Biology subjects

Langdon, C.

Publications and source records attributed to Langdon, C..

6 recordsLinked to original sources

bioRxiv2026

Working memory limitations and dopamine modulation in probabilistic reasoning

Difficult decisions require gathering evidence over extended periods, placing demands on working memory. Yet, how working memory limitations affect decision-making remains largely unknown. We trained two macaque monkeys to perform a probabilistic reasoning task that involved extended sequential evidence sampling, requiring reliance on working memory. Monkeys made choices informed by a stream of briefly presented cues, each providing probabilistic evidence about which choice would be rewarded. In both animals, choices were significantly affected by working memory decay, primacy, recency, and priming. Despite individual differences in working memory limitations, both monkeys adopted sampling strategies that made their behavior nearly optimal. To test how dopamine affects working memory constraints on evidence accumulation, we systemically applied dopamine D1 receptor agonist and antagonist drugs midway during selected sessions. Activation of D1 receptors reduced priming. Blockade of D1 receptors reduced working memory decay and the subjective evidence weights assigned to individual cues. Our results reveal that complex decisions are constrained by working memory limitations and identify dopamine as a key modulator of this process, with potential implications for cognitive disorders and their treatment.

neuroscience↗

bioRxiv2025

Local alkalinity enhancement using artificial substrates increases survivorship of early-stage coral recruits

Efforts to restore coral reefs using sexually derived coral recruits are often hindered by their low survivorship and growth, hence scalable interventions to improve these parameters are urgently needed. Here, we developed novel settlement substrates that modify the local chemical and hydrodynamic environments to provide local alkalinity enhancement (AE) within the laminar boundary layer to aid in coral restoration. Cement tiles with four different chemistries and two different surface topographies were tested in a novel flume system to quantify their ability to change local pH under reef-like conditions and their effect on larval settlement, survivorship, and growth of the endangered Caribbean coral, Orbicella faveolata. Chemistry had a minimal effect on the initial settlement of coral larvae, and textured tiles were preferred over smooth tiles. However, substrates that created a more alkaline local environment increased post-settlement survivorship. The increased survivorship of O. faveolata recruits on AE tiles was not due to increased growth on AE tiles, although trends in growth were dependent on chemistry and topography of tiles. Our results indicate that mixing sodium bicarbonate or sodium carbonate into cement used to fabricate artificial reef structures could be an effective means to enhance the development of coral cover. Significance StatementReef-building coral populations in South Florida and the Caribbean are nearing crisis, with low survivorship rates of new recruits being identified as a critical bottleneck limiting their recovery. Since ocean acidification is known to stress corals and hinder their growth, we hypothesized that enhancing substrate alkalinity could help mitigate ocean acidification effects by boosting coral growth and increasing survivorship during their critical early stages. This hypothesis was experimentally tested by adding sodium bicarbonate or sodium carbonate to settlement substrates and studying coral settlement preference, and coral spat growth and survival. Our results showed significantly higher survivorship on alkalinity enhanced substrates, indicating that this could be a promising restoration intervention.

ecology↗

bioRxiv2023

A Brain-Wide Map of Neural Activity during Complex Behaviour

A key challenge in neuroscience is understanding how neurons in hundreds of interconnected brain regions integrate sensory inputs with prior expectations to initiate movements and thereby make decisions. It is difficult to meet this challenge if different laboratories apply different analyses to different recordings in different regions during different behaviours. Here, we report a comprehensive set of recordings from 621733 neurons across 139 mice in 12 labs performing a decision-making task with sensory, motor, and cognitive components, obtained with 699 Neuropixels probe insertions covering 279 brain areas in the left forebrain and midbrain and the right hindbrain and cerebellum. We provide an initial appraisal of this brain-wide map, assessing how neural activity encoded key task variables. Representations of visual stimuli appeared transiently in classical visual areas after stimulus onset and then spread to ramp-like activity in a collection of mid- and hindbrain regions that also encoded choices. Neural responses correlated with motor action almost everywhere in the brain. Responses to reward delivery and consumption versus negative feedback were also widespread. This publicly available dataset represents an unprecedented resource for understanding how computations distributed across and within brain areas drive behaviour.

