Regulation of LTP of synaptic plasticity in rat Schaffer-CA1 by broadband mixed-frequency micromagnetic stimulation

The aim of this study was to investigate the modulation of hippocampal Schaffer-CA1 synaptic LTP by broad-band mixed-frequency micro-magnetic stimulation (μMS), to break through the limitations of traditional single-frequency stimulation, and to explore the potential of multi-frequency synergistic effect on cognitive function enhancement.

A μMS system was constructed on a flexible PCB using a micro-coil (0402 size, 1 μH) to generate single-frequency and mixed-frequency magnetic fields. The signal was synthesized by Gnuradio, and the magnetic field strength of around 2 mT was output via a power amplifier. LTP was induced by applying high-frequency electrical stimulation to isolated hippocampal slices of Sprague-Dawley rats, and after the intervention with μMS, field excitatory postsynaptic potentials (fEPSPs) were recorded using the MEA2100 and analyzed for the modulation effect on LTP.

Single-frequency stimulation showed frequency-dependent modulation: 70 kHz significantly enhanced LTP (57%, p < .05) and 1 kHz inhibited LTP (-38%, p < .05). Broadband mixed-frequency stimulation showed synergistic effects: the high-frequency band (50-90 kHz) enhanced LTP (33%, p < .05), and the high and low-frequency mixed-band (1-1.4 kHz + 50-70 kHz) enhanced LTP (27%, p < .05), and the experimental success rate was higher than that of single-frequency stimulation (36% vs 21%). The lower frequency band (500-1400 Hz) inhibited LTP (-27%, p < .05).

Wide-band mixed-frequency μMS has frequency-dependent modulation of LTP, high-frequency mixed-frequency stimulation has an enhancement effect, low-frequency mixed-frequency stimulation has an inhibitory effect, while high and low-frequency mixed-frequency stimulation reflect high-frequency enhancement characteristics and improve the stability of LTP modulation, which provides an experimental basis for cross-frequency and multi-scale neuromodulation.