News briefs

What we hear is processed by the brain in waves

Australian and Italian researchers have provided important new evidence for the cyclical nature of perception in an article published in Current Biology. They found that the sensitivity for detecting weak sounds is not constant in humans, but fluctuates regularly. The oscillation in sensitivity occurs separately for the two ears, first one then the other, switching every one-tenth of a second. This occurs so rapidly that we are normally unaware of it, but it can be detected in highly sensitive experiments. Oscillations have previously been reported for visual perception but not in audition. One reason for the failure to detect auditory oscillations previously is that the sensitivity of the two ears have been assessed together, whereas the new work shows that sensitivity alternates between the two ears, a subtle phenomenon missed by past studies. The new findings are important for many reasons. First, they show that oscillations are a general feature of perception, and not specific to vision. Second, the alternation in sensitivity between the two ears suggests that the brain samples input from each alternately, focusing attention on one ear at a time, allowing the brain to tag the ear of origin, important for many perceptual tasks. Third, the study showed that not only does sensory sensitivity alternate at a specific rhythm, but decision criterion also oscillates at a subtly different frequency.

http://www.cell.com/current-biology/fulltext/S0960-9822(17)31320-9

Is vitamin D linked to fertility treatment success?

UK researchers are calling for a randomised clinical trial to investigate the potential role of vitamin D supplementation in improving live birth rates after assisted reproduction treatment (ART). This follows a review and meta-analysis published in Human Reproduction that found a strong link between low vitamin D concentrations (≤ 75 nmol/L) in women and lower live birth rates after ART than in women with adequate levels (> 75 nmol/L). The researchers cautioned that their findings did not mean that vitamin D supplementation necessarily improved a woman’s chance of a baby following ART, as their research detected an association between vitamin D levels and live birth rate, but was not designed to determine a causal link. The researchers analysed data from 11 published studies that included 2700 women undergoing ART (in vitro fertilisation, intracytoplasmic sperm injection, or frozen embryo transfer) and whose blood levels of vitamin D had been measured. They found that the live birth rate was one-third higher in women with adequate vitamin D levels than in those with low levels. A similar result was seen when the researchers examined the results of pregnancy tests and clinical pregnancies (where a fetal heartbeat could be detected). Compared with women who had deficient (≤ 75 nmol/L) or insufficient concentrations of vitamin D (≤ 50 nmol/L), women with sufficient vitamin D were 34% more likely to have a positive pregnancy test and 46% more likely to achieve a clinical pregnancy. No associations were found between miscarriage and vitamin D concentrations.

https://academic.oup.com/humrep/advance-article/doi/10.1093/humrep/dex326/4582928