Acoustic Startle Response (ASR)
Materials and Methods
Acoustic Startle Expansion Package Med-ASR-315A, Med Associates, Inc., USA
(including acoustic cubicle with stimulation package, platform with load cell, amplifier, filter, animal holder)
Grid floor accessory, ENV 263B - GF
Scrambler module, ENV 414SR
DIG-729 High Speed Serial Microcontroller
Analog to Digital Converter DIG-729ADC
The ASR is determined using the program and software available from Med Associates. In preparation for the trial runs, the startle boxes should be carefully checked, i.e. check platform connections to amplifiers, stimulators, filters, PC, and the equipment should be calibrated once a month. Each animal should then be placed into its holder and acoustic cubicle.
The first 40 trials consist of 24 PPI (Pre-Pulse Inhibition) and 16 Noise Burst (at 112 dB) trials presented in random sequence; PPI trials consist of 8 trials presented at three different pre-pulse frequencies, i.e. 20, 12, and 4 KHz, at 70 dB and 100msec prior to the startling noise. The following 15 trials consist of 5 Noise Burst trials, randomly presented at 80dB, 90 or 100 dB.
The resulting data (displacement of the load cell as expressed in Volt) can be used to determine ASR as well as PPI scores. Mice with ASR responses determined to be 2 SD below the mean are retested, and are subsequently, following confirmation of the first test response, tested for their acoustic brainstem responses. Animals confirmed to be hearing impaired are classified as deviants.
