Neuromodulation‐dependent effect of gated high‐frequency, LFMS‐like electric field stimulation in mouse cortical slices

Abstract

Low‐field magnetic stimulation (LFMS) is a gated high‐frequency noninvasive brain stimulation method (500 Hz gated at 2 Hz) with a proposed antidepressant effect. However, it has remained unknown how such stimulation paradigms modulate neuronal network activity and how the induced changes depend on network state. Here we examined the immediate and outlasting effects of the gated high‐frequency electric field associated with LFMS on the cortical activity as a function of neuromodulatory tone that defines network state. We used a sham‐controlled study design to investigate effects of stimulation (20 minutes of 0.5s trains of 500 Hz charge‐balanced pulse stimulation patterned at 0.5 Hz) on neural activity in mouse medial prefrontal cortex in vitro. Bath application of cholinergic and noradrenergic agents enabled us to examine the stimulation effects as function of neuromodulatory tone. The stimulation attenuated the increase in firing rate of layer V cortical neurons during post‐stimulation period in presence of cholinergic activation. The same stimulation had no significant immediate or outlasting effect in absence of exogenous neuromodulators or in the presence of noradrenergic activation. These results provide electrophysiological insights into the neuromodulatory‐dependent effects of gated high‐frequency stimulation. More broadly, our results are the first to provide a mechanistic demonstration of how behavioral states and arousal levels may modify the effects of non‐invasive brain stimulation.

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