Biology subjects

Dudok, B.

Publications and source records attributed to Dudok, B..

5 recordsLinked to original sources

bioRxiv2026

Hippocampal microcircuits constrain the generation of epileptiform activity

Epilepsy is largely characterized using macroscale measures of neural activity, such as electroencephalography, which are unable to resolve the underlying cellular-level substrates of pathological activity. Although there is a growing understanding that hippocampal microcircuits, comprised of distinct CA1 principal cells (PCs), inhibitory neurons, and input/output relationships, route information through parallel hippocampal pathways, the relevance of this microscale organization in epilepsy is poorly understood. To address this gap, we focally knocked out the {beta}3 subunit of the GABAA receptor from CA1 PCs, which strongly impaired parvalbumin-mediated inhibition to deep PCs, but not superficial PCs - potentially promoting a microcircuit-selective epilepsy manifestation. Indeed, we observed robust interictal epileptiform discharges (IEDs) at the site of focal knockout with features consistent with a potential CA2-to-deep CA1 PC generation mechanism. In line with prior observations that CA2 inputs potently drive deep PCs under physiological conditions, IEDs could be reliably evoked by optogenetic stimulation of CA2 in {beta}3 focal knockout mice. Resolving cellular activity across the CA1 PC network during IEDs, in vivo 2-photon calcium imaging demonstrated stronger activation of deep versus superficial PCs. Altogether, these data demonstrate that macroscopic electrophysiological patterns such as IEDs can have underlying microcircuit constraints, which has important implications for designing therapies that target the underlying microcircuit generators of epileptiform activity.

neuroscience↗

bioRxiv2026

Designer indicators for two-photon recording of subthreshold voltage dynamics

Subthreshold voltage dynamics are critical for neuronal information integration, yet they remain understudied in vivo due to the limitations of current tools. While genetically encoded voltage indicators (GEVIs) offer a promising alternative, their application for deep-tissue recording using two-photon (2P) microscopy--a preferred method for deep-tissue recording--has been hindered by insufficient sensitivity for detecting millivolt-scale subthreshold signals. Here, we refined our multiparametric two-photon high-throughput screening platform to develop two novel GEVIs, JEDI3sub and JEDI3hyp, tailored explicitly for subthreshold voltage detection. Through fast 2P optical recording in awake, behaving mice, we demonstrated the superior sensitivity of JEDI3 indicators compared to JEDI-2P. We also showed that JEDI3sub can track population-level subthreshold optical tuning, while JEDI3hyp reliably captured subthreshold dynamics associated with sharp-wave ripple oscillations in hippocampal PV interneurons. Finally, JEDI3hyp facilitated extended imaging of brain-state-dependent, millivolt-scale subthreshold voltage changes across deep-layer somas, fine dendritic structures, and diverse cell types. By addressing the critical gap in 2P optical recording of subthreshold voltage dynamics, JEDI3 indicators open new avenues for studying neural information processing and its alterations in health and disease.

neuroscience↗

bioRxiv2025

Nanoscale synaptic remodeling at corticostriatal circuits predicts flexible action control

Synaptic plasticity is a fundamental substrate of behavioral adaptation, yet the underlying molecular dynamics remain poorly defined. We tested the hypothesis that, within striatal circuits, flexibility relies on nanoscale remodeling of synaptic machinery coupling anterograde glutamatergic transmission to retrograde endocannabinoid signaling, a process disrupted in states of rigidity and aging. In the dorsolateral striatum, we found cell-type-specific facilitation of metabotropic glutamate receptor 5 (mGlu5)-dependent, endocannabinoid-mediated long-term depression at cortico-striatal synapses of indirect pathway neurons in flexible goal-directed behavior, but not after training promoting inflexibility. Stochastic Optical Reconstruction Microscopy (STORM) super-resolution imaging revealed that behavioral adaptation, but not rigidity, is accompanied by increased postsynaptic abundance of mGlu5 and diacylglycerol lipase- (DAGL), an endocannabinoid-synthesizing enzyme, and presynaptic CB1 cannabinoid receptors. In parallel, the nanoscale distance between mGlu5 and DAGL is reduced in postsynaptic spine heads. These nanoscale changes emerged within the time window required for behavioral updating. Intriguingly, the molecular densities of mGlu5, DAGL, and CB1 receptors predict the strength of behavioral adaptation. In aging mice, these nanoscale changes were absent in association with behavioral rigidity. These findings identify a nanoscale synaptic remodeling mechanism that enables behavioral flexibility and reveal how its failure contributes to rigidity, including that observed in aging.

