**2.3. Neurofeedback**

**2. Material and methods**

the procedures had been fully explained to them.

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

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

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

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

or a human (distractor condition). The response interval lasted from 100 to 1000 ms.

results of the second testing were compared with the pretreatment baseline.

**2.1. Participants**

78 Biofeedback

**2.2. EEG investigation**

distracting beep tone) as stimuli [41].

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) with a high-resolution monitor.

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 features:


The two parameters selectable by the clinician are:


Until 2006, the signal processing was very similar to the classical beta-SMR scheme [44]. However, the reward frequency setting of a 3 Hz wide variable bandpass-filter was useradjustable over the entire conventional EEG spectrum from 1.5 to 40 Hz in center frequency. For that purpose, a horizontal slider was implemented in the graphical user interface. The inhibits were comprised 10 separate filter blocks in fixed frequency steps in the range between 1 and 40 Hz. For both the reward and inhibit scheme, threshold setting was auto-corrected to maintain a chosen level of difficulty, the "percent success."

signal-processing scheme, the slider influences the natural frequency of the control loop that the brain forms with the feedback system during neurofeedback on a continuous signal. It

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

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

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Training was performed with bipolar placement of silver/silver chloride scalp electrodes applied using Ten20 conductive electrode paste at one or both of two initial placements, T4-P4 and T4-T3 (according to the standard 10–20 system). These are relied upon to characterize the response of the trainee and to guide further optimization. Subsequently, T4-Fp2 and T3-Fp1

Each trainee received 20 separate 30–45 min neurofeedback sessions over 7–8 weeks. For each subject, the target frequency in the infra-low frequency region was optimized with each of the standard placements. The placement of electrodes was the standard one developed by

Two-way repeated measures ANOVA with factors condition (before-after) and location (19 electrode positions) was used to estimate the statistical significance of the training effect on the slow EEG oscillations. The Greenhouse-Geisser procedure was used to compensate for

After completion of 20 NFB sessions, all participants indicated improvement of their state. Most of them noticed a decrease of inner tension and reactivity to stressful factors. Further, they reported on stability of mood, improved body and space awareness, increase of energy

The post-training EEG patterns in all eight subjects revealed significant enhancement of spectral power in 0–0.5 Hz frequency band compared to the pre-training EEG. The locations of the most prominent changes were different: in some subjects, the dramatic ILF power increase was observed over the frontal-central region, in other cases over the posterior brain

**Figure 1** presents the EEG recordings before and after ILF NF course in one of the participants

**Figure 2** demonstrates the increase of the level of infra-slow activity in 0.03–0.05 Hz range in the post-training EEG in this participant. This increase is most prominent over frontal

Two-way ANOVA revealed a significant main effect of the factor "Condition" for the slow activity in 0–0.5 Hz frequency band F [1,7] = 18.4, p < 0.01. This effect is illustrated in **Figure 3**.

are added to the protocol as needed. The "ground" electrode was placed at Fpz.

functions effectively as a kind of gain control.

Othmer [46] and adopted in the Othmer Method.

deviations from sphericity or circularity.

level and of cognitive performance.

**2.4. Statistical analysis**

**3. Results**

areas.

region.

of our study.

Specific design parameters in the signal-processing chain between initial EEG acquisition and ultimate feedback animation have always been assessed and optimized by means of an empirical approach based on qualitative evidence criteria. (A useful analogy to this process is the optimization of the suspension system of a car, where human factors come prominently into play.)

By expanding the underlying model of neurofeedback to incorporate the current understanding of the brain as a self-organizing dynamical system that interacts with itself by means of neurofeedback, improved approaches to signal processing and coupling to the feedback animations have been sought. This process got underway in 2001. In that regard, also slow cortical potentials were investigated. With the availability of greater computer power for additional signal processing as well as advanced signal acquisition technologies, it was found that the addition of such slow potentials appears to offer the brain a more direct and effective feedback interaction. It turned out that also with this scheme, tailoring of the parameter setting to the individual patient is beneficial or even necessary, just as was previously found for frequency-band training in the conventional EEG spectrum [45].

In contrast to the classical concept of a rewarding experience that is controlled by the amplitude of the EEG in a given frequency band, the goal here is to present the brain with the most relevant representation of its slow cortical potential. For that purpose, derivations from the measured signal control various features in the feedback animation in a way that optimizes the brain's opportunity to engage with them.

For the purpose of continuity of the clinician's experience with the earlier era, the terminology of "reward frequency" was retained, as the rules for settings and for the optimization procedure carried over into the ILF region. However, the absence of discrete rewards in the ILF training meant that the traditional terminology of reward had lost its meaning. The unfolding of the continuous ILF signal allowed for no external reinforcers. Additionally, the slider that controlled the target frequency within the EEG regime was retained in the new design, but its function in the ILF regime must be understood differently. With the adopted signal-processing scheme, the slider influences the natural frequency of the control loop that the brain forms with the feedback system during neurofeedback on a continuous signal. It functions effectively as a kind of gain control.

Training was performed with bipolar placement of silver/silver chloride scalp electrodes applied using Ten20 conductive electrode paste at one or both of two initial placements, T4-P4 and T4-T3 (according to the standard 10–20 system). These are relied upon to characterize the response of the trainee and to guide further optimization. Subsequently, T4-Fp2 and T3-Fp1 are added to the protocol as needed. The "ground" electrode was placed at Fpz.

Each trainee received 20 separate 30–45 min neurofeedback sessions over 7–8 weeks. For each subject, the target frequency in the infra-low frequency region was optimized with each of the standard placements. The placement of electrodes was the standard one developed by Othmer [46] and adopted in the Othmer Method.
