Cellular mechanisms preventing sustained activation of cortex during subcortical high-frequency stimulation

Area of Science:

• Neuroscience
• Neurophysiology
• Brain Stimulation

Background:

• Axonal excitation is a proposed mechanism for therapeutic brain stimulation.
• Understanding how stimulation affects neural circuits is crucial for developing effective therapies.

Purpose of the Study:

• To investigate the effects of high-frequency stimulation (HFS) on postsynaptic responses in cortical neurons.
• To determine the mechanism behind the observed changes in neuronal activity.

Main Methods:

• Whole-cell recordings were performed in rat brain slices, specifically in the primary motor cortex (M1) and ventral thalamus.
• High-frequency stimulation (HFS) was applied to subcortical white matter tracts projecting to the motor cortex.

Main Results:

• Neurons in M1 exhibited only initial depolarization followed by a return to prestimulation levels during HFS.
• A prolonged suppression of excitation was observed, independent of GABAergic inhibition or action potential failure.
• HFS specifically depressed excitatory synaptic currents from the stimulated subcortical input.

Conclusions:

• Axonal HFS induces a functional deafferentation of postsynaptic targets.
• Neurotransmitter depletion is the likely cause of this functional deafferentation.