Two experiments were conducted. The first was a control condition and used the probe signal method similar to Greenberg and Larkin (1968) to see if a filter-like attentional mechanism was acting when listeners were presented with pure tone stimuli in the presence of background noise. The second experiment also used the probe signal method of Greenberg and Larkin (1968) to investigate the extent to which listeners direct their attention to a particular fundamental frequency (f0) when detecting complex tones masked by noise. Twenty adult listeners ranging from 23 years to 54 years with a median age of 28 years participated in both experiments. Of the 20 listeners, 8 were male and 14 were female. Both experiments used a Two Interval Forced Choice (2IFC) procedure. There were two types of trials, the target signal trial and the probe signal trial. The target frequency was presented on 71% of trials, and the probe frequencies on the remaining 29%. The results of Experiment 1 were similar to those obtained in Greenberg and Larkin’s (1968) pioneering study. The 1000 Hz target tone was detected at a significantly higher proportion than probe signals differing in frequency (p < 0.05). Detection scores were observed to be higher when probe signals had a frequency close to the 1000 Hz signal compared to when they had a frequency positioned further from the 1000 Hz target tone. Experiment 2 using complex target tones with f0 of 115 Hz (part 1) and 220 Hz (part 2) revealed a similar pattern to Experiment 1. Listener’s detection scores decreased the further the f0 of probe tones were positioned from the f0 of the target tone, revealing the shape of a band-pass filter. This pattern is consistent with the presence of an auditory attentional filter in the f0 domain for complex tones

Children and adolescents with autism spectrum disorder (ASD) were compared to age-matched typically developing controls in the context of phase synchrony statistics acquired through magnetoencephalography. Subjects performed a “low-attention” task, pressing a button to a single, repeated auditory tone, and this was contrasted to an “oddball” task where they were required to button press only to deviant tones. The differences in task outcomes were primarily thought to relate to differences in sensory and executive attention. Regardless of task condition, ASD subjects showed greater magnitudes of synchrony between the parietal hemispheres which variably extended across frequencies. Additionally, for ASD subjects, increases in synchrony from the “low-attention” task to the “oddball” task were observed; whereas an opposite tendency occurred for controls. Furthermore, rates of fluctuation of phase differences showed more stable parietal synchrony within ASD across the hemispheric midline. Implications including the possibility of coordination as an indicator of ASD are discussed.

Current theories of auditory attention are largely based upon studies examining either the presentation of a single auditory stimulus or requiring the identification and labeling of stimuli presented sequentially. Whether or not these theories apply in more complex ecologically-valid environments where multiple sound sources are simultaneously active is still unknown. This study examined the pattern of neuromagnetic responses elicited when participants had to perform a search in an auditory language-based `scene` for a stimulus matching an imperative target held in working memory. The analysis of source waveforms revealed left lateralized patterns of activity that distinguished target present from target absent trials. Similar source waveform amplitudes were found when the target was presented in the left or right hemispace. The results suggest that auditory search for speech sounds engage a left lateralized process in the superior temporal gyrus.

Children and adolescents with autism spectrum disorder (ASD) were compared to age-matched typically developing controls in the context of phase synchrony statistics acquired through magnetoencephalography. Subjects performed a “low-attention” task, pressing a button to a single, repeated auditory tone, and this was contrasted to an “oddball” task where they were required to button press only to deviant tones. The differences in task outcomes were primarily thought to relate to differences in sensory and executive attention. Regardless of task condition, ASD subjects showed greater magnitudes of synchrony between the parietal hemispheres which variably extended across frequencies. Additionally, for ASD subjects, increases in synchrony from the “low-attention” task to the “oddball” task were observed; whereas an opposite tendency occurred for controls. Furthermore, rates of fluctuation of phase differences showed more stable parietal synchrony within ASD across the hemispheric midline. Implications including the possibility of coordination as an indicator of ASD are discussed.

Current theories of auditory attention are largely based upon studies examining either the presentation of a single auditory stimulus or requiring the identification and labeling of stimuli presented sequentially. Whether or not these theories apply in more complex ecologically-valid environments where multiple sound sources are simultaneously active is still unknown. This study examined the pattern of neuromagnetic responses elicited when participants had to perform a search in an auditory language-based `scene` for a stimulus matching an imperative target held in working memory. The analysis of source waveforms revealed left lateralized patterns of activity that distinguished target present from target absent trials. Similar source waveform amplitudes were found when the target was presented in the left or right hemispace. The results suggest that auditory search for speech sounds engage a left lateralized process in the superior temporal gyrus.

Selective attention refers to the ability to enhance the processing of relevant stimuli, while suppressing the processing of irrelevant distractors. The neural mechanisms of selective attention are vulnerable in children from lower socioeconomic status families, yet these neural mechanisms can also be enhanced with evidence-based, targeted training. The series of studies presented in this dissertation investigated the individual differences in development and neuroplasticity of selective auditory attention in association with nonverbal cognitive abilities, in relation to genetic influences, and in the context of gene x intervention interactions. To this end, a multi-method approach was adopted, combining several methodologies such as event-related potentials (ERPs), behavioral measures, molecular genetics, and a randomized, controlled intervention design. In the first study, individual differences in neural mechanisms of selective auditory attention were studied, in association with nonverbal cognitive abilities. More robust ERP selective attention effects were associated with superior nonverbal IQ performance. These results indicated a noteworthy relationship between neural mechanisms of selective attention and nonverbal IQ performance in lower socioeconomic status (SES) preschoolers. In the second study, the relationship between 5-HTTLPR polymorphism and neural mechanisms of selective auditory attention was assessed. ERPs of selective attention effect were larger in children who carried at least one short allele of 5-HTTLPR, in comparison to long-homozygotes. These results associated being homozygous for the long allele with weaker neural mechanisms of selective attention in lower SES children. In the third study, these genetic influences were investigated in the context of an effective family-based training program previously shown to improve neural mechanisms of selective attention in lower SES preschoolers. The long-homozygote children, who initially displayed more attenuated ERPs of selective auditory attention than their short-carrier peers, showed robust ERPs of selective attention at posttest, but only if they were randomly assigned to the training program. These findings demonstrated that an effective family-based training could moderate the genetic influences of 5-HTTLPR on the neural mechanisms of selective attention. Taken together, the studies presented in this dissertation contribute to elucidating individual differences in development and neuroplasticity of selective auditory attention in lower SES preschoolers. This dissertation includes unpublished co-authored material.

