Cognitive, Behavioral, and Systems NeuroscienceResearch PaperTranscranial direct current stimulation over Broca's region improves phonemic and semantic fluency in healthy individuals
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.
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