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3 Fundamentals of the Formation of Biosignals

SA node

AV node

His bundle / Purkinje-Complex

ECG

time units

Fig. 3.30: Signals during ECG generation of the three-oscillator-model in Figure 3.29.

be causally linked to the external event of "opening the eyes". The resulting signals

are called visually evoked signals.

In most cases, however, such a connection is not so easy to detect and requires

the use of special biosignal processing methods for quantification. One such method

is brainstem audiometry to perform hearing tests on newborns. Since the newborn

itself is not capable of providing information about the perception of acoustic stimuli,

brainstem audiometry evaluates the electrical signals of the brain immediately after

an acoustic provocation in order to gain information about the infant’s hearing ability.

Such signals are called acoustically evoked signals.

Evoked signals occur mainly in connection with sensory stimuli. These stimuli

trigger electrical potential changes in the sensory areas of the cerebral cortex. Depend-

ing on the stimulation, a distinction is made:

1.

Acoustically evoked potentials (AEP), which allow assessment of the auditory

pathway: from the cochlea, via the auditory nerve to the brainstem (early AEP,