Sleep

Local sleep and learning. Huber, R. et al. Nature 6 June 2004 (10.1038/nature02663)

After performing a motor learning task that activates the right parietal cortex, subjects slept while their electroencephalogram was recorded. Slow-wave activity showed a local increase over the right parietal cortex in those subjects who had undergone the learning task. The local increase in slow-wave activity resembled the more global increase that is seen after prolonged wakefulness and is thought to represent sleep pressure, and also correlated with a subsequent improvement in performance.

Functional Imaging

The hippocampal system mediates logical reasoning about familiar spatial environments. Goel, V. et al. J. Cogn. Neurosci. 16, 654–664 (2004)

Logical reasoning about familiar situations engages a different brain network from logical reasoning about unfamiliar situations. Goel et al. show that this dissociation also holds for logical reasoning about spatial environments. A reasoning task that involved familiar spatial environments, such as countries, activated a hippocampal network, whereas one that involved unfamiliar spatial environments, such as fictitious labs, activated areas that are associated with visuospatial processing.

Development

The prepattern transcription factor Irx2, a target of the FGF8/MAP kinase cascade, is involved in cerebellum formation. Matsumoto, K. et al. Nature Neurosci. 7, 605–612 (2004)

Matsumoto and colleagues characterise Irx2, a homeobox gene that is expressed in the rhombic lip of the rostral hindbrain, which develops into the cerebellum. FGF8, expressed by the isthmus, organizes the developing cerebellum. The activation of Irx2 is modulated by the FGF8 and mitogen-activated protein kinase signalling pathway. When Irx2 and Fgf8a are coexpressed in the chick midbrain, this area develops into cerebellum, showing the importance of Irx2 as a prepattern transcription factor.

Cell Biology of the Neuron

Intraflagellar transport genes are essential for differentiation and survival of vertebrate sensory neurons. Tsujikawa, M. & Malicki, J. Neuron 42, 703–716 (2004)

Many sensory neurons have cilia, and these tiny structures have important roles. Tsujikawa and Malicki show that, in the zebrafish, mutation of the ovl gene causes a deficit in ciliary transport that prevents photoreceptors, auditory hair cells and olfactory neurons from being able to maintain their cilia. Loss of cilia is followed by degeneration of the sensory cells.