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Subcortical Source and Modulation of the Narrowband Gamma Oscillation in Mouse Visual Cortex
Aman B Saleem1, Anthony D Lien2, Michael Krumin3
1UCL Institute of Ophthalmology, University College London, London WC1E 6BT, UK; UCL Institute of Neurology, University College London, London WC1E 6BT, UK; Department of Neuroscience, Physiology, and Pharmacology, University College London, London WC1E 6BT, UK.
Neuron
|January 20, 2017
Summary
The study reveals two distinct gamma rhythms in the visual cortex. A narrowband gamma oscillation originates from the lateral geniculate nucleus (LGN) and is modulated by light intensity, unlike broadband gamma activity.
Area of Science:
- Neuroscience
- Visual System Research
- Brain Oscillations
Background:
- The primary visual cortex displays two gamma rhythms: broadband (30-90 Hz) and narrowband (~60 Hz) in mice.
- Understanding the origins and modulation of these rhythms is crucial for deciphering visual processing.
Purpose of the Study:
- Investigate the sources of the narrowband gamma oscillation.
- Identify factors influencing its strength.
- Determine its relationship with broadband gamma activity.
Main Methods:
- Electrophysiological recordings in the primary visual cortex and lateral geniculate nucleus (LGN).
- Optogenetic manipulation to silence cortical activity.
- Analysis of gamma rhythm power, peak frequency, and correlation with visual stimuli (contrast, light intensity).
Main Results:
- Narrowband and broadband gamma power were uncorrelated.
- Visual contrast differentially affected the rhythms: increasing broadband power while suppressing narrowband power.
- The narrowband oscillation was strongest in layer 4, driven by LGN inputs, and increased with light intensity.
- Optogenetic silencing of the cortex did not abolish the narrowband oscillation in LGN firing or cortical currents.
Conclusions:
- The narrowband gamma oscillation originates from the lateral geniculate nucleus (LGN).
- Its strength is modulated by light intensity and visual contrast.
- Evidence suggests a unidirectional flow of signals from the thalamus to the cortex underlies this oscillation.
