In Brief

Cognitive neuroscience

Shrinkage of the entorhinal cortex over five years predicts memory performance in healthy adults. Rodrigue, K. M. & Raz, N. J. Neurosci. 24, 956–963 (2004)

In a five-year longitudinal study, Rodrigue and Raz tested whether shrinkage of the entorhinal cortex, hippocampus or prefrontal cortex of healthy adults could predict episodic memory performance. Although none of the regional volumes was associated with memory performance, greater shrinkage in the entorhinal cortex was associated with poorer memory performance at the end of the study. The shrinkage of the hippocampus and prefrontal cortex did not predict memory performance.

Sensory physiology

Mustard oils and cannabinoids excite sensory nerve fibres through the TRP channel ANKTM1. Jordt, S. -E. et al. Nature 427, 260–265 (2004)

Isothiocyanate compounds, such as the active ingredients in mustard, produce pain, inflammation and hypersensitivity when applied to the skin. Jordt and colleagues show that the application of mustard oil depolarizes the same primary sensory neurons as are activated by capsaicin, the 'hot' ingredient in chilli peppers, and by Δ⁹-tetrahydrocannabinol (THC), the active ingredient in marijuana. Both allyl isothiocyanate and THC activate a TRP (transient receptor potential) ion channel called ANKTM1.

Development

Paraxial mesoderm specifies zebrafish primary motoneuron subtype identity. Lewis, K. E. & Eisen, J. S. Development 131, 891–902 (2004)

Signals from the paraxial mesoderm specify distinct populations of motor neurons in vertebrates. Lewis and Eisen show that the paraxial mesoderm is also the origin of signals that control the more precise patterning of primary motor neurons in the zebrafish, giving rise to a segmentally repeated pattern of two subtypes of motor neuron. In the absence of paraxial mesoderm-derived signals, primary motor neurons seem to have a hybrid identity.

Glia

Astrocyte-mediated activation of neuronal kainate receptors. Liu, Q. -S. et al. Proc. Natl Acad. Sci. USA 6 February 2004 (10.1073/pnas.0306731101)

To test whether glutamate released by astrocytes in rat hippocampal slices activates kainate receptors on neighbouring neurons, Liu et al. used o-nitrophenyl-EGTA to uncage Ca²⁺. Increases in intracellular Ca²⁺ in astrocytes increased action-potential-driven spontaneous inhibitory postsynaptic currents in nearby interneurons. The effect was blocked by kainate receptor antagonists but not by antagonists of other glutamate receptor subtypes. Astrocytes might therefore be an important modulator of neuronal function in the hippocampus.