Micro-coil-induced Inhomogeneous Electric Field Produces sound-driven-like Neural Responses in Microcircuits of the Mouse Auditory Cortex In Vivo

•The acute effect of magnetic stimulation on cortical microcircuit was investigated in vivo using a micro-coil.•The spatiotemporal pattern of neural activity was highly similar for magnetic and acoustic stimulation-driven responses.•The horizontally inhomogeneous electric field is suggested to have...

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Veröffentlicht in:Neuroscience 2018-02, Vol.371, p.346-370
Hauptverfasser: Osanai, Hisayuki, Minusa, Shunsuke, Tateno, Takashi
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Sprache:eng
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Zusammenfassung:•The acute effect of magnetic stimulation on cortical microcircuit was investigated in vivo using a micro-coil.•The spatiotemporal pattern of neural activity was highly similar for magnetic and acoustic stimulation-driven responses.•The horizontally inhomogeneous electric field is suggested to have a large effect on cortical activation.•The underlying cortical microcircuitry constrains should affect the magnetic stimulation-evoked activity profile. Magnetic stimulation is widely used in neuroscience research and clinical treatment. Despite recent progress in understanding the neural modulation mechanism of conventional magnetic stimulation methods, the physiological mechanism at the cortical microcircuit level is not well understood due to the poor stimulation focality and large electric artifact in the recording. To overcome these issues, we used a sub-millimeter-sized coil (micro-coil) to stimulate the mouse auditory cortex in vivo. To determine the mechanism, we conducted the first direct electrophysiological recording of micro-coil-driven neural responses at multiple sites on the horizontal surface and laminar areas of the auditory cortex. The laminar responses of local field potentials (LFPs) to the magnetic stimulation reached layer 6, and the spatiotemporal profiles were very similar to those of the acoustic stimulation, suggesting the activation of the same cortical microcircuit. The horizontal LFP responses to the magnetic stimulation were evoked within a millimeter-wide area around the stimulation coil. The activated cortical area was dependent on the coil orientation, providing useful information on the effective position of the coil relative to the brain surface for modulating cortical circuitry activity. In addition, numerical calculation of the induced electric field in the brain revealed that the inhomogeneity of the horizontal electric field to the surface is critical for micro-coil-induced cortical activation. The results suggest that our micro-coil technique has the potential to be used as a chronic, less-invasive and highly focal neuro-stimulator, and is useful for investigating microcircuit responses to magnetic stimulation for clinical treatment.
ISSN:0306-4522
1873-7544
DOI:10.1016/j.neuroscience.2017.12.008