Biology subjects

Martial, F. P.

Publications and source records attributed to Martial, F. P..

3 recordsLinked to original sources

bioRxiv2026

Parallel visual processing in the suprachiasmatic region of a diurnal mammal.

Light shapes mammalian physiology and behaviour through hypothalamic pathways, yet how these pathways process visual information in day-active species remains poorly understood. Based largely on work in nocturnal rodents, the suprachiasmatic nucleus (SCN) is classically viewed as a retinal target that encodes ambient illumination for circadian entrainment. We combine anatomical tracing, light-evoked c-Fos mapping and high-density silicon-probe electrophysiology to define visual processing in the suprachiasmatic region of the diurnal murid Rhabdomys pumilio. We find that retinal input and light-evoked activity extend beyond the SCN into rostral and lateral peri-SCN hypothalamus. Within the SCN, neurons encode irradiance with graded changes in maintained firing broadly similar to those observed in parallel recordings of nocturnal Mus domesticus. Across the wider suprachiasmatic region, Rhabdomys neurons show selectivity for more dynamic visual stimuli, including luminance transitions, contrast and temporal structure. Unsupervised clustering identifies five functionally distinct hypothalamic visual response classes with different anatomical distributions. These findings reveal an expanded hypothalamic visual network in a diurnal mammal, placing SCN irradiance coding within a broader system for processing dynamic visual features.

neuroscience↗

bioRxiv2025

Efficient mixed representation of active and passive motion in the mouse visual thalamus during natural behaviour

Most retinal motion is generated by the observer's movements. These are often self-generated (active) but can also arise from external forces such as gravity (passive). Active movements modulate spontaneous and visually evoked activity throughout the visual system, providing neural circuits with information about behavioural state. By contrast, much less is known about how visual circuits represent passive movements. Critically, it remains unclear whether the retina-recipient thalamus tracks passive motion and, if so, whether this representation is separable from active motion. To address these questions, we developed a paradigm that dissociates active and passive motion in freely moving mice and used it to examine their effects on neural activity. Mice actively explored an arena while intermittent floor tilts induced passive movement. By combining 3D reconstructions of animal pose and arena motion, we quantified active and passive linear and angular motion independently, even when they occurred simultaneously. We found that neurons in the dorsal lateral geniculate nucleus (dLGN) and surrounding regions tracked combinations of active and passive motion signals both in the dark and during visual stimulation. Individual neurons differentially weighted active and passive motion signals. This diversity enabled active and passive motion signals to be linearly decoded and partially separated from population activity, while recurrent dynamics retained passive motion information over timescales of several seconds. These findings identify a coding strategy through which early visual circuits integrate active and passive motion into an estimate of self-motion while preserving information about whether visual inputs arise from self-generated or externally imposed movements.

neuroscience↗

bioRxiv2019

Measuring vision using innate behaviours in mice with intact and impairedretina function

Measuring vision in rodents is a critical step for understanding vision, improving models of human disease, and developing therapies. Established behavioural tests for perceptual vision, such as the visual water task, rely on learning. The learning process, while effective for sighted animals, can be laborious and stressful in animals with impaired vision, requiring long periods of training. Current tests that that do not require training are based on sub-conscious, reflex responses (e.g. optokinetic nystagmus) that dont require involvement of visual cortex and higher order thalamic nuclei. A potential alternative for measuring vision relies on using visually guided innate defensive responses, such as escape or freeze, that involve cortical and thalamic circuits. In this study we address this possibility in mice with intact and degenerate retinas. We first develop automatic methods to detect behavioural responses based on high dimensional tracking and changepoint detection of behavioural time series. Using those methods, we show that visually guided innate responses can be elicited using parametisable stimuli, and applied to describing the limits of visual acuity in healthy animals and discriminating degrees of visual dysfunction in mouse models of retinal degeneration.

neuroscience↗