Elsevier

Neuroscience

Volume 183, 2 June 2011, Pages 64-70
Neuroscience

Cognitive, Behavioral, and Systems Neuroscience
Research Paper
Transcranial direct current stimulation over Broca's region improves phonemic and semantic fluency in healthy individuals

https://doi.org/10.1016/j.neuroscience.2011.03.058Get rights and content

Abstract

Previous studies have demonstrated that transcranial direct current stimulation (tDCS) can be proficiently used to modulate attentional and cognitive functions. For instance, in the language domain there is evidence that tDCS can fasten picture naming in both healthy individuals and aphasic patients, or improve grammar learning. In this study, we investigated whether tDCS can be used to increase healthy subjects' performance in phonemic and semantic fluency tasks, that are typically used in clinical assessment of language. Ten healthy individuals performed a semantic and a phonemic fluency task following anodal tDCS applied over Broca's region. Each participant underwent a real and a sham tDCS session. Participants were found to produce more words following real anodal tDCS both in the phonemic and in the semantic fluency. Control experiments ascertained that this finding did not depend upon unspecific effects of tDCS over levels of general arousal or attention or upon participants' expectations. These data confirm the efficacy of tDCS in transiently improving language functions by showing that anodal stimulation of Broca's region can enhance verbal fluency. Implications of these results for the treatment of language functions in aphasia are considered.

Highlights

▶Fluency tasks are typically used in clinical assessment of language. ▶tDCS can be proficiently used to modulate cognitive functions. ▶Participants performed a semantic and a phonemic fluency task following anodal tDCS over the Broca's region. ▶Participants produced more words following real compared to sham anodal tDCS in both fluency tasks. ▶Our data confirm the efficacy of tDCS in transiently improving language functions.

Section snippets

Participants

Ten neurologically unimpaired individuals (four Males, mean age 23.6 years, SD=3.2) took part in the experiment. All participants were native Italian speaker undergraduate students; they were naive as to the experimental procedure, and the purpose of the study. All subjects were right-handed (as assessed by means of the Edinburgh Inventory Questionnaire, Oldfield, 1971) and with normal or corrected-to-normal vision. They had no history of chronic or acute neurologic, psychiatric, or medical

Experiment 2

Although there is evidence that participants cannot distinguish between Real and Sham stimulation condition when 1 mA tDCS using 5×5 cm2 electrodes (current density=0.04 mA/cm2) is used (Gandiga et al., 2006), in our experiment 2 mA tDCS was applied and 5×7 cm2 electrodes were used (current density=0.057 mA/cm2). Given these differences in current intensity and density, we cannot exclude that at least some of our participants may have been able to distinguish between Sham and Real stimulation,

Discussion

Our results show that anodal tDCS over Broca's region (compared to sham stimulation) significantly improved participants' performance in both semantic and phonemic fluency. Overall participants generated more words following semantic cues (i.e. the name of a category) than phonological cues (i.e. a letter), in line with previous evidence (Gollan et al., 2002; Grogan et al., 2008; Novelli et al., 1986), but the effect of tDCS over the Broca's region was comparable in the two tasks. Although one

Acknowledgments

This study was supported by a FAR grant to C.P.

References (77)

  • P.P. Hurks et al.

    Verbal fluency over time as a measure of automatic and controlled processing in children with ADHD

    Brain Cogn

    (2004)
  • L.J. Lauro et al.

    A case for the involvement of phonological loop in sentence comprehension

    Neuropsychologia

    (2010)
  • J.P. Lefaucheur et al.

    The use of repetitive transcranial magnetic stimulation (rTMS) and transcranial direct current stimulation (tDCS) to relieve pain

    Brain Stimul

    (2008)
  • K.B. McDermott et al.

    A procedure for identifying regions preferentially activated by attention to semantic and phonological relations using functional magnetic resonance imaging

    Neuropsychologia

    (2003)
  • C. Miniussi et al.

