Biology subjects

Dasgupta, D.

Publications and source records attributed to Dasgupta, D..

10 recordsLinked to original sources

bioRxiv2025

Biophysically relevant network model of the piriform cortex predicts odor frequency encoding using network mechanisms

Olfactory-guided animals utilize fast concentration fluctuations in turbulent odor plumes to perceive olfactory landscapes. Recent studies have demonstrated that the olfactory bulb (OB) encodes such temporal features present in natural odor stimuli. However, whether this temporal information is encoded in the piriform cortex (PCx) remains unknown. Hence, we developed a biophysically relevant PCx network model and simulated it using previously recorded in vivo activities of mitral and tufted cells in response to 2Hz and 20Hz odor frequencies for three stimulus mixtures. Analysis of single-cell activity across trials revealed that individual pyramidal neurons (PYRs) were largely ineffective at discriminating between 2Hz and 20Hz. However, the trial-averaged activity of the PYR population could discriminate between the two frequencies significantly. Moreover, using log-likelihood scores we further discovered that odor frequency discrimination happened through a highly distributed mechanism among the PYRs. One-dimensional convolutional neural network models trained and tested on PYRs activities achieved discrimination accuracies up to 95%. Using virtual synaptic knockout models, we found that eliminating either feedback or feedforward inhibition onto PYRs improved the decoding accuracy across all odor conditions. Conversely, eliminating recurrent excitation among PYRs or simultaneously eliminating recurrent inhibition within both interneuron populations degraded decoding performance. Removing recurrent connections within individual interneuron populations had minimal effects on the performance. Overall, our PCx model demonstrates that it can discriminate between 2Hz and 20Hz odor stimuli, with a bidirectional capability of performance modulation by specific circuit motifs. These findings predict that the piriform cortex encodes and processes temporal features of odor stimuli. New & NoteworthyWe simulated the first biophysically relevant network model of the piriform cortex (PCx) to show differential encoding of odor frequencies at 2Hz and 20Hz. 1D convolutional neural networks demonstrated a distributed role of pyramidal neurons in the encoding. Surprisingly, eliminating feedforward or feedback inhibition improves frequency discrimination, while eliminating recurrency impairs it. Specific circuit motifs, not just baseline activity levels, determine odor frequency representation. Overall, our results predict the PCxs capacity for temporal odor processing.

neuroscience↗

bioRxiv2025

Mice discriminate odour source distance via sub-sniff temporal features of odour plumes

Rodents rely on olfaction to navigate complex environments, particularly where visual cues are limited. Yet how they estimate the distance to an odour source remains unclear. The spatiotemporal dynamics of natural odour plumes, shaped by airflow turbulence, offer valuable cues for locating odour sources. Here, we show that mice can discriminate odour sources placed at different distances by extracting information from the sub-sniff temporal structure of naturalistic odour plumes. Using a wind tunnel and an olfactory virtual reality system, we generated dynamic plumes and demonstrated, through high-throughput automated behaviour, that mice distinguish near from far sources based on odour fluctuations operating faster than their respiratory cycle. Two-photon calcium imaging of olfactory bulb projection neurons revealed that distance-dependent responses are present in a small subset of mitral and tufted cells, and that population activity encodes source distance. Critically, neural responses correlated more strongly with high-frequency plume features than with mean odour concentration. Our results identify a neural basis for distance estimation from odour dynamics and highlight the importance of rapid temporal processing in mammalian olfaction.

neuroscience↗

bioRxiv2024

Nrf2 regulates the activation-driven expansion of CD4+ T-cells by differentially modulating glucose and glutamine metabolism