neuroscience↗

bioRxiv2023

Brain-wide representations of prior information in mouse decision-making

The neural representations of prior information about the state of the world are poorly understood. To investigate them, we examined brain-wide Neuropixels recordings and widefield calcium imaging collected by the International Brain Laboratory. Mice were trained to indicate the location of a visual grating stimulus, which appeared on the left or right with prior probability alternating between 0.2 and 0.8 in blocks of variable length. We found that mice estimate this prior probability and thereby improve their decision accuracy. Furthermore, we report that this subjective prior is encoded in at least 20% to 30% of brain regions which, remarkably, span all levels of processing, from early sensory areas (LGd, VISp) to motor regions (MOs, MOp, GRN) and high level cortical regions (ACAd, ORBvl). This widespread representation of the prior is consistent with a neural model of Bayesian inference involving loops between areas, as opposed to a model in which the prior is incorporated only in decision-making areas. This study offers the first brain-wide perspective on prior encoding at cellular resolution, underscoring the importance of using large scale recordings on a single standardized task.

neuroscience↗

bioRxiv2022

A marine probiotic treatment against the bacterial pathogen Vibrio coralliilyticus to improve the performance of Pacific (Crassostrea gigas) and Kumamoto (C. sikamea) oyster larvae

Oyster larvae reared in hatcheries on the U.S. West coast often experience severe Vibrio coralliilyticus-related mortalities early in their development. Current treatment options for these molluscs are either not available or feasible; however, for decades, probiotics have been successfully used in finfish and crustacean shellfish culture. Consequently, the objectives of this work were to 1) isolate marine bacteria from oysters and evaluate their protective activity against Vibrio coralliilyticus infection of Pacific oyster (Crassostrea gigas) larvae, and 2) to determine the long-term effects of probiotic additions on growth and metamorphosis of larval Pacific and Kumamoto oysters (C. sikamea). A combination of three probiotic strains applied once 24 hours post-fertilization was more effective in improving survival of larval C. gigas exposed to lethal concentrations of V. coralliilyticus strain RE22, compared with separate additions of individual probiotics. In addition, a single application of the probiotic combination to one-day-old larvae increased the larval metamorphosis success of C. sikamea and both the Midori and Myiagi stocks of C. gigas. These results suggest that probiotics are effective at preventing bacterial infections and can significantly improve performance of oyster larvae, using a single application early in their development. Highlights* A combination of marine bacteria improved survival of Pacific oyster larvae exposed to virulent V. coralliilyticus. * Metamorphosis was increased after adding a single dose of probiotics to one-day-old larvae. * Repetitive dosing after each water change was not superior to a single dose one day post egg-fertilization. * A single dose of the probiotic combination resulted in larger size on day 12.

microbiology↗

bioRxiv2022

Latent circuit inference from heterogeneous neural responses during cognitive tasks

Higher cortical areas carry a wide range of sensory, cognitive, and motor signals supporting complex goal-directed behavior. These signals are mixed in heterogeneous responses of single neurons tuned to multiple task variables. Dimensionality reduction methods used to analyze neural responses rely merely on correlations, leaving unknown how heterogeneous neural activity arises from connectivity to drive behavior. Here we present a framework for inferring a low-dimensional connectivity structure--the latent circuit--from high-dimensional neural response data. The latent circuit captures mechanistic interactions between task variables and their mixed representations in single neurons. We apply the latent circuit inference to recurrent neural networks trained to perform a context-dependent decision-making task and find a suppression mechanism in which contextual representations inhibit irrelevant sensory responses. We validate this mechanism by confirming the behavioral effects of patterned connectivity perturbations predicted by the latent circuit structure. Our approach can reveal interpretable and causally testable circuit mechanisms from heterogeneous neural responses during cognitive tasks.

neuroscience↗