Yuk Hoi Yiu: A model of extrinsic and intrinsic hippocampal theta sequences
| When |
Oct 31, 2023
from 05:15 PM to 05:45 PM |
|---|---|
| Where | Bernstein Center, Lecture Hall, ground floor, Hansastr. 9a |
| Contact Name | Fiona Siegfried |
| Contact Phone | 0761 203 9549 |
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Abstract
In the rodent hippocampus, spatial trajectories are represented through the sequential activation of place cells on the theta timescale during spatial navigation, a phenomenon known as theta sequences. However, these one-dimensional (1D) spatial trajectories can assume arbitrary shapes within a two-dimensional (2D) space, raising questions about how a 2D space can be effectively represented through 1D temporal sequences.
We propose that the sequential activities of place cells propagate along two types of 1D manifolds within a 2D space. The first of these follows the running trajectory of the animal, driven by the extrinsic sensorimotor inputs, while the second corresponds to the spatial pathways determined by the unidirectional projections of the intrinsic hippocampal connectivity. To support our theory, we conducted simulations utilizing a spiking neural network consisting of two layers of place cells in the dentate gyrus and cornu ammonis 3. Our model can generate theta sequences that align with experimental observations, particularly regarding variations in phase precession properties from different running directions. The intrinsic component of theta sequences can serve as stable spatial memories, even in the presence of changing sensorimotor inputs. These results shed light on how intrinsic circuitry contributes to memory functions through temporal coding.