Ferraris, M. | bioRxiv Science

bioRxiv2023

Long-term near-continuous recording with Neuropixels probes in healthy and epileptic rats

Neuropixels probes have become a crucial tool for high-density electrophysiological recordings. Although most research involving these electrodes is in acute preparations, some scientific inquiries require long-term recordings in freely moving animals. Recent reports have presented prosthesis designs for chronic recordings, but some of them do not allow for probe recovery, which is desirable given their cost. Others appear to be fragile, as these articles describe numerous broken implants. This fragility presents a challenge for recordings in rats, particularly in epilepsy models where strong mechanical stress impinges upon the prosthesis. To overcome these limitations, we present a new prosthesis specifically designed to protect the probes from strong shocks and enable the safe retrieval of electrodes after experiments. This implant was successfully used to record from healthy and epileptic rats for up to three weeks almost continuously, with a probe retrieval and reuse success rate of 91%, improving previously described recycling performances.

neuroscience↗

bioRxiv2018

Spatio-temporal organization of cell assemblies in Nucleus Reuniens during slow oscillations

The nucleus reuniens (NR) is an important anatomical and functional relay between the medial prefrontal cortex (mPFC) and the hippocampus (HPC). Whether the NR controls neuronal assemblies, a hallmark of information exchange between the HPC and mPFC for memory transfer/consolidation, is not known. Using simultaneous LFP and unit recordings in NR, HPC and mPFC in rats during slow oscillations under anesthesia, we identified a reliable sequential activation of NR neurons at the beginning of UP states, which preceded mPFC ones. NR sequences were spatially organized, from dorsal to ventral NR. Chemical inactivation of the NR disrupted mPFC sequences at the onset of UP states as well as HPC sequences present during sharp-wave ripples. We conclude that the NR contributes to the coordination and stabilization of mPFC and HPC neuronal sequences during slow oscillations, possibly via the early activation of its own sequences. Significance StatementNeuronal assemblies are believed to be instrumental to code/encode/store information. They can be recorded in different brain regions, suggesting that widely distributed networks of networks are involved in such information processing. The prefrontal cortex, the hippocampus and the thalamic nucleus reuniens constitute a typical example of a complex network involved in memory consolidation. In this study, we show that spatially organized cells assemblies are recruited in the nucleus reuniens at the UP state onset during slow oscillations. Nucleus reuniens activity appears to be necessary to the stability of prefrontal cortex and hippocampal cell assembly formation during slow oscillations. This result further highlights the role of the Nucleus Reuniens as a functional hub for exchanging and processing memories.

neuroscience↗