The effect of ethanol on cortisol metabolism in man : a thesis presented in partial fulfilment of the requirements for the degree of Master of Science in Biochemistry at Massey University.

Methods were developed for the estimation of human plasma cortisol by radioimmunoassay and urinary 6β-hydroxycortisol (6βOHF) by colorimetry after separation by thin layer chromatography (TLC). In addition profiles of urinary neutral steroids were obtained by gas chromatographic separation of methoxime-trimethylsilyl derivatives from urine extracts on a glass capillary column. This approach was found to be more sensitive and reproducible than profile studies based on TLC separation and colorimetric estimation. Pilot studies of the plasma cortisol levels of normal subjects showed a consistent rise in cortisol during alcohol loading under the conditions of the observations, but in hospital patients admitted with acute alcohol intoxication, variability in the experimental conditions masked any consistent changes. Large variations in method reproducibility as well as subject differences affected results from the measurement of 6βOHF and chloroform extractable 17-hydroxycorticosteroids in one normal and four alcoholic subjects, rendering apparent initial differences insignificant. The results suggest, but do not demonstrate, that alcohol ingestion may divert normal cortisol metabolism into a pathway leading to the production of 6βOHF. Urinary steroid profiles obtained from two normal subjects, one normal subject under conditions of alcohol load and one alcoholic subject suggest that any effects of alcohol on cortisol metabolism are subtle and would require study of a large number of cases to define them. This work has served to delineate the faults and potential of various approaches to the study of cortisol metabolism and the possible effects of alcohol thereon. It would seem that their application in carefully designed and well controlled experiments to a larger number of subjects is necessary to obtain the information desired

Richard Carlyon: A Retrospective

Published in conjunction with the multisite exhibition Richard Carlyon: A Retrospective, which opened on September 11, 2009, and was organized by the Anderson Gallery, School of the Arts, Virginia Commonwealth University; Reynolds Gallery; 1708 Gallery; and Visual Arts Center of Richmond, all in Richmond, Va.https://scholarscompass.vcu.edu/anderson_gallery/1001/thumbnail.jp

Primary school teachers crossing boundaries: The experiences of transitioning between different class levels in primary schools from a teachers' perspective.

Teachers cross a number of boundaries during their teaching careers. In this study crossing boundaries refers specifically to teachers transitioning between different class levels in primary schools. The study focuses on the benefits and challenges teachers face from this boundary crossing and how the practice of transitioning between different class levels is implemented in primary schools. A key principle that underpins this study is the importance of teachers becoming critical reflective practitioners to improve their teaching. A case study approach grounded in an interpretive methodology has been used for this study. Data were collected through semi-structured interviews with teachers who have transitioned between different class levels. Three broad themes emerged as being central to teachers transitioning: benefits of transitioning between different class levels; the impact of school culture and leadership on teachers transitioning; and the role of mentors in teachers’ transitions. The major findings from the study indicate that transitioning between different class levels in primary schools is a critical component of teachers’ ongoing personal and professional growth, learning and development. Transitioning between different class levels highlights a kind of horizontal development which requires a shift away from the singular vertical notion that tends to dominate in teachers’ development. The study indicates that in order for teachers to become extended professionals who have a broad understanding of the learning needs of all students, schools should support and actively encourage teachers to transition between different class levels

Temporal variation in reproductive characteristics of an introduced and abundant island population of koalas

Reproductive characteristics of a wildlife population are typically sensitive to changes in environmental conditions and intrinsic factors. Knowledge of these relationships is critical for understanding population dynamics and effective long-term management of a population. We examined temporal variation in reproductive parameters of an abundant, genetically compromised, and high-density population of koalas (Phascolarctos cinereus) on Kangaroo Island, South Australia, over 3 breeding seasons spanning 9 years: November–May of 1997–1998, 2005–2006, and 2006–2007. Timing of the breeding season was consistent between years, but fecundity, sex ratio of young, and the percentage of independent females (those not accompanying a lactating female) , 6 kg varied. Fecundity was lower than in other island populations, suggesting that the quality and distribution of food resources or inbreeding may be impacting the Kangaroo Island population. We did not test for Chlamydophila (synonym =Chlamydia), and clinical signs of this disease were not reported for any of the koalas in this study. However, historical evidence of Chlamydophila-infected koalas on Kangaroo Island exists, and the potential impact of this disease on fecundity warrants further investigation

Further simulations of the effect of cochlear-implant pre-processing and head movement on interaural level differences

We simulated the effect of several automatic gain control (AGC) and AGC-like systems and head movement on the output levels, and resulting interaural level differences (ILDs) produced by bilateral cochlear-implant (CI) processors. The simulated AGC systems included unlinked AGCs with a range of parameter settings, linked AGCs, and two proprietary multi-channel systems used in contemporary CIs. The results show that over the range of values used clinically, the parameters that most strongly affect dynamic ILDs are the release time and compression ratio. Linking AGCs preserves ILDs at the expense of monaural level changes and, possibly, comfortable listening level. Multichannel AGCs can whiten output spectra, and/or distort the dynamic changes in ILD that occur during and after head movement. We propose that an unlinked compressor with a ratio of approximately 3:1 and a release time of 300-500 ms can preserve the shape of dynamic ILDs, without causing large spectral distortions or sacrificing listening comfort

On musical interval perception for complex tones at very high frequencies.

