Browsing by Subject "Auditory"

Now showing 1 - 3 of 3
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    The effect of biological and anthropogenic sound playbacks and self-generated movement on the hearing sensitivity of the Oyster Toadfish, Opsanus tau
    (2019-08) Rogers, Loranzie
    Within the fish inner ear, three otolithic end organs (utricle, saccule and lagena) serve both auditory and vestibular roles. The Oyster toadfish (Opsanus tau) is a vocal fish species that has been extensively studied to understand both the vestibular and auditory functions of the fish inner ear. Previous studies, however, have primarily been conducted on restrained or stationary fishes so it remains unclear how self-generated movement impacts the otolithic end organs. Additionally, the effects of self-generated and anthropogenic sound on fish hearing remains to be known. To address these questions, microwire electrodes were inserted into utricle of free-swimming toadfish using an implantable micromanipulator. Experiments measured the neural response of the utricle to playbacks of conspecific vocalizations at variable speeds while swimming. During movement, fish remained sensitive to conspecific playbacks, indicating that the inner ear can detect auditory stimuli during movement. Additionally, acoustic evoked potential recordings were conducted to measure the auditory sensitivity of toadfish pre- and post-exposure to conspecific vocalizations and anthropogenic sound. Toadfish exhibited auditory sensitivity between 100 and 500 Hz, which overlaps the frequency range of conspecific vocalizations and anthropogenic sound, such as those generated by ship traffic. Exposure to conspecific vocalizations had no significant effect on toadfish auditory sensitivity; however, exposure to anthropogenic sound caused significant auditory impairment that was sustained for at least 3 days. For vocal fishes, the ability to detect and localize conspecific vocalizations is critical for their reproductive success. In the following chapters, I show that toadfish are capable of sound detection while swimming and after exposure to conspecific vocalizations, but their hearing is impaired by anthropogenic sound.
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    Human auditory source discrimination.
    (2011-07) Gardeen, Stephen J.
    The aim of this study is to examine the auditory system's ability to process low energy frequency transpositions of complex sounds. The auditory processing of complex sounds such as musical instruments, voice, or environmental events is currently an active area of research. Some propose that auditory "objects" are represented by neurons which encode the `invariant' spectro-temporal acoustic properties (Griffiths & Warren,2004). These sound features tend to be heavily damped and very transient and, therefore, frequency rich. This study shows the auditory's sensitivity to detect these adjustments by detecting the pre-attentive magnetic mismatch response (MMNm) from 8 subjects passively listening to complex audio stimulations. Responses were detected from most subjects even though participants could not attentively discriminate the sounds. This result is somewhat controversial in that current views suggests that a mismatch response indicates processing that is available for higher processing i.e. should be attentively discriminable (Näätänen et al., 2010). Localization results suggest the mismatch processing is performed in the auditory associations regions (superior temporal sulcus, insula) of the auditory cortex. These results suggest that transient sounds might be essential to auditory object identification, and that the auditory system is able to distinguish at a sensory level, shifts in the heavily damped spectral structure of complex sounds even though some cannot do so attentively. This could be due to the greater analysis given by the human brain to determining the pitch center rather then the sound timbre, yet some trained musicians have the ability to distinguish these subtle differences (i.e. differences between manufacturers of the same kinds of instruments).
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    Investigating rapid divergence of sensory systems between satellite populations of the Mexican tetra (Astyanax mexicanus)
    (2022-01) Enriquez, Maya
    The Mexican tetra (Astyanax mexicanus) has two primary ecotypes: cave fish and surface fish. Cave fish are characterized by troglomorphic phenotypes, such as vestigial eyes and reduced pigmentation. Studies have documented phenotypic differences in these ecotypes, which likely diverged between 0.2 to 1 million years ago. However, surface A.mexicanus fish were introduced relatively recently to the Edwards-Trinity aquifer in Texas in the early 1900s, and subsequent cave colonization by portions of this population show evidence of divergence through rapid phenotypic and behavioral evolution. The establishment of these satellite populations from cave and surface river invasions are a case study into the rapid evolution of traits within a new environment, allowing observation on how sensory systems may adapt in real time. Auditory evoked potentials (AEPs), particle acceleration (PAL) and electroretinography (ERG) assays were conducted to quantify sensory differences between satellite cave and surface populations. Honey Creek cave fish were found to be significantly more sensitive (p < 0.05) than Honey Creek surface fish to sound pressure levels between 0.5 kHz - 0.8 kHz, while some pairwise differences were found between San Antonio Zoo surface, Blue Hole cave and San Pedro Springs cave populations between 0.5 kHz - 0.7kHz (p < 0.05). Particle acceleration assays also showed significant differences between Honey Creek cave and surface (p < 0.05) as well as San Antonio Zoo surface, San Pedro Springs cave and Blue Hole cave (p < 0.05) within the same range of frequencies tested. Electroretinography data indicated that Honey Creek cave fish were significantly less sensitive (p < 0.05) to light than Honey Creek surface fish at 530 nm, while no differences were found between San Antonio Zoo surface, San Pedro Springs cave and Blue Hole cave. Collectively, these results indicate rapid divergence of A.mexicanus in cave habitats at the most sensitive ranges of their visual and auditory sensory systems, and future monitoring may demonstrate continual divergence of sensory systems in populations exposed to new environments.