Combining Transcranial Direct Current Stimulation With Tai Chi to Improve Dual-Task Gait Performance in Older Adults With Mild Cognitive Impairment: A Randomized Controlled Trial.

Introduction: Engaging in a secondary task while walking increases motor-cognitive interference and exacerbates fall risk in older adults with mild cognitive impairment (MCI). Previous studies have demonstrated that Tai Chi (TC) may improve cognitive function and dual-task gait performance. Intriguingly, with emerging studies also indicating the potential of transcranial direct current stimulation (tDCS) in enhancing such motor-cognitive performance, whether combining tDCS with TC might be superior to TC alone is still unclear. The purpose of this study was to investigate the effects of combining tDCS with TC on dual-task gait in patients with MCI. Materials and Methods: Twenty patients with MCI were randomly assigned to receive either anodal or sham tDCS, both combined with TC, for 36 sessions over 12 weeks. Subjects received 40 min of TC training in each session. During the first 20 min, they simultaneously received either anodal or sham tDCS over the left dorsolateral prefrontal cortex. Outcome measures included dual-task gait performance and other cognitive functions. Results: There were significant interaction effects between groups on the cognitive dual task walking. Compared to sham, the anodal tDCS group demonstrated a greater improvement on cadence and dual task cost of speed. Conclusion: Combining tDCS with TC may offer additional benefits over TC alone in enhancing dual-task gait performance in patients with MCI. Clinical Trial Registration: [www.ClinicalTrials.gov], identifier [TCTR20201201007].

High-Frequency External Muscle Stimulation Reduces Depressive Symptoms in Older Male Veterans: A Pilot Study.

OBJECTIVE: Late-life depression (LLD) is a severe public health problem. Given that pharmacological treatments for LLD are limited by their side effects, development of efficient and tolerable nonpharmacological treatment for LLD is urgently required. This study investigated whether high-frequency external muscle stimulation could reduce depressive symptoms in LLD. METHODS: Twenty-two older male veterans with major depression were recruited and randomized into a treatment (n = 9) or sham control group (n = 13). The groups received high-frequency external muscle stimulation or sham intervention 3 times per week for 12 weeks. Clinical symptoms and muscle strength were evaluated at baseline and every 2 weeks. RESULTS: The 2 groups were homogeneous in age, baseline clinical symptoms, and muscle strength. The treatment group showed significant improvement in depression and anxiety scores and muscle strength (all P < .01), whereas the control group showed no significant change after the 12-week follow-up. Compared to the control group, the treatment group showed significant improvements in depression (Geriatric Depression Scale, P = .009; Hamilton Depression Rating Scale, P = .007) and anxiety scores (HAMA, P = .008) and muscle strength (all P < .001). Changes in depression and anxiety levels were significantly correlated with changes in muscle strength after the study. In the treatment group, we observed a trend of correlation between the reduction in depression and muscle strength gains. CONCLUSION: High-frequency external muscle stimulation appears to be an effective treatment for older patients with LLD. Large studies with more tests and/or conducted in different populations are warranted to validate these preliminary findings.

Smaller magnets for smarter minds?

Human brain stimulation for therapeutic purposes has many short- and long-term limitations. The possibility of implanting magnetic, rather than electrical, stimulation devices would present a possible solution to some of the problems. The development of a new microscopic magnetic stimulation device provides a glimpse of the realisation.

Modulating behavioral inhibition by tDCS combined with cognitive training.

Cognitive training is an effective tool to improve a variety of cognitive functions, and a small number of studies have now shown that brain stimulation accompanying these training protocols can enhance their effects. In the domain of behavioral inhibition, little is known about how training can affect this skill. As for transcranial direct current stimulation (tDCS), it was previously found that stimulation over the right inferior frontal gyrus (rIFG) facilitates behavioral inhibition performance and modulates its electrophysiological correlates. This study aimed to investigate this behavioral facilitation in the context of a learning paradigm by giving tDCS over rIFG repetitively over four consecutive days of training on a behavioral inhibition task (stop signal task (SST)). Twenty-two participants took part; ten participants were assigned to receive anodal tDCS (1.5 mA, 15 min), 12 were assigned to receive training but not active stimulation. There was a significant effect of training on learning and performance in the SST, and the integration of the training and rIFG-tDCS produced a more linear learning slope. Better performance was also found in the active stimulation group. Our findings show that tDCS-combined cognitive training is an effective tool for improving the ability to inhibit responses. The current study could constitute a step toward the use of tDCS and cognitive training as a therapeutic tool for cognitive control impairments in conditions such as attention-deficit hyperactivity disorder (ADHD) or schizophrenia.

Suppressing sensorimotor activity modulates the discrimination of auditory emotions but not speaker identity.

Our ability to recognize the emotions of others is a crucial feature of human social cognition. Functional neuroimaging studies indicate that activity in sensorimotor cortices is evoked during the perception of emotion. In the visual domain, right somatosensory cortex activity has been shown to be critical for facial emotion recognition. However, the importance of sensorimotor representations in modalities outside of vision remains unknown. Here we use continuous theta-burst transcranial magnetic stimulation (cTBS) to investigate whether neural activity in the right postcentral gyrus (rPoG) and right lateral premotor cortex (rPM) is involved in nonverbal auditory emotion recognition. Three groups of participants completed same-different tasks on auditory stimuli, discriminating between the emotion expressed and the speakers' identities, before and following cTBS targeted at rPoG, rPM, or the vertex (control site). A task-selective deficit in auditory emotion discrimination was observed. Stimulation to rPoG and rPM resulted in a disruption of participants' abilities to discriminate emotion, but not identity, from vocal signals. These findings suggest that sensorimotor activity may be a modality-independent mechanism which aids emotion discrimination.

