Polarity and Subfield Specific Effects of Transcranial Direct Current Stimulation on Hippocampal Plasticity
Journal Article - Open Access
NAVAL MEDICAL RESEARCH UNIT (DAYTON) WRIGHT-PATTERSON AFB OH WRIGHT-PATTERSON AFB United States
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An increasing number of studies using human subjects substantiate the use of transcranial direct current stimulation tDCS as a noninvasive approach to treat various neurological symptoms. tDCS has been tested in conditions from motor to cognition dysfunctions. Performance enhancement of healthy subjects using tDCS has also been explored. The underlying physiological mechanism for tDCS effects is hypothesized to be through changes in neuroplasticity and we have previously demonstrated that in vivo anodal tDCS can enhance neuroplasticity of hippocampal CA1 neurons. The purpose of this study was to determine whether the underlying electrophysiological changes that occur following in vivo tDCS are polarity specific. We also examined both the CA1 and CA3 regions of the hippocampus to determine whether the tDCS effects were subfield specific. We conducted in vivo tests of cathodal tDCS versus anodal tDCS on synaptic plasticity of CA1 and CA3 neurons of male rats. In each region we assessed long term potentiation LTP, paired pulse facilitation PPF and long term depression LTD. In the CA1 region, we found anodal tDCS significantly enhanced not only LTP and PPF, but also LTD. There was no statistical difference in LTP, PPF or LTD of hippocampal CA1 neurons resulting from cathodal tDCS. Neither anodal nor cathodal tDCS induced significant changes in neuroplasticity of hippocampal CA3 neurons. Results indicate that the effects of tDCS are subfield specific and polarity dependent with anodal tDCS having greater impact on synaptic activity in the rat hippocampus than cathodal tDCS.
- Anatomy and Physiology