SUMMARYUpon antigenic stimulation, CD4+T-cells undergo clonal expansion, elevating their bioenergetic demands and utilization of nutrients like glucose and glutamine. The nuclear factor erythroid 2-related factor 2 (Nrf2) is a well-known regulator of oxidative stress, but its involvement in modulating the metabolism of CD4+T-cells remains unexplored. Here, we elucidate the role of Nrf2 beyond the traditional antioxidation, in modulating activation-driven expansion of CD4+T-cells by influencing their nutrient metabolism. T-cell-specific activation of Nrf2 enhances early activation and IL-2 secretion, upregulates TCR-signaling, and increases activation-driven proliferation of CD4+T-cells. Mechanistically, high Nrf2 inhibits glucose metabolism through glycolysis but promotes glutamine metabolism via glutaminolysis to support increased T-cell proliferation. Further, Nrf2 expression is temporally regulated in activated CD4+T-cells with elevated expression during the early activation, but decreased expression thereafter. Overall, our findings uncover a novel role of Nrf2 as a metabolic modulator of CD4+T-cells, thus providing a framework for improving Nrf2-targeting therapies and T-cell immunotherapies.

immunology↗

bioRxiv2023

Gestures Of Hunger: Uncovering Intentional Gestural Communication In Free-Ranging Hanuman Langurs

Contrary to previous beliefs, intentional gestural communication (IGC) is not exclusive to the hominoid lineage but is also present in other non-human primates. Here, we report the presence of IGC among free-ranging Hanuman langur troop in Dakshineswar, West Bengal, India. These langurs exhibit a food-requesting behaviour wherein they use several gestures to communicate with the humans nearby. Moreover, they can also assess the recipients mental state and persistently check if the signal (food request) has been received, waiting until they receive the desired food item. We have identified eight begging gestures used by langurs of all ages, except infants. The most common gesture is by holding cloth (BGc), but provocation-initiated begging (BGpi) and begging by embracing legs (BGe) efficiently direct these events to its success. The frequency of successful begging events is higher in the evening due to increased human interactions. Our findings suggest that ontogenetic ritualization might be at play here among these troop members as this gestural communication has been learned through imitation and reinforced by the reward of receiving food. Moreover, these successful begging events serve as an effective foraging strategy for urban-adapted langurs, allowing them to acquire high-calorie processed food items within a human-modified urban ecosystem.

animal behavior and cognition↗

bioRxiv2023

Wireless monitoring of respiration with EEG reveals relationships between respiration, behaviour and brain activity in freely moving mice

Active sampling in the olfactory domain is an important aspect of mouse behaviour. Numerous methods are being used to measure active sampling behaviour, yet reliable observation of respiration in untethered, freely moving animals is challenging. So far, methods for measuring this have largely been restricted to head-fixed sniff monitoring, which makes it difficult to understand how sniff changes are related to natural mouse behaviour. Here, we implant a telemetry-based pressure sensor into the right jugular vein, which allows respiration to be measured via wireless thoracic pressure sensing in awake and freely moving, untethered mice. After verifying this technique against standard head-fixed respiration measurements, we investigated respiration patterns across a range of experiments in freely moving animals. Respiration frequency increased as mice voluntarily explored novel environmental cues. Combining wireless respiration measurements with EEG/EMG recording, we then used an evolving partial coherence analysis to uncover the direct relationships between respiration and brain activity in different frequency bands over the same exploration period. Finally, we examined respiration patterns across different vigilance states, revealing changes in passive respiration frequency across wakefulness, deep (NREM) sleep and dreaming (REM) sleep, and odour-triggered respiration increases in the absence of brain activity changes during NREM sleep. As it can be combined with behavioural assays and brain recordings, we anticipate that wireless respiration monitoring will be a valuable tool to increase our understanding of how mice use olfaction to process and interact with the environment around them.

neuroscience↗

bioRxiv2023

Left or right: Handedness in free-ranging Hanuman langurs (Semnopithecus entellus) residing in an urban ecosystem.

