Different theta frameworks coexist in the rat hippocampus and are coordinated during memory-guided and novelty tasks

[EN] Hippocampal firing is organized in theta sequences controlled by internal memory processes and by external sensory cues, but how these computations are coordinated is not fully understood. Although theta activity is commonly studied as a unique coherent oscillation, it is the result of complex interactions between different rhythm generators. Here, by separating hippocampal theta activity in three different current generators, we found epochs with variable theta frequency and phase coupling, suggesting flexible interactions between theta generators. We found that epochs of highly synchronized theta rhythmicity preferentially occurred during behavioral tasks requiring coordination between internal memory representations and incoming sensory information. In addition, we found that gamma oscillations were associated with specific theta generators and the strength of theta-gamma coupling predicted the synchronization between theta generators. We propose a mechanism for segregating or integrating hippocampal computations based on the flexible coordination of different theta frameworks to accommodate the cognitive needs.European Regional Development Fund BFU2015-64380-C2-1-R Santiago Canals European Regional Development Fund BFU2015-64380-C2-2-R David Moratal European Regional Development Fund PGC2018-101055-B-I00 Santiago Canals Horizon 2020 Framework Programme 668863 (SyBil-AA) Santiago Canals Agencia Estatal de Investigacion SEV-2017-0723 Santiago Canals Ministerio de Economia y Competitividad TEC2016-80063-C3-3-R Claudio R Mirasso Ministerio de Economia y Competitividad TEC2016-80063-C3-2-R Ernesto Pereda Agencia Estatal de Investigacion MDM-2017-0711 Claudio R Mirasso Ministerio de Economi ' a y Competitividad SAF2016-80100-R Oscar Herreras The funders had no role in study design, data collection and interpretation, or the decision to submit the work for publication.López-Madrona, VJ.; Pérez-Montoyo, E.; Alvarez-Salvado, E.; Moratal, D.; Herreras, O.; Pereda, E.; Mirasso, CR.... 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Memory encoding and brain-wide functional connectivity is controlled by dentate gyrus parvalbumin interneurons

Resumen del trabajo presentado al DANDRITE (Danish Research Institute of Translational Neuroscience-DANDRITE) Internal Meeting, celebrado el 25 de noviembre de 2022.Peer reviewe

Binding experience-relevant neuronal assemblies through disinhibition

Trabajo presentado al 12th Federation of European Neuroscience Societies (FENS): Virtual Forum of NeuroScience, celebrado del 11 al 15 de julio de 2020.Granule cells in the dentate gyrus (DGgc), a brain region important for spatial learning, are part of the engrams formed when an animal explores a new context. Previous work showed that modulation of DGgc activity by perisomatic inhibition bidirectionally regulates memory encoding. Whether this result is due to a differential recruitment of experience-relevant neuronal assemblies or the functional connectivity between them, is not yet known. We combined pharmacogenetic tools (DREADDs) to increase or decrease the activity of parvalbumin (PV)-interneurons in DG while mice encoded spatial information in the Novel Object Location task (NOL). Sixty min after memory encoding in the NOL task animals were sacrificed and their brains processed and quantified for c-Fos staining. Exploration in the NOL task induced a robust increase in the number of c-Fos+ cells across hippocampal subfields. However, the number of c-Fos+ cells, both in the hippocampus and extra-hippocampal structures like the medial prefrontal cortex (mPFC) and the nucleus accumbens, was constant regardless of the inhibitory tone in the DG. Only a moderate increase in c-Fos intensity per cell in DGgc was found in the PV-cell inhibition group. In contrast, we found a significant increase in the correlation between the number of c-Fos+ cells in all quantified neuronal assemblies during PV-inhibition, and a decrease during activation. Together, these data reveal a critical regulatory role of perisomatic inhibition in the dentate gyrus in binding experience-relevant neuronal assemblies in memory.This work was supported by the Spanish Ministerio de Economía y Competitividad (MINECO) and FEDER funds under the grant PGC2018-101055-B-100).Peer reviewe

Low-Power Lossless Data Compression for Wireless Brain Electrophysiology

Wireless electrophysiology opens important possibilities for neuroscience, especially for recording brain activity in more natural contexts, where exploration and interaction are not restricted by the usual tethered devices. The limiting factor is transmission power and, by extension, battery life required for acquiring large amounts of neural electrophysiological data. We present a digital compression algorithm capable of reducing electrophysiological data to less than 65.5% of its original size without distorting the signals, which we tested in vivo in experimental animals. The algorithm is based on a combination of delta compression and Huffman codes with optimizations for neural signals, which allow it to run in small, low-power Field-Programmable Gate Arrays (FPGAs), requiring few hardware resources. With this algorithm, a hardware prototype was created for wireless data transmission using commercially available devices. The power required by the algorithm itself was less than 3 mW, negligible compared to the power saved by reducing the transmission bandwidth requirements. The compression algorithm and its implementation were designed to be device-agnostic. These developments can be used to create a variety of wired and wireless neural electrophysiology acquisition systems with low power and space requirements without the need for complex or expensive specialized hardware

Different pathway specific theta frameworks coexist in the hippocampus and are coordinated during exploratory and memory guided behaviors

Trabajo presentado al 12th Federation of European Neuroscience Societies (FENS): Virtual Forum of NeuroScience, celebrado del 11 al 15 de julio de 2020.This work was supported in part by the Spanish Ministerio de Economía y Competitividad (and FEDER funds under the grant PGC2018-101055-B-I00 We acknowledge financial support from the Spanish State Research Agency, through the Severo Ochoa” Programme for Centres of Excellence in R&D ref SEV2017-0723 EPM was supported by a studentship from the Consellería de Educación Investigación Cultura y Deporte (ACIF/2016/110).Peer reviewe