About Peter Petersen

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So far Peter Petersen has created 14 blog entries.

Paper on bioRxiv: Brain temperature affects quantitative features of hippocampal sharp wave ripples

Biochemical mechanisms are temperature-dependent. Brain temperature shows wide variations across brain states, and such changes may explain quantitative changes in network oscillations.  Here we report on the coupling of various hippocampal sharp wave ripple features to brain temperature. Ripple frequency, occurrence rate, and duration correlated with temperature dynamics. By focal manipulation of the brain temperature in the hippocampal CA1 region, we show that ripple frequency can be increased and decreased by local heating and cooling, respectively. Changes of other parameters, such as the rate of SPW-R   and ripple duration were not consistently affected. Our findings suggest that brain temperature in the CA1 region plays a leading role in affecting the ripple frequency, whereas other parameters of SPW-Rs may be determined by mechanisms upstream from the CA1 region. These findings illustrate that physiological variations of brain temperature exert important effects on hippocampal circuit operations.

Peter C. Petersen*, Mihly Vrslakos*, Gyrgy Buzski. “Brain temperature affects quantitative features of hippocampal sharp wave ripples”. *cofirst author. bioRxiv, January 2022. [pdf] [link]

 

2022-02-01T20:07:49+01:00February 1st, 2022|News|

Paper published in Neuron: CellExplorer: A framework for visualizing and characterizing single neurons

The large diversity of neuron types provides the means by which cortical circuits perform complex operations. Neuron can be described by biophysical and molecular characteristics, afferent inputs, and neuron targets. To quantify, visualize, and standardize those features, we developed the open-source, MATLAB-based framework CellExplorer. It consists of three components: a processing module, a flexible data structure, and a powerful graphical interface. The processing module calculates standardized physiological metrics, performs neuron-type classification, finds putative monosynaptic connections, and saves them to a standardized, yet flexible, machine-readable format. The graphical interface makes it possible to explore the computed features at the speed of a mouse click. The framework allows users to process, curate, and relate their data to a growing public collection of neurons. CellExplorer can link genetically identified cell types to physiological properties of neurons collected across laboratories and potentially lead to interlaboratory standards of single-cell metrics.

Illustration by Andrea Navas-Olive

Highlights

  • An open-source framework for single-cell characterization and visualization
  • A processing module that calculates a set of standardized physiological metrics
  • A graphical interface to explore computed features at the speed of a mouse click
2021-11-12T10:55:45+01:00November 12th, 2021|News|

New paper on bioRxiv: Movement is governed by rotational population dynamics in spinal motor networks

Although the nervous system is elegantly orchestrating movements, the underlying neural principles remain unknown. Since flexor- and extensor-muscles alternate during movements like walking, it is often assumed that the responsible neural circuitry is similarly alternating in opposition. Here, we present ensemble-recordings of neurons in the turtle lumbar spinal cord that indicate that, rather than alternation, the population is performing a “rotation” in neural space, i.e. the neural activity is cycling through all phases continuously during the rhythmic behavior. The radius of rotation correlates with the intended muscle force. Since existing models of spinal motor control offer inadequate explanation of this dynamics, we propose a new theory of neural generation of movement from which rotation and other unresolved issues, such as speed regulation, force control, and multi-functionalism, are conveniently explained.

Henrik Linden, Peter C. Petersen, Mikkel Vestergaard, Rune W Berg. “Movement is governed by rotational population dynamics in spinal motor networks”. bioRxiv, Submitted, September 2021. [pdf] [link]

2021-09-17T09:05:59+02:00September 17th, 2021|News, Uncategorized|

Paper published in Bio-protocol: 3D-printed recoverable microdrive and base plate system for rodent electrophysiology

Extracellular recordings in freely moving animals allow the monitoring of brain activity from populations of neurons at single-spike temporal resolution. While state-of-the-art electrophysiological recording devices have been developed in recent years (e.g., µLED and Neuropixels silicon probes), implantation methods for silicon probes in rats and mice have not advanced substantially for a decade. The surgery is complex, takes time to master, and involves handling expensive devices and valuable animal subjects. In addition, chronic silicon neural probes are practically single implant devices due to the current low success rate of probe recovery. To successfully recover silicon probes, improve upon the quality of electrophysiological recording, and make silicon probe recordings more accessible, we have designed a miniature, low cost, and recoverable microdrive system. The addition of a novel 3D-printed skull baseplate makes the surgery less invasive, faster, and simpler for both rats and mice. We provide detailed procedural instructions and print designs, allowing researchers to adapt and flexibly customize our designs to their experimental usage.