Examining manual lateralization (handedness) in nonhuman primates might be an interesting approach to gaining insight into the evolution of asymmetry in humans. Moreover, handedness could also reflect the effect of environmental alterations on the free-ranging animals who are forced to live with anthropogenic interferences. Despite addressing the handedness among monkeys and apes, only a few studies have focused on these free-ranging urban-adapted nonhuman primates, which could challenge our perception of habitat loss and deforestation. Here, we conducted 193 field-based experimental trials with two experimental tasks, one unimanual (simple reaching) and one bimanual (tube task) to explore manual lateralization in a highly human-provisioned group of free-ranging Hanuman langur (Semnopithecus entellus). Experimental outcomes revealed an asymmetrical hand-use distribution, with a bias toward the left hand. As bimanual tasks evoked a higher degree of lateralization, these tasks seem to be more suited to study manual laterality, and our results also highlight the significance of experimental tasks in establishing hand preference in langurs. Furthermore, this study also reveals that such lateralization developed with age as adults distinctly displayed their preference toward left-hand usage in contrast to juveniles and subadults who used both hands comparably. Mostly considered to be arboreal, the langurs of our study group spend a considerable amount of time with humans on the ground, thereby portraying a terrestrial tendency. Postural Origin Theory states that terrestrial animals tend to use their right hand and arboreal their left. Therefore, here the presence of group-level left-hand biasness in the adult langurs of Dakshineswar creates a dilemma in the Postural Origin Theory.

animal behavior and cognition↗

bioRxiv2020

Coupling of mouse olfactory bulb projection neurons to fluctuating odour pulses

Odours are transported by turbulent air currents, creating complex temporal fluctuations in odour concentration. Recently, we have shown that mice can discriminate odour stimuli based on their temporal structure, indicating that information present in the temporal structure of odour plumes may be extracted by the mouse olfactory system. Here using in vivo electrophysiological recordings, we show that mitral and tufted cells (M/TCs), the projection neurons of the mouse olfactory bulb, can encode the dominant temporal frequencies present in odour stimuli up to frequencies of at least 20 Hz. We show that M/TCs couple their membrane potential to odour concentration fluctuations; coupling was variable between M/TCs but independent of the odour presented and with TCs displaying slightly elevated coupling compared to MCs in particular for higher frequency stimulation (20Hz). Pharmacologically blocking the inhibitory circuitry strongly modulated frequency coupling. Together this suggests that both cellular and circuit properties contribute to the encoding of temporal odour features in the mouse olfactory bulb.

neuroscience↗

bioRxiv2020

Altered food habits? Understanding the feeding preference of free-ranging Grey langur (Semnopithecus entellus) within an urban settlement.

Urbanization affects concurrent human-animal movements as a result of altered resource availability and land use pattern, which leads to considerable ecological consequences. While some animals find themselves adrift, homeless with the uncertainty of resources resulting from the urban encroachment, few of them manage to survive by altering their natural behavioural patterns, and co-exist with humans. Folivorous colobines, such as grey langur, whose feeding repertoire largely consists of plant parts, tend to be more attuned to the urban high-calorie food sources to attain maximum fitness benefits within the concrete jungle having an insignificant green cover. However, such a mismatch between their generalized feeding behaviour and specialized gut physiology reminds us of the Liems paradox and demands considerable scientific attention which could tell us the story behind colobines successful co-existence within human settlements. Besides understanding their population dynamics, the effective management of these urbanized, free-ranging, non-human primate populations also depends on their altered feeding preferences, altogether which could lead us to the development of an ecologically sound urban ecosystem. Here, we have used a field-based experimental set up which allows langurs to choose between natural and urban food options, being independent of any inter-specific conflicts over resources due to food scarcity. The multinomial logit model reveals the choice-based decision making of these free-ranging grey langurs in an urban settlement of West Bengal, India, where they have not only learned to approach the human-provisioned urban food items but also shown a keen interest in it. While urbanization imposes tremendous survival challenges to these animals, it also opens up for various alternative options for human-animal co-existence which is reflected in this study, and could guide us for the establishment of a sustainable urban ecosystem in the future. HIGHLIGHTSO_LIThe feeding repertoire of free-ranging grey langurs at Dakshineswar largely consists of urban food items in contrast to the langurs of Nangi, and Nalpur who mostly depend on natural food sources. C_LIO_LIHigh human-langur interactions together with the scarcity of natural plant-based food sources could be considered as an intriguing driving force behind langurs altered feeding habits in Dakhineswar. C_LIO_LIThe field-based experimental set up allows free-ranging langurs to choose between natural and urban food options in an urban settlement like Dakhineswar. C_LIO_LIUrban food items outperformed natural food items as the most chosen one, indicating langurs altered feeding preferences which facilitate their successful co-existence within an urban ecosystem. C_LI

animal behavior and cognition↗

bioRxiv2020

An in-silico based clinical insight on the effect of noticeable CD4 conserved residues of SARS-CoV-2 on the CD4-MHC-I interactions

