Acoustic Startle & Prepulse Inhibition
Overview
Acoustic startle response (ASR) and prepulse inhibition (PPI) measure sensorimotor gating — the brain's ability to filter sensory information by attenuating the motor response to a startling stimulus when it is preceded by a weaker prepulse. The animal is placed in a startle chamber on a motion-sensitive platform, and a loud acoustic pulse (typically 120 dB, 40 ms) elicits a whole-body flinch quantified by the accelerometer/force transducer.
In PPI trials, a non-startling prepulse (e.g., 74, 78, or 82 dB, 20 ms) precedes the startle pulse by 30–100 ms. Normal animals show 40–70% reduction in startle amplitude on prepulse trials compared to startle-alone trials. Deficits in PPI are a robust endophenotype of schizophrenia, observed in patients and in pharmacological (amphetamine, PCP, MK-801) and genetic (Disc1, Nrg1) rodent models.
ConductMaze controls the acoustic stimulus delivery (background noise, prepulses, startle pulses), records platform displacement via the transducer, and computes startle amplitude, %PPI at each prepulse intensity, habituation across trial blocks, and input-output (I/O) functions. The software supports randomized trial orders, variable inter-trial intervals, and null (no-stimulus) trials for baseline movement assessment.
Trial Flow
Acclimate
Place animal in startle chamber; 5 min acclimation with background noise (65 dB)
Habituation Block
5 startle-alone trials (not analyzed) to stabilize baseline
Present Stimulus
Deliver trial type: startle-alone, prepulse+startle, prepulse-alone, or no-stimulus
Record Response
Capture platform displacement (peak amplitude in 100 ms post-stimulus window)
Randomize Next
Select next trial type from pseudorandom sequence
ITI
Variable inter-trial interval (10–20 s)
End
Complete all trial blocks; compute %PPI per prepulse intensity
Parameters
| Parameter | Type | Default | Description |
|---|---|---|---|
| Background noise | dB | 65 | Continuous white noise background level |
| Startle pulse | dB | 120 | Startle stimulus intensity |
| Startle duration | ms | 40 | Duration of startle pulse |
| Prepulse intensities | dB | 74, 78, 82 | Prepulse levels above background (typically 3 levels) |
| Prepulse duration | ms | 20 | Duration of prepulse stimulus |
| Lead interval | ms | 100 | Time from prepulse onset to startle onset |
| ITI range | seconds | 10–20 | Variable inter-trial interval range |
| Trials per type | integer | 10 | Number of trials per stimulus condition |
Metrics
| Metric | Unit | Description |
|---|---|---|
| Startle amplitude | arbitrary | Peak force/acceleration in 100 ms response window (startle-alone trials) |
| %PPI | % | 100 × (1 − prepulse trial amplitude / startle-alone amplitude) |
| Startle habituation | % | Decrease in startle amplitude from first to last block |
| Null activity | arbitrary | Baseline movement on no-stimulus trials |
| PPI dose-response | slope | Slope of %PPI across increasing prepulse intensities |
| Startle threshold | dB | Minimum pulse intensity to elicit reliable startle (I/O function) |
Sample Data
| Subject | Group | Startle Amplitude | %PPI (74 dB) | %PPI (78 dB) | %PPI (82 dB) |
|---|
Representative data for illustration purposes. Actual values will vary by species, strain, and experimental conditions.
Applications
- 1Schizophrenia models — PPI deficit is a translational endophenotype; reversed by atypical antipsychotics
- 2Sensorimotor gating — quantifies pre-attentive filtering across multiple prepulse intensities
- 3Antipsychotic screening — clozapine, olanzapine, and novel compounds normalize PPI deficits
- 4Neurodevelopmental disorders — PPI deficits in maternal immune activation and neonatal lesion models
- 5Startle reactivity — baseline startle amplitude indexes anxiety-like states and arousal
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