gamma oscillations

Targeting gamma oscillations to improve cognition

Minute-scale periodic sequences in medial entorhinal cortex

The medial entorhinal cortex (MEC) hosts many of the brain’s circuit elements for spatial navigation and episodic memory, operations that require neural activity to be organized across long durations of experience. While location is known to be encoded by a plethora of spatially tuned cell types in this brain region, little is known about how the activity of entorhinal cells is tied together over time. Among the brain’s most powerful mechanisms for neural coordination are network oscillations, which dynamically synchronize neural activity across circuit elements. In MEC, theta and gamma oscillations provide temporal structure to the neural population activity at subsecond time scales. It remains an open question, however, whether similarly coordination occurs in MEC at behavioural time scales, in the second-to-minute regime. In this talk I will show that MEC activity can be organized into a minute-scale oscillation that entrains nearly the entire cell population, with periods ranging from 10 to 100 seconds. Throughout this ultraslow oscillation, neural activity progresses in periodic and stereotyped sequences. The oscillation sometimes advances uninterruptedly for tens of minutes, transcending epochs of locomotion and immobility. Similar oscillatory sequences were not observed in neighboring parasubiculum or in visual cortex. The ultraslow periodic sequences in MEC may have the potential to couple its neurons and circuits across extended time scales and to serve as a scaffold for processes that unfold at behavioural time scales.

Hippocampal gamma oscillations mediating cortico-hippocampal oscillations and shaping hippocampal temporal code

Cortical-like dynamics in recurrent circuits optimized for sampling-based probabilistic inference

Sensory cortices display a suite of ubiquitous dynamical features, such as ongoing noise variability, transient overshoots, and oscillations, that have so far escaped a common, principled theoretical account. We developed a unifying model for these phenomena by training a recurrent excitatory-inhibitory neural circuit model of a visual cortical hypercolumn to perform sampling-based probabilistic inference. The optimized network displayed several key biological properties, including divisive normalization, as well as stimulus-modulated noise variability, inhibition-dominated transients at stimulus onset, and strong gamma oscillations. These dynamical features had distinct functional roles in speeding up inferences and made predictions that we confirmed in novel analyses of awake monkey recordings. Our results suggest that the basic motifs of cortical dynamics emerge as a consequence of the efficient implementation of the same computational function — fast sampling-based inference — and predict further properties of these motifs that can be tested in future experiments

The role of gamma oscillations in stimulus encoding during a sequential memory task in the human Medial Temporal Lobe

Bernstein Conference 2024

The emergence of gamma oscillations as a signature of gain control during context integration.

COSYNE 2022

Gamma oscillations deficit in the recovering perilesional cortex : origin and correction

A hybrid computational model of the hippocampal formation to replicate theta-nested gamma oscillations and theta phase reset during neurostimulation

Hypersynchronised gamma oscillations in the medial prefrontal cortex and hippocampus in a rat model of Fragile X Syndrome

Studying Gamma oscillations and consciousness during sleep using SSVEPs

Interneuron nonlinear dendrites regulate theta-nested gamma oscillations in hippocampal networks

FENS Forum 2024

Temporal frequency tuning of gamma oscillations varies differently with stimulus contrast and size in macaque V1

FENS Forum 2024