Evaluation
With the help of electroencephalography (EEG), an electroencephalogram is created on which the course and strength of the bioelectrical activity of the brain is recorded. This electroencephalogram contains waves that are evaluated according to certain frequency patterns (frequency bands), amplitude patterns, local activity patterns and their frequency of occurrence. Generally speaking, it is considered which curves are present, how fast they are, whether they are deformed and whether the curves have certain patterns.
Special computer-aided methods (e.g. spectral analysis) can also be used for evaluation. Particularly information-rich in the evaluation are the frequency bands, which can generally be divided into four categories:Delta-wave frequencies from 0.5 to 3 Hz: This frequency band can be observed especially in deep sleep and is characterized by slow and large amplitudes in the electroencephalogram. Theta-wave frequencies from 4 to 7 Hz: These frequencies occur during deep relaxation or while falling asleep.
Slow theta waves are normal in children and adolescents. In adults who are awake, the permanent occurrence of theta waves (and also delta waves) is a conspicuous finding. Alpha waves Frequencies between 8 to 13 Hz: These frequencies represent the basic rhythm of the biolelectric activity of the brain and appear in the electroencephalogram when the patient’s eyes are closed and the patient is at rest. Beta-wave frequencies from 14 to 30 Hz: This band of frequencies appears when sensory stimuli occur (i.e., in the normal waking state) or during mental tension.