The study is aimed to unveil the conserved residues of CD4 in the context of its purposeful interaction with MHC-II at the receptor-binding domain (RBD) of SARS-CoV-2 compared with the envelope (Env) glycoprotein (gp) 120 of HIV-1. The paired CD4 conserved residues, including the matched CD4 interacting MHC-II epitopes of the structural viral protein domains, were chosen for the protein modelling using the SWISS-MODEL online server. Energy minimization and structural validation of the modelled viral protein domains, including the CD4 and MHC-II protein were achieved by CHIMERA and PROCHECK-Ramachandran Plot respectively. Protein-protein docking was performed by the HADDOCK online tool. The binding affinity score was measured using the PRODIGY online server. As per our docking report, the Env gp120 of HIV-1 with three identical and three conserved residues of CD4 exhibited the highest binding affinity (-13.9 kcal/mol) with MHC-II than the second-highest RBD-S1-SARS-CoV-2 (-12.5 kcal/mol) with three identical and a single conserved residue of CD4. With a noticeable single salt bridge formation identified at the interacting residues Lys305 (of Env gp120-HIV-1) and Glu139 (of MHC-II); the Env gp120 interaction with MHC-II occupied the crucial His144 and Glu194 (salt-bridge) interacting residues of CD4 with the measured buried surface area 2554.8{+/-}40.8 [A]2. Similarly, the RBD-S1-SARS-CoV-2-MHC-II complex showed two salt bridge formations at the residue sites: 1) Arg567 (of SARS-CoV-2)-Glu194 (of MHC-II) 2) 2) Asp568(of SARS-CoV-2)-Arg165 (of MHC-II) with the increased buried surface area of 1910.9{+/-}97.1 [A]2 over the SARS-CoV score 1708.2{+/-}50.8 [A]2; that camouflaged all crucial CD4 interacting residues of MHC-II. In conclusion, the noticeable conserved residues of CD4 at the RBD-S1 sites of SARS-CoV-2 could interrupt the aspired CD4-MHC-II interactions of adaptive immune activation.

bioinformatics↗

bioRxiv2019

Mammalian olfaction is a high temporal bandwidth sense

Odours are transported in turbulent plumes resulting locally in highly fluctuating odour concentration (Celani et al., 2014; Murlis et al., 1992; Mylne and Mason, 1991; Shraiman and Siggia, 2000). Yet, whether mammals can make use of the ensuing temporal structure (Celani et al., 2014; Crimaldi and Koseff, 2001; Murlis et al., 1992; Mylne and Mason, 1991; Schmuker et al., 2016; Vickers, 2000) to extract information about the olfactory environment remains unknown. Here, we use dual-energy photoionisation recording with >300 Hz bandwidth to simultaneously determine odour concentrations of two odours in air. We show that temporal correlation of odour concentrations reliably predicts whether odorants emerge from the same or different sources in normal turbulent environments outside and in laboratory conditions. To replicate natural odour dynamics in a reproducible manner we developed a multichannel odour delivery device allowing presentation of several odours with 10 ms temporal resolution. Integrating this device in an automated operant conditioning system we demonstrate that mice can reliably discriminate the correlation structure of odours at frequencies of up to 40 Hz. Consistent with this finding, output neurons in the olfactory bulb show segregated responses depending on the correlation of odour stimuli with populations of 10s of neurons sufficient to reach behavioural performance. Our work thus demonstrates that mammals can perceive temporal structure in odour stimuli at surprisingly fast timescales. This in turn might be useful for key behavioural challenges (Jacobs, 2012) such as odour source separation (Hopfield, 1991), figure-ground separation (Rokni et al., 2014) or odour localisation (Vergassola et al., 2007; Vickers, 2000).

neuroscience↗