Development of the head, pinnae, and acoustical cues to sound location in a precocial species, the guinea pig ( Cavia porcellus )

Abstract

The morphology of the head and pinna shape the spatial and frequency dependence of sound propagation that give rise to the acoustic cues to sound source location. During early development, the physical dimensions of the head and pinna increase rapidly. Thus, the binaural (interaural time and level differences, ITD and ILD) and monaural (spectral shape) cues are also hypothesized to change rapidly. Complex interactions between the size and shape of the head and pinna limit the accuracy of simple acoustical models (e.g. spherical) and necessitate empirical measurements. Here, we measured the cues to location in the developing guinea pig, a precocial species commonly used for studies of the auditory system. We measured directional transfer functions (DTFs) and the dimensions of the head and pinna in guinea pigs from birth (P0) through adulthood. Dimensions of the head and pinna increased by 87% and 48%, respectively, reaching adult values by ~8 weeks (P56). The monaural acoustic gain produced by the head and pinna increased with frequency and age, with maximum gains at higher frequencies (>8 kHz) reaching values of 10–21 dB for all ages. The center frequency of monaural spectral notches also decreased with age, from higher frequencies (~17 kHz) at P0 to lower frequencies (~12 kHz) in adults. In all animals, ILDs and ITDs were dependent on both frequency and spatial location. Over development, the maximum ILD magnitude increased from ~15 dB at P0 to ~30 dB in adults (at frequencies >8 kHz), while the maximum low frequency ITDs increased from ~185 µs at P0 to ~300 µs in adults. These results demonstrate that the changes in the acoustical cues are directly related to changes in head and pinna morphology.

Spatial hearing ability of the pigmented Guinea pig (Cavia porcellus): Minimum audible angle and spatial release from masking in azimuth

“…Animals were weighed at the beginning of each test session, which varied between 0.6 and 1.2 kg (generally increasing with age). Head and pinna dimensions were not routinely measured, but were stable and generally consistent with values measured during acoustical measurements on different groups of guinea pigs (Anbuhl et al, 2017a; Greene et al, 2014).…”

“…Furthermore, the acoustics of the guinea pig external ears, head, and torso have been assessed in several studies (Carlile et al, 1987b; Sinyor et al, 1973; Sterbing et al, 2003). In particular, our lab recently described the directional transfer functions (DTFs) of adult (Greene et al, 2014) and developing (Anbuhl et al, 2017a) guinea pigs. Acoustical measurements suggest that all three cues to sound location, including the monaural (i.e., spectral shapes) and binaural cues (interaural time [ITD] and level [ILD] differences), are available to the guinea pig and are likely utilized for sound localization behavior.…”

Characterization of Auditory and Binaural Spatial Hearing in a Fragile X Syndrome Mouse Model

“…On average, Fmr1 mice tended to weigh less (23.5 Ϯ 0.75 g) than wild-type animals (25.8 Ϯ 0.43 g; p ϭ 0.01). Pinna morphology was measured using methods described in the study by Anbuhl et al (2017) by measuring the height and width of each ear and estimating the effective diameter (square root of the height ϫ width). There was no significant difference in pinna morphology between B6 and Fmr1 animals (p ϭ 0.9026; diameter: B6,8.79 Ϯ 0.36;Fmr1,8.84 Ϯ 0.21).…”

Multisensory activation of ventral cochlear nucleus D‐stellate cells modulates dorsal cochlear nucleus principal cell spatial coding

“…We surmise that conservation of the notch‐inhibition mechanism across the tonotopic axis is developmentally beneficial, as head‐related transfer functions change with head/pinna size growth and vary across individuals (Anbuhl et al . ). In many auditory nuclei, neurons across the tonotopic gradient have similar characteristics, and exhibit virtually identical sound localization coding ability despite the fact that low‐BF and high‐BF neurons receive distinctly different sound localization cues (Griffin et al .…”