Hippocampal Place Cells Modulated by Fast and Slow Gamma Rhythms Contribute to the Development of Theta Sequence Representations

Kernekoncepter

The development of temporospatially compressed theta sequence representations in the hippocampus is predominantly dependent on a subgroup of place cells that are phase-locked to fast gamma rhythms. These fast gamma-modulated cells exhibit slow gamma phase precession, which facilitates the integration of compressed spatial information within theta cycles.

Resumé

The study investigated the roles of fast and slow gamma rhythms in the coordination of hippocampal place cells during the experience-dependent development of theta sequences. The key findings are:

A subgroup of place cells (FG-cells) that were phase-locked to fast gamma rhythms played a crucial role in the development of theta sequences. Excluding a sufficiently high proportion of FG-cells disrupted the sweep-ahead structure of theta sequences, compared to excluding an equivalent number of non-fast gamma-locked (NFG) cells.

The FG-cells exhibited slow gamma phase precession within single theta cycles throughout the developing process of theta sequences. This slow gamma phase precession was positively correlated with the development of the sweep-ahead structure of theta sequences.

In contrast, the NFG-cells showed experience-dependent slow gamma phase precession, which only emerged during the late stage of theta sequence development.

These results suggest that the fast gamma-modulated FG-cells, with their consistent slow gamma phase precession, may serve as a core network mechanism for the development of temporospatially compressed theta sequence representations, which could facilitate memory encoding and retrieval.

Statistik

"The proportion of hippocampal place cells that were significantly phase-locked to fast gamma rhythms was 23.2%."
"The mean vector length of fast gamma phase-locking was significantly higher in FG-cells compared to NFG-cells."
"The weighted correlation of theta sequences decoded by excluding FG-cells spikes was much lower than that of theta sequences decoded by excluding down-sampled NFG-cells spikes."
"The weighted correlation of theta sequences was significantly increased with running laps, but the running speed did not change across laps."

Citater

"The sweep-ahead structure of the exFG-sequences (red) was disrupted compared to that of exNFG-sequences (yellow)."
"The temporospatially compressed structure of theta sequences may require a larger percentage of FG-cells."
"The slow gamma phase precession of FG-cells was stable across trials, while the slow gamma phase precession of NFG-cells was experience-dependent."

Vigtigste indsigter udtrukket fra

Dynamic Gamma Modulation of Hippocampal Place Cells Predominates Development of Theta Sequences

by Wang,N., Wan... kl. www.biorxiv.org 03-30-2024

https://www.biorxiv.org/content/10.1101/2024.03.27.586908v2

Dybere Forespørgsler

How do the fast gamma-modulated FG-cells interact with other hippocampal cell types, such as interneurons, to coordinate the development of theta sequences

The fast gamma-modulated FG-cells interact with other hippocampal cell types, such as interneurons, to coordinate the development of theta sequences through a complex network mechanism. FG-cells, which are a subset of place cells phase-locked to fast gamma rhythms, likely receive inputs from the medial entorhinal cortex and rapidly encode ongoing novel information in the context. These cells exhibit phase precession patterns and are crucial for the development of theta sequences.
Interneurons, particularly parvalbumin (PV)-expressing interneurons, play a significant role in modulating the activity of FG-cells. PV-interneurons are known to regulate the timing and synchronization of neuronal firing, contributing to the generation of gamma oscillations. In the context of theta sequence development, PV-interneurons may provide inhibitory control over FG-cells, shaping their firing patterns and facilitating the integration of spatial information within theta cycles. This coordination between FG-cells and interneurons helps in the precise temporal organization of neural activities required for the formation of theta sequences.

What are the potential implications of disrupted fast gamma-slow gamma coordination in neurological disorders that affect spatial memory, such as Alzheimer's disease

Disrupted coordination between fast gamma and slow gamma rhythms in the hippocampus can have significant implications for neurological disorders that affect spatial memory, such as Alzheimer's disease. In Alzheimer's disease, there is evidence of alterations in gamma oscillations and impaired theta sequence formation, leading to deficits in spatial memory and navigation.
Fast gamma rhythms, which are associated with encoding novel information and rapid processing, may be dysregulated in Alzheimer's disease, leading to difficulties in forming coherent spatial representations. This disruption in fast gamma modulation can impact the coordination with slow gamma rhythms, which are responsible for integrating learned information and compressing spatial details within theta cycles. As a result, the development of theta sequences, critical for memory encoding and retrieval, may be compromised in Alzheimer's disease.
Understanding the specific mechanisms underlying the fast gamma-slow gamma coordination in theta sequence development could provide insights into the pathophysiology of Alzheimer's disease and potentially offer new therapeutic targets for restoring spatial memory function in affected individuals.

Could the principles of fast gamma-slow gamma modulation of theta sequences be extended to understand the development of other types of temporally structured neural representations in the brain

The principles of fast gamma-slow gamma modulation of theta sequences can be extended to understand the development of other types of temporally structured neural representations in the brain. The coordination between different frequency bands of neural oscillations, such as fast gamma and slow gamma, plays a crucial role in organizing neural activities for various cognitive processes.
For example, in the context of episodic memory formation, the dynamic interplay between gamma rhythms at different frequencies may facilitate the encoding and retrieval of complex memory traces. By temporally organizing neuronal firing patterns within specific frequency bands, the brain can create temporally compressed representations of information, enabling efficient storage and recall of memories.
Furthermore, the principles of gamma modulation can be applied to other cognitive functions, such as attention, decision-making, and sensory processing. By investigating how different neural oscillations interact and coordinate neural activities, researchers can gain insights into the underlying mechanisms of various cognitive processes and potentially develop new strategies for modulating brain activity in health and disease.