Biology subjects

Rozenblit, F.

Publications and source records attributed to Rozenblit, F..

4 recordsLinked to original sources

bioRxiv2022

Filter-based models of suppression in retinal ganglion cells: comparison and generalization across species and stimuli

The dichotomy of excitation and suppression is one of the canonical mechanisms explaining the complexity of neural activity. Computational models of the interplay of excitation and suppression in single neurons aim at investigating how this interaction affects a neurons spiking responses and shapes the encoding of sensory stimuli. Here, we compare the performance of three filter-based stimulus-encoding models for predicting retinal ganglion cell responses recorded from axolotl, mouse, and marmoset retina to different types of temporally varying visual stimuli. Suppression in these models is implemented via subtractive or divisive interactions of stimulus filters or by a response-driven feedback module. For the majority of ganglion cells, the subtractive and divisive models perform similarly and outperform the feedback model as well as a linear-nonlinear (LN) model with no suppression. Comparison between the subtractive and the divisive model depended on cell type, species, and stimulus components, with the divisive model generalizing best across temporal stimulus frequencies and visual contrast and the subtractive model capturing in particular responses for slow temporal stimulus dynamics and for slow axolotl cells. Overall, we conclude that the divisive and subtractive models are well suited for capturing interactions of excitation and suppression in ganglion cells and perform best for different temporal regimes of these interactions.

neuroscience↗

bioRxiv2022

Diversity of Ganglion Cell Responses to Saccade-like Image Shifts in the Primate Retina

Saccades are a fundamental part of natural vision. They interrupt fixations of the visual gaze and rapidly shift the image that falls onto the retina. These stimulus dynamics can cause activation or suppression of different retinal ganglion cells, but how they affect the encoding of visual information in different types of ganglion cells is largely unknown. Here, we recorded spiking responses to saccade-like shifts of luminance gratings from ganglion cells in isolated marmoset retinas and investigated how the activity depended on the combination of pre- and post-saccadic images. All identified cell types, On and Off parasol and midget cells as well as a type of Large Off cells, displayed distinct response patterns, including particular sensitivity to either the pre- or the post-saccadic image or combinations thereof. In addition, Off parasol and Large Off cells, but not On cells, showed pronounced sensitivity to whether the image changed across the transition. Stimulus sensitivity of On cells could be explained based on their responses to step changes in light intensity, whereas Off cells, in particular, parasol and the Large Off cells, seem to be affected by additional interactions that are not triggered during simple light-intensity flashes. Together, our data show that ganglion cells in the primate retina are sensitive to different combinations of pre- and post-saccadic visual stimuli. This contributes to the functional diversity of the retinas output signals and to asymmetries between On and Off pathways and provides evidence of signal processing beyond what is triggered by isolated steps in light intensity.

neuroscience↗

bioRxiv2022

Novel transient cell clusters provide a possible link between early neural activity and angiogenesis in the neonatal mouse retina

Developing neurons become spontaneously active while growing blood vessels begin to irrigate their surroundings. However, surprising little is known about early interactions between neural activity and angiogenesis. In the neonatal mouse retina, spontaneous waves of impulses sweep across the ganglion cell layer (GCL), just underneath the growing superficial vascular plexus. We discovered clusters of transient auto-fluorescent cells in the GCL, forming an annulus that co-localizes with the frontline of the growing plexus. Blood vessel density is highest within cluster areas, suggesting their involvement in angiogenesis. Once the clusters and blood vessels reach the retinal periphery by the end of the first postnatal week, the clusters disappear, eliminated by microglial phagocytosis. Electrical imaging suggests that they have their own electrophysiological signature. Blocking Pannexin1 (PANX1) hemi-channels with probenecid blocks the waves and the fluorescent clusters disappear following prolonged exposure to the drug. Spontaneous waves initiation points follow a developmental center-to-periphery progression similar to the cluster cells. We suggest that these transient cells are specialized, hyperactive neurons residing in the GCL. They generate spontaneous activity hotspots, thereby triggering waves through purinergic paracrine signaling via PANX1 hemi-channels. The strong activity generated around these hotspots triggers angiogenesis, attracting new blood vessels that provide local oxygen supply. Signaling through PANX-1 attracts microglia that establish contact with these cells, eventually leading to their elimination by phagocytosis. These cluster cells may provide the first evidence that specialized transient neuronal populations guide angiogenesis in the developing CNS through neural activity.

neuroscience↗

bioRxiv2019

Evidence for novel transient clusters of cholinergic ganglion cells in the neonatal mouse retina

Waves of spontaneous activity sweep across the neonatal mouse retinal ganglion cell (RGC) layer, driven by directly interconnected cholinergic starburst amacrine cells from postnatal day (P) 0-10, followed by waves driven by glutamatergic bipolar cells. We found transient clusters of auto-fluorescent cells in the RGC layer during the period of cholinergic waves. They appear around the optic nerve head at P2 and become gradually displaced towards the periphery between P2-8 and then they disappear. Pan-retinal multielectrode array recordings reveal that cholinergic wave origins follow a similar, non-random developmental center-to-periphery pattern. Electrical imaging unmasks hotspots of dipole electrical activity occurring in the vicinity of wave origins. We propose that these activity hotspots are the sites for wave initiation and may originate from the transient cell clusters, reminiscent of activity in transient subplate neurons in the developing cortex, suggesting a universal hyper-excitability mechanism in developing CNS networks during the critical period for brain wiring.

neuroscience↗