This study explores the possibility of noninvasively inducing long-term changes in human corticomotor excitability by means of a brain-computer interface, which enables users to exert internal control over the cortical rhythms recorded from the scalp. We demonstrate that self-regulation of electroencephalogram rhythms in quietly sitting, naive humans significantly affects the subsequent corticomotor response to transcranial magnetic stimulation, producing durable and correlated changes in neurotransmission. Specifically, we show that the intrinsic suppression of alpha cortical rhythms can in itself produce robust increases in corticospinal excitability and decreases in intracortical inhibition of up to 150%, which last for at least 20 min. Our observations may have important implications for therapies of brain disorders associated with abnormal cortical rhythms, and support the use of electroencephalogram-based neurofeedback as a noninvasive tool for establishing a causal link between rhythmic cortical activities and their functions.

We often change our behavior to conform to real or imagined group pressure. Social influence on our behavior has been extensively studied in social psychology, but its neural mechanisms have remained largely unknown. Here we demonstrate that the transient downregulation of the posterior medial frontal cortex by theta-burst transcranial magnetic stimulation reduces conformity, as indicated by reduced conformal adjustments in line with group opinion. Both the extent and probability of conformal behavioral adjustments decreased significantly relative to a sham and a control stimulation over another brain area. The posterior part of the medial frontal cortex has previously been implicated in behavioral and attitudinal adjustments. Here, we provide the first interventional evidence of its critical role in social influence on human behavior.

Research to date has focused on the effect of cTBS on the target area, but less is known about its effects on the resting state functional connectivity between different brain regions. We investigated this issue by applying cTBS to the occipital cortex and probing its influence in retinotopically defined regions in early visual cortex using functional MRI. We found that occipital cTBS reliably decreased the resting state functional connectivity (i.e., the correlation of spontaneous activity) between regions of the early visual cortex. In the context of a perceptual task, such an effect could mean that cTBS affects the strength of the perceptual signal, its variability, or both. We investigated this issue in a second experiment in which subjects performed a perceptual discrimination task and indicated their level of certainty on each trial. The results showed that occipital cTBS decreased both subjects' accuracy and confidence. Signal detection modeling suggested that these impairments resulted primarily from a decreased strength of the perceptual signal, with a nonsignificant trend of a decrease in signal variability. We discuss the implications of these experiments for understanding the mechanisms by which cTBS influences brain activity and perceptual processes. cTBS; fMRI; visual cortex; perception; resting state connectivity; signal detection theory REPETITIVE TRANSCRANIAL MAGNETIC stimulation is a popular technique used to transiently affect neural activity in a noninvasive manner. One recently developed variant of repetitive transcranial magnetic stimulation (TMS), continuous theta burst stimulation (cTBS;Huang et al. 2005), has shown promise because of its rapid application (Ͻ1 min), its ability to produce behavioral effects for up to 1 h after stimulation, and its connection to known neuronal mechanisms, such as long-term potentiation and depression (LTD). Indeed, research has shown that cTBS reduces motor cortical excitability in a manner consistent with LTD effects (Allen et al. 2007;Di Lazzaro et al. 2005Gentner et al. 2008;Huang et al. 2005Huang et al. , 2007.When applied to the occipital cortex, cTBS has been found to increase phosphene thresholds (PTs), such that higher stimulation intensity is needed to produce conscious visual experience (Franca et al. 2006). One possibility is that such an increase in PTs is, at least in part, due to decreased connectivity between areas in the early visual cortex, which would make the Here we tested for this possibility by investigating the resting state connectivity between retinotopically defined regions in the early visual cortex after occipital application of cTBS. We identified areas V1, V2, and V3 as three separate regions of interest (ROIs) and found that cTBS decreased the resting state functional connectivity between each pair of regions. In separate analyses, we separated the left and right hemisphere of each of these areas and observed that cTBS decreased the inter-and intrahemispheric resting state connectivity between these retinotopically defined re...

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Transcranial direct current stimulation (tDCS) is a noninvasive brain stimulation technique that alters cortical excitability. Interestingly, in recent animal studies facilitatory effects of tDCS have also been observed on subcortical structures. Here, we sought to provide evidence for the potential of tDCS to facilitate subcortical structures in humans as well. Subjects received anodal-tDCS and sham-tDCS on two separate testing days in a counterbalanced order. After stimulation, we assessed the effect of tDCS on two responses that arise from subcortical structures; (1) wrist and ankle responses to an imperative stimulus combined with a startling acoustic stimulus (SAS), and (2) automatic postural responses to external balance perturbations with and without a concurrent SAS. During all tasks, response onsets were significantly faster following anodal-tDCS compared to sham-tDCS, both in trials with and without a SAS. The effect of tDCS was similar for the dominant and non-dominant leg. The SAS accelerated the onsets of ankle and wrist movements and the responses to backward, but not forward perturbations. The faster onsets of SAS-induced wrist and ankle movements and automatic postural responses following stimulation provide strong evidence that, in humans, subcortical structures - in particular the reticular formation - can be facilitated by tDCS. This effect may be explained by two mechanisms that are not mutually exclusive. First, subcortical facilitation may have resulted from enhanced cortico-reticular drive. Second, the applied current may have directly stimulated the reticular formation. Strengthening reticulospinal output by tDCS may be of interest to neurorehabilitation, as there is evidence for reticulospinal compensation after corticospinal lesions.