Loudness Perception in the Domestic Cat: Reaction Time Estimates of Equal Loudness Contours and Recruitment Effects

Abstract

The domestic cat is the primary physiological model of loudness coding and recruitment. At present, there are no published descriptions of loudness perception in this species. This study used a reaction time task to characterize loudness perception in six behaviorally trained cats. The psychophysical approach was based on the assumption that sounds of equal loudness elicit responses of equal latency. The resulting equal latency contours reproduced well-known features of human equal loudness contours. At the completion of normal baseline measures, the cats were exposed to intense sound to investigate the behavioral correlates of loudness recruitment, the abnormally rapid growth of loudness that is commonly associated with hearing loss. Observed recruitment effects were similar in magnitude to those that have been reported in hearing-impaired humans. Linear hearing aid amplification is known to improve speech intelligibility but also exacerbate recruitment in impaired listeners. The effects of speech spectra and amplification on recruitment were explored by measuring the growth of loudness for natural and amplified vowels before and after sound exposure. Vowels produced more recruitment than tones, and the effect was exacerbated by the selective amplification of formant structure. These findings support the adequacy of the domestic cat as a model system for future investigations of the auditory processes that underlie loudness perception, recruitment, and hearing aid design.

Equal latency contours and auditory weighting functions for the harbour porpoise (Phocoena phocoena)

“…The harbour porpoise inner ear has an acoustic fovea on the basilar membrane with high ganglion cell densities in the region where these echolocation frequencies are processed (Ketten, 1997); the relatively short RTs that were found in this study may have been the result of increased neural activity generated in the foveal region. In addition, the RTs of other mammalian species for frequencies higher than ~16 kHz reported elsewhere (Green, 1975;May et al, 2009;Kastelein et al, 2011) were also lower than expected from the equal loudness contours measured to date, suggesting that the correlation between RT and loudness is consistently weaker at these very high frequencies.…”

“…RT has therefore been used in subjects for which loudness assessment with standard methods is very difficult or impossible, such as human infants (Leibold and Werner, 2002) and non-human animals (Dooling et al, 1978;Green, 1975;Kastelein et al, 2011;May et al, 2009;Moody, 1973;Pfingst et al, 1975a;Stebbins, 1966;Ridgway et al, 2001). Functionally, the RT reflects the combined duration of the sensory, cognitive and motor processes needed to generate the response (Sanders, 1998).…”

“…In animals, equal latency contours have been obtained for the crab-eating macaque (Macaca irus) (Stebbins, 1966), common squirrel monkey (Saimiri sciureus) (Green, 1975), rhesus macaque (Macaca mulatta) (Pfingst et al, 1975a;Pfingst et al, 1975b), house finch (Carpodacus mexicanus) (Dooling et al, 1978) and domestic cat (Felis catus) (May et al, 2009); near-threshold contours have been obtained for the harbour seal (Phoca vitulina) (Kastelein et al, 2011). The equal latency contours of the animals tested to date are similar to the equal loudness contours of humans and the bottlenose dolphin, which suggests that RTs are also related to perceived loudness in other animals.…”

Loudness

“…Data from noise-exposed cats (May et al 2009) appear roughly consistent with psychoacoustical data from humans with noise-induced hearing losses. For example, the bandwidth of vowels appears qualitatively consistent with loudness summation data from a group of humans with noise-induced hearing losses (Florentine and Zwicker 1979;Florentine et al 1980).…”

“…The relationship between sound level and reaction time has been measured for nonhuman primates (Stebbins and Miller 1964;Pfingst et al 1975) and the 1 Loudness domestic cat (May et al 2009). Attempts have been made to relate equal loudness contours from humans to equal latency contours from reaction times in both species (Stebbins 1966;Pfingst et al 1975;May et al 2009).…”