit trials were further characterized by greater synchrony between the output layers of the cortex during spontaneous activity, while the stimulus-evoked period showed elevated synchrony in the feed-forward pathway. Taken together, these results suggest that a state of elevated arousal and stable retinal images allow enhanced processing of sensory stimuli, which contributes to hits at perceptual threshold.

neuroscience↗