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D.Litt. et Phil. (Psychology) / The purpose of the present study was to investigate whether robust and verifiable evoked potential components exist which can reliably be associated with temperament. The evoked potential (EP) procedures included the auditory brainstem response procedure (ABR), the auditory N1-P2 middle latency response procedure (AMR) utilising different stimulus intensities, the auditory P300 response utilising frequent and rare repetitions of stimuli (the "oddball paradigm" ) and a number of composite measures of the AMR and P300. The temperament dimensions which were assessed, were sensation seeking, measured by Zuckerman's sensation Seeking Scale (SSS) Form 5, stimulus augmenting-reducing measured by Vando's Augmenting-reducing scale, properties of the nervous system, measured by Strelau's Temperament Inventory (STI) and introversion-extroversion, measured by Schepers' Personality Questionnaire. The statistical population chosen for the research was the first year Behavioural Sciences students of 1991 and 1992 at a South African university (N = 640). A sample of 391 students (81 males and 210 females, aged 17 to 22 years) was randomly selected from the statistical population. All the Subjects completed the Psychological battery (the various temperament scales) and the Neurophysiological battery (the various evoked potential procedures). The reliabilities of the various scales and procedures were established prior to administering the batteries. Hotelling's T-test was used to determine if the vectors of means of the males and females in respect of the subtests of the Psychological battery and the measurements of the various EP procedures differed statistically significantly or not. Student's t-test was used to determine in respect of which variables the genders differed. All Subsequent analyses were performed separately for the males and females. Three contrasting groups with low, medium and high scores, respectively, were formed with regard to each temperament trait.

Indiana University-Purdue University Indianapolis (IUPUI) / Non-invasive surface recording of bioelectric potentials continues to be an essential tool in a variety of research and medical diagnostic procedures. However, the integrity of these recordings, and hence the reliability of subsequent analysis, diagnosis, or recommendations based on the recordings, can be significantly compromised when various types of noise are allowed to penetrate the recording circuit and contaminate the signals. In particular, for bioelectric phenomena in which the amplitude of the biosignal is relatively low, such as muscle activity (typically on the order of millivolts) or neural traffic (microvolts), external noise may substantially contaminate or even completely overwhelm the signal. In such circumstances, the tissue-electrode interface is typically the primary point of signal contamination since its impedance is relatively high compared to the rest of the recording circuit. Therefore, in the recording of low-amplitude biological signals, it is of paramount importance to minimize the impedance of the tissue-electrode interface in order to consistently obtain low-noise recordings. The aims of the current work were (1) to complete the development of a set of tools for rapid, simple, and reliable full-spectrum characterization and analytical modeling of the complex impedance of the tissue-electrode interface, and (2) to characterize the interfacial impedance and signal-to-noise ratio (SNR) at the surface of the skin across a variety of preparation methods and determine a factor or set of factors that contribute most effectively to the reduction of tissue-electrode impedance and noise contamination during recording. Specifically, we desired to test an initial hypothesis that surface abrasion is the principal determining factor in skin preparation to achieve consistently low-impedance, low-noise recordings. During the course of this master’s study, (1) a system with portable, battery-powered hardware and robust acquisition/analysis software for broadband impedance characterization has been achieved, and (2) the effects of skin preparation methods on the impedance of the tissue-electrode interface and the SNR of surface electromyographic recordings have been systematically quantified and compared in human subjects. We found our hypothesis to be strongly supported by the results: the degree of surface abrasion was the only factor that could be correlated to significant differences in either the interfacial impedance or the SNR. Given these findings, we believe that abrasion holds the key to consistently obtaining a low-impedance contact interface and high-quality recordings and should thus be considered an essential component of proper skin preparation prior to attachment of electrodes for recording of small bioelectric surface potentials.