    Efficacy of repetitive transcranial magnetic stimulation/transcranial direct current stimulation in cognitive neurorehabilitation

    Brain Stimul

    (2008)
  • M.A. Nitsche et al.

    Treatment of depression with transcranial direct current stimulation (tDCS): a review

    Exp Neurol

    (2009)
  • M.A. Nitsche et al.

    Transcranial direct current stimulation: state of the art 2008

    Brain Stimul

    (2008)
  • M.A. Nitsche et al.

    Criteria for transcranial direct current stimulation (tDCS) in humans

    Clin Neurophysiol

    (2003)
  • R.C. Oldfield

    The assessment and analysis of handedness: the Edinburgh Inventory

    Neuropsychologia

    (1971)
  • W. Paulus

    Transcranial direct current stimulation (tDCS)

    Suppl Clin Neurophysiol

    (2003)
  • C. Poreisz et al.

    Safety aspects of transcranial direct current stimulation concerning healthy subjects and patients

    Brain Res Bull

    (2007)
  • A. Priori

    Brain polarization in humans: a reappraisal of an old tool for prolonged noninvasive modulation of brain excitability

    Clin Neurophysiol

    (2003)
  • A. Priori et al.

    Repetitive transcranial magnetic stimulation or transcranial direct current stimulation?

    Brain Stimul

    (2009)
  • K.L. Sakai et al.

    Selective priming of syntactic processing by event-related transcranial magnetic stimulation of Broca's area

    Neuron

    (2002)
  • S. Schwartz et al.

    Distinct patterns of word retrieval in right and left frontal lobe patients: a multidimensional perspective

    Neuropsychologia

    (2001)
  • S. Schwartz et al.

    Pervasive influence of semantics in letter and category fluency: a multidimensional approach

    Brain Lang

    (2003)
  • R. Sparing et al.

    Enhancing language performance with non-invasive brain stimulation—a transcranial direct current stimulation study in healthy humans

    Neuropsychologia

    (2008)
  • A. Spek et al.

    Verbal fluency in adults with high functioning autism or Asperger syndrome

    Neuropsychologia

    (2009)
  • K.S. Utz et al.

    Electrified minds: transcranial direct current stimulation (tDCS) and galvanic vestibular stimulation (GVS) as methods of non-invasive brain stimulation in neuropsychology—a review of current data and future implications

    Neuropsychologia

    (2010)
  • F.G. Yang et al.

    Figurative language processing after traumatic brain injury in adults: a preliminary study

    Neuropsychologia

    (2010)
  • J.M. Baker et al.

    Using transcranial direct-current stimulation to treat stroke patients with aphasia

    Stroke

    (2010)
  • J.V. Baldo et al.

    Letter and category fluency in patients with frontal lobe lesions

    Neuropsychology

    (1998)
  • Barwood CH, Murdoch BE, Whelan BM, Lloyd D, Riek S, O' Sullivan JD, Coulthard A, Wong A (in press) Improved language...
  • A.R. Brunoni et al.

    Neuromodulation approaches for the treatment of major depression: challenges and recommendations from a working group meeting

    Arq Neuro Psiquiatr

    (2010)
  • P.A. Chouinard et al.

    The lateral-occipital and the inferior-frontal cortex play different roles during the naming of visually presented objects

    Hum Brain Mapp

    (2009)
  • S.G. Costafreda et al.

    A systematic review and quantitative appraisal of fMRI studies of verbal fluency: role of the left inferior frontal gyrus

    Hum Brain Mapp

    (2006)
  • S.G. Costafreda et al.

    Pattern of neural responses to verbal fluency shows diagnostic specificity for schizophrenia and bipolar disorder

    BMC Psychiatry

    (2011)
  • J.T. Devlin et al.

    Semantic processing in the left inferior prefrontal cortex: a combined functional magnetic resonance imaging and transcranial magnetic stimulation study

    J Cogn Neurosci

    (2003)
  • Cited by (0)

    View full text