Excitatory anodal transcranial direct current stimulation (A-tDCS) over the left dorsal prefrontal cortex (DPFC) has been shown to improve language production.
The present study examined neurophysiological underpinnings of this effect.
In a single-blinded within-subject design, we traced effects of A-tDCS compared to sham stimulation over the left DPFC using electrophysiological and behavioural correlates during overt picture naming.
Online effects were examined during A-tDCS by employing the semantic interference (SI-)Effect - a marker that denotes the functional integrity of the language system.
The behavioural SI-Effect was found to be reduced, whereas the electrophysiological SI-Effect was enhanced over left compared to right temporal scalp-electrode sites.
This modulation is suggested to reflect a superior tuning of neural responses within language-related generators.
After -(offline) effects of A-tDCS were detected in the delta frequency band, a marker of neural inhibition.
After A-tDCS there was a reduction in delta activity during picture naming and the resting state, interpreted to indicate neural disinhibition. Together, these findings demonstrate electrophysiological modulations induced by A-tDCS of the left DPFC. They suggest that A-tDCS is capable of enhancing neural processes during and after application.
The present functional and oscillatory neural markers could detect positive effects of prefrontal A-tDCS, which could be of use in the neuro-rehabilitation of frontal language functions.
2011-11-23
Eng.
University Hospital of Psychiatry, Department of Psychiatric Neurophysiology, Bern, Switzerland. Miranka.wirth [at] gmail.com
Neuropsychologia. 2011 Dec;49(14):3989-98
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