Investigation of the effects of transcranial direct current stimulation and neurofeedback by continuous performance test

Transcranial direct current stimulation (tDCS) is a noninvasive neuromodulation technique based on weak direct current stimulation through the scalp. Neurofeedback (NFB) is a learning strategy that may help alter to brain wave parameters, by monitoring electroencephalography (EEG) feedback via special programs. We aimed to investigate the supportive effects of tDCS in addition to NFB training. 16 healthy volunteers were divided equally into two groups. One of the groups was trained by NFB with the sensorimotor rhythm (SMR) protocol; 2 days per week, 10 sessions of 30 min, the other group received 10 min of tDCS before each NFB sessions. Continuous Performance Test (CPT) was used to measure, response time and suppression and to determine selective attention condition. Also, Beck Depression and Anxiety Inventories were used to exclude people with depression and anxiety. Depression scores of NFB + tDCS group were decreased significantly. CPT scores were better at last sessions for both groups compared to the first sessions. Sessions were analyzed by comparing 1st, 2nd, 5th and 10th sessions. While the NFB + tDCS group had statistically significant changes at theta/beta ratios with SMR and alpha band amplitudes, NFB group statistics had changed at theta/SMR ratios. NFB training shows its effects at the end of 10 sessions. Despite an increase in the latencies of correct and commission responses on the task of CPT, additional use of tDCS improves cognitive performance. Also, tDCS has a supportive effect on the healthy participants who have mild anxiety and depression; also inhibition deficits of subjects were clear

Auditory on- and off-responses and alpha oscillations in the human EEG

In the present study, the wide band alpha and sub-bands of alpha in the auditory on- and off-responses to different stimulation frequencies were evaluated. Auditory on- and off-responses of 12 healthy volunteers (average 17 years. old) were recorded from five locations (Fz, Cz, Pz, P3, and P4). The auditory stimuli of 80 dB SPL and 1000 ms duration were delivered at six different stimulation frequencies (f1-f6; 0.2, 0.6, 1, 2, 3, and 4 kHz, respectively). In using individual alpha frequency (IAF) as individual anchor point, wide band alpha and three different alpha frequency sub-bands with a bandwidth of 2 Hz each were defined: lower-1 alpha, lower-2 alpha, and upper alpha. The Root Mean Square (RMS) values of the alpha frequency bands were computed for two time periods: +/-3 sd around the mean peak latency of the auditory on-responses (t1-on and t2-on) and a time window of the same length of the auditory off-responses (t1-off and t2-off). The alpha RMS values of both on- and off responses showed significant differences between t1 and t2 periods on wide band, lower-1 and lower-2 alpha bands, especially at 0.2, 0.6, 1, 2, and 3 kHz stimulation frequencies in all recording places. Amplitudes in anterior locations (Fz, Cz) were higher than the others. These observations may provide a preliminary but nonetheless important understanding of how information may be processed in the brain

The effects of losartan and immobilization stress on heart rate variability and plasma corticosterone levels in rats

In this study, the effects of losartan, an angiotensin II receptor antagonist, on heart rate variability and the changes of plasma corticosterone levels caused by immobilization stress were investigated. Losartan (3 mg/kg, p.o.) significantly prevented increases in plasma corticosterone levels in both losartan+acute stress and losartan +chronic stress groups. But, losartan did not prevent the diminution of the power of heart rate variability caused by stress. Our results supported the idea that the renin-angiotensin system is also involved in the stress-induced cardiovascular response, besides the autonomic nervous system. But, the effects of losartan on heart rate variability remained controversial

Electroencephatographic characterization of scopolamine-induced convulsions in fasted mice after food intake

The present study was conducted to evaluate scopolamine-induced convulsions in fasted mice after food intake effects on the cortical electroencephalogram (EEG). Continuous EEG recordings were taken with Neuroscan for 10 min in freely moving mice with six chronic cortical electrode implants. Animals were weighed and deprived of food for 48 h. EEG recordings were taken at the 24th and 48th hour after their food deprivations. Later, all animals were treated with saline or scopolamine of 3 mg/kg i.p. and EEG recordings were repeated for 10 min. Twenty minutes later, they were given food pellets and were allowed to eat ad libitum. All animals were observed for 60 min to determine the incidence and onset of convulsions and EEG recordings were taken simultaneously. The present results demonstrate that food deprivation causes differences in EEG in the elapsed time. The changes in EEG induced after food deprivation become different with scopolamine administration. In scopolamine treatment group, eating caused a series of high-voltage polyspikes and synchronized spikes with a predominant frequency in the 1-3 Hz range and fast activity that represents a typical epileptiform manifestation. It was concluded that the EEG properties and the behavioral patterns of these convulsions are in accordance with each other. (C) 2006 British Epilepsy Association. Published by Elsevier Ltd. All rights reserved

Dynamic properties of the responses to fast omitted stimulus potential paradigm in human

Visual evoked potentials (VEPs) and omitted stimulus potentials (OSPs) were analyzed on scalp recordings of 10 healthy subjects. OSP responses, obtained after the due-time of the first omitted stimulus at the end of a conditioning stimulus train have been studied mostly in animals. Two types of visual OSP responses were observed in the previous studies: slow (less than or equal to 2 Hz) and fast (greater than or equal to 5 Hz). In this study, some dynamic properties of the responses to high frequency flash stimulation were investigated. Very short conditioning trains and even only two stimuli were found to be sufficient for the generation of an OSP response. With longer conditioning periods, of ca. 250 ms the OSP response develops and reaches its final size and shape, similar to the results obtained from animal studies. In the topographical analysis, the steady state response (SSR) amplitudes were found to be larger in the occipital and parietal regions while the OSP responses spread homogeneously in all subjects