Opinion in 2009

In this Opinion article, the similarities in molecular composition, organization and function of chemosensory receptive endings and neuron–neuron synapses are considered. Based on these parallels, Shai Shaham suggests that chemosensory structures will provide useful models of the neuronal synapse.

The orbitofrontal cortex has a role in flexible behaviour. schoenbaum and colleagues discuss recent data suggesting that it signals expected outcomes and propose that this role also explains how it can mediate flexible behaviour in the face of unexpected outcomes.

MicroRNAs have crucial regulatory roles at the post-transcriptional level and are emerging as key players in the development of the nervous system in many species. In this Opinion article, Kosik discusses how these non-coding transcripts could drive evolutionary change.

In this provocative Perspective, Jerry Siegel shows that many aspects of sleep differ greatly between species and conditions, such that a universal, vital function of sleep is unlikely. He argues that sleep benefits animals simply by increasing the efficiency of their activity.

The olfactory glomeruli represent a remarkable example of nervous system organization — each glomerulus is innervated exclusively by sensory neurons expressing one of more than 1,000 olfactory receptors. Firestein and colleagues discuss recent insights into glomerular development that highlight the importance of signalling activity in this process.

Recent advances in brain–machine interface technology have allowed neuroscientists to gain insights into the principles underlying information processing in the CNS. Nicolelis and Lebedev propose a series of principles of neural ensemble physiology that have arisen from this research.

Understanding the mode of cortical cholinergic neurotransmission, which is thought to mediate attentional tasks, is key to finding effective treatments for a range of cognitive disorders. Sarter and colleagues contrast evidence for volume and phasic transmission and conclude that the latter is more significant for attentional tasks.

Two neurons can be connected by multiple synaptic contacts with different likelihoods of neurotransmitter release. Branco and staras discuss the role of feedback regulation from the postsynaptic site in determining this probability at individual synapses and consider the possible functional advantages of variable neurotransmitter release.

Stress induces the release of many stress mediators in the brain. Joëls and Baram show that the spatial and temporal niches of action of these mediators overlap and discuss how different mediators interact to enable appropriate responses to diverse stressors.

Imaging studies show activation of the motor cortex during speech perception. In this Perspective, Scott and colleagues discuss different possible roles for the motor system in speech processing and propose that it has a specific function in conversation.

The effects of the glial scar on regeneration after injury have traditionally been viewed as inhibitory. Schwartz and colleagues discuss the evidence that scar tissue can have a beneficial role in the repair process and propose that the timing of scar generation and degradation is crucial in determining its effects.

The existence of neural stem cells (NSCs) in the walls of the lateral ventricle is well known, yet debate about the precise identity of these cells continues. Weiss and colleagues describe tools used to study NSCs and consider the controversies in the field.

The anterior insular cortex is activated by a wide range of conditions and behaviours that go beyond interoception. In a provocative Perspective, Bud Craig proposes that the anterior insula has a fundamental role in human awareness.