Calcium turns sinister in left-right asymmetry

A major challenge in deciphering the development of left-right asymmetry in vertebrates is uncovering how subtle early differences between the left and right sides are translated into robust differences in gene expression. Recently, Raya and colleagues suggested that asymmetric localization of extracellular calcium ions at the node could differentially modulate Notch signalling, resulting in asymmetric expression of the signalling molecule Nodal on the left side of the node. In this article, I examine the implications of this finding and explore their relevance to the evolution of asymmetry in vertebrates and invertebrates.

The neural processing of masked speech: evidence for different mechanisms in the left and right temporal lobes

It has been previously demonstrated that extensive activation in the dorsolateral temporal lobes associated with masking a speech target with a speech masker, consistent with the hypothesis that competition for central auditory processes is an important factor in informational masking. Here, masking from speech and two additional maskers derived from the original speech were investigated. One of these is spectrally rotated speech, which is unintelligible and has a similar (inverted) spectrotemporal profile to speech. The authors also controlled for the possibility of "glimpsing" of the target signal during modulated masking sounds by using speech-modulated noise as a masker in a baseline condition. Functional imaging results reveal that masking speech with speech leads to bilateral superior temporal gyrus (STG) activation relative to a speech-in-noise baseline, while masking speech with spectrally rotated speech leads solely to right STG activation relative to the baseline. This result is discussed in terms of hemispheric asymmetries for speech perception, and interpreted as showing that masking effects can arise through two parallel neural systems, in the left and right temporal lobes. This has implications for the competition for resources caused by speech and rotated speech maskers, and may illuminate some of the mechanisms involved in informational masking.