Mick CraigMy new year's resolution was to work through the pile of almost-finished papers so... #PrePrintAlert #Neuroscience. This is an update to one we put out late 2021, which got delayed with Lilya (lead author) going on maternity leave (yay, lab baby! đ„°). Download it from: https://www.biorxiv.org/content/10.1101/2021.09.30.462517v3
Prefrontal - hippocampal communication is needed for spatial working memory and decision-making. But, remarkably, no direct PFC to HPC connection exists (see our 2023 paper looking at this https://elifesciences.org/articles/77364). Instead, prefrontal input to HPC is presumably relayed via thalamus. So we sought to have a look at thalamic projections to hippocampus proper, which go from nucleus reuniens (NRe) to CA1, where the fibres terminate in SLM. We used optogenetics and patching to map the inputs to CA1 but we could never find a pyramidal cell that responded to NRe inputs.
In CA1, we only ever found interneurons (mostly neurogliaform cells) responding to NRe input. But moving into prosubiculum or subiculum, and we did see small EPSCs in pyrs from NRe axon stimulation (10s of pA). Looking at entorhinal cortex (EC) and PFC, we found big, fat NRe-driven currents. NRe inputs to neurogliaform cells in CA1 had huge NMDA currents, many times larger than the AMPA current. So NRe is more likely to modulate hippocampal activity (via feedforward inhibition) when there is ongoing activity. We wrote a wee piece on this in 2022: https://www.science.org/doi/abs/10.1126/science.add2681
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Fabrizio Musacchio
