Our aim was to enhance the spontaneous slow-frequency EEG activity during the resting state using oscillating transcranial direct currents (tDCS) with a stimulation frequency that resembles the spontaneous oscillations of sleep onset. Accordingly, in this preliminary study, we assessed EEG after-effects of a frontal oscillatory tDCS with different frequency (0.8 vs. 5 Hz) and polarity (anodal, cathodal, and sham). Two single-blind experiments compared the after effects on the resting EEG of oscillatory tDCS [Exp. 1=0.8 Hz, 10 subjects (26.2 ± 2.5 years); Exp. 2=5 Hz, 10 subjects (27.4 ± 2.4 years)] by manipulating its polarity. EEG signals recorded (28 scalp derivations) before and after stimulation [slow oscillations (0.5-1 Hz), delta (1-4 Hz), theta (5-7 Hz), alpha (8-12 Hz), beta 1 (13-15 Hz) and beta 2 (16-24 Hz)] were compared between conditions as a function of polarity (anodal vs. cathodal vs. sham) and frequency of stimulation (0.8 vs. 5 Hz). We found a significant relative enhancement of the delta activity after the anodal tDCS at 5 Hz compared to that at 0.8 Hz. This increase, even though not reaching the statistical significance compared to sham, is concomitant to a significant increase of subjective sleepiness, as assessed by a visual analog scale. These two phenomena are linearly related with a regional specificity, correlations being restricted to cortical areas perifocal to the stimulation site. We have shown that a frontal oscillating anodal tDCS at 5 Hz results in an effective change of both subjective sleepiness and spontaneous slow-frequency EEG activity. These changes are critically associated to both stimulation polarity (anodal) and frequency (5 Hz). However, evidence of frequency-dependence seems more unequivocal than evidence of polarity-dependence.

Oscillating transcranial direct current stimulation (osc-tDCS) modulates the spontaneous brain activity in a frequency-specific manner. Most studies evaluated cortical effects of osc-tDCS through spectral measures, without differentiating components associated with rhythmic and non-rhythmic activity. Since osc-tDCS mainly affects brain oscillatory activity, our aim was to investigate on the specific changes of EEG oscillations following a frontal osc-tDCS at 0.8 and at 5 Hz. 20 healthy subjects (26.8 ± 2.5 years) participated in one of two experiments (Exp.1= 0.8-Hz tDCS, n= 10; Exp.2= 5-Hz tDCS, n= 10), consisting of 3 within-subject sessions: two active conditions with different stimulation polarity (anodal osctDCS, cathodal osc-tDCS), and a control condition (sham). EEG oscillatory components (28 cortical derivations) at the stimulation frequency were measured by the Better OSCillation detection method (BOSC). Variations between before and after the osc-tDCS were compared between conditions as a function of polarity (anodal vs. cathodal vs. sham) and frequency (0.8 vs. 5 Hz) of stimulation. The main finding is a significant local increase of 0.81-Hz slow oscillations (F(1,18)=19.97; p=0.0004) and 5.3-Hz theta oscillations (F(1,18)=26.93; p= 0.0001) after 5 Hz compared to 0.8-Hz tDCS. Our study shows larger frequency-specific and cross-frequency effects of 5-Hz compared to 0.8-Hz stimulation, not revealed by conventional FFT analyses. This finding is consistent with a more effective induction of EEG synchronization during wakefulness by means of a stimulation in the theta range, and it suggests to combine measurement of EEG power and EEG oscillations in future studies involving transcranial stimulations.

Transcranial Direct Current Stimulation is a non-invasive method to modulate cortical excitability, depolarizing or hyperpolarizing neurons, by continuous (c-tDCS), oscillatory (so-tDCS) or alternating current (tACS). We used the tACS (<1 mA, 0.8–5 Hz for 10 min) to actively induce changes in electrophysiological measures of sleepiness. Waking EEG was recorded from 28 derivations before and after tACS stimulation in 10 subjects for the tACS and sham (control). Mean EEG power was calculated for the following bands: delta (1–4 Hz), theta (5–7 Hz), alpha (8–12 Hz), beta1 (13–15 Hz) and beta2 (16–24 Hz). The two conditions (active vs. sham), for each band and for each derivation, were compared by t-tests, and corrected for multiple comparisons. In the eyes-closed condition, the results point to an increase in delta activity at the frontal area after tACS at 0.8 Hz frequency. In the eye-open condition, the increased delta activity was confirmed at the right temporal area after tACS at 5 Hz, while an decrease of beta1 activity was found at the right parietal area after tACS at 0.8 Hz. According to the a priori hypothesis, tACS affects spontaneous EEG activity in both conditions (i.e., eyes-closed and open), because it mainly facilitates the increase in the delta activity, that is an EEG marker of diurnal sleepiness.

The aim of the present article is to review research on the between physical activity and involvement in sports and suicidality This review of the literature indicated that physical activity and sports participation may have a beneficial impact on suicidality at least in boys and men and in some ethnic groups However it is not clear whether physical activity arty directly on suicidality (e g affecting the serotonergic system in the central nervous system) or through a mediating variable such as depression or higher self-esteem Furthermore, the review bar identified some inconsistency in the results, and methodological problems with the research have been identified