Abstract
Objective: 1) Be able to design-low-cost ABR equipment. 2) Learn the possibility of mainstream technology applied for laboratory equipment use and be able to standardize the results with commercially available ABR equipment. 3) Apply this technology for research and neurophysiology laboratories.
Method: Animal experimentation study. This system comprises a differential amplifier, high-pass and low-pass filters, a main rejection notch filter, an analog to digital converter, and software programs for data acquisition and processing automation. Amplifier and filters were designed using low-cost and readily available commercial components. Auditory stimuli were reproduced by a portable music player and a miniature rechargeable speaker. The stimuli comprising auditory clicks, tone pips and tone bursts, were generated numerically by the software and transferred digitally to the music player. 25 female and male Sprague-Dawley rats were tested with amplitude and threshold protocols.
Results: Results demonstrate a linear correlation and morphology with ABR previously recorded by other teams. Amplitude in the response was little affected by the hardware but strongly modified by electrode position. A regression analysis demonstrated a coincidence r = 0.92 with the physiological measured threshold using RMS analysis. Ketamine affects the first 20 minutes of recordings by delaying latency in all waves, the effect fades away after that. Morphological changes were observed by blocking the ear canal in accordance with previous studies.
Conclusion: The ABRs obtained compare favorably with other published results in similar conditions. Clear amplification with subdermal electrodes are seen consistently and very little EEG noise is obtain with the recordings, with no significant difference between individuals and results from other studies. The system will rapid determine auditory threshold with good accuracy. We are confident that this approach will make hardware more accessible for low budget research facilities.
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