Back to U19 Main Page
Theta rhythm perturbation by focal cooling of the septal pacemaker in awake rats
Abstract
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
Dataset details
It is a unique dataset in the sense that the animals had brain temperature manipulations and temperature probes implanted together with bilateral silicon probes while they were performing behavioral/spatial tasks. Thermometer implanted in Medial Septum together with a thermal perturbation probe in freely awake Long Evans rats. 2000 single cells spike sorted, up to 150 bilateral simultaneous cells recorded from CA1, all sessions with behavior.
Behaviors
Circular track: up to 180 alternation trials, always with 40 control trials, - Linear track, - Wheel running. Most sessions were recorded with Optitrack, a 3D tracking system (120Hz), and a ceiling-mounted video camera recorded at 10Hz. The animal's positional data was determined with Optitrack.
All data collected for this paper: Cooling of Medial Septum Reveals Theta Phase Lag Coordination of Hippocampal Cell Assemblies Peter Christian Petersen, György Buzsáki. Neuron, June 2020. Further information in our databank with links for downloading: https://buzsakilab.com/wp/projects/entry/4919/
Back to U19 Main Page