The functionally plastic rod photoreceptors in the simplex retina of Little skate (Leucoraja erinacea) exhibit a hybrid rod-cone morphology and enhanced synaptic connectivity.

Magana-Hernandez, L.; Wagh, A. S.; Fathi, J. G.; Robles, J. E.; Rubio, B.; Yusuf, Y.; Rose, E. E.; Brown, D. E.; Perry, P. E.; Hamada, E.; Anastassov, I. A.

doi:10.1101/2023.06.28.546621

bioRxiv · 10.1101/2023.06.28.546621

The functionally plastic rod photoreceptors in the simplex retina of Little skate (Leucoraja erinacea) exhibit a hybrid rod-cone morphology and enhanced synaptic connectivity.

Magana-Hernandez, L.·Wagh, A. S.·Fathi, J. G.·Robles, J. E.·Rubio, B.·Yusuf, Y.·Rose, E. E.·Brown, D. E.·Perry, P. E.·Hamada, E.·Anastassov, I. A.

View original source ↗Export metadata ↓

Abstract

The retinas of the vast majority of vertebrate species are termed "duplex" - that is, they contain both rod and cone photoreceptor neurons in different ratios. The retina of Little skate (Leucoraja erinacea) is a rarity among vertebrates because it contains only rod photoreceptors and is thus "simplex". This unique retina provides us with an important comparative model and an exciting opportunity to study vertebrate rod circuitry within the context of a functional, evolutionarily optimized system, all without the concern about artifacts from genetically modified rod-only mouse models. Perhaps even more importantly, the Leucoraja retina is able to function under both scotopic and photopic ranges of illumination with a single complement of photoreceptors. It is currently unknown what structural characteristics mediate this remarkable functional plasticity. To address this question, we performed serial block-face electron microscopy imaging and examined the structure of rods and their post-synaptic partners. We find that skate rods exhibit ultrastructural characteristics that are either common to rods or cones in other vertebrates (e.g., outer segment architecture, synaptic ribbon number, terminal extensions), or are uniquely in-between those of a typical vertebrate rod or cone (e.g., number of invaginating contacts, clustering of multiple ribbons over a single synaptic invagination). We therefore hypothesize that the unique hybrid rod-cone structure of skate rods and their post-synaptic partners is correlated with the ability of the skate visual system to function across scotopic and photopic ranges of illumination. These findings have the potential to reveal as yet undescribed principles of vertebrate retinal design. Significance statementThe vast majority of vertebrate retinas are duplex and have mixed rod-cone populations of photoreceptors in varying ratios. The processing of visual information in a duplex retina tends to be separated between rod and cone systems, which mediate function under scotopic and photopic lighting conditions, respectively. However, the cartilaginous fish Little skate (Leucoraja erinacea) has a simplex retina, comprised solely of rod photoreceptors. Skate rods are also unusual because they have the ability to retain function over a full range of lighting conditions. We have little knowledge about the ultrastructural anatomy of the skate retina, and we hypothesize that this functional plasticity can be traced back to morphological adaptations at the level of individual photoreceptors and the downstream retinal circuitry, thus illuminating new pathways for the processing of visual information among vertebrates.

Explore related subjects

neuroscience Preprint

Keep this discovery

Explore connections, maps & timelines

BibTeX RIS

Magana-Hernandez, L., Wagh, A. S., Fathi, J. G., Robles, J. E., Rubio, B., Yusuf, Y., Rose, E. E., Brown, D. E., Perry, P. E., Hamada, E., Anastassov, I. A.. 2023-06-30. The functionally plastic rod photoreceptors in the simplex retina of Little skate (Leucoraja erinacea) exhibit a hybrid rod-cone morphology and enhanced synaptic connectivity.. https://doi.org/10.1101/2023.06.28.546621

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

KEEP EXPLORING

Related preprints

bioRxiv2026

Connexin 40 deficiency alters the temporal profile of postictal oxygen dynamics following focal seizures.

