Prepulse inhibition
Prepulse inhibition (PPI also, engl. Prepulse inhibition ) refers to a physiological phenomenon in startle response . There is usually a certain startle response to startle stimuli. If, however, a weaker stimulus (“prepulse”) occurs beforehand, the startle response to the actual startle stimulus that follows is softened (inhibited) and is less pronounced.
basis
The prepulse inhibition corresponds physiologically to the filter function of the healthy brain for external stimuli. With weaker stimuli, the brain adjusts to possible further stimuli. This reduces the frightening effect. A sensory overload is thus prevented. This phenomenon can be seen in numerous species, including humans.
Measurement
The startle reaction in the form of muscle contractions of the facial muscles ("startle reflex") can be measured using electromyography (EMG). The eyelid closing reflex is usually measured for this purpose , and the EMG is derived from the orbicularis oculi muscle . To trigger the startle reaction, auditory stimuli are usually used, that is, loud tones. The prepulse is a short and quiet acoustic stimulus that is usually not consciously perceived by the test person. Stimuli in other sensory modalities can also be used to measure prepulse inhibition, but are rarely used for reasons of practicality.
Diagnostic use
The stimulus filter function of the healthy brain, which manifests itself in the form of prepulse inhibition, is only available to a limited extent in numerous clinical pictures. Among other things, this is observed in schizophrenia . The measurement of prepulse inhibition can therefore be used for diagnostic purposes.
See also
swell
- ↑ David L. Braff, Mark A. Geyer, Neal R. Swerdlow: Human studies of prepulse inhibition of startle: normal subjects, patient groups, and pharmacological studies. In: Psychopharmacology. 156, 2001, pp. 234-258, doi : 10.1007 / s002130100810 .