Biology subjects

Verhulst, S.

Publications and source records attributed to Verhulst, S..

4 recordsLinked to original sources

bioRxiv2018

Supra-threshold psychoacoustics and envelope-following response relations: normal-hearing, synaptopathy and cochlear gain loss

The perceptual consequences of cochlear synaptopathy are presently not well understood as a direct quantification of synaptopathy is not possible in humans. To study its role for human hearing, recent studies have instead correlated changes in basic supra-threshold psychoacoustic tasks with individual differences in subcortical EEG responses, as a proxy measure for synaptopathy. It is not clear whether the reported missing relationships between the psychoacoustic quantities and the EEG are due to the adopted methods, or to a minor role of synaptopathy for sound perception. We address this topic by studying the theoretical relationship between subcortical EEG and psychoacoustic methods for different sensorineural hearing deficits.

neuroscience↗

bioRxiv2018

Body mass aging trajectory is modulated by environmental conditions but independent of lifespan

How lifespan associates with aging trajectories of health and disease is an urgent question in societies with increasing lifespan. Body mass declines with age are associated with decreased organismal functioning in many species. We tested whether two factors that decreased lifespan in zebra finches, sex and manipulated environmental quality, accelerated the onset and/or rate of within-individual body mass declines. We subjected 597 birds for nine years to experimentally manipulated foraging costs (harsh = H, benign = B) during development and in adulthood in a 2x2 design. This yielded four treatment combinations (HH, HB, BH, BB). Harsh environments during development and in adulthood decreased average body mass additively. In males, the aging trajectory was quadratic, with a maximum between 3.5 and 4 years, and independent of the environment (HH=HB=BH=BB). In females, the shape of the aging trajectory differed between environments: a quadratic trajectory as in males in the benign adult environment (HB=BB), a linear decline when benign development was followed by harsh adulthood (BH) and a linear increase when in a lifelong harsh environment (HH). We found no evidence for an association between lifespan and body mass aging trajectories either between or within experimental groups. However, females lived shorter than males, and their body mass decline started earlier for most treatment combinations. Thus, we conclude that foraging conditions can affect the shape of body mass aging trajectories, but these are independent of lifespan.

ecology↗

bioRxiv2018

Contributions of Low- and High-Frequency Sensorineural Hearing Deficits to Speech Intelligibility in Noise

The degree to which supra-threshold hearing deficits affect speech recognition in noise is poorly understood. To clarify the role of hearing sensitivity in different stimulus frequency ranges, and to test the contribution of low- and high-pass speech information to broadband speech recognition, we collected speech reception threshold (SRTs) for low-pass (LP < 1.5 kHz), high-pass (HP > 1.6 kHz) and broadband (BB) speech-in-noise stimuli in 34 listeners. Two noise types with similar long-term spectra were considered: stationary (SSN) and temporally modulated noise (ICRA5-250). Irrespective of the tested listener group (i.e., young normal-hearing, older normal- or impaired-hearing), the BB SRT performance was strongly related to the LP SRT. The encoding of LP speech information was different for SSN and ICRA5-250 noise but similar for HP speech, suggesting a single noise-type invariant coding mechanism for HP speech. Masking release was observed for all filtered conditions and related to the ICRA5-250 SRT. Lastly, the role of hearing sensitivity to the SRT was studied using the speech intelligibility index (SII), which failed to predict the SRTs for the filtered speech conditions and for the older normal-hearing listeners. This suggests that supra-threshold hearing deficits are important contributors to the SRT of older normal-hearing listeners.

neuroscience↗

bioRxiv2018

Epigenetic inheritance of telomere length in wild birds

Telomere length (TL) predicts health and lifespan in humans and other organisms, making the identification of the causes of TL variation of interest. At conception, zygotes inherit genes that regulate TL during early development, but at the same time already express a phenotype, which is the TL of the parental gametes that formed the zygote. Whether the effect of gamete TL is transient or affects TL for life depends on the extent to which regulatory genes compensate for gamete TL variation during early development. A carry-over effect of parental TL, resulting in epigenetic inheritance, has been suggested to explain the observed relationship between parental age and offspring TL in humans and other species. However, reports of parental age effects are based on cross-sectional data, and age at reproduction has numerous confounds. Furthermore, parental age may affect offspring telomere dynamics between conception and sampling, which could also explain the paternal age effect. Using longitudinal telomere data of jackdaw parents and their chicks, we show that chicks hatched with shorter telomeres as individual fathers aged, whereas mother age had no effect. By cross-fostering eggs, we confirmed the paternal age effect to be independent of paternal care after conception. The epigenetic effect accounted for 34% of the variance in offspring TL that was explained by paternal telomere length; the remaining 66% we ascribe to a combination of environmental and additive genetic effects. Thus, our results strongly indicate epigenetic inheritance of TL, with potential consequences for offspring fitness prospects.\n\nSignificance statementTelomeres are DNA-protein structures at chromosome ends and their length predicts remaining lifespan in humans and other organisms. Variation in telomere length is thought to be largely of genetic origin, but telomere inheritance may be unusual because a fertilised cell already has a telomere length (most traits are first expressed later in life). Telomeres shorten with age, and, using long-term individual-based data of jackdaw families, we show that as fathers aged, they produced chicks with shorter telomeres. This shows that paternal telomere length directly affects offspring telomere length, i.e. is inherited genetically but without the involvement of genes. This is known as an epigenetic effect and explained a large part ([≥]34%) of the telomere resemblance between fathers and their offspring.

genetics↗