Perceptual learning describes the effect whereby experience with a specific signal alters a listener’s perceptual processes during subsequent encounters with that same signal. Research investigating perceptual learning with foreign-accented speech (e.g.2) and artificially degraded acoustic signals (e.g.3) provides substantial evidence regarding the perceptual benefit of prior exposure. While such findings may have significant implications for the management of neurological speech disorders, existing research with such populations is minimal and study findings have been equivocal.
Sixty healthy listener participants were randomly assigned to one of three perceptual learning conditions: (1) control; (2) passive familiarisation; and (3) explicit familiarisation. Word accuracy of listener transcriptions of phrase level stimuli produced by speakers with a moderate hypokinetic dysarthria secondary to Parkinson’s disease were used to document the magnitude and stability of effects of a familiarisation experience on speech intelligibility. In addition, listener transcripts were analysed for lexical boundary errors (suprasegmental level) and syllable perception (segmental level) to investigate the cognitive-perceptual processes which may underlie any benefit associated with familiarisation.
Statistically significant improvements in intelligibility were observed for familiarised listeners relative to the control group, with explicitly familiarised listeners demonstrating greatest intelligibility gains following exposure to the degraded signal. At follow-up, intelligibility for listeners who received explicit familiarisation remained significantly higher than controls, however no lasting intelligibility gains were observed for listeners who received passive familiarisation. Statistically significant differences were also observed for all groups on syllable level measures and type and distribution of lexical boundary error patterns.
Findings provide compelling evidence that listeners can “learn” to better understand neurologically degraded speech, and furthermore, that explicit familiarisation facilitates largest and lasting intelligibility gains. Changes to both segmental and suprasegmental levels of perceptual processing advance the current understanding of learning mechanisms associated with perception of neurologically-disordered speech, and provide direction for future research.
- Norris, D., McQueen, J. M., & Cutler, A. (2003). Perceptual learning in speech.Cognitive Psychology, 47, 204-238.
- Bradlow, A. R. and T. Bent (2008). "Perceptual adaption to non-native speech." Cognition 106: 707-729.
- Davis, M. H., I. S. Johnsrude, et al. (2005). "Lexical information drives perceptual learning of distorted speech: Evidence from the comprehension of noise-vocoded sentences." Journal of Experimental Psychology: General 134(2): 222-241.
Urinary cystatin C (uCysC) has been proposed as a marker of tubular kidney injury. Albuminuria may interfere with tubular reabsorption of uCysC. We evaluated whether albuminuria induced in rats via intraperitoneal (IP) bovine serum albumin (BSA) would increase uCysC.
Seven male and female (6-8 week old) Sprague-Dawley rats received5 mg.day-1.g body wt-1 IP BSA in saline. Four rats of each sex received saline only. Injections were given twice daily for 2 consecutive days. Rats were placed in metabolic cages with free access to food and water on the day before injection (Time 1), the day following the last injection (Time 2) and, 96 hours later (Time 3). Timed collections of spontaneously voided urine was obtained to measure albumin, total protein, and uCysC. Rate of uCysC, protein, and albumin excretion were calculated. Repeated measures two-way ANOVA was used to find the effects of sex, BSA injection, and time of sampling. Post-hoc, Fisher’s LSD and Pearson’s correlation were used to explore the primary effects and interactions.
Male rats excreted more protein, albumin, and uCysC than female rats (p<0.0001, <0.0001, and <0.01, respectively). In both sexes, BSA treatment caused an increase in the rates of excretion of protein (p<0.01), albumin (p<0.05), and uCysC (p<0.05). The rates of protein and albumin excretion were significantly correlated with the rate of uCysC excretion (r2= 0.54 and r2= 0.29 respectively; p<0.01). In BSA treated rats, urine analytes were similar between Time 1 and Time 3, which show a transient effect of BSA overload. The control groups showed no significant changes in urine analytes over time.
