Tone-Evoked Acoustic Change Complex (ACC) Recorded in a Sedated Animal Model

Abstract

The acoustic change complex (ACC) is a scalp-recorded cortical evoked potential complex generated in response to changes (e.g., frequency, amplitude) in an auditory stimulus. The ACC has been well studied in humans, but to our knowledge, no animal model has been evaluated. In particular, it was not known whether the ACC could be recorded under the conditions of sedation that likely would be necessary for recordings from animals. For that reason, we tested the feasibility of recording ACC from sedated cats in response to changes of frequency and amplitude of pure-tone stimuli. Cats were sedated with ketamine and acepromazine, and subdermal needle electrodes were used to record electroencephalographic (EEG) activity. Tones were presented from a small loudspeaker located near the right ear. Continuous tones alternated at 500-ms intervals between two frequencies or two levels. Neurometric functions were created by recording neural response amplitudes while systematically varying the magnitude of steps in frequency centered in octave frequency around 2, 4, 8, and 16 kHz, all at 75 dB SPL, or in decibel level around 75 dB SPL tested at 4 and 8 kHz. The ACC could be recorded readily under this ketamine/azepromazine sedation. In contrast, ACC could not be recorded reliably under any level of isoflurane anesthesia that was tested. The minimum frequency (expressed as Weber fractions (df/f)) or level steps (expressed in dB) needed to elicit ACC fell in the range of previous thresholds reported in animal psychophysical tests of discrimination. The success in recording ACC in sedated animals suggests that the ACC will be a useful tool for evaluation of other aspects of auditory acuity in normal hearing and, presumably, in electrical cochlear stimulation, especially for novel stimulation modes that are not yet feasible in humans.

Cortical Auditory Evoked Potentials in Response to Frequency Changes with Varied Magnitude, Rate, and Direction

“…The response evoked by a change in a continuous stimulus is often called the acoustic change complex (ACC). This response can be elicited in response to changes within speech stimuli (Ostroff et al 1998; Martin and Boothroyd 2000; Tremblay et al 2003; Friesen and Tremblay 2006) and to intensity or frequency changes within continuous tones (McCandless and Rose 1970; Arlinger et al 1976; Harris et al 2007, 2008; Dimitrijevic et al 2008; Pratt et al 2009; Presacco and Middlebrooks 2018).…”

“…Recent literature has shown interest in the ACC and investigated its possible clinical applications (He et al 2012; Brown et al 2015, 2017; Chen and Small 2015; Kim 2015). The ACC has been reported to correlate with psychophysical measures in normal hearing adult subjects (He et al 2012; Brown et al 2017), and moreover, the ACC has been reliably evoked in various types of subjects such as young children, hearing aid users, cochlear implant users, and sedated cats (Tremblay et al 2006; He et al 2012; Brown et al 2015; Chen and Small 2015; Presacco and Middlebrooks 2018). The ACC might therefore possess characteristics, which can be used for objective auditory assessment.…”

“…The majority of studies using a pure tone stimulus, followed by a frequency change, studied only one direction of frequency change (frequency increase or decrease). With respect to rate of the frequency change, some authors did not report rates (Pratt et al 2009; Brown et al 2017) while others reported a constant duration of the change with varying magnitudes, thus resulting in varying velocities (Dimitrijevic et al 2008; Harris et al 2008; Presacco and Middlebrooks 2018). Thus, since evidence is lacking on the effect of rate and direction, we aim to investigate the extent to which suprathreshold ACC is influenced by rate and direction, next to magnitude.…”

Cochlear Implant Research and Development in the Twenty-first Century: A Critical Update

“…Further complications arise from the use of anaesthesia in the physiological studies (Chung et al 2016), from the use of different outcome measures, such as behavioural judgements for humans and single-unit recordings for animals, and from between-species differences in the anatomy of the auditory nerve (Rattay et al 2013). Recently, researchers have begun to bridge this gap by combining physiological experiments with threshold and supra-threshold behavioural measures using animals (Kadner and Scheich 2000;Vollmer et al 2001;Pfingst et al 2011;Benovitski et al 2014;King et al 2016;Rosskothen-Kuhl et al 2021), and by developing electrophysiological measures of stimulus discrimination and cortical selectivity in humans that may in principle be applied to animal studies (Mathew et al 2017(Mathew et al , 2018Presacco and Middlebrooks 2018;Carlyon et al 2021).…”

Cochlear implant research and development in the 21st century: A critical update

“…Further complications arise from the use of anaesthesia in the physiological studies (Chung et al, 2016) and from the use of different outcome measures, such as behavioural judgements in humans and single-unit recordings in animals. Recently researchers have begun to bridge this gap by combining physiological experiments with threshold and supra-threshold behavioural measures in animals (Kadner and Scheich, 2000;Vollmer et al, 2001;Pfingst et al, 2011;Benovitski et al, 2014;King et al, 2016;Rosskothen-Kuhl et al, 2021), and by developing electrophysiological measures of stimulus discrimination in humans that may in principle be applied to animal studies (Mathew et al, 2017;Mathew et al, 2018;Presacco and Middlebrooks, 2018).…”