title: Enhanced Control of Cortical Pyramidal Neurons With Micromagnetic Stimulation.
abstract: Magnetic stimulation is less sensitive to the inflammatory reactions that plague conventional electrode-based cortical implants and therefore may be useful as a next-generation (implanted) cortical prosthetic. The fields arising from micro-coils are quite small however and thus, their ability to modulate cortical activity must first be established. Here, we show that layer V pyramidal neurons (PNs) can be strongly activated by micro-coil stimulation and further, the asymmetric fields arising from such coils do not simultaneously activate horizontally-oriented axon fibers, thus confining activation to a focal region around the coil. The spatially-narrow fields from micro-coils allowed the sensitivity of different regions within a single PN to be compared: while the proximal axon was most sensitive in naïve cells, repetitive stimulation over the apical dendrite led to a change in state of the neuron that reduced thresholds there to below those of the axon. Thus, our results raise the possibility that regardless of the mode of stimulation, penetration depths that target specific portions of the apical dendrite may actually be more effective than those that target Layer 6. Interestingly, the state change had similar properties to state changes described previously at the systems level, suggesting a possible neuronal mechanism underlying such responses.
authors.forename: Seung Woo
authors.initials: SW
authors.lastname: Lee
authors.forename: Shelley I
authors.initials: SI
authors.lastname: Fried
mesh_terms: D000200:Action Potentials / Q000502:physiology* / Q000528:radiation effects; D000818:Animals; D002540:Cerebral Cortex / Q000502:physiology* / Q000528:radiation effects; D004307:Dose-Response Relationship, Radiation; D004567:Electrodes, Implanted; D004867:Equipment Design; D019544:Equipment Failure Analysis; D060526:Magnetic Fields; D051379:Mice; D008810:Mice, Inbred C57BL; D008904:Miniaturization; D017966:Pyramidal Cells / Q000502:physiology* / Q000528:radiation effects; D011829:Radiation Dosage; D015203:Reproducibility of Results; D012680:Sensitivity and Specificity; D050781:Transcranial Magnetic Stimulation / Q000295:instrumentation* / Q000379:methods*