Biology subjects

Heldman, R.

Publications and source records attributed to Heldman, R..

5 recordsLinked to original sources

bioRxiv2026

Spatially confined dopamine from locus coeruleus axons selectively shapes hippocampal dynamics and action timing

Neuromodulatory systems project broadly, yet computations engage specific neuronal populations. Whether neuromodulation can selectively influence task-engaged neurons remains unclear. During goal-directed navigation, neurons in the locus coeruleus (LC), the brain's principal norepinephrine source, responded at navigation onset. Concurrently, dopamine transients arose in micrometer-scale domains around LC axons in CA1. These transients preferentially enhanced nearby CA1 neurons with ramping dynamics, whose higher activity predicted later reward-anticipatory action. Brief LC activation evoked local dopamine, enhanced ramping dynamics, and delayed action initiation seconds later. Blocking D1-like, but not adrenergic, receptors weakened ramping dynamics and impaired reward anticipation. Modeling showed that selectivity can emerge when localized dopamine coincides with strong ongoing neuronal activity, without dedicated wiring. Thus, a widely projecting system can selectively modulate task-engaged neurons and shape behavior.

neuroscience↗

bioRxiv2026

A scalable hippocampal code for flexible interval timing through persistent activity

The brains ability to accurately estimate time across various intervals is crucial for flexible behavior. Through the discovery of "time cells", the hippocampus has emerged as a critical region for temporal processing. However, the hippocampal dynamics underlying flexible interval timing remain elusive. Here, utilizing behavioral perturbations, two-photon calcium imaging, and extracellular recordings in dorsal CA1, we identified a previously unknown pyramidal neuron subpopulation that flexibly scales its activity during interval timing. As mice performed a time-estimation task, CA1 time cells were scarce during the delay period. In contrast, persistently active cells (PACs) exhibited sustained activity from the onset of timing until the animals behavioral response. PACs demonstrated temporal scaling: their activity stretched or compressed both with trial-to-trial variations in response time and across different delay durations. PACs comprised two subgroups with complementary ramping dynamics, and their population activity supported reliable decoding of elapsed time. Furthermore, PAC prevalence increased as behavior improved with learning, consistent with their behavioral relevance. Together, these findings revealed scalable sustained dynamics that complement canonical time cell sequences, providing a distinct hippocampal mechanism to support flexible timing behavior.

neuroscience↗

bioRxiv2025

Two-Phase Coding Strategy by CA1 Pyramidal Neurons: Linking Spatiotemporal Integration to Predictive Behavior

Space and time are fundamental components of memory, yet how the brain encodes these dimensions to guide behavior remains unclear. Using virtual-reality environments, we uncovered a two-phase neural code in hippocampus CA1 that represents time or distance through two functional pyramidal subpopulations, PyrUp and PyrDown. In Phase I, PyrUp activity synchronously increases to mark the initiation of encoding; In Phase II, their activity decays at heterogeneous, neuron-specific rates, creating a gradual divergence in across-population firing rates that scales with elapsed time. Conversely, PyrDown activity initially decreases before gradually rising. The crossover point, where rising PyrDown activity surpasses declining PyrUp activity, precedes predictive licking behavior. Combining optogenetics and computational modeling, we provided circuit-level evidence that PyrUp neurons primarily process locomotion-related inputs regulated by somatostatin-positive interneurons, whereas PyrDown neurons mainly receive reward-related inputs gated by parvalbumin-positive interneurons. These findings advance our understanding of how hippocampal circuits compute spatiotemporal information to inform behavior.

neuroscience↗

bioRxiv2023

A CA1 circuit motif that signals the start of information integration

To navigate their environments effectively, animals frequently integrate distance or time information to seek food and avoid threats. This integration process is thought to engage hippocampal neurons that fire at specific distances or times. Using virtual-reality environments, we uncovered two previously unknown functional subpopulations of CA1 pyramidal neurons that encode distance or time through a novel two-phase coding mechanism. The first subpopulation exhibits a collective increase in activity that peaks at similar times, marking the onset of integration; subsequently, individual neurons gradually diverge in their firing rates due to heterogeneous decay rates, enabling time encoding. In contrast, the second subpopulation initially decreases its activity before gradually ramping up. Closed-loop optogenetic experiments revealed that inactivating somatostatin-positive (SST) interneurons disrupts the first subpopulation, behaviorally impairing integration accuracy, while inactivating parvalbumin-positive (PV) interneurons disrupts the second subpopulation, impairing behavior during integration initiation. These findings support the conclusion that SST interneurons establish an integration window, while PV interneurons generate a reset to reinitiate integration. This study elucidates parallel neural circuits that facilitate distinct aspects of distance or time integration, offering new insights into the computations underlying navigation and memory encoding.

neuroscience↗

bioRxiv2017

Sex differences in the genetic architecture of obsessive-compulsive disorder

Obsessive-compulsive disorder (OCD), a highly heritable complex phenotype, demonstrates sexual dimorphism in age of onset and clinical presentation, suggesting a possible sex difference in underlying genetic architecture. We present the first genome-wide characterization of the sex-specific genetic architecture of OCD, utilizing the largest set of OCD cases and controls available from the Psychiatric Genomics Consortium. We assessed evidence for several mechanisms that may contribute to sexual-dimorphism including a sexually dimorphic liability threshold, the presence of individual sex-specific risk variants on the autosomes and the X chromosome, genetic and phenotypic heterogeneity, and sex-specific pleiotropic effects. We observed a strong genetic correlation between male and female OCD and no evidence for a sexually dimorphic liability threshold model. While we did not detect any sex-specific genome-wide associations, we observed that the SNPs with sexually dimorphic effects showed an enrichment of regulatory variants influencing expression of genes in immune tissues. Furthermore, top sex-specific genome-wide associations were enriched for regulatory variants in different tissues, suggesting evidence for potential sex difference in the biology underlying risk for OCD. These findings suggest that future studies with larger sample sizes hold great promise for the identification of sex-specific risk factors for OCD, significantly advancing our understanding of the differences in the genetic basis of sexually dimorphic neuropsychiatric traits.

genomics↗