| Clinical application of electric fields to the brain are promising non-invasive approaches for the treatment of psychiatric, neurological, and pain disorders. Low-magnitude electric fields, which do not cause neuronal firing but only create changes to the voltage necessary for inducing neuronal firing by approximately 1%, are known to have substantial behavioral effects and therapeutic outcomes. Transcranial direct current stimulation is one electric stimulation modality that induces such low-magnitude electric fields. Electric fields of magnitude sufficient to directly trigger neuronal firing may be induced by transcranial electric stimulation and transcranial magnetic stimulation. Many therapeutic advances have been made using these techniques, and they create new experimental approaches to increase our knowledge of how the brain works. Still, the fundamental mechanisms as to how these electric fields may affect neuronal elements of the brain are not fully understood. Chapter 1 of this thesis creates a mechanistic model describing how an electric field of any small magnitude may still have an effect on neuronal processing by changes in spike timing. This mechanistic framework has implications for the effects of endogenous, brain-generated electric fields as well as electric stimulation modalities. The second chapter of this thesis develops a model of how cortical neuronal morphology and cell type may be used to predict changes in polarization and firing caused by electric fields. Both of these studies employed techniques to record from single cells in the brain, and all models described have been experimentally verified through these techniques. |
