Alterations in Leg Muscle Glucose Uptake and Inter-Limb Asymmetry after a Single Session of tDCS in Four People with Multiple Sclerosis

Effects of bilateral dorsolateral prefrontal cortex high-definition transcranial direct-current stimulation on time-trial performance in cyclists with type 1 diabetes mellitus

BACKGROUND

HD-tDCS is capable to increase the focality of neuromodulation and has been recently applied to improve endurance performance in healthy subjects.

OBJECTIVE/HYPOTHESIS

Whether these putative advantages could be exploited in active subjects with type 1 diabetes mellitus (T1D) remains questionable.

METHODS

In a double-blind, randomized crossover order, 11 high-level cyclists (27 ± 4.3 years; weight: 65.5 ± 8.6 kg; height: 180 ± 8 cm; VO₂peak: 67.5 ± 2.9 mL min^-1 kg^-1) with T1D underwent either HD-tDCS (F3, F4) or control (SHAM) and completed a constant-load trial (CLT) at 75% of the 2nd ventilatory threshold plus a 15-km cycling time-trial (TT).

RESULTS

After HD-tDCS, the total time to cover the TT was 3.8% faster (P < 0.01), associated with a higher mean power output (P < 0.01), and a higher rate of power/perception of effort (P < 0.01) and power/heart rate at iso-time (P < 0.05) than the SHAM condition. Physiological parameters during CLT and TT did not differ in both conditions.

CONCLUSIONS

These findings suggest that upregulation of the prefrontal cortex could enhance endurance performance in high-level cyclists with T1D, without altering physiological and perceptual responses at moderate intensity. Present data open to future applications of HD-tDCS to a wider population of active T1D-subjects.

Effects of Transcranial Direct Current Stimulation Over the Left Primary Motor Cortex on Verbal Intelligence

Previous studies have shown that changes in gray matter density and volume in the left primary motor cortex are significantly associated with changes in individuals’ verbal intelligence quotient (VIQ), but not with their performance intelligence quotient (PIQ). In the present study, we examined the effects of transcranial direct current stimulation (tDCS) over the left primary motor cortex on performance in intelligence tests. We chose four subtests (two each for VIQ and PIQ) of the Wechsler Adult Intelligence Scale-Chinese Revised version and randomized participants into anodal, cathodal, and sham groups. We found that anodal stimulation significantly improved performance in verbal intelligence subtests compared to cathodal and sham stimulation, while performance intelligence subtest scores did not change in any stimulation condition. These findings suggest that the excitation level of the left primary motor cortex has a unique effect on verbal intelligence.

On the Effects of Transcranial Direct Current Stimulation on Cerebral Glucose Uptake During Walking: A Report of Three Patients With Multiple Sclerosis

Common symptoms of multiple sclerosis (MS) include motor impairments of the lower extremities, particularly gait disturbances. Loss of balance and muscle weakness, representing some peripheral effects, have been shown to influence these symptoms, however, the individual role of cortical and subcortical structures in the central nervous system is still to be understood. Assessing [¹⁸F]fluorodeoxyglucose (FDG) uptake in the CNS can assess brain activity and is directly associated with regional neuronal activity. One potential modality to increase cortical excitability and improve motor function in patients with MS (PwMS) is transcranial direct current stimulation (tDCS). However, tDCS group outcomes may not mirror individual subject responses, which impedes our knowledge of the pathophysiology and management of diseases like MS. Three PwMS randomly received both 3 mA tDCS and SHAM targeting the motor cortex (M1) that controls the more-affected leg for 20 min on separate days before walking on a treadmill. The radiotracer, FDG, was injected at minute two of the 20 min walk and the subjects underwent a Positron emission tomography (PET) scan immediately after the task. Differences in relative regional metabolism of areas under the tDCS anode and the basal ganglia were calculated and investigated. The results indicated diverse and individualized responses in regions under the anode and consistent increases in some basal ganglia areas (e.g., caudate nucleus). Thus, anodal tDCS targeting the M1 that controls the more-affected leg of PwMS might be capable of affecting remote subcortical regions and modulating the activity (motor, cognitive, and behavioral functions) of the circuitry connected to these regions.