The auditory steady state response: Far-field recordings from the chinchilla

Abstract

Objective: Previous studies in our lab have found that the presentation of multiple ASSR-generating stimuli results in a decrease in ASSR amplitude when recorded from an electrode implanted in the chinchilla inferior colliculus. The purpose of the present experiment was to determine whether this same effect occurs in far-field recordings, i.e. recordings similar to those made in human subjects. The effect of inhalant anesthesia on ASSR amplitude in response to multiple stimuli was also investigated. Design: Stimuli consisted of three sinusoidally-amplitude modulated tones with carrier/modulation frequencies of (1/.095 kHz), (2/.1 kHz), or (4/.107 kHz). The modulated carriers were presented to the right ear either alone or in combination, while recordings were made from subdermal needle electrodes placed on the head. Study sample: Nine adult chinchillas. Results: A 20%–70% decrease in the response amplitude with the presentation of multiple ASSR-generating stimuli was found, which depended on both carrier frequency as well as stimulus pairing. In general, both the ASSR and the noise floor were reduced under anesthesia. Conclusions: The time savings obtained from presenting multiple stimuli simultaneously may not be as great as initially predicted, as the time saving is at least partially offset by the observed amplitude reduction.

Key Words::

• Auditory steady-state response (ASSR)
• chinchilla
• MASTER
• sinusoidally-amplitude modulated (SAM)
• isoflurane anesthesia

Acknowledgements

Mary Lou Coad is thanked for her help with data collection. Sasha John is thanked for his help during various phases of this research project and for editing the manuscript. Data from this study was presented at the March 6–8, 2008, American Auditory Society Meeting in Scottsdale, Arizona. The presentation was entitled ʽChinchilla Farfield ASSR: Effects of multiple stimuli and anesthesia.

Declaration of interest: All authors confirm that they have no conflicts of interest to declare.