Biology subjects

Mozumder, R.

Publications and source records attributed to Mozumder, R..

5 recordsLinked to original sources

bioRxiv2026

Repeatable, low-drift recordings in behaving non-human primates using flexible microelectrodes

Neurophysiological recordings from non-human primates (NHPs) have traditionally relied on rigid microelectrode arrays made from stainless steel or silicon. While these devices enable high-quality recordings, a fundamental mechanical mismatch between rigid materials and soft brain tissue leads to inflammation, gliosis, and signal instability. In particular, brain micromotion causes continuous drifting of neurons relative to fixed electrodes, compromising single-unit tracking during both chronic and acute recordings. Flexible, penetrating electrodes offer a promising solution, but their adoption in NHPs has been hindered by the technical challenges of delivering ultra-thin polymers through thick dura mater. Here, we demonstrate a comprehensive approach for acute, repeated recordings in awake, behaving NHPs using flexible arrays. We fabricated a microelectrode array that spans cortical layers with 32 cellular-scale recording sites embedded in 7 m-thick Parylene-C. We developed a novel "telescopic" insertion method that combines concentric guide tubes with a retractable microwire shuttle. Our technique is compatible with standard chronic recording chambers and allowed for repeated penetration of free-floating arrays through intact dura over weeks without the need for a new craniotomy. Across two awake rhesus macaques, we optimized the electrode geometry and insertion procedure to achieve an 80% single-unit recording success rate. As animals performed an oculomotor delayed response task, we recorded task-responsive neurons from prefrontal and posterior parietal cortex with stable single-unit activity throughout 1-2-hour behavioral sessions. Critically, by comparing our flexible arrays to rigid probes in the same animals and recording chambers, we provide quantitative evidence that flexible electrodes reduce total single-unit drift from hundreds to tens of microns. Our work establishes flexible microelectrode arrays as a practical, dependable technology for NHP neuroscience and paves the way toward long-term, ultra-stable neurophysiology in large animal models.

neuroscience↗

bioRxiv2025

Asynchronous firing and off-states in working memory maintenance

Persistent spiking activity and activity-silent mechanisms have been proposed as neural correlates of working memory. To determine their relative contribution, we recorded neural activity from the lateral prefrontal and posterior parietal cortex of two male macaques using high-density microelectrode probes. We found that, when averaged across all neurons, persistent delay activity was observable throughout the duration of single trials in populations of prefrontal neurons with silent periods that did not deviate significantly from chance. However, temporal fluctuations in activity-dependent mnemonic information were present and weakly correlated between the prefrontal and posterior parietal cortices, suggesting at least partial, long-distance synchronization of off-states. Decoding accuracy of neurons recorded simultaneously was also reduced relatively to pseudo-populations constructed by splicing different trials together. Our results support an asynchronous state of working memory, maintained by the distributed pattern of persistent discharges across cortical neurons, which is subject to widely distributed fluctuations in information representation fidelity.

neuroscience↗

bioRxiv2025

Integration of Audiovisual Motion in Dorsolateral Prefrontal Cortical Neurons

The dorsolateral prefrontal cortex is well recognized for its role in cognitive functions and activating action plans. In contrast, the properties of prefrontal neurons with respect to multisensory processing are less well studied. To address this question, we recorded single units from areas 8a and 46 of two female rhesus macaques while they were presented with visual, auditory, and audiovisual motion stimuli. The majority of dorsolateral prefrontal neurons responded to these sensory stimuli, with similar percentages of auditory-only, visual-only and audiovisual neurons. Approximately one third of responsive neurons exhibited significant super- or sub-additive interactions in response to the pairing of auditory and visual stimuli, revealing significant nonlinearities in their response profiles. Decoding motion signals from the population activity robustly differentiated multisensory from unisensory trials and also unisensory auditory and visual trials from each other. These results demonstrate that dorsolateral prefrontal neurons integrate auditory and visual motion signals, extending multisensory computations beyond sensory cortices into prefrontal circuits that support higher-order cognition. New & NoteworthyWe recorded single neurons in macaque dorsolateral prefrontal cortex during visual, auditory, and audiovisual motion. Nearly half of responsive neurons were multisensory and a third displayed significant super- or sub-additive interactions, while ensemble activity reliably decoded stimulus modality. These findings provide the strongest evidence to date that DLPFC performs rapid, nonlinear audiovisual integration, extending multisensory computations beyond classical posterior regions into the prefrontal circuits that support cognition.

neuroscience↗

bioRxiv2023

Single-neuron and population measures of neuronal activity in working memory tasks

Information represented in working memory is reflected in the firing rate of neurons in the prefrontal cortex and brain areas connected to it. In recent years, there has been an increased realization that population measures capture more accurately neural correlates of cognitive functions. We examined how single neuron firing in the prefrontal and posterior parietal cortex of two male monkeys compared with population measures in spatial working memory tasks. Persistent activity was observed in the dorsolateral prefrontal and posterior parietal cortex and firing rate predicted working memory behavior, particularly in the prefrontal cortex. These findings had equivalents in population measures, including trajectories in state space that became less separated in error trials. We additionally observed rotations of the stimulus space for different task conditions, which was not obvious in firing rate measures. These results suggest that population measures provide a richer view of how neuronal activity is associated with behavior, however, largely confirm that persistent activity is the core phenomenon that maintains visual-spatial information in working memory. NEW & NOTEWORTHYRecordings from large numbers of neurons led to a re-evaluation of neural correlates of cognitive functions, which traditionally were defined based on responses of single neurons, or averages of firing rates. Analysis of neuronal recordings from the dorsolateral prefrontal and posterior parietal cortex revealed that properties of neuronal firing captured in classical studies of persistent activity can account for population representations, though some population characteristics did not have clear correlates in single neuron activity.

neuroscience↗

bioRxiv2023

Influence of Fast-Spiking Prefrontal Neurons on Working Memory Behavior

Working memory is a limited-capacity system for maintaining and manipulating information for recall. Neurons that generate persistent activity in the primate dorsolateral prefrontal and posterior parietal cortex have been shown to be predictive of behavior in working memory tasks, though subtle differences between them have been observed in how information was represented, in some tasks. The role of different neuron types in each of these areas has not been investigated at depth. We thus compared the activity of neurons classified as fast-spiking, putative interneurons, and regular-spiking, putative pyramidal neurons, recorded from the prefrontal and posterior parietal cortex of male monkeys, to analyze their role in the maintenance of working memory. Our results demonstrate that fast-spiking neurons are active during a range of tasks and generate persistent activity during the delay period over which stimuli need to be maintained in memory. Furthermore, the activity of fast spiking neurons, particularly in the prefrontal cortex, is predictive of the subjects recall no less than that of regular-spiking neurons, which are exclusively projection neurons in the cortex and thus capable of transmitting signals from the prefrontal cortex into other areas. Our results shed light onto the fundamental neural circuits that determine subjects memories and judgments.

neuroscience↗