Reviews & Analysis

I