neuroscience↗

bioRxiv2020

A fluorescent sensor for spatiotemporally resolved endocannabinoid dynamics in vitro and in vivo

Endocannabinoids (eCBs) are retrograde neuromodulators that play an important role in a wide range of physiological processes; however, the release and in vivo dynamics of eCBs remain largely unknown, due in part to a lack of suitable probes capable of detecting eCBs with sufficient spatiotemporal resolution. Here, we developed a new eCB sensor called GRABeCB2.0. This genetically encoded sensor consists of the human CB1 cannabinoid receptor fused to circular-permutated EGFP, providing cell membrane trafficking, second-resolution kinetics, high specificity for eCBs, and a robust fluorescence response at physiological eCB concentrations. Using the GRABeCB2.0 sensor, we monitored evoked changes in eCB dynamics in both cultured neurons and acute brain slices. Interestingly, in cultured neurons we also observed spontaneous compartmental eCB transients that spanned a distance of approximately 11 m, suggesting constrained, localized eCB signaling. Moreover, by expressing GRABeCB2.0 in the mouse brain, we readily observed foot shock-elicited and running-triggered eCB transients in the basolateral amygdala and hippocampus, respectively. Lastly, we used GRABeCB2.0 in a mouse seizure model and observed a spreading wave of eCB release that followed a Ca2+ wave through the hippocampus. Thus, GRABeCB2.0 is a robust new probe for measuring the dynamics of eCB release under both physiological and pathological conditions.

neuroscience↗

bioRxiv2020

The Neurovascular Basis of Postictal Amnesia

Long-lasting confusion and memory difficulties during the postictal state remain a major unmet problem in epilepsy that lacks pathophysiological explanation and treatment. We previously identified that long-lasting periods of severe postictal hypoperfusion/hypoxia, not seizures per se, are associated with memory impairment after temporal lobe seizures. While this observation suggests a key pathophysiological role for insufficient energy delivery, it is unclear how the networks that underlie episodic memory respond to vascular constraints that ultimately give rise to amnesia. Here, we focused on cellular/network level analyses in the CA1 of hippocampus in vivo to determine if neural activity, network oscillations, synaptic transmission, and/or synaptic plasticity are impaired following kindled seizures. Importantly, the induction of severe postictal hypoperfusion/hypoxia was prevented in animals treated by a COX-2 inhibitor, which experimentally separated seizures from their vascular consequences. We observed complete activation of CA1 pyramidal neurons during brief seizures, followed by a short period of reduced activity and flattening of the local field potential that resolved within minutes. During the postictal state, constituting tens of minutes to hours, we observed no changes in neural activity, network oscillations, and synaptic transmission. However, long-term potentiation of the temporoammonic pathway to CA1 was impaired in the postictal period, but only when severe local hypoxia occurred. Lastly, we tested the ability of rats to perform object-context discrimination, which has been proposed to require temporoammonic input to differentiate between sensory experience and the stored representation of the expected object-context pairing. Deficits in this task following seizures were reversed by COX-2 inhibition, which prevented severe postictal hypoxia. These results support a key role for hypoperfusion/hypoxia in postictal memory impairments and identify that many aspects of hippocampal network function are resilient during severe hypoxia except for long-term synaptic plasticity.

neuroscience↗