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Thalamic-evoked synaptic interactions in barrel cortex revealed by optical imaging.
N Laaris1, G C Carlson, A Keller
1Department of Anatomy, Program in Neuroscience, University of Maryland School of Medicine, Baltimore, Maryland 21201, USA.
Summary
Neural activity spread in the mouse barrel cortex is modulated by thalamic input timing. NMDA receptor activity influences this spread, impacting sensory processing during behaviors like whisking.
Area of Science:
- Neuroscience
- Systems Neuroscience
- Cortical Circuits
Background:
- The barrel cortex processes sensory information from the thalamus.
- Understanding the spatiotemporal dynamics of cortical activity is crucial.
Purpose of the Study:
- To investigate how thalamocortical input patterns influence activity spread in the mouse barrel cortex.
- To elucidate the role of NMDA receptors in modulating cortical network dynamics.
Main Methods:
- Optical imaging of voltage-sensitive dye signals in an in vitro mouse barrel cortex slice preparation.
- Stimulation of thalamocortical afferents with varying current intensities and temporal patterns.
- Pharmacological manipulation using GABA(A) receptor antagonist bicuculline and NMDA receptor antagonist AP5.
Main Results:
- Low-intensity thalamic stimulation evoked localized activity.
- NMDA receptor activation (Mg(2+) removal) or high-frequency input trains dramatically increased activity spread across layers and columns.
- This enhanced spread was suppressed by AP5.
- Bicuculline modulated signal amplitude but not propagation dynamics at low concentrations; higher concentrations induced paroxysmal activity.
Conclusions:
- Thalamic input timing and NMDA receptor activation are key determinants of spatiotemporal activity spread in the barrel cortex.
- These mechanisms may underlie sensory processing during natural behaviors such as whisking.