News & Views in 2005

Immature neurons in many brain regions are electrically coupled through gap junctions, which are lost as chemical synaptic transmission matures. This developmental uncoupling is now shown to require NMDA receptor activation.

The Rho-family GTPases act downstream of axon guidance receptors, controlling proteins that remodel the cytoskeleton. New work now suggests that these GTPases also team up to regulate activation of the semaphorin-3A receptor itself.

Pheromones acting through the vomeronasal system influence sexual behavior and neuroendocrine function. Two new studies show that the main olfactory system also contributes to behavioral and possibly endocrine regulation.

A study in Nature reports that nematodes can learn to associate different chemosensory stimuli with illness and to avoid these stimuli in a choice test. Elevated serotonin in a particular type of neuron was critical for this learning.

How are we able to focus our attention on the task at hand while ignoring myriad distractions? An elegant neuroimaging study in this issue finds that, contrary to a widely held view, the prefrontal cortex implements attentional control by amplifying task-relevant information, rather than by inhibiting distracting stimuli.

Not all axons in a peripheral nerve are myelinated. A recent study shows that the expression of neuregulin-1 on an axon membrane determines whether immature Schwann cells will differentiate into myelinating Schwann cells.

A new paper reports that long-term potentiation in the hippocampus, a model of learning and memory, can induce sharp wave-ripple complexes, which are thought to be critical for the stabilization of memory traces in cortex.

Why are some neurons selectively targeted for death in neurodegenerative diseases? A recent paper combines genetics in the fruit fly and mouse to uncover mechanisms underlying the vulnerability of Purkinje cells in spinocerebellar ataxia-1.

Individuals with neglect fail to process stimuli on the left. A new paper uses functional imaging to show that a restricted lesion, usually caused by a stroke, may influence the network of areas associated with attention shifts.

Cerebellin 1 is abundant in the cerebellum, but its function remains a mystery. Hirai et al. now show that this gene is required to maintain parallel fiber-Purkinje cell synapses, via the orphan glutamate receptor subunit Grid2. These findings provide further evidence that there is a molecular pathway devoted to maintenance of synapses.

Orexins are known to regulate sleep and feeding, but a study in Nature now shows that they are also involved in drug-seeking behavior. This suggests a larger role for orexin-producing neurons as an interface between internal states and motivated behaviors.

SFRPs are endogenous inhibitors of Wnt signaling. New work shows that, independently of its interaction with Wnts, SFRP1 can act as a repulsive guidance molecule for retinal axons on their way to the tectum, signaling through the receptor Fz2.

Synaptic currents become faster with age. A new study uses electron microscopy, physiology and modeling to show that the progressive speeding of AMPA receptor–mediated synaptic currents during development results from changes in the structure of the synapse rather than the composition of postsynaptic receptors.

Inhibitory cortical neurons are thought to generate temporally precise signals important for information processing, but a new study shows that CCK-expressing interneurons continue to release GABA for several hundred milliseconds after bursts of action potentials.

The attentional blink reveals a fundamental limit in the temporal resolution of attention. By describing the entire sequence of electrophysiological events underlying the blink, a new study provides the first glimpse into the neural cause of this bottleneck.

Certain Wnts attract ascending somatosensory axons up the spinal cord toward the brain. A study in this issue shows that other Wnts guide corticospinal axons down the spinal cord, not by an attractive mechanism but by repulsion through the receptor Ryk.