Perception of musical timbre by cochlear implant listeners: a multidimensional scaling study.

International audienceOBJECTIVES: Several studies have shown that the ability to identify the timbre of musical instruments is reduced in cochlear implant (CI) users compared with normal-hearing (NH) listeners. However, most of these studies have focused on tasks that require specific musical knowledge. In contrast, the present study investigates the perception of timbre by CI subjects using a multidimensional scaling (MDS) paradigm. The main objective was to investigate whether CI subjects use the same cues as NH listeners do to differentiate the timbre of musical instruments. DESIGN: Three groups of 10 NH subjects and one group of 10 CI subjects were asked to make dissimilarity judgments between pairs of instrumental sounds. The stimuli were 16 synthetic instrument tones spanning a wide range of instrument families. All sounds had the same fundamental frequency (261 Hz) and were balanced in loudness and in perceived duration before the experiment. One group of NH subjects listened to unprocessed stimuli. The other two groups of NH subjects listened to the same stimuli passed through a four-channel or an eight-channel noise vocoder, designed to simulate the signal processing performed by a real CI. Subjects were presented with all possible combinations of pairs of instruments and had to estimate, for each pair, the amount of dissimilarity between the two sounds. These estimates were used to construct dissimilarity matrices, which were further analyzed using an MDS model. The model output gave, for each subject group, an optimal graphical representation of the perceptual distances between stimuli (the so-called "timbre space"). RESULTS: For all groups, the first two dimensions of the timbre space were strikingly similar and correlated strongly with the logarithm of the attack time and with the center of gravity of the spectral envelope, respectively. The acoustic correlate of the third dimension differed across groups but only accounted for a small proportion of the variance explained by the MDS solution. Surprisingly, CI subjects and NH subjects listening to noise-vocoded simulations gave relatively more weight to the spectral envelope dimension and less weight to the attack-time dimension when making their judgments than NH subjects listening to unprocessed stimuli. One possible reason for the relatively higher salience of spectral envelope cues in real and simulated CIs may be that the degradation of local fine spectral details produced a more stable spectral envelope across the stimulus duration. CONCLUSIONS: The internal representation of musical timbre for isolated musical instrument sounds was found to be similar in NH and in CI listeners. This suggests that training procedures designed to improve timbre recognition in CIs will indeed train CI subjects to use the same cues as NH listeners. Furthermore, NH subjects listening to noise-vocoded sounds appear to be a good model of CI timbre perception as they show the same first two perceptual dimensions as CI subjects do and also exhibit a similar change in perceptual weights applied to these two dimensions. This last finding validates the use of simulations to evaluate and compare training procedures to improve timbre perception in CIs

Perception of musical timbre by cochlear-implant listeners

International audienc

Differential Determinants of Tubular Phosphate Reabsorption: Insights on Renal Excretion of Phosphates in Kidney Disease

International audienceWe assessed the tubular reabsorption of phosphate (TRP) and maximal renal threshold for phosphate reabsorption to glomerular filtration rate (TmPi/GFR) and their determinants in 64 stages 2-4 chronic kidney disease (CKD) patients in order to define the early changes in phosphate metabolism in CKD. In multivariable analysis, TmPi/GFR correlates were estimated GFR (eGFR), intact parathyroid hormone (iPTH), and hemoglobin (R-2 = 0.417), while TRP correlates were eGFR, iPTH, 24-h phosphaturia, and calcitriol (R-2 = 0.72). This suggests that TmPi/GFR and TRP, respectively, assess hemoglo-bin-phosphate and bowel-kidney phosphate regulation axis. Iron supplementation based on TmPi/GFR or earlier phosphate restriction based on TRP should be investigated in view of modifying clinical outcomes in CKD. (C) 2018 S. Karger AG, Base

Impact of chronic maternal separation on metabolism, food motivation and brain gene expression profiles in C57BL/6J and C3H/Hen mice

PosterEarly life adversity during infancy influences the development of child and exerts long-lasting effects on physiological functions and vulnerability to psychiatric disorders in particular depression and anxiety. Recent studies also suggest a higher prevalence of metabolic dysfunctions and obesity as well as risks of food addiction in adulthood in subjects exposed to childhood adversity. Maternal separation (MS) in rodents is a well-studied model of early life stress. Several studies demonstrate that chronic MS leads to an exaggerated hypothalamic-pituitary-adrenal axis response to stress and impairs emotional behavior in adult offspring. In contrast, the impact of MS on metabolism and food motivation remain poorly characterized. The aim of the present study was to explore in 2 mouse strains (C57BL/6J and C3H/HeN) differing by their initial maternal behavior, the impact of MS on motivation for palatable food in adult male and female offspring. MS lasted 3 h/day from postnatal day (PND) 2 to PND14 and was combined with a chronic unpredictable stress in dams. We found that MS reduced body weight growth in C3H pups at PDN 15 but had no effect in C57 mice. This effect persisted into adulthood in male C3H but not in females. To investigate MS impact on motivation for palatable food, we used operant conditioning chambers, in which mice, fed ad libitum, must press one (FR1) or several times (Variable Ratio 5, VR10 and VR20) on a lever to obtain a food reward (sweet milk). MS exacerbated the motivation to obtain the palatable reward in male and female C3H mice but not in C57. In conclusion, vulnerability to early stress strongly differs between strain mice. C3H strain seems more susceptible to the long lasting effects of MS on metabolism and on motivation for food reward. Finally, to better understand the brain changes associated with MS in C3H mice, we used microarray to examine gene expression in the hypothalamus, the nucleus accumbens and the medial prefrontal cortex, three regions related to stress and reward functions

Strain-specific changes in nucleus accumbens transcriptome and motivation for palatable food reward in mice exposed to maternal separation

International audienceIntroduction In humans, adversity in childhood exerts enduring effects on brain and increases the vulnerability to psychiatric diseases. It also leads to a higher risk of eating disorders and obesity. Maternal separation (MS) in mice has been used as a proxy of stress during infancy. We hypothesized that MS in mice affects motivation to obtain palatable food in adulthood and changes gene expression in reward system. Methods Male and female pups from C57Bl/6J and C3H/HeN mice strains were subjected to a daily MS protocol from postnatal day (PND) 2 to PND14. At adulthood, their motivation for palatable food reward was assessed in operant cages. Results Compared to control mice, male and female C3H/HeN mice exposed to MS increased their instrumental response for palatable food, especially when the effort required to obtain the reward was high. Importantly, this effect is shown in animals fed ad libitum . Transcriptional analysis revealed 375 genes differentially expressed in the nucleus accumbens of male MS C3H/HeN mice compared to the control group, some of these being associated with the regulation of the reward system (e.g., Gnas , Pnoc ). Interestingly, C57Bl/6J mice exposed to MS did not show alterations in their motivation to obtain a palatable reward, nor significant changes in gene expression in the nucleus accumbens. Conclusion MS produces long-lasting changes in motivation for palatable food in C3H/HeN mice, but has no impact in C57Bl/6J mice. These behavioral alterations are accompanied by drastic changes in gene expression in the nucleus accumbens, a key structure in the regulation of motivational processes

Imported Malaria, Collapsing Glomerulopathy, and Focal and Segmental Glomerulosclerosis

International audienc