Brain bioelectrical signals
The research is targeted to estimation of the effect of internal (mental disorders) and external (electromagnetic radiation) factors on the brain bioelectric activity, electroencephalographyc (EEG) signal and cognitive processes (event related potential – ERP) and to development of new signal analysis methods for this purpose.
The main aims are:
- development of signal processing methods sensitive for detecting alterations in brain bioelectric signals hidden in their natural variability;
- finding EEG features characteristic for various mental and neural disorders;
- finding relationships between brain electrical oscillations (EEG and ERP), visual cognition and external electromagnetic radiation.
EEG analysis provides promising results to diagnose several nervous diseases which produce alterations in the EEG waveforms (epilepsy) and has been proven being useful for evaluation of the depth of anaesthesia. However, the majority of the EEG signals are close to normal in mental and neurodegenerative disorders (depression, stress, anxiety, Alzheimer, Parkinson disease). Alterations in EEG related to the low-level electromagnetic radiation effects are small. Abnormalities in waveforms are generally mild, hidden in natural variability of the signal and therefore very difficult to detect. New methods are developed by our team: spectral asymmetry index (SASI) (US8244341B2) for distinguishing depression and integration of differences for detecting the effect electromagnetic radiation.
Fast rhythm of modern life and everyday stress raised significantly the role of mental disorders in our society. A total of 260 million European citizens experience some form of brain related neurodegenerative disorders or mental disorders. According to WHO report, depressive disorder is a leading cause of burden of disease nowadays and it is projected to take the first place in the world in 2030. The diagnosis for mental disorders is based on evaluation of the intensity of subjective symptoms by psychiatrists. Therefore, there is a great need for methods for determining depression based on objective symptoms before the subjective symptoms appear. There is a need for objective monitoring of possible appearance of depressive conditions or other mental disorders of high-risk or high-stress workers such as military personnel, police, and rescue workers. Developed in our department new measure SASI based on EEG spectral asymmetry in a single-channel EEG is proved being effective for differentiating between healthy and depressive persons providing discrimination accuracy comparable to that of nonlinear EEG analysis methods. Inexpensive and patient-friendly method is promising for screening of population.
- Hinrikus H, Bachmann M, Suhhova A, Aadamsoo K, Võhma U, Lass J, Tuulik V. 2009. Electroencephalographic spectral asymmetry index for detection of depression. Med Biol Eng Comput, 47:1291-1299.
- Bachmann M, Lass J, Suhhova A, Hinrikus H. 2013. Spectral Asymmetry and Higuchi’s Fractal Dimension Measures of Depression Electroencephalogram. Comput Math Methods Med. 2013:251638.
Increased use of electronic and telecommunication equipment, especially mobile phones, has raised the problem of possible effects of the radio-frequency electromagnetic field (EMF) on human brain physiology and cognition. Reports on possible non-thermal EMF effects have been contradictory and mechanisms behind the effects unclear during decades. Our team proposed and proved experimentally the parametric excitation mechanism of modulated microwave effect on brain bioelectric oscillations based on EMF influence on hydrogen bonding and diffusion. We detected alterations in EEG at the radiation level much lower recommended health protection limits.
Hinrikus H, Bachmann M, Lass J. 2011. Parametric mechanism of excitation of the electroencephalographic rhythms by modulated microwave radiation. International Journal of Radiation Biology, 87:1077-1085.