, 2011). This enhances the acquisition and retention of motor learning when applied over motor cortex (Nitsche et al., 2003b; Antal et al., 2004a; Reis et al., 2009), probably by increasing GPCR & G Protein inhibitor the associated long-term potentiation which underlies cortical plasticity (Stagg & Nitsche, 2011). These effects have been extended by research showing that anodal tDCS over Wernicke’s or Broca’s areas can enhance artificial language learning (Floel et al., 2008; Vries et al., 2010). Only one study has so far examined the effects of tDCS on perceptual learning, finding only a transient enhancement of visual learning by anodal stimulation before the effect dissipated with more training (Fertonani et al.,

2011). Our initial aim was to determine whether auditory perceptual learning, like motor learning, is enhanced by increasing excitability of its primary cortical representation, as it is underpinned by similar use-dependent plasticity, which anodal tDCS is thought

to enhance. We instead found that anodal tDCS did not enhance frequency discrimination learning but unexpectedly degraded frequency discrimination. We conducted two further experiments examining the effects of anodal tDCS on the Selleckchem LEE011 place and temporal coding processes that underlie auditory frequency discrimination to determine the cause of this degradation. Cumulative evidence suggests the auditory system uses duplex coding, with temporal processes dominant at lower frequencies (Moore, 1973; Moore & Glasberg, 1989) and place processes dominant at higher frequencies (Johnson, 1980). We took psychophysical Amino acid measurements of place and temporal coding and showed that the degradation of frequency discrimination was probably due to interference with temporal coding. Twenty adult volunteers (14 females) aged between 18 and 27 years (median = 23 years), all of whom reported normal hearing, participated in the three experiments. This sample size is consistent with previous psychophysical studies (Demany & Semal, 2002; Mathys et al., 2010). Fifteen subjects completed the frequency discrimination learning task reported in Experiment 1. As learning

was being examined, subjects with extensive psychoacoustic experience or with more than 1 year’s musical experience were not recruited. Seven subjects (four of whom participated in Experiment 1) were recruited for Experiment 2A. Six subjects (two of whom competed both Experiments 1 and 2A and two who completed only Experiment 2A) participated in Experiment 2B. Author M.F.T. completed Experiments 2A and 2B but was blind to stimulation condition with the procedure being performed by another experimenter and was not informed of stimulation condition until after testing was completed. All other subjects were blind to the stimulation condition and Naïve to the experimental aims. No formal audiometric assessment was performed; instead stimulus levels were tailored to each subject’s sensitivity.