The use of EEG biofeedback to improve memory, concentration, attention and reduce emotional tension Zastosowanie EEG biofeedback w celu poprawy pamięci, koncentracji, uwagi i zmniejszenia napięcia emocjonalnego

Biofeedback is a method of giving patients computerised feedback signals about changes in the physiological state of their body. This allows them to learn how to consciously modify functions not controlled consciously. This method allows active and conscious involvement of the patient in controlling their own physiological processes. The therapy aims to regulate the frequency of human brain waves. The human brain produces different ranges of waves that are characteristic of different types of human activity, a mechanism used in this method. The use of this method in routine rehabilitation with a specifically designed computer programme provides physicians, physiotherapists, neuropsychologists and speech therapists with a new tool for treatment, opportunities for improvement in treatment, and helps them better plan and develop treatment strategies using Evidence-Based Medicine. The aim of the work is to discuss how EEG Biofeedback software can be applied in neurorehabilitation and to discuss the use of EEG Biofeedback software in order to improve memory, concentration, attention, reduce emotional tension, increase resistance to stress, improve self-control, self-esteem and relaxation.


INTRODUCTION
EEG Biofeedback (EEG-BFB) is recognised in Poland by the Polish Society of Clinical Neurophysiology as one of the five disciplines of clinical neurophysiology in addition to electromyography, electroencephalography, autonomic system studies and evoked potentials. It belongs to forms of neuromodulation, which means "change in neuronal functioning" 1,2 . EEG-BFB technology has been shown to promote recovery due to the neuroplasticity-related properties of the brain 3-6 . The EEG-BFB method, which is one of the methods of applied psychophysiology, assumes that specific brain wave patterns correlate with mental disorders or syndromes. Irregularities in the area of appropriate mental functions are characterised by a specific image of brain waves, appropriate for a given disorder [7][8] . The improvement of behavioural functioning is possible by changing the percentage of specific brain waves and their amplitudes. These changes occur as a result of enhancing the desired frequencies and inhibiting those undesirable. Jiang et al. indicate that EEG-BFB therapy increases patient's self-esteem, improves mood and motivation, and slows down biological aging process 9 .

STUDY AIM AND METHODOLOGY
The aim of the work was to present the operating principles and possibilities of using EEG-BFT in memory, concentration and attention disorders as well as increased emotional tension. The study was based on a narrative review of literature on the subject and the authors' own experience of working at the University Clinical Hospital.
The following research questions were posed: 1. In what disease entities is EEG-BFB used? 2. What is the operating principle, course of therapy and EEG-BFB training protocol?

RESULTS
The use of EEG-BFB after stroke, head and brain injuries, in the treatment of cerebral palsy, migraines, chronic headaches, in asthma, bedwetting, diabetes, cardiovascular diseases, attention deficit hyperactivity disorder -ADHD, in autism, dyslexia, dysgraphy, dyslalia, dyscalculia, concentration, attention, memory and sleep disorders, in Alzheimer's and Parkinson's disease, Tourette's syndrome, anorexia, bulimia, neurosis, anxiety, depression, mood disorders, schizophrenia and addiction treatment [10][11][12] , as well as the possibility of using this method in healthy people, has been described in the literature 13 .

The way EEG Biofeedback works
The use of EEG-BFB together with methodological and clinical recommendations has been presented in many review articles 5,8,[14][15] . EEG Biofeedback uses the biological link between the patient's mental state and neurophysiological brain function. The application of this method in patient therapy is possible thanks to computer technology, the function of which is to perform qualitative and quantitative assessment of EEG recordings. The wave amplitude is processed by a computer programme via quantitative electroencephalogram analysis technology. EEG recording depends on many factors such as age, maturity level of the central nervous system (CNS) or psychomotor state of the subject. It is assumed that synchronous rhythms generated in different areas of the brain, and above all, the temporal and spatial correlations between them, are a reflection of mental processes related to perception, memory and attention 16 . Sensorimotor rhythm (SMR) activity at a frequency of 12-15 Hz correlates with the processing of sensory information received by the senses. SMR is associated with a state of mental serenity, alertness and concentration. A 15-20 Hz beta rhythm correlates with mental activity, promoting logical thinking and verbal communication. Theta rhythm with a frequency of 4-8 Hz correlates with drowsiness, internal orientation, lack of concentration regarding external stimuli. It is associated with extracting information from the memory and the ability to control responses to specific stimuli. In adults, the dominance of this rhythm is associated with attention deficit disorder. A beta2 rhythm of 20-35 Hz correlates with anxiety, nervousness, and irritation 17 .

EEG biofeedback training protocol
The EEG-BFB therapy plan contains information on which regions of the brain the therapist will affect and what rhythms of the brain will be inhibited and which will be strengthened 18 . The decision to choose a rehabilitation plan depends on the result of neurophysiological and psychological assessment of the type and severity of the patient's dysfunction. This decision is made after neuropsychological diagnosis and so-called brain mapping, which provides information about the quantitative EEG pattern. The use of various EEG-BFB protocols and research methods 10,11 is described in the subject-based literature. Kober et al. use therapeutic protocols that seek to reduce excessive slow waves and enhance brain bioelectrical activity within the 10-12 Hz range. In addition, protocols that compare the effects of enhancing brain bioelectrical activity from the 10-12 Hz and 12-15 Hz ranges are used 14 , or protocols enhancing brain bioelectrical activity within the 12-15 Hz range 1 . The most commonly applied treatment protocols mainly focus on strengthening the alpha or beta rhythm, or inhibiting theta and beta2 10,19 . Many variables influence the selection of the best training protocol. In addition to the patient's physical and mental state, it is important how s/he reacts to therapy. Gender, education and socioeconomic status are not without significance. Moreover, the patient may have individual goals that s/he would like to achieve as a result of therapy. The most common determinant of the effectiveness of therapy are the results of patients' functioning before and after EEG-BFB therapy, performed using neuropsychological tests.