Double dissociation of format-dependent and number-specific neurons in human parietal cortex.

Based on neuroimaging methods, it is a commonly held view that numerical representation in the human parietal lobes is format independent. We used a transcranial magnetic stimulation adaptation paradigm to examine the existence of functionally segregated overlapping populations of neurons for different numerical formats and to reveal how numerical information is encoded and represented. Based on 2 experiments, we found that right parietal lobe stimulation showed a dissociation between digits and verbal numbers, whereas the left parietal lobe showed a double dissociation between the different numerical formats. Further analysis and modeling also excluded pre- or postrepresentational components as the source of the current effects. These results demonstrate that both parietal lobes are equipped with format-dependent neurons that encode quantity.

Sensory and association cortex in time perception.

The recent upsurge of interest in brain mechanisms of time perception is beginning to converge on some new starting points for investigating this long under studied aspect of our experience. In four experiments, we asked whether disruption of normal activity in human MT/V5 would interfere with temporal discrimination. Although clearly associated with both spatial and motion processing, MT/V5 has not yet been implicated in temporal processes. Following predictions from brain imaging studies that have shown the parietal cortex to be important in human time perception, we also asked whether disruption of either the left or right parietal cortex would interfere with time perception preferentially in the auditory or visual domain. The results show that the right posterior parietal cortex is important for timing of auditory and visual stimuli and that MT/V5 is necessary for timing only of visual events.

Efficacy of repetitive transcranial magnetic stimulation/transcranial direct current stimulation in cognitive neurorehabilitation.

Cognitive deficits are a common consequence of neurologic disease, in particular, of traumatic brain injury, stroke, and neurodegenerative disorders, and there is evidence that specific cognitive training may be effective in cognitive rehabilitation. Several investigations emphasize the fact that interacting with cortical activity, by means of cortical stimulation, can positively affect the short-term cognitive performance and improve the rehabilitation potential of neurologic patients. In this respect, preliminary evidence suggests that cortical stimulation may play a role in treating aphasia, unilateral neglect, and other cognitive disorders. Several possible mechanisms can account for the effects of transcranial magnetic stimulation (TMS) and transcranial direct current stimulation (tDCS) on cognitive performance. They all reflect the potential of these methods to improve the subject's ability to relearn or to acquire new strategies for carrying out behavioral tasks. The responsible mechanisms remain unclear but they are most likely related to the activation of impeded pathways or inhibition of maladaptive responses. Modifications of the brain activity may assist relearning by facilitating local activity or by suppressing interfering activity from other brain areas. Notwithstanding the promise of these preliminary findings, to date no systematic application of these methods to neurorehabilitation research has been reported. Considering the potential benefit of these interventions, further studies taking into consideration large patient populations, long treatment periods, or the combination of different rehabilitation strategies are needed. Brain stimulation is indeed an exciting opportunity in the field of cognitive neurorehabilitation, which is clearly in need of further research.

Infant learning: music and the baby brain.

When it comes to listening to music, infants literally have a more open mind than their parents. Studies which investigate listening behaviour of babies and adults have shown that, as we learn to discriminate the musical sounds in our own environment, we become less sensitive to those of other cultures.

Magnetic and electrical stimulation of the auditory cortex for intractable tinnitus. Case report.

Tinnitus is a distressing symptom that affects up to 15% of the population for whom no satisfactory treatment exists. The authors present a novel surgical approach for the treatment of intractable tinnitus, based on cortical stimulation of the auditory cortex. Tinnitus can be considered an auditory phantom phenomenon similar to deafferentation pain, which is observed in the somatosensory system. Tinnitus is accompanied by a change in the tonotopic map of the auditory cortex. Furthermore, there is a highly positive association between the subjective intensity of the tinnitus and the amount of shift in tinnitus frequency in the auditory cortex, that is, the amount of cortical reorganization. This cortical reorganization can be demonstrated by functional magnetic resonance (fMR) imaging. Transcranial magnetic stimulation (TMS) is a noninvasive method of activating or deactivating focal areas of the human brain. Linked to a navigation system that is guided by fMR images of the auditory system, TMS can suppress areas of cortical plasticity. If it is successful in suppressing a patient's tinnitus, this focal and temporary effect can be perpetualized by implanting a cortical electrode. A neuronavigation-based auditory fMR imaging-guided TMS session was performed in a patient who suffered from tinnitus due to a cochlear nerve lesion. Complete suppression of the tinnitus was obtained. At a later time an extradural electrode was implanted with the guidance of auditory fMR imaging navigation. Postoperatively, the patient's tinnitus disappeared and remains absent 10 months later. Focal extradural electrical stimulation of the primary auditory cortex at the area of cortical plasticity is capable of suppressing contralateral tinnitus completely. Transcranial magnetic stimulation may be an ideal method for noninvasive studies of surgical candidates in whom stimulating electrodes might be implanted for tinnitus suppression.