Biology subjects

Srivathsa, S.

Publications and source records attributed to Srivathsa, S..

3 recordsLinked to original sources

bioRxiv2026

Hippocampus-evoked polysynaptic responses in the medial prefrontal cortex are attenuated in aged rats.

The hippocampus-medial prefrontal cortex (mPFC) circuit is critical for spatial working memory and decision-making. Age-associated changes to these functions are attributed to alterations in this circuit, although the exact mechanisms remain unclear. These regions are connected via monosynaptic projections from the intermediate (iHC) and ventral (vHC) hippocampus to the infralimbic (IL) and prelimbic (PL) regions of the mPFC. We examined the functional connection between these regions in young (10-12 months) and aged (23-26 months) male F344 rats. High-density Neuropixels probes were used to record mPFC field potentials (fEPSPs) and single-unit responses to electrical stimulation of iHC and vHC. We observed that hippocampal stimulation evoked both short-latency (5-35 ms) monosynaptic and long-latency (35-100 ms) polysynaptic responses in PL and IL cortices. Monosynaptic responses, reflecting direct hippocampal-prefrontal synaptic transmission, had lower vHC-evoked IL fEPSP amplitude in aged rats, while other subregional HC-mPFC connections and evoked neural firing were preserved. The polysynaptic responses, reflecting local mPFC circuit recruitment, also had lower IL fEPSP amplitude in aged rats, while evoked neural firing in the polysynaptic window was diminished in both mPFC regions. Age-associated polysynaptic changes in mPFC neural responses differed by the HC stimulation site. In aged rats, iHC stimulation resulted in a lower proportion of recruited neurons, while vHC stimulation resulted in diminished evoked mPFC firing rates, compared to young rats. Our findings demonstrate that aging selectively impairs vHC-mPFC direct synaptic transmission and mPFC local responses, with infralimbic circuits showing particular vulnerability. These circuit-level deficits may contribute to age-related impairments in cognitive flexibility. Significance StatementAging impairs spatial working memory and decision making which require hippocampus-prefrontal communication. We examined the age-related changes in the functional connection of the intermediate (iHC) and ventral (vHC) hippocampus direct projection onto prelimbic (PL) and infralimbic (IL) regions of the mPFC. We found the vHC-evoked IL monosynaptic excitatory field potential amplitude was lower in aged rats, while other HC-mPFC connections were preserved. The evoked polysynaptic excitatory field potentials and single-unit responses were attenuated with age in both mPFC regions with responses differing between HC stimulation sites. These results identify subregional changes in how hippocampal inputs alter mPFC local recruitment in aging that may explain related impairments in cognitive flexibility.

neuroscience↗

bioRxiv2019

Mate-finding dispersal reduces local mate limitation and sex bias in dispersal

O_LISex-biased dispersal (SBD) often skews the local sex ratio in a population. This can result in a shortage of mates for individuals of the less-dispersive sex. Such mate limitation can lead to Allee effects in populations that are small or undergoing range expansion, consequently affecting their survival, growth, stability and invasion speed. C_LIO_LITheory predicts that mate shortage can lead to either an increase or a decrease in the dispersal of the less-dispersive sex. However, neither of these predictions have been empirically validated. C_LIO_LITo investigate how SBD-induced mate limitation affects dispersal of the less-dispersive sex, we used Drosophila melanogaster populations with varying dispersal propensities. To rule out any mate-independent density effects, we examined the behavioral plasticity of dispersal in presence of mates as well as same-sex individuals with differential dispersal capabilities. C_LIO_LIIn the presence of high-dispersive mates, the dispersal of both male and female individuals was significantly increased. However, the magnitude of this increase was much larger in males than in females, indicating that the former show greater mate-finding dispersal. Moreover, the dispersal of either sex did not change when dispersing alongside high- or low-dispersive individuals of the same sex. This suggested that the observed plasticity in dispersal was indeed due to mate-finding dispersal, and not mate-independent density effects. C_LIO_LIStrong mate-finding dispersal can diminish the magnitude of sex bias in dispersal. This can modulate the evolutionary processes that shape range expansions and invasions, depending on the population size. In small populations, mate-finding dispersal can ameliorate Allee effects. However, in large populations, it can dilute the effects of spatial sorting. C_LI

ecology↗

bioRxiv2017

Pre-dispersal conditions and presence of opposite sex modulate density dependence and sex bias of dispersal

Density-dependent dispersal (DDD) has been demonstrated in many species and has several ecological and evolutionary consequences. Yet we know little about how robust DDD is to the various conditions experienced by individuals. In this study, we use three independent experiments on laboratory populations of Drosophila melanogaster to examine the effects of pre-dispersal adult density, sex of the dispersers and presence of mates on the robustness of DDD patterns. We show that DDD can be greatly affected by both pre-dispersal density and interaction between the sexes. Moreover, the direction of sex-biased dispersal can reverse completely due to an interaction between the pre-dispersal and dispersal densities. We also show that interaction between the sexes can lead to negative DDD at the population level, even if, by themselves, neither sex exhibits DDD. Finally, we discuss potential implications of our results for processes like evolutionary rescue from extinctions and genetic divergence of populations.

ecology↗