EEG biofeedback course of therapy
Before starting therapy, a computer diagnostic examination of the brain wave recording is performed, thanks to which the therapy is adapted to the individual needs of each patient. During diagnostics and therapy, electrodes are placed on the patient's head in accordance with the "10-20" standard, approved by the International Federation of Electroencepha-col are highlighted ( Figure 2). The therapist selects the stimulation board depending on the purpose of the training. During EEG-NFB (Electroencephalographic neurofeedback) therapy, information about the amplitude and frequency of the generated rhythms appears on the therapist's monitor. The patient's task is to open the sashes of the window (strengthening the promoted rhythm of SMR and beta). The patient opens the curtains by halting the theta rhythm, while a better view outside the window (without fog) is achieved by inhibiting the beta2 rhythm. The patient receives a "reward" in the form of points and a sound signal when his/her brain produces a rhythm with the desired frequency and amplitude. In this way, s/ he obtains the ability to consciously control the bioelectrical activity of the brain. With repeated EEG-BFB sessions, the desired behaviours lead to a permanent changes in brain function 18 . The number of therapeutic sessions is individually adjusted to the patient's clinical condition. The results of EEG-BFB training sessions are available in the form of a report (tables with values of rhythm amplitudes, percentages and coefficients). After completing EEG-NFB therapy, the thera-pist has the opportunity to analyse its effects in the form of a so-called patient learning curve.
In the opinions of some authors, the use of EEG biofeedback is disputable, therefore, it would be advisable to conduct clinical trials involving a broader group of patients. In the case of EEG biofeedback, the difficulty is to design tests with a double-blind trial to exclude or confirm the placebo effect. Long-term, randomised, double-blind, non-controlled trials could ultimately settle doubts about the introduction of new therapeutic methods into standard care. Unfortunately, long-term studies using placebos are often not possible because they may contradict medical ethics.

CONCLUSIONS
Supporting therapy with the use of special computer programmes provides new tools and possibilities for rehabilitation and facilitates the organisation as well as planning of treatment strategies based on Evidence-Based Medicine. IT applications allow to diversify tedious and long-term therapy, increasing the patient's motivation to practice. The essence of the EEG-BFB  method is based on the plasticity of the nervous system, thanks to which, even after deep brain damage, it is possible to recover lost mental, motor, sensory and vegetative functions [21][22][23] . In response to damage, the brain initiates spontaneous repair processes 24 . Complex rehabilitation of patients started early, leads to the recovery of lost functions by developing compensatory mechanisms. The course of this process is faster if systematic stimulation is additionally delivered externally, as is the case of the EEG-BFB method. The process of structural and functional changes within the neural networks is initiated. These changes are an important mechanism of the learning process 25,26 . EEG-BFB therapy improves the pattern of brain bioelectrical activity, which is related to successive clinical improvement in the sphere of speech and memory disorders 18 . Plasticity changes in the brain depend on the frequency of stimuli repetitions and the duration of intervals between them 27 . Rehabilitative exercises, based on EEG-BFB mechanisms, strengthen brain plasticity by reinforcing the flow of information in existing synaptic connections and influencing the creation of new ones 28,29 . Neuroplasticity processes have been shown to be age-dependent. Many authors have described the effect of weakening neurogenesis as a result of aging of the body 25,26,30,31 . In recent studies using EEG-BFB, it is shown that the age of patients should be taken into account when selecting a rehabilitation plan 32 . According to the criteria of the Association for Applied Psychophysiology and Biofeedback and the International Society for Neuronal Regulation of 2002, five levels of effectiveness of EEG-BFB 33 therapy are distinguished. Compared to pharmacological and placebo treatment, EEG-BFB therapy has statistically higher effectiveness in anxiety, ADHD and migraine disorders as well as stress urinary incontinence in women 5 . Cho et al. point to the effectiveness of EEG-BFB therapy in patients after stroke, especially in improving concentration 10 . They argue that, on the one hand, it has a positive effect on memory functions, while on the other, it leads to the normalisation of bioelectrical activity of the patient's brain with pathological brain activation patterns. Reichert et al. demonstrate improved functioning in the area of non-verbal and verbal learning tasks 10 . They claim that enhancing the SMR rhythm amplitude can be successfully used in stroke patients and seniors. Researchers also point to the prolonged effects of EEG-BFB therapy in the form of reducing anxiety, increasing levels of motivation, learning ability, improving intellectual function and quality of sleep 17,[34][35][36] . In a study by Kober et al., 70% of patients undergoing EEG-BFB therapy achieved significant improvement in shortand long-term memory, regardless of the protocol used. Patients in whom the SMR protocol was applied exhibited greater improvement regarding short-term, visual-spatial memory, while in the group of patients with the beta-enhancing protocol, working memory was mainly improved. The enhancement of cognitive function in both groups was greater than the improvement in cognitive function in the group where only traditional rehabilitation methods were used 14 . The question of the duration of EEG biofeedback therapy is a debatable issue. Some researchers say that these changes are permanent 37 , while others indicate that the effects of training sessions last up to 6 months after the completion of therapy 38,39 .