title: Transcranial Direct Current Stimulation (tDCS) Enhances the Excitability of Trigemino-Facial Reflex Circuits.
abstract: BACKGROUND
  Transcranial direct current stimulation (tDCS) causes a tiny burning sensation through activation of local cutaneous trigeminal afferents.
  
  
  OBJECTIVE
  Trigeminal sensory inputs from tDCS may generate excitability changes in the trigemino-facial reflex circuits.
  
  
  OBJECTIVE
  Sixteen healthy volunteers were submitted to 20 minutes tDCS sessions with two types of electrode-montage conditions: 1. Real vs Sham 'bi-hemispheric' tDCS (cathode/anode: C4/C3), for blinded assessment of effects, and 2. 'uni-hemispheric' tDCS (cathode/anode: Fp3/C3), for assessment of laterality of the effects. Supraorbital nerve stimuli were used to obtain blink reflexes before, during (10 minutes from onset) and after (30 minutes from onset) the tDCS session. Outcome measures were R2 habituation (R2H) to repeated stimuli, the blink reflex excitability recovery (BRER) to paired stimuli and the blink reflex inhibition by a prepulse (BRIP).
  
  
  RESULTS
  Real but not sham bi-hemispheric tDCS caused a significant decrease of R2H and leftward shift of BRER curve (p < 0.05 for all measures). The effects of uni-hemispheric tDCS on BRER and BRIP were larger on ipsilateral than on contralateral blink reflexes (p < 0.05). Excitability changes were still present 10 minutes after the end of stimulation in a lesser extent.
  
  
  CONCLUSIONS
  This study shows that 20 minute tDCS enhances the excitability of trigemino-facial reflex circuits. The finding of larger ipsilateral than contralateral effects suggests that sensitization through cutaneous trigeminal afferents adds on other possible mechanisms such as activation of cortico-nuclear or cortico-reticular connections.
authors.affiliation: EMG Unit, Neurology Department, Hospital Clinic of Barcelona, Barcelona, Spain; IDIBAPS (Institut d'Investigació Augustí Pi i Sunyer), Facultat de Medicina, University of Barcelona, Barcelona, Spain. Electronic address: ccabibitalia@yahoo.it.
authors.forename: Christopher
authors.initials: C
authors.lastname: Cabib
authors.affiliation: Dipartimento di Scienze Mediche, Chirurgiche, Neurologiche, Metaboliche e dell'Invecchiamento, Seconda Università degli studi di Napoli, Naples, Italy.
authors.forename: Federica
authors.initials: F
authors.lastname: Cipullo
authors.affiliation: EMG Unit, Neurology Department, Hospital Clinic of Barcelona, Barcelona, Spain; IDIBAPS (Institut d'Investigació Augustí Pi i Sunyer), Facultat de Medicina, University of Barcelona, Barcelona, Spain.
authors.forename: Merche
authors.initials: M
authors.lastname: Morales
authors.affiliation: EMG Unit, Neurology Department, Hospital Clinic of Barcelona, Barcelona, Spain; IDIBAPS (Institut d'Investigació Augustí Pi i Sunyer), Facultat de Medicina, University of Barcelona, Barcelona, Spain.
authors.forename: Josep
authors.initials: J
authors.lastname: Valls-Solé
mesh_terms: D000328:Adult; D001767:Blinking / Q000502:physiology; D004311:Double-Blind Method; D004566:Electrodes; D005145:Face / Q000502:physiology*; D064368:Healthy Volunteers; D006801:Humans; D012018:Reflex / Q000502:physiology*; D065908:Transcranial Direct Current Stimulation; D014276:Trigeminal Nerve / Q000502:physiology*; D055815:Young Adult
keywords: Blink reflex excitability; Brainstem excitability; Prepulse inhibition; Transcranial direct current stimulation; Trigemino-facial reflexes