title: Transcranial direct current stimulation based metaplasticity protocols in working memory.
abstract: BACKGROUND
  It has been already shown that delivering tDCS that are spaced by an interval alters its impact on motor plasticity. These effects can be explained, based on metaplasticity in which a previous modification of activity in a neuronal network can change the effects of subsequent interventions in the same network. But to date there is limited data assessing metaplasticity effects in cognitive functioning.
  
  
  OBJECTIVE
  The aim of this study was to test several tDCS-based metaplasticity protocols in working memory (WM), by studying the impact of various interstimulation intervals in the performance of a 3-back task.
  
  
  METHODS
  Fifteen healthy volunteers per experiment participated in this study. Experiments 1 and 2 tested an anodal tDCS-induced metaplasticity protocol (1 mA, 10 + 10') with 3 interstimulation intervals (10, 30, and 60 min). Experiment 3 determined the effects of a similar protocol-with a 10-min interval between two sessions of cathodal tDCS or anodal plus cathodal tDCS (1 mA, 10 + 10').
  
  
  RESULTS
  Two consecutive sessions of anodal tDCS delivered with a 10 min interval between them did not improve WM performance (P = .095). This effect remained the same if the interval was increased to 30 or 60 min. In contrast, when a 10 min interval was given between two consecutive cathodal tDCS sessions, performance in the 3 back task increased (P = .042).
  
  
  CONCLUSIONS
  These results suggest that the polarity effects of tDCS on working memory are dependent on the previous level of activity of the recruited neural population.
authors.affiliation: Neuropsychophysiology Laboratory, CIPsi, School of Psychology (EPsi), University of Minho, Campus de Gualtar, 4710-057 Braga, Portugal; Spaulding Neuromodulation Center, Department of Physical Medicine and Rehabilitation, Spaulding Rehabilitation Hospital, Harvard Medical School, Boston, MA, USA; Department of Physical Medicine and Rehabilitation, Massachusetts General Hospital, Harvard Medical School, Boston, MA, USA. Electronic address: sandrarc@psi.uminho.pt.
authors.forename: Sandra
authors.initials: S
authors.lastname: Carvalho
authors.affiliation: Social and Cognitive Neuroscience Laboratory and Developmental Disorders Program, Center for Health and Biological Sciences, Mackenzie Presbyterian University, 01241-001 Sao Paulo, Brazil.
authors.forename: Paulo S
authors.initials: PS
authors.lastname: Boggio
authors.affiliation: Neuropsychophysiology Laboratory, CIPsi, School of Psychology (EPsi), University of Minho, Campus de Gualtar, 4710-057 Braga, Portugal; Spaulding Neuromodulation Center, Department of Physical Medicine and Rehabilitation, Spaulding Rehabilitation Hospital, Harvard Medical School, Boston, MA, USA; Department of Physical Medicine and Rehabilitation, Massachusetts General Hospital, Harvard Medical School, Boston, MA, USA; Department of Counseling and Applied Educational Psychology, Bouvé College of Health Sciences, Northeastern University, Boston, USA.
authors.forename: Óscar F
authors.initials: ÓF
authors.lastname: Gonçalves
authors.affiliation: Neuropsychophysiology Laboratory, CIPsi, School of Psychology (EPsi), University of Minho, Campus de Gualtar, 4710-057 Braga, Portugal.
authors.forename: Ana Rita
authors.initials: AR
authors.lastname: Vigário
authors.affiliation: Neuropsychophysiology Laboratory, CIPsi, School of Psychology (EPsi), University of Minho, Campus de Gualtar, 4710-057 Braga, Portugal.
authors.forename: Marisa
authors.initials: M
authors.lastname: Faria
authors.affiliation: Neuropsychophysiology Laboratory, CIPsi, School of Psychology (EPsi), University of Minho, Campus de Gualtar, 4710-057 Braga, Portugal.
authors.forename: Soraia
authors.initials: S
authors.lastname: Silva
authors.affiliation: Social and Cognitive Neuroscience Laboratory and Developmental Disorders Program, Center for Health and Biological Sciences, Mackenzie Presbyterian University, 01241-001 Sao Paulo, Brazil.
authors.forename: Gabriel
authors.initials: G
authors.lastname: Gaudencio do Rego
authors.affiliation: Spaulding Neuromodulation Center, Department of Physical Medicine and Rehabilitation, Spaulding Rehabilitation Hospital, Harvard Medical School, Boston, MA, USA; Department of Physical Medicine and Rehabilitation, Massachusetts General Hospital, Harvard Medical School, Boston, MA, USA.
authors.forename: Felipe
authors.initials: F
authors.lastname: Fregni
authors.affiliation: Neuropsychophysiology Laboratory, CIPsi, School of Psychology (EPsi), University of Minho, Campus de Gualtar, 4710-057 Braga, Portugal; Spaulding Neuromodulation Center, Department of Physical Medicine and Rehabilitation, Spaulding Rehabilitation Hospital, Harvard Medical School, Boston, MA, USA; Department of Physical Medicine and Rehabilitation, Massachusetts General Hospital, Harvard Medical School, Boston, MA, USA.
authors.forename: Jorge
authors.initials: J
authors.lastname: Leite
mesh_terms: D003071:Cognition; D005260:Female; D006801:Humans; D008297:Male; D008570:Memory, Short-Term / Q000502:physiology*; D009473:Neuronal Plasticity / Q000502:physiology*; D017397:Prefrontal Cortex / Q000502:physiology*; D013997:Time Factors; D065908:Transcranial Direct Current Stimulation; D055815:Young Adult
keywords: DLPFC; Metaplasticity; N-Back; Pre-conditioning and conditioning tDCS; Working memory