Thesis (Ph. D.)--University of Texas at Austin, 2000. / Vita. Includes bibliographical references. Available also from UMI/Dissertation Abstracts International.

Thesis (Ph. D.)--University of Texas at Austin, 2000. / Vita. Includes bibliographical references (leaves 126-134). Available also in a digital version from Dissertation Abstracts.

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Thesis (Ph.D.)--University of Texas at Dallas, 2008. / Includes vita. Includes bibliographical references (leaves 89-92)

Thesis (Ph. D.)--University of Hong Kong, 1991.

Thesis (Ph. D.)--University of Texas at Austin, 1999. / Vita. Includes bibliographical references (leaves 116-134). Available also in a digital version from Dissertation Abstracts.

Thesis (Ph.D.)--Boston University. / Rats were trained on three schedules of reinforcement, a sound aversive schedule, a light aversive schedule and a sound and light discrimination schedule. On the aversive schedules a press response terminated the aversive stimulus. On the discrimination schedule a response in the presence of either stimulus produced food. An auditory threshold was measured on this schedule. Following training the animals received electrolytic lesions in the ventral auditory system of the medulla. Following this they were tested on the behavioral schedules. The brain of each animal was then removed and impregnated with protargol for microscopic examination. Six rats received unilateral lesions, seven received bilateral lesions and six received sham operations. The results were as follows. Of the six animals who received unilateral lesions, one showed a substantial loss of the sound aversive behavior. Of the seven who received bilateral lesions five suffered a loss of the aversive behavior. Of these five, two had a substantial increase in the discriminative threshold. The behavior of the animals who received sham operations was essentially unaffected. There was a consistent relation between extensive damage to the large fiber pathway, the superior olivary pathway and the small fiber pathway and loss of the auditory aversive behavior. Destruction of the superior olivary pathway was not sufficient to produce a loss of the aversive behavior. The suggestion in the literature that the large fiber pathway is responsible for the maintenance of the aversive behavior was confirmed. Destruction of the superior olivary pathway either alone or in combination with destruction of the large fiber pathway did not materially change the auditory discriminative threshold. Destruction of all ventral acoustic pathways caused a loss of both aversive and discriminative auditory behaviors. Dorsal auditory pathways did not by themselves support either behavior. It has not been possible to determine if destruction of the small fiber pathway by itself can cause a loss of discriminative behavior. It was not possible to determine if return of the release response was due to the lesion or due to the loss of the press response.

published_or_final_version / Physiology / Doctoral / Doctor of Philosophy

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The detection of specific temporal patterns in communication signals may be of vital importance for certain organisms. In crickets, for instance, a female will move towards a singing male only if she can recognize the appropriate pulse rate characteristic to its own species' song. Additionally, in order to evade predatory insectivorous bats, flying crickets must be able to track the predator's ultrasonic echolocation signals, which are emitted at a variety of pulse rates. In this thesis, the temporal processing, or the integration of stimulus through time, in the peripheral1 auditory system of the cricket will be investigated. / The ON1 interneuron temporal processing was first examined and compared at high (bat-like) and low carrier (cricket-like) frequencies in three different experimental paradigms. First, integration time, which corresponds to the time it takes for a neuron to reach threshold when stimulated at the minimum effective intensity, was found to be significantly shorter at high carrier frequency than at low carrier frequency. Second, phase locking to sinusoidally amplitude modulated (SAM) signals was more efficient at high frequency, especially at high modulation rates and low modulation depths. Finally, we examined the efficiency with which ON1 detects gaps in a constant tone. As reflected by the decrease in firing rate in the vicinity of the gap, ON1 is better at detecting gaps at low carrier frequency. Following a gap, firing rate increases beyond the pre-gap level. This "rebound" phenomenon is similar for low and high carrier frequencies. / To determine the source of this differential temporal processing, the sensory afferents making synapses with ON1 were investigated. Low frequency (MT-type) and ultrasound auditory receptors were compared on the basis of latency, maximum firing rate, adaptation, information transmission, bursting and feature detection. Ultrasound receptors (HFs) were found to have a shorter latency, a higher maximum firing rate and stronger adaptation than low-frequency receptors (LFs). Individual HFs transmitted more linear (lower-bound) information than LFs. However, HFs' responses were more correlated than LFs' (i.e. they had larger mutual information), so that when superposing the spike trains of LFs, information transmission in the lowest amplitude modulation rates was greatly improved, and, in some cases, reached the level of HFs. Feature detection by spike in HFs was better than in LFs. Feature detection by bursts was better than for spikes, but equivalent in both types of receptors. The level of bursting in HFs, however, was much higher than in LFs, making them better feature detectors in general. / 1Because it lies in the prothoracic ganglion, ON1 is technically part of the central nervous system. For the purpose of this thesis, however, because ON1 receives direct input from the receptors, it will be considered to be part of the peripheral auditory systems.