While there have been some important successes using implantable mi-croelectrodes to activate non-functioning portions of the CNS, there are also several intrinsic limitations associated with their use that impede additional progress. It is dif-ficult to control the spread of activation with electrodes thereby limiting the resolution that can be achieved. Inadvertent activation of passing axons and/or non-targeted neurons can lead to a further spread of activation.
Magnetic stimulation from microcoils may be an attractive alternative to conven-tional electrodes because the asymmetry in the fields they produce allows improved selectivity in targeting neurons, e.g., vertically oriented pyramidal neurons of the cor-tex can be activated without also activating horizontally oriented passing axons, thus better confining activation to focal regions. A second advantage of microcoils arises from the high permeability of biological materials to magnetic fields, including high-resistance tissues such as bone that strongly impede the passage of electric fields. Thus, time-varying magnetic fields can be used to ‘carry’ an electric field across a high-impedance boundary that is difficult to target with conventional electrodes.
In this talk, I will describe recent progress with microcoils including studies in sev-eral regions of cortex, deep brain regions and the retina that demonstrate their effec-tiveness. I will also describe more recent experiments using microcoil stimulation of the cochlea to assess the potential of micromagnetic stimulation for use in a next-generation cochlear implant. Some important limitations with coils that will need to be overcome will be presented as well.
Date: December 6th 2022, 4:00 pm