**2. Material and methods**

## **2.1. Participants**

Eight individuals (mean age 33.1; range 21–50) participated in our study: five males (mean age 36.2; range 23–50) and three females (mean age 28.0; range 21–35). All of them had normal mental and physical development, no history of head injury, convulsions or neurological diseases, and were not currently taking any medication or drugs. Despite the absence of any medical diagnosis, participants still reported physical or mental complaints. Some of them experienced fatigue, depressed mood, symptoms of anxiety or mood swings; others had headaches and sleep problems. Most subjects were not satisfied with their concentration and memory function, or with their high reactivity to stress factors. The investigation was carried out in accordance with the Declaration of Helsinki. All subjects gave informed consent after the procedures had been fully explained to them.

The epochs with excessive amplitude of nonfiltered EEG and/or excessive high and slow frequency activity were automatically marked and excluded from further analysis. Eye blink artifacts were corrected by zeroing the activation curves corresponding to eye blinks. The

Effect of Infra-Low Frequency Neurofeedback on Infra-Slow EEG Fluctuations

http://dx.doi.org/10.5772/intechopen.77154

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Continuous artifact-free EEG epochs were selected manually for analysis. The duration of

The average spectral density in the 0–0.5 Hz frequency band was estimated for each electrode, each subject and each condition separately using the Thomson's multitaper method, and log-

The instrument used for the clinical neurofeedback was the Cygnet system (bee Medic), consisting of the NeuroAmp II and Cygnet software, integrated with Somatic Vision video feedback and run on a Windows 7 operating system using a standard personal computer (PC)

The Othmer Method utilizes evidence-based and well-established neurofeedback protocols, the implementation of which has been refined through empirical optimization procedures and A-B testing over a large number of neurofeedback clients referred for a variety of conditions. The method is protocol-based and is further characterized by the following essential

• It is a symptom-guided approach in which the symptom presentation from anamnesis is used to identify one of several basic patterns of dysregulation that are then targeted in a

• The training is process-oriented, involving the ongoing optimization of feedback parameters according to observed symptom changes during sessions and from session to

• The method utilizes bipolar EEG montages exclusively, and as such is oriented toward

• The method involves continuous waveform-following for the low-frequency aspect of the training in combination with conventional discrete reinforcements for inhibit-based

• The inhibit-based training is triggered on transient anomalies observable within the con-

• The method utilizes mainly audio-visual real-time animations in order to deliver the ILF

training the functional relationships between key cortical sites;

method is similar to the one described in Vigario [42] and in Jung et al. [43].

arithmically transformed for normalization before further statistical analysis.

these epochs varied among the subjects from 550 to 1100 s.

**2.3. Neurofeedback**

features:

session;

training;

with a high-resolution monitor.

protocol-based manner;

ventional EEG spectrum;

feedback signal beneath conscious awareness.

### **2.2. EEG investigation**

EEG was recorded using a Mitsar 21 channel EEG system (Mitsar, Ltd). Nineteen silver-chloride electrodes were applied according to the International 10–20 system. The input signals referenced to linked ears were filtered between 0 and 50 Hz and digitized at a rate of 250 Hz. The ground electrode was placed on the forehead. All electrode impedances were kept below 5kOhm. EEG was recorded during performance of the visual cued GO/NOGO task that uses pictures of 20 different animals, 20 different plants, and 20 different humans (together with a distracting beep tone) as stimuli [41].

One trial consisted of the sequential presentation of two pictures (prime and target), presented for 100 ms each, with an ISI of 1000 ms (SOA = 1100 ms). Trials were separated by 1500 ms. Patients were instructed to press the left button of the computer mouse as quickly as possible when an animal was followed by an animal (Go-condition) and not to respond when an animal was followed by a plant (NoGo-condition), or when a plant was followed by a plant or a human (distractor condition). The response interval lasted from 100 to 1000 ms.

The task consisted of 100 Go-trials, 100 NoGo trials, and 200 distractor trials. Trials were presented pseudo-randomly with equal probability. All trials were presented to the subject on a computer screen 1.5 m in front of them using the Psytask software (Mitsar Ltd.). The centrally presented stimuli subtended an approximate visual angle of 3°. Trials with omission and commission errors were excluded from analysis. Quantitative data were obtained using the WinEEG software.

The baseline investigation consisted of quantitative electroencephalogram (qEEG) in Visual Go/NoGo test, which took place 1–7 days before undertaking the course of NF training sessions. qEEG parameters were compared with the Human Brain Institute (HBI) normative Database. All the tests were repeated after 20 sessions in 1–7 days after the last session. The results of the second testing were compared with the pretreatment baseline.

The epochs with excessive amplitude of nonfiltered EEG and/or excessive high and slow frequency activity were automatically marked and excluded from further analysis. Eye blink artifacts were corrected by zeroing the activation curves corresponding to eye blinks. The method is similar to the one described in Vigario [42] and in Jung et al. [43].

Continuous artifact-free EEG epochs were selected manually for analysis. The duration of these epochs varied among the subjects from 550 to 1100 s.

The average spectral density in the 0–0.5 Hz frequency band was estimated for each electrode, each subject and each condition separately using the Thomson's multitaper method, and logarithmically transformed for normalization before further statistical analysis.
