Biology subjects

Jutras, M. J.

Publications and source records attributed to Jutras, M. J..

3 recordsLinked to original sources

bioRxiv2026

Physiological landmarks reveal the laminar organization of the primate hippocampus

The laminar anatomy of the hippocampal microcircuit is conserved across mammals, and its physiology has been characterized extensively in rodents, yet how this circuitry is organized physiologically in the primate brain remains poorly understood. Here we used high-density Neuropixels probes to record simultaneously across the subfields of CA1, CA3 and the dentate gyrus in two awake macaques. Sharp-wave ripples and dentate spikes produced current source density signatures that provided physiological landmarks for CA1 and the dentate gyrus, enabling alignment of recordings to hippocampal cytoarchitecture. Theta-band (3-7 Hz) oscillatory activity occurred in discrete bouts whose prevalence peaked in the stratum lacunosum-moleculare. In CA1, gamma-band amplitude was modulated by theta-band phase, with fast and slow gamma preferentially coupled to distinct phases of the theta cycle. Putative principal cells and two interneuron classes differed systematically in firing rate, burstiness, and rhythmic modulation, with principal cells showing theta-rhythmic firing and wide-waveform interneurons showing alpha- and beta-rhythmic firing. Cross-correlogram analyses revealed sparse, distance-dependent functional coupling with a consistent directional hierarchy in which principal cells led interneurons. Together, these results identify the laminar microcircuit organization of the primate hippocampus in vivo and provide a new physiological framework for interpreting primate hippocampal recordings.

neuroscience↗

bioRxiv2026

Neural representations of beliefs in a multi-dimensional inference task

Adaptive behavior requires maintaining and updating probabilistic beliefs about the world, yet how distributed brain circuits implement such computations remains unknown. We recorded from over 1,400 neurons across six brain regions in monkeys performing a multi-dimensional inference task requiring them to infer hidden rules through trial-and-error learning. Behavior was well-described by models based on Bayesian updating of beliefs over rule features. Neural representations of both observable variables (stimuli, rewards) and latent beliefs (rule preferences, confidence) were broadly distributed across hippocampus, amygdala, prefrontal cortex, anterior cingulate, striatum, and inferior temporal cortex. Belief representations were present throughout all task periods but exhibited region- and epoch-specific dynamics. Critically, trial-to-trial changes in population activity reflected Bayesian belief updating: neural responses evolved according to the integration of prior beliefs with new evidence. Additionally, we identified confidence representations that were independent of specific beliefs and showed distinct temporal profiles. These results demonstrate that probabilistic inference emerges from coordinated dynamics across distributed brain systems, with different regions contributing flexibly according to computational demands at different states of learning and decision-making.

neuroscience↗

bioRxiv2023

Comparing rapid rule-learning strategies in humans and monkeys

Inter-species comparisons are key to deriving an understanding of the behavioral and neural correlates of human cognition from animal models. We perform a detailed comparison of macaque monkey and human strategies on an analogue of the Wisconsin Card Sort Test, a widely studied and applied multi-attribute measure of cognitive function, wherein performance requires the inference of a changing rule given ambiguous feedback. We found that well-trained monkeys rapidly infer rules but are three times slower than humans. Model fits to their choices revealed hidden states akin to feature-based attention in both species, and decision processes that resembled a Win-stay lose-shift strategy with key differences. Monkeys and humans test multiple rule hypotheses over a series of rule-search trials and perform inference-like computations to exclude candidates. An attention-set based learning stage categorization revealed that perseveration, random exploration and poor sensitivity to negative feedback explain the under-performance in monkeys.

animal behavior and cognition↗