Recognizing that two sounds are the same is a part of accurate vocal imitation, and the teaching of vocal imitation is an important part of language training for persons with developmental disabilities (DD) and children with autism. Researchers have developed an Auditory-Auditory Identity Matching Prototype Task (AAIM PT) to assess whether persons with DD can identify whether two sounds are the same (Harapiak, Martin, & Yu, 1999). Thus far, the one study (Sewell, 2005) that attempted to teach AAIM tasks to persons with DD who failed the AAIM PT had little success in doing so. The purpose of this research was to evaluate several procedures for teaching AAIM tasks to persons with DD and children with autism. In Experiment 1, the trainer said a word, a matching word was played out of one computer speaker, and a non-matching word was played out of another. The participant was required to point to the speaker that played the matching word. In a single-subject alternating-treatments design, volume fading of the non-matching word (from zero to full volume) was compared to the fading out of a pointing prompt to the speaker that played the matching word. Only one of five participants learned an AAIM task, and that participant did not pass the AAIM PT. Three pilot studies were then conducted to explore various prompting and fading strategies for teaching AAIM tasks, and all were unsuccessful. In Experiment 2, I examined a procedure for teaching AAIM in which the participant was actively involved in producing the sample sound and the matching and non-matching comparison sounds. This procedure also incorporated visual cues and sounds from the operation of a toy airplane as a possible natural, built-in reinforcer. In a single-subject AB design with replication within and across three participants (one person with DD and two children with autism), all three participants learned two AAIM tasks, two participants generalized to a third AAIM task, and one participant passed the AAIM PT. The encouraging results from Experiment 2 provide a promising starting point for future research on teaching AAIM tasks to persons with DD and children with autism.

Recognizing that two sounds are the same is a part of accurate vocal imitation, and the teaching of vocal imitation is an important part of language training for persons with developmental disabilities (DD) and children with autism. Researchers have developed an Auditory-Auditory Identity Matching Prototype Task (AAIM PT) to assess whether persons with DD can identify whether two sounds are the same (Harapiak, Martin, & Yu, 1999). Thus far, the one study (Sewell, 2005) that attempted to teach AAIM tasks to persons with DD who failed the AAIM PT had little success in doing so. The purpose of this research was to evaluate several procedures for teaching AAIM tasks to persons with DD and children with autism. In Experiment 1, the trainer said a word, a matching word was played out of one computer speaker, and a non-matching word was played out of another. The participant was required to point to the speaker that played the matching word. In a single-subject alternating-treatments design, volume fading of the non-matching word (from zero to full volume) was compared to the fading out of a pointing prompt to the speaker that played the matching word. Only one of five participants learned an AAIM task, and that participant did not pass the AAIM PT. Three pilot studies were then conducted to explore various prompting and fading strategies for teaching AAIM tasks, and all were unsuccessful. In Experiment 2, I examined a procedure for teaching AAIM in which the participant was actively involved in producing the sample sound and the matching and non-matching comparison sounds. This procedure also incorporated visual cues and sounds from the operation of a toy airplane as a possible natural, built-in reinforcer. In a single-subject AB design with replication within and across three participants (one person with DD and two children with autism), all three participants learned two AAIM tasks, two participants generalized to a third AAIM task, and one participant passed the AAIM PT. The encouraging results from Experiment 2 provide a promising starting point for future research on teaching AAIM tasks to persons with DD and children with autism.

Lesions in the brainstem result in widespread damage to a number of sensorimotor systems including oculomotor and auditory neural circuits. Although these systems are spatially separate and highly specialised, they are also co-located. This thesis, investigates whether lesions in the oculomotor system will also cause co-morbid dysfunction in the auditory pathways. Specifically, we investigated the usefulness of the Auditory Brainstem Response (ABR) in two oculomotor conditions: slow saccades in Gaucher disease (GD) and opsoclonus in Dancing Eye Syndrome (DES). We present four empirical studies. In our first study we systematically investigated the ABR in GD. We found that multimodal testing can better delineate underlying neurological deficits in neuronopathic GD (nGD) and distinguish between phenotypes. In the second study we examined the ABR's utility as a longitudinal, objective marker of disease burden and in a randomised clinical control trial. ABRs continued to deteriorate regardless of treatment. In our third study we assessed audiological function in DES. We found that at least 43% of DES patients have hyperacusis. We also found subtle abnormalities in the auditory brainstem, as shown by the ABR. Our final study explored the onset-offset response in the ABR and assessed its utility as a clinical marker. Overall, this thesis provides new evidence that auditory pathways are also affected in diseases which are traditionally assumed to be ‘oculomotor’ in nature. We believe that there is sufficient evidence to warrant the inclusion of audiological testing, such as the ABR, as part of the standard assessment of newly diagnosed GD patients and that they undergo these tests prior to commencing treatment. These tests may also have a wider application as longitudinal outcome measures for use in clinical trials or as markers of neurological burden in GD and we believe may be useful in other metabolic diseases; we found that current therapies for GD have low efficacy. Understanding the underlying neurological deficits in these debilitating illnesses can only help to improve treatments and the long-term outlook for these patients.

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Eight experiments were performed to investigate factors affecting the discrimination of two characteristics of very brief tones. The subjects (adults with normal hearing) were asked to rate targets that differed either by amplitude envelope or by a change in frequency. For the majority of the trials, a target was followed (after a brief silent interval) by a pure tone referred to as a "mask". Two factors affecting discrimination within this simple paradigm were examined in detail; the frequency separation and the duration of the silent interval between the target and the mask. For most of the other conditions, a target and mask were embedded in a series of sounds that were presented with an isochronous rhythm. Several features of these "background" sounds were varied across the experiments, including their timbre, presentation rate and frequency relationships with the target and mask. / Superior discrimination was obtained when targets were able to perceptually "emerge" from a background of tones or noises. Specifically, performance was strongest when a target was easily segregated from the other sounds in the series by timing factors or through having a unique frequency. Discrimination was also enhanced when the interfering effects of the mask were removed through association with other tones in the sequence. The data suggest that a simple "interruption" model of processing, in which the presence of a mask disrupts subjects' ability to process individual characteristics of a target, does not adequately explain the differences in discrimination observed across the conditions. A more comprehensive explanation could consider attentional factors that may influence subjects' ability to accurately identify which tone in a sequence is to be rated. However, a perspective based on auditory segregation seems to most consistently explain the data; individual characteristics of a target were most easily discriminated when the target was perceived as belonging outside of an auditory group formed by the background sounds. This was especially true when the mask was likely to have been perceived as belonging within the group due to frequency proximity and/or rhythmic regularity.

Eight experiments examined the effects of placing a sequential organization cue (the frequency proximity between successive tones) into competition with various binaural cues. The sequential organization of an alternating pair of monaural pure tones (A and B) was found to oppose the effect of a contralateral noise burst (synchronous with B) to delateralize B's perceived position and to distort its perceived purity. Similarly, the sequential organization of a monaural tone with the same-ear component of a dichotic tone was found to often oppose the perceptual integration of the components of the dichotic tone. These findings were interpreted as suggesting that sequential cues compete with certain binaural cues during lateralization and dichotic integration decisions. However, sequential cues were found not to influence the fusion of identical sinusoids presented at opposite ears. Thus, binaural fusion appeared to occur independently of sequential organization processes. These findings were discussed in terms of levels and mechanisms of processing, and of ecological demands.

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