Background: It has long been suspected that music instruction has benefits for children’s neural and cognitive development, including auditory abilities. Although the effect of music on attention has been investigated it has predominantly focused on visual attention, selected auditory attention, or divided auditory attention. Consequently, the impact of music on sustained auditory attention is not well defined and therefore demands investigation and clarity. In order to contextualise the topic this study provides a comprehensive review of literature regarding auditory development and attention, in addition to the systematic review of ten eligible studies. Objectives: The study aims to critically appraise peer-reviewed articles from the past decade pertaining to the correlation between music instruction and sustained auditory attention in typically developing five- to ten-year-old children. Method: A systematic search of literature was conducted with five electronic databases, using primary and secondary search phrases. The PRISMA-P guidelines were followed to identify ten studies for inclusion in the review. These studies were assessed in terms of quality, using the HTA quality checklists, and in terms of bias, using the Cochrane Collaborations tool for risk of bias for quantitative studies and the CASP checklist for qualitative studies. Results: Music instruction has a predominantly positive correlation with sustained auditory attention in children yet is limited by associated variables, such as complex sound environments and age of commencement of music instruction. Several causes are suggested for SAA enhancements, such as alterations in neural structure and function, transfer of musical skills to other domains, and the use of specific musical characteristics. Although the evidence favours the study’s hypothesis (i.e. music instruction does lead to enhanced sustained auditory attention), limitations are present. Furthermore, the studies included in the systematic review did not always examine sustained auditory attention directly, rather focusing on highly interlinked functions (e.g. attentional control). Conclusion: Recent research evidence suggests that music instruction contributes to enhanced sustained auditory attention in young children yet is limited by a number of variables. Therefore, should educators wish to improve children’s sustained auditory attention in the classroom and during learning, they should be cognisant of these factors and make efforts to enforce them. / Dissertation (MMus)--University of Pretoria, 2019. / Music / MMus / Unrestricted

The objective of this dissertation research is to identify sounds that grab a listener's attention. These sounds that draw a person's attention are sounds that are considered salient. The focus here will be on investigating the role of saliency in the auditory attentional process. In order to identify these salient sounds, we have developed a computational auditory saliency model inspired by our understanding of the human auditory system and auditory perception. By identifying salient sounds we can obtain a better understanding of how sounds are processed by the auditory system, and in particular, the key features contributing to sound salience. Additionally, studying the salience of different auditory stimuli can lead to improvements in the performance of current computational models in several different areas, by making use of the information obtained about what stands out perceptually to observers in a particular scene. Auditory saliency also helps to rapidly sort the information present in a complex auditory scene. Since our resources are finite, not all information can be processed equally. We must, therefore, be able to quickly determine the importance of different objects in a scene. Additionally, an immediate response or decision may be required. In order to respond, the observer needs to know the key elements of the scene. The issue of saliency is closely related to many different areas, including scene analysis. The thesis provides a comprehensive look at auditory saliency. It explores the advantages and limitations of using auditory saliency models through different experiments and presents a general computational auditory saliency model that can be used for various applications.

Past studies have shown that the effects of selective auditory attention are evident in medial olivocochlear (MOC) activity, manifested as the contralateral suppression (CS) of transient evoked otoacoustic emissions (TEOAEs). This finding suggests the use of TEOAEs in the design of an auditory-based access technology as a potential access solution for children with severe disabilities. Thirteen participants with normal hearing threshold and normal middle ear function completed this study. The participants were instrumented with a TEOAE ear probe and presented with a contralateral acoustic stimulus. They were instructed to alternate auditory attention conditions as visually cued by symbols on an LCD display. Attentive and non-attentive conditions were detected with an overall accuracy of 70.17 +/- 12.54% at 2.44 +/- 0.3 bits per minute in a participant-specific classifier, and 65.92 +/- 13.91% in a participant-independent classifier. Detection of auditory attention exceeded random chance levels for 11 of 13 participants.

Past studies have shown that the effects of selective auditory attention are evident in medial olivocochlear (MOC) activity, manifested as the contralateral suppression (CS) of transient evoked otoacoustic emissions (TEOAEs). This finding suggests the use of TEOAEs in the design of an auditory-based access technology as a potential access solution for children with severe disabilities. Thirteen participants with normal hearing threshold and normal middle ear function completed this study. The participants were instrumented with a TEOAE ear probe and presented with a contralateral acoustic stimulus. They were instructed to alternate auditory attention conditions as visually cued by symbols on an LCD display. Attentive and non-attentive conditions were detected with an overall accuracy of 70.17 +/- 12.54% at 2.44 +/- 0.3 bits per minute in a participant-specific classifier, and 65.92 +/- 13.91% in a participant-independent classifier. Detection of auditory attention exceeded random chance levels for 11 of 13 participants.