Prepulse inhibition

Prepulse inhibition ( PPI also, Eng. Prepulse inhibition ) refers to a physiological phenomenon in startle response. In fright stimuli usually takes place in a specific startle response. If previously, however, a weaker stimulus ( " prepulse " ) occurs, the startle response is mitigated on the following actual startle ( inhibited ) and will be less.

Basis

The prepulse inhibition corresponds physiologically the filter function of the healthy brain to external stimuli. Due to weaker stimuli, the brain is a possibility that other stimuli. Thus, the Erschreckungseffekt decreased. One of sensory overload is prevented that. This phenomenon is reflected in numerous species, including humans.

Measurement

The startle response in the form of this occurring muscle contractions of the facial muscles ( " startle reflex ," engl. " Startle reflex" ) can be measured by electromyography ( EMG). Usually, the blink reflex is measured for this purpose, the derivative of the EMG done on orbicularis oculi muscle. To trigger the startle response in this case auditory stimuli are usually used, ie loud sounds. The prepulse here is a short and quieter acoustic stimulus, which is usually deliberately not perceived by the subjects. Stimuli in other sensory modalities can also be used to measure the prepulse inhibition, however, come for reasons of practicality rarely used.

Diagnostic use

The stimulus filter function of the healthy brain, which manifests itself in the form of prepulse inhibition is restricted in numerous pathologies present. Among other things, this is observed in schizophrenia. Measuring the prepulse inhibition may therefore be employed for diagnostic purposes.