- Factors determining theta phase preference across CA1 sublayers -
Instituto Cajal CSIC, Madrid – Spain
Hippocampal pyramidal cells fire selectively to build abstract representations of a contingency of visual, auditory, somatosensory and behavioural events. While moving around these “spaces”, sequences of hippocampal “place cells” are activated in an orderly manner coordinated by the theta rhythm (4-12 Hz). One mechanism determining these sequences is theta phase precession, which occurs anytime the animal traverses a “place field”. However, hippocampal cells also exhibit a specific phase preference, which can be influenced by the global brain state.
Here, we aim to study factors underlying theta phase preference across deep and superficial CA1 pyramidal sublayers during theta oscillations. First, we obtained juxtacellular and multi-site recordings in awake head-fixed mice and freely-moving rats. We found a characteristic bimodality in the distribution of the preferred firing phases of CA1 pyramidal cells. In order to understand the underlying factors, we built a biophysically realistic model that includes most of the known excitatory and inhibitory inputs converging in deep and superficial cells. The sublayer location was one factor explaining firing bimodality, but we found other influencing axes as well such as entorhinal and intra-hippocampal inputs.
We tested some of the model predictions using cell-type specific chemogenetic approaches and unsupervised dynamical analysis of LFP activity. We discuss on the multiple dimensions determining phase preference and speculate about their potential role in defining episodic memory function.
Invited by : Stefania Sarno & Marco Bocchio
Inmed meeting room, Monday December 9th, 11 am