PPI Lab: Pre Pulse Inhibition

PPL Lab: Pre Pulse Inhibition

Pre Pulse Inhibition (PPI) is a system diagnostics which uses acoustic prepulse inhibition.

The primary use of the device is automated support performance testing that uses an acoustic PPI. The results are useful in psychiatry as a complementary method eg. in the diagnosis of schizophrenia. Its use is also applicable into medical and nonmedical biological experiments in psychology, natural science and human research.

Device in a minimum configuration consists of a measuring unit, earphones with acousticpressure up to 120 dB and a connection for the measuring electrode to scan electromyographic signal (EMG) as the startle response to a stimulus. Electromyographic response is monitored typically around the eyes, where the muscle twitching response is strong enough. For stimulation, it can either be used a ready-made set of stimulus sequences with classic prepulzy and pulses of white noise, or setany intrinsic stimulating sequence, including the use of external pre-recorded sounds. In addition to recording electromyographic signal response, the unit has the possibility of simultaneous recording of additional variables including:

1) ECG monitoring,
2) Brasscurves,
3) Body temperature,
4) Physical activity,
3) Skin resistance.

The system is connected to the PC using a standard USB interface, which comes with every notebook or desktop PC. User-friendly PPI Evaluator software can be running on a desktop PC, laptop or tablet. The software enables convenient and simple design examination and automatic calculation of all required parameters of PPI – calculation of habituation, the average amplitude of the individual pulses and pulses with prepulzem, delay and amplitude reactions etc. Easy browsing areas surrounding stimuli while using the mouse or arrow keys is also presented. There are 4 different options of views visualizing areas for easier determination of the presence of the startle response. Export evaluated data into Excel spreadsheet or relational database for further processing is included as well. Another function represents parallel visualization and evaluation of additional quantities, e.g. module for calculating the course of heart rate variability – HRV analysis, or evaluation module intensity motor response of the mechanical acceleration sensor.

Selected system parameters

The sensor unit

  • 1-2 bipolar channels electromyographic (EMG) signal, an optional sampling rate of 500 Hz to 5000 Hz, resolution 24-bit, AD converter. It can be used as a disposable stick-on electrodes, or as a miniature electrode.
  • 1 channel bipolar ECG signal. The sampling frequency is the same as the EMG channels. Resolution converter 24 bits. Possible to use standard disposable adhesive ECG electrodes or chest belt known from fitness centers
  • 1 channel breathing curve derived from changes in the bioimpedance of the chest
  • 1 channel body temperature – an external probe, range 10-50 C°, accuracy 0.1 C°
  • 1 channel skin resistance. the range is between 10 Kohms to 5 Mohms.
  • Axelerometer probe for registration mechanical response startle reactions.
  • Module for acoustic stimulation: quality audio earphones with sound pressure of up to 120 dB
  • Communication: USB 2.0, inside the instrument, galvanically isolated from the PC
  • Power: via USB, electrically isolated

The measuring software

  • for acoustic stimulation, can be used peset stimulation sequences with specific timing and intensity of pulses and prepulses.
  • it is possibile to have a preview of the behaviour of the response signals (EMG and additional signals from ECG, accelerometer etc.) in real time,
  • optional entry of user and synchronizing marks,
  • visualisation system to display the stimulation in synchronisation with all responses (all data channels).
  • interactive semi-automatic analysis of series of stimuli and responses with the calculation of selected diagnostic parameters, characterizing the degree of the PPI (e.g. percentage of habituation, the amplitude of selected graphoelements signal, the average amplitude of the individual pulses and pulses with prepulse, etc.).
  • connections to the server databases subjects / patients, with the ability to create reports for statistical analysis,
  • export of test results (patient report – charts and graphs) into Excel spreadsheets.