Inhibition of motor cortex excitability with 15 Hz transcranial alternating current stimulation (tACS)

There remains a lack of solid evidence showing whether transcranial stimulation with weak alternating current (transcranial alternating current stimulation, tACS) can in fact induce significant neurophysiological effects. Previously, a study in which tACS was applied for 2 and 5 min with current density = 0.16-0.25 A/m(2) was unable to show robust effects on cortical excitability. Here we applied tACS at a significantly higher current density (0.80 A/m(2)) for a considerably longer duration (20 min) and were indeed able to demonstrate measurable changes to cortical excitability. Our results show that active 15 Hz tACS of the motor cortex (electrodes placed at C3 and C4) significantly diminished the amplitude of motor evoked potentials and decreased intracortical facilitation (ICF) as compared to baseline and sham stimulation. In addition, we show that our method of sham tACS is a reliable control condition. These results support the notion that AC stimulation with weak currents can induce significant changes in brain excitability; in this case, 15 Hz tACS led to a pattern of inhibition of cortical excitability. We propose that tACS may have a dampening effect on cortical networks and perhaps interfere with the temporal and spatial summation of weak subthreshold electric potentials. (C) 2010 Elsevier Ireland Ltd. All rights reserved.

A randomized, double-blind clinical trial on the efficacy of cortical direct current stimulation for the treatment of major depression

Preliminary findings suggest that transcranial direct current stimulation (tDCS) can have antidepressant effects. We sought to test this further in a parallel-group, double-blind clinical trial with 40 patients with major depression, medication-free randomized into three groups of treatment: anodal tDCS of the left dorsolateral prefrontal cortex (active group-`DLPFC`); anodal tDCS of the occipital cortex (active control group-`occipital`) and sham tDCS (placebo control group-`sham`). tDCS was applied for 10 sessions during a 2-wk period. Mood was evaluated by a blinded rater using the Hamilton Depression Rating Scale (HDRS) and Beck Depression Inventory (BDI). The treatment was well tolerated with minimal side-effects that were distributed equally across all treatment groups. We found significantly larger reductions in depression scores after DLPFC tDCS [HDRS reduction of 40.4 % (+/-25.8%)] compared to occipital [HDRS reduction of 21.3 % ( +/-12.9%)] and sham tDCS [HDRS reduction of 10.4 % (+/-36.6%)]. The beneficial effects of tDCS in the DLPFC group persisted for 1 month after the end of treatment. Our findings support further investigation on the effects of this novel potential therapeutic approach - tDCS - for the treatment of major depression.

Infection control practices among a cohort of Brazilian dentists

Objective: To evaluate infection control practices among dentists in private and public practice. Design: Survey and cross-sectional analysis. Setting: Sertaozinho city, Brazil. Participants: All dentists who were currently working at the study city, and agreed to participate, resulting in a study population of 135 dentists. Methods: Participants were personally interviewed and variables were submitted to X(2) or Fisher`s exact test. Results: Hand washing before and after each patient was reported by 86.7% of dentists, but private practitioners used liquid soap and paper towels more often than their public colleagues (p<0.001). Most of the study population (97.8%) used gloves routinely during clinical sessions, but 8.2% reused them. Dry-heat was the main method employed for sterilisation of heat-stable devices by 80.0% of dentists, but adequate temperature and time of exposure was accomplished by only 32.1% of public and 70.0% of private professionals (p<0.001). Heat-sensitive devices were disinfected with an adequate substance by 60.0% of both affiliation dentists (p=0.908). Conclusions: There is a large gap between infection control recommendations and practices observed among the study population, and the situation is worse in public services. To reverse that situation, infection control issues must be openly debated by professional associations, dental schools and health authorities.