White matter and reaction time: Reply to commentaries

We appreciate the many comments we received on our discussion paper and believe that they reflect a recognition of the importance of this topic worldwide. We point out in this reply that there appears to be a confusion between the role of oscillations in creating white matter and other functions of oscillations in communicating between neural areas during task performance or at rest. We also discuss some mechanisms other than the enhancement of white matter that must influence reaction time. We recognize the limited understanding we have of transfer and outline some future directions designed to improve our understanding of this process.

How changes in white matter might underlie improved reaction time due to practice

Why does training on a task reduce the reaction time for performing it? New research points to changes in white matter pathways as one likely mechanism. These pathways connect remote brain areas involved in performing the task. Genetic variations may be involved in individual differences in the extent of this improvement. If white matter change is involved in improved reaction time with training, it may point the way toward understanding where and how generalization occurs. We examine the hypothesis that brain pathways shared by different tasks may result in improved performance of cognitive tasks remote from the training.

Developments in real-time radon monitoring at Stromboli volcano

We present the results of one year of continuous radon monitoring at Stromboli volcano collected at two automated real-time stations. These were deployed on the NE flank (at 520 m a.s.l.) and within the summit area (900 m a.s.l.). Higher daily emissions at the lower station approached 4,200 Bq/m³, with bulk averages around 1,800 (±980) Bq/m³; whereas the summit station reached peak values of 23,000 Bq/m³ and bulk averages of 12,500 Bq/m³ (±4,000). Negative correlations are observed between radon emissions, soil temperature and, to a lesser extent, atmospheric pressure. In contrast, increases in radon concentrations were observed during periods of higher rainfall conditions. Therefore, trends in radon concentrations may be decoupled from those of other geochemical parameters (CO₂ fluxes and CO₂/SO₂ plume ratios) during periods of heavy to moderate rainfalls. Multiple Linear Regression statistics (including the effects of soil temperature, atmospheric pressure and tidal forces) led us to compute the residuals given by the difference of measured and calculated ²²²Rn concentrations. The cross-check between the daily measured radon activities and the absolute variations in radon residuals, for the data collected at the summit station, give us the opportunity to suggest a methodological approach that can be used in the attempt of predicting some major changes in volcanic activity.

Cornichon regulates transport and secretion of TGFα-related proteins in metazoan cells

Cornichon proteins are structurally related transmembrane proteins that have been studied in and Drosophila and yeast. In Drosophila, Cornichon (Cni) is involved in embryo polarization by the TGFα-related Gurken. In yeast, the Cni-related Erv14 is required for axial budding. A cargo receptor function has been proposed for Erv14 and Cni. Four mammalian Cni-like sequences have been identified. We carried out parallel functional analyses of the human Cni ortholog CNIH and Drosophila Cni in the processing and presentation of TGFα family proteins. Human CNIH complements the loss of Erv14 in yeast. Human CNIH and Drosophila Cni are primarily localized in the endoplasmic reticulum and associate with immature TGFα family proteins. Alterations of cornichon expression result in changes in transport, processing and secretion of TGFα proteins. In particular, increased cornichon expression retains TGFα proteins in the endoplasmic reticulum, whereas cornichon is required for their transport and secretion. Thus, cornichon proteins represent a functionally conserved protein family that acts in the selective transport and maturation of TGFα family proteins.

Effect of low-frequency ultrasound on peritoneal transport in rabbits

It has recently been suggested that sonophoresis, or the application of ultrasound (US) in the kilohertz range, could enhance peritoneal mass transport. To examine this hypothesis, six nephrectomized rabbits were exposed to ultrasound while under isoflurane anesthesia. An additional five also had bilateral nephrectomies and were used as a control group. Each group underwent four exchanges of 90 minutes duration with 1.5% dextrose while anesthetized. Dialysate samples were taken at 0, 30, 60, and 90 minutes and assayed for urea, creatinine, glucose, and protein. Blood samples were taken pre- and postexchange. In the US group, 20 kHz ultrasound was applied during exchanges 2 and 3 at 47.5 W and 95 W, respectively, using a Virsonic 475 cell disrupter acoustically coupled to the abdomen through a water column and gel-coated PVC membrane. Results were analyzed by calculating the mass transfer area coefficient (MTAC) and 90-minute D/P values for each exchange. No significant differences were observed in the absolute means of either parameter between the control and US groups. However, when exchanges 2 to 4 were normalized with respect to exchange 1, the resulting urea D/P means were less for the US exchanges compared to the control (p < 0.05). This suggests a possible decrease in transport through US application.