Listeners appear able to extract a residue pitch from high-frequency harmonics for which phase locking to the temporal fine structure is weak or absent. The present study investigated musical interval perception for high-frequency harmonic complex tones using the same stimuli as Lau, Mehta, and Oxenham [J. Neurosci. 37, 9013-9021 (2017)]. Nine young musically trained listeners with especially good high-frequency hearing adjusted various musical intervals using harmonic complex tones containing harmonics 6-10. The reference notes had fundamental frequencies (F0s) of 280 or 1400 Hz. Interval matches were possible, albeit markedly worse, even when all harmonic frequencies were above the presumed limit of phase locking. Matches showed significantly larger systematic errors and higher variability, and subjects required more trials to finish a match for the high than for the low F0. Additional absolute pitch judgments from one subject with absolute pitch, for complex tones containing harmonics 1-5 or 6-10 with a wide range of F0s, were perfect when the lowest frequency component was below about 7 kHz, but at least 50% of responses were incorrect when it was 8 kHz or higher. The results are discussed in terms of the possible effects of phase-locking information and familiarity with high-frequency stimuli on pitch

An information theoretic characterisation of auditory encoding.

The entropy metric derived from information theory provides a means to quantify the amount of information transmitted in acoustic streams like speech or music. By systematically varying the entropy of pitch sequences, we sought brain areas where neural activity and energetic demands increase as a function of entropy. Such a relationship is predicted to occur in an efficient encoding mechanism that uses less computational resource when less information is present in the signal: we specifically tested the hypothesis that such a relationship is present in the planum temporale (PT). In two convergent functional MRI studies, we demonstrated this relationship in PT for encoding, while furthermore showing that a distributed fronto-parietal network for retrieval of acoustic information is independent of entropy. The results establish PT as an efficient neural engine that demands less computational resource to encode redundant signals than those with high information content

A Re-examination of the Effect of Masker Phase Curvature on Non-simultaneous Masking.

Forward masking of a sinusoidal signal is determined not only by the masker's power spectrum but also by its phase spectrum. Specifically, when the phase spectrum is such that the output of an auditory filter centred on the signal has a highly modulated ("peaked") envelope, there is less masking than when that envelope is flat. This finding has been attributed to non-linearities, such as compression, reducing the average neural response to maskers that produce more peaked auditory filter outputs (Carlyon and Datta, J Acoust Soc Am 101:3636-3647, 1997). Here we evaluate an alternative explanation proposed by Wotcjzak and Oxenham (Wojtczak and Oxenham, J Assoc Res Otolaryngol 10:595-607, 2009). They reported a masker phase effect for 6-kHz signals when the masker components were at least an octave below the signal frequency. Wotcjzak and Oxenham argued that this effect was inconsistent with cochlear compression, and, because it did not occur at lower signal frequencies, was also inconsistent with more central compression. It was instead attributed to activation of the efferent system reducing the response to the subsequent probe. Here, experiment 1 replicated their main findings. Experiment 2 showed that the phase effect on off-frequency forward masking is similar at signal frequencies of 2 and 6 kHz, provided that one equates the number of components likely to interact within an auditory filter centred on the signal, thereby roughly equating the effect of masker phase on the peakiness of that filter output. Experiment 3 showed that for some subjects, masker phase also had a strong influence on off-frequency backward masking of the signal, and that the size of this effect correlated across subjects with that observed in forward masking. We conclude that the masker phase effect is mediated mainly by cochlear non-linearities, with a possible additional effect of more central compression. The data are not consistent with a role for the efferent system

Predictive Top-Down Integration of Prior Knowledge during Speech Perception

A striking feature of human perception is that our subjective experience depends not only on sensory information from the environment but also on our prior knowledge or expectations. The precise mechanisms by which sensory information and prior knowledge are integrated remain unclear, with longstanding disagreement concerning whether integration is strictly feedforward or whether higher-level knowledge influences sensory processing through feedback connections. Here we used concurrent EEG and MEG recordings to determine how sensory information and prior knowledge are integrated in the brain during speech perception. We manipulated listeners' prior knowledge of speech content by presenting matching, mismatching, or neutral written text before a degraded (noise-vocoded) spoken word. When speech conformed to prior knowledge, subjective perceptual clarity was enhanced. This enhancement in clarity was associated with a spatiotemporal profile of brain activity uniquely consistent with a feedback process: activity in the inferior frontal gyrus was modulated by prior knowledge before activity in lower-level sensory regions of the superior temporal gyrus. In parallel, we parametrically varied the level of speech degradation, and therefore the amount of sensory detail, so that changes in neural responses attributable to sensory information and prior knowledge could be directly compared. Although sensory detail and prior knowledge both enhanced speech clarity, they had an opposite influence on the evoked response in the superior temporal gyrus. We argue that these data are best explained within the framework of predictive coding in which sensory activity is compared with top-down predictions and only unexplained activity propagated through the cortical hierarchy