There was a significant increase of uCysC excretion in rats with induced albuminuria. The degree of cystatinuria and albuminuria were correlated. Males had higher albuminuria and cystatinuria than females.
Eating disorders are often chronic illnesses which significantly impact on the lives of those affected. In those with eating disorders, appetite is ignored, and individuals learn to ignore hunger signals or are unable to stop eating in response to satiety signals. Disregard of these signals has a deleterious impact on wellbeing, including weight status. As such, studying satiety hormones such as ghrelin may contribute to the development of new treatments. Ghrelin, a 28-peptide neurohormone, is the only known peripheral orexigenic hormone. Laboratory studies show fasting and energy restriction increase circulating ghrelin whereas normal food intake and over-eating reduce ghrelin levels. It seems likely that insulin may modulate this response.
This study investigated ghrelin and insulin in 44 women with binge eating (bulimia nervosa (BN) and binge eating disorder (BED)) compared to 44 women without binge eating matched for age and body mass index (BMI). The relationship between ghrelin and the frequency of bingeing, purging and restricting was also investigated. Participants presented after fasting overnight, and blood samples were taken at regular intervals pre- and post- an oral glucose load.
The control group showed the expected pattern of an increase in insulin and a decrease in ghrelin after ingestion of the glucose. There was a similar pattern overall in the BN group, however, the increase in insulin was smaller and ghrelin secretion was lower. Women with BED showed a different pattern with a trend towards higher insulin levels but reduced ghrelin secretion than controls. The BMI of the BED group was higher than the BN group and it is likely that this contributed to the higher insulin levels. Frequency of bingeing and purging was positively correlated with ghrelin in the BN group. These results suggest that eating disorder pathology may influence ghrelin secretion.
Recent advances in computed tomography (CT) scanner technologies have generated a great deal of interest in dual-energy CT. With dual energy computed tomography quickly becoming the clinical standard, spectral X-ray imaging is the next step clinical imaging. In this study, we assess the ability of high resolution multi-energy MARS-CT in imaging excised atherosclerotic plaque components. The MARS research group based at Canterbury and Otago Universities in New Zealand have constructed a multi energy CT scanner using the Medipix detectors. This scanner provides high resolution imaging of tissue components without the use of contrast agents. This technology is being developed to generate high resolution spectral images of atherosclerotic plaque showing the location of calcium, lipid and soft tissues. The fine structure and composition of the atherosclerotic lesion, rather than the degree of stenosis, are currently considered to be the important determinants for acute clinical events.1
Human atherosclerotic plaque specimens, which had been imaged in vivo, were excised during surgery and set in plastic to stabilise the tissue for imaging in the MARS-CT scanner. The scanner uses a microfocus X-ray tube operating at 75 kV with a target current of 0.15 mA. For the scan 303 projects were taken, each been recorded at eight separate energies levels ranging from 14.45 keV to 39.2 keV. This allowed for high resolution CT images at a resolution of 43 μm to be obtained with spectral information.2Colour X-ray CT images of atherosclerotic plaques were obtained using Principal Component Analysis (PCA).
The plaque with calcium is clearly distinguishable from the non-calcified plaque by both the magnitude of the attenuation values and also spectroscopically. Images obtained from spectral CT provide advantages in imaging of human plaques giving novel characterisation of complex atherosclerotic lesions in vivo and offering new insight into plaque development.
- AC van der Wal, AE Becker, CM van der Loos and PK Das. Site of intimal rupture or erosion of thrombosed coronary atherosclerotic plaques is characterized by an inflammatory process irrespective of the dominant plaque morphology. Circulation, Vol 89, pp.36–44, 1994.
- A.P.H. Butler, N.G. Anderson, R. Tipples, N. Cook, R.Watts, J. Meyer, A.J. Bell, T.R. Melzer and P.H. Butler, “Bio-medical x-ray imaging with spectroscopic pixel detectors", Nuclear Instruments and Methods in Physics Research, 591 (1), pp. 141-146, 2008.