Biology subjects

Hedger, N.

Publications and source records attributed to Hedger, N..

4 recordsLinked to original sources

bioRxiv2026

Gut Microbiota Signatures of Brain and Peripheral gamma-amino butyric acid (GABA) in Healthy Adult Males

Gamma-aminobutyric acid (GABA), the principal inhibitory neurotransmitter in the mature human nervous system, plays a central role in neurodevelopment, emotion regulation, and sensory processing. Many psychiatric drugs act on the GABAergic system, highlighting its importance for healthy brain function. Individual differences in brain and circulating GABA levels have traditionally been attributed to genetic variation. However, several gut bacteria produce neuroactive compounds, including GABA, raising the possibility that microbial variation influences peripheral and central GABA levels and related measures in humans. This relationship remains largely unexplored. In a cross-sectional study of 251 healthy adults, we investigated associations between gut microbiota composition, central and peripheral GABA, and associated features. Brain GABA was quantified using magnetic resonance spectroscopy, blood GABA using enzyme-linked immunosorbent assays, and gut microbiota profiles using absolute and relative abundance measures derived from Flow Cytometry Fluorescent In Situ Hybridisation and 16S rRNA gene sequencing. Motor cortex GABA+ levels were positively associated with greater numbers of Bacteroides/Prevotella bacteria. A similar association was observed for blood GABA, which was additionally associated with greater numbers of lactic acid bacteria, Eubacterium rectale/Clostridium coccoides, and Clostridium histolyticum groups, and with predicted microbial gene pathways involved in GABA, propionate, and butyrate biosynthesis. No association was observed between brain and blood GABA concentrations. These findings provide new evidence for relationships between gut bacterial groups and central and peripheral GABA pools, supporting future longitudinal studies of causal links between gut microbiota and host GABA levels, as well as the potential for future intervention studies to influence GABAergic processing.

neuroscience↗

bioRxiv2024

Vicarious Somatotopic Maps Tile Visual Cortex

Our sensory systems work together to generate a cohesive experience of the world around us. Watching others being touched activates brain areas representing our own sense of touch: the visual system recruits touch-related computations to simulate bodily consequences of visual inputs. One long-standing question is how the brain implements this interface between visual and somatosensory representations. To address this question, we developed a method to simultaneously map somatosensory body part tuning and visual field tuning throughout the brain. Applying this method on ongoing co-activations during rest resulted in detailed maps of the body-part tuning in the brains endogenous somatotopic network. During movie watching, somatotopic tuning explains responses throughout the entire dorsolateral visual system, revealing an array of somatotopic body maps that tile the cortical surface. The tuning of these maps aligned with those of visual maps, and predicted both preferences for visual field locations and the visual-category preferences for body parts. These results reveal a mode of brain organization in which aligned visual-somatosensory topographic maps connect visual and bodily reference frames. This cross-modal interface is ideally situated to translate raw sensory impressions into more abstract formats useful for action, social cognition, and semantic processing.

neuroscience↗

bioRxiv2024

Hierarchical cortical plasticity in congenital sight impairment

A robust learning system balances adaptability to new experiences with stability of its foundational architecture. To investigate how the human brain implements this we used a new approach to study plasticity and stability across hierarchical processing stages in visual cortex. We compare the rod system of individuals born with rod-only photoreceptor inputs (achromatopsia) to the typically developed rod system, allowing us to dissociate impacts of life-long versus transient responses to altered input. Cortical input stages (V1) exhibited high stability, with input-deprived cortex showing no retinotopic remapping and exhibiting structural hallmarks of deprivation. However, plasticity manifested as reorganised read-out of these inputs by higher-order cortex, in a pattern that could compensate for the lower resolution of a rod-only system and its lack of high-density foveal input. We propose that these hierarchical dynamics robustly optimize processing of available input and could reflect a broader principle of brain organisation with important implications for emerging sight-rescue therapies.

neuroscience↗

bioRxiv2021

Naturalistic Audiovisual Stimulation Reveals the Topographic Organization of Human Auditory Cortex

Despite the importance of audition in spatial, semantic, and social function, there is no consensus regarding the detailed organisation of human auditory cortex. Using a novel application of a population receptive field model to a high-powered naturalistic audiovisual movie-watching dataset, we simultaneously estimate the basic spectral tuning properties and category selectivity of human auditory cortex. This revealed unprecedentedly clear tonotopic maps which showcase the modes of organization and computational motifs of the auditory cortex. Specifically, we find that regions more remote from the auditory core exhibit more compressive, non-linear response properties with finely-tuned, speech selectivity in low frequency portions of their tonotopic maps. These patterns of organisation mirror aspects of the visual cortical hierarchy, wherein tuning properties progress from a stimulus category-agnostic front end towards more advanced regions increasingly optimised for behaviorally relevant stimulus categories.

neuroscience↗