Frontoparietal thetagamma interactions track working memory enhancement with training and tDCS Abstract   Despite considerable interest in enhancing, preserving, and rehabilitating working memory (WM), efforts to elicit sustained behavioral improvements have been met with limited success. Here, we paired WM training with transcranial direct current stimulation (tDCS) to the frontoparietal network over four days. Active tDCS enhanced WM performance by modulating interactions between frontoparietal theta oscillations and gamma activity, as measured by pre and posttraining highdensity electroencephalography (EEG). Increased phaseamplitude coupling (PAC) between the prefrontal stimulation site and temporoparietal gamma activity explained behavioral improvements, and was most effective when gamma occurred near the prefrontal theta peak. These results demonstrate for the first time that tDCSlinked WM training elicits lasting changes in behavior by optimizing the oscillatory substrates of prefrontal control.

Transcranial direct current stimulation (tDCS) elicits stimulusspecific enhancement of cortical plasticity. Abstract   Background  Deficits in plasticity underlie many severe psychiatric disorders. Transcranial direct current stimulation (tDCS) is a promising method for modulating plasticity. However, given its nonfocal nature, there are open questions as to how targeting and outcome specificity can best be achieved.    Objective  Understanding how tDCS interacts with concurrent brain activity is necessary for the rational advancement of tDCS. In the present study, we use an eventrelated potential (ERP) paradigm to assess the stimulusspecific effects of tDCS on cortical plasticity.    Methods  22 healthy volunteers underwent a blinded, shamcontrolled plasticity paradigm in a crossover design. High frequency presentation of auditory stimuli was used to induce potentiation in specific components of the ERP. We investigated whether anodal tDCS targeting the auditory cortex would modulate plasticity induction across time. Two pure tones were used as stimuli, only one of the tones, the target tone, was used for plasticity induction. Plasticity was quantified as change in the mean amplitude of the N100 component relative to baseline.    Results  TDCS significantly modulated plasticity in the target tone compared to sham (pxe2x80xafxe2x80xaf0.02) but had no effect on the control tone (pxe2x80xafxe2x80xaf0.73). This effect was time dependent, with tDCS effects no longer apparent 30xe2x80xafmin after stimulation.    Conclusions  Our results indicate that tDCS can modulate cortical plasticity in the auditory cortex in an activitydependent manner. These findings bolster the idea that tDCS can be an effective tool to target and modulate plasticity both for research and therapeutic purposes.