Mihály Vöröslakos, Hiroyuki Miyawaki, Sebastien Royer, Kamran Diba, Euisik Yoon, Peter C. Petersen* and György Buzsáki*. “3D-printed recoverable microdrive and base plate system for rodent electrophysiology”. *corresponding author, Bio-protocol, August 20, 2021. [pdf] [link] [website]

2021-09-17T09:02:46+02:00September 17th, 2021|News, Uncategorized|

Paper published in eLife: Metal microdrive and head cap system for silicon probe recovery in freely moving rodent

High-yield electrophysiological extracellular recording in freely moving rodents provides a unique window into the temporal dynamics of neural circuits. Recording from unrestrained animals is critical to investigate brain activity during natural behaviors. The use and implantation of high-channel-count silicon probes represent the largest cost and experimental complexity associated with such recordings making a recoverable and reusable system desirable. To address this, we have designed and tested a novel 3D printed head-gear system for freely moving mice and rats. The system consists of a recoverable microdrive printed in stainless steel and a plastic head cap system, allowing researchers to reuse the silicon probes with ease, decreasing the effective cost, and the experimental effort and complexity. The cap designs are modular and provide structural protection and electrical shielding to the implanted hardware and electronics. We provide detailed procedural instructions allowing researchers to adapt and flexibly modify the head-gear system.

Mihály Vöröslakos*, Peter C. Petersen*, Balázs Vöröslakos*, György Buzsáki. “Metal microdrive and head cap system for silicon probe recovery in freely moving rodent”. *cofirst author, eLife, May 19, 2021. [link] [github] [pdf]

2021-06-14T20:49:10+02:00June 14th, 2021|News|

Paper published in Neuron: Cooling of medial septum reveals theta phase lag coordination of hippocampal cell assemblies

Hippocampal theta oscillations coordinate neuronal firing to support memory and spatial navigation. The medial septum (MS) is critical in theta generation by two possible mechanisms: either a unitary “pacemaker” timing signal is imposed on the hippocampal system, or it may assist in organizing target subcircuits within the phase space of theta oscillations. We used temperature manipulation of the MS to test these models. Cooling of the MS reduced both theta frequency and power and was associated with an enhanced incidence of errors in a spatial navigation task, but it did not affect spatial correlates of neurons. MS cooling decreased theta frequency oscillations of place cells and reduced distance-time compression but preserved distance-phase compression of place field sequences within the theta cycle. Thus, the septum is critical for sustaining precise theta phase coordination of cell assemblies in the hippocampal system, a mechanism needed for spatial memory.

Highlights

  • Cooling the medial septum slowed down theta oscillations in the hippocampus
  • The spatial representation in the hippocampus remained intact
  • Choice errors increased in a spatial task
  • Distance-time, but not distance-theta phase, compression was altered

Cooling of Medial Septum Reveals Theta Phase Lag Coordination of Hippocampal Cell Assemblies Peter Christian Petersen, György Buzsáki. Neuron, June 2020. [PDF] [Link]

2021-06-14T20:51:02+02:00July 25th, 2020|News|

CellExplorer: a graphical user interface and standardized pipeline for characterizing spiking features of single neurons

Framework for single-cell classification

The large diversity of cell types of the brain provides the means by which circuits perform complex operations. Understanding such diversity is one of the key challenges of modern neuroscience. These cells have many unique electrophysiological and behavioral features from which parallel cell types classification can be inferred. The CellExplorer is a framework for analyzing and characterizing single cells recorded using extracellular electrodes. A high dimensional representation is built from electrophysiological and functional features including the spike waveform, spiking statistics, behavioral spiking dynamics, spatial firing maps, and various brain rhythms. Moreover, we are incorporating opto-tagget cells in this pipeline (ground-truth cell types). The user-friendly graphical interface allows for verification, classification, and exploration of those same features. The framework is built entirely in Matlab making it fast and intuitive to implement your own code and incorporate the CellExplorer in your overall pipeline and analysis scripts.

Learn more about the CellExplorer at the dedicated website: CellExplorer.org

Peter C Petersen, György Buzsáki (2020). CellExplorer: a graphical user interface and standardized pipeline for visualizing and characterizing single neuron features. bioRxiv 2020.05.07.083436; doi: https://doi.org/10.1101/2020.05.07.083436. [github]

2020-12-29T00:05:29+01:00January 21st, 2020|News|

Paper on bioRxiv: Cooling of medial septum reveals theta phase lag coordination of hippocampal cell assemblies

Hippocampal theta oscillations coordinate neuronal firing to support memory and spatial navigation. The medial septum (MS) is critical in theta generation by two possible mechanisms: either a unitary ‘pacemaker’ timing signal is imposed on the hippocampal system or it may assist in organizing subcircuits within the phase space of theta oscillations. We used temperature manipulation of the MS to confront these models. Cooling of the MS reduced both theta frequency and power, was associated with enhanced incidence of errors in a spatial navigation task, but did not affect the spatial map. MS cooling decreased theta frequency oscillations of place cells, reduced distance-time compression but preserved distance-phase compression of place field sequences within the theta cycle. We suggest that reciprocal MS-hippocampal communication is essential for sustaining theta phase-coordination of cell assemblies and, in turn, supporting its role in spatial memory.

Link to paper: https://www.biorxiv.org/content/10.1101/2019.12.19.883421v1.abstract

 

2020-01-21T00:45:31+01:00January 21st, 2020|News|
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