Hippocampal rhythm modulation via frequency-tuned trigeminal nerve stimulation.

Area of Science:

• Neuroscience
• Brain Stimulation
• Computational Neuroscience

Background:

• Trigeminal nerve stimulation (TNS) modulates brain activity via peripheral pathways.
• The effects of sinusoidal alternating current stimulation of the trigeminal nerve (TN-ACS) on hippocampal activity are not well understood.
• Existing research primarily uses pulse-based TNS, leaving sinusoidal stimulation effects unexplored.

Purpose of the Study:

• To investigate the impact of TN-ACS at 8 Hz (theta) and 40 Hz (gamma) on rat hippocampal network activity.
• To analyze frequency-specific effects on neuronal firing, local field potentials, and interregional coherence.
• To determine if TN-ACS can selectively influence hippocampal dynamics.

Main Methods:

• Applied 3-minute TN-ACS at 8 Hz and 40 Hz to rats.
• Recorded hippocampal neural activity using multi-channel electrophysiology.
• Analyzed spike-phase entrainment, spike rates, LFP power spectra, and spike-field coherence.

Main Results:

• TN-ACS demonstrated frequency-specific modulation of hippocampal dynamics.
• 40 Hz TN-ACS significantly enhanced CA1 spike-phase locking.
• Theta-band coherence between CA3 LFPs and CA1 spikes decreased during 8 Hz and increased during 40 Hz stimulation, without altering spike rates.

Conclusions:

• This study is the first to show TN-ACS can entrain hippocampal spike timing and modulate interregional coherence.
• TN-ACS selectively shapes deep brain rhythms without affecting overall neuronal firing rates.
• 40 Hz TN-ACS shows promise as an intervention for targeting memory-related processes.