Epilepsy is increasingly recognized as a disorder involving both neuronal and vascular dysfunction. While connexin signaling has been implicated in epileptogenesis, the contribution of vascular connexins to seizure associated cerebrovascular pathology remains poorly understood. Connexin40 (Cx40) is an endothelial gap junction protein that plays a crucial role in vascular communication and blood-flow regulation. Seizures induce dynamic changes in cerebral perfusion and oxygenation, including prolonged postictal hypoperfusion/hypoxia. To determine whether Cx40 influences postictal hypoxia following focal seizures, we examined seizure characteristics and postictal oxygen dynamics in Cx40 knockout (Cx40-/-) mice using an established focal hippocampal seizure model. Electrically kindled seizures were elicited in wild-type and Cx40-/- mice, and local hippocampal tissue oxygenation was continuously monitored before and after seizure induction. Seizure duration did not differ between genotypes, indicating comparable seizure severity. Interestingly, Cx40 deletion altered the temporal pattern of postictal oxygen recovery, producing greater early hypoxia and a delayed secondary rebound in pO2 despite similar peak oxygen levels and overall hypoxic burden. These findings demonstrate that loss of Cx40 selectively alters the temporal profile of postictal oxygen dynamics without affecting seizure duration. Taken together, the results suggest that endothelial gap junctional communication contributes to postictal vascular recovery and identify Cx40 as a potential modulator of seizure associated neurovascular dysfunction.

neuroscience↗

bioRxiv2026

Attention Across Scales: From Individual Variation to Social Hierarchies and Brain Networks in Semi-Free-Ranging Macaques

Attention is a fundamental brain function supporting perception, decision-making, and social behavior, and its dysfunction profoundly impairs daily life. It is both dynamic and stable, varying across observations and individuals, changing across the lifespan, and being shaped by social and environmental experience. Yet capturing this complexity remains a central challenge in neuroscience. Here, we integrated longitudinal behavioral assessments of semi-free-ranging macaques living in naturalistic social groups with resting-state fMRI. We quantified performance across days, ages, and social hierarchies and related it to intrinsic brain organization. Distinct attentional phenotypes emerged, including individuals with reduced attentional control. Performance followed an inverted-U lifespan trajectory, improving from childhood to adulthood before declining. Social status modulated attentional performance. Critically, nonlinear lifespan trajectories and associations with individual attentional differences were most clearly expressed in frontoparietal connectivity. Together, these findings reveal how sustained attention is organized across scales, providing a biological framework for its individual diversity, social modulation, and neural basis.

neuroscience↗

bioRxiv2026

Decoding natural scenes from patterned optogenetic responses in mouse visual cortex

A central challenge in developing visual cortical prostheses is to determine how visual stimuli should be transformed into effective patterns of cortical stimulation. Although advances in stimulation technologies, including optogenetics, provide increasingly precise control over cortical activity, it remains unclear whether artificially evoked activity can reproduce the information content of naturally evoked visual representations. Here we establish a quantitative framework for evaluating visual encoding strategies by decoding cortical responses evoked by natural vision and patterned optogenetic stimulation. We developed a novel dual-modal paradigm in awake mice to bridge the gap between endogenous photostimulation and artificial network driving. By co-expressing the high-performance calcium indicator GCaMP6s and the red-shifted, ultra-sensitive opsin rsChRmine-oScarlet in the primary visual cortex (V1), we successfully translated dynamic natural movie frames into patterned, spatiotemporal optogenetic stimulation. Quantitative comparisons of macro-scale dynamics demonstrated that this patterned optogenetic injection evokes cortical states highly comparable and representationally aligned with those driven by actual visual photostimulation. To systematically evaluate the fidelity of these responses, we developed STAR, a deep learning model featuring spatial and temporal attention mechanisms, and successfully reconstructed the frames of natural movies from V1 signals under both experimental modalities. Collectively, our results demonstrate that complex sensory information can be both naturally encoded and synthetically injected into V1 circuits with high decoding fidelity. This work provides an empirical and computational proof-of-concept for intelligent, closed-loop biomimetic encoders, establishing a robust framework for next-generation cortical visual neuroprostheses and bidirectional brain-machine interfaces.

neuroscience↗