title: Direct Current Stimulation Alters Neuronal Input/Output Function.
abstract: Direct current stimulation (DCS) affects both neuronal firing rate and synaptic efficacy. The neuronal input/output (I/O) function determines the likelihood that a neuron elicits an action potential in response to synaptic input of a given strength. Changes of the neuronal I/O function by DCS may underlie previous observations in animal models and human testing, yet have not been directly assessed.
  
  
  
  Test if the neuronal input/output function is affected by DCS METHODS: Using rat hippocampal brain slices and computational modeling, we provide evidence for how DCS modulates the neuronal I/O function.
  
  
  
  We show for the first time that DCS modulates the likelihood of neuronal firing for a given and fixed synaptic input. Opposing polarization of soma and dendrite may have a synergistic effect for anodal stimulation, increasing the driving force of synaptic activity while simultaneously increasing spiking probability at the soma. For cathodal stimulation, however, the opposing effects tend to cancel. This results in an asymmetry in the strength of the effects of stimulation for opposite polarities.
  
  
  
  Our results may explain the asymmetries observed in acute and long term effects of transcranial direct current stimulation.
authors.affiliation: Department of Biomedical Engineering, The City College of the City University of New York, New York, NY, USA. Electronic address: belulafon@gmail.com.
authors.forename: Belen
authors.initials: B
authors.lastname: Lafon
authors.affiliation: Department of Biomedical Engineering, The City College of the City University of New York, New York, NY, USA.
authors.forename: Asif
authors.initials: A
authors.lastname: Rahman
authors.affiliation: Department of Biomedical Engineering, The City College of the City University of New York, New York, NY, USA.
authors.forename: Marom
authors.initials: M
authors.lastname: Bikson
authors.affiliation: Department of Biomedical Engineering, The City College of the City University of New York, New York, NY, USA.
authors.forename: Lucas C
authors.initials: LC
authors.lastname: Parra
mesh_terms: D000818:Animals; D004558:Electric Stimulation / Q000379:methods; D004566:Electrodes; D019706:Excitatory Postsynaptic Potentials / Q000502:physiology*; D006624:Hippocampus / Q000502:physiology*; D006801:Humans; D008297:Male; D009044:Motor Cortex / Q000502:physiology; D009474:Neurons / Q000502:physiology*; D009924:Organ Culture Techniques; D051381:Rats; D017208:Rats, Wistar; D065908:Transcranial Direct Current Stimulation / Q000379:methods*
keywords: DCS; Electrical stimulation; Excitability; Input-output; Two-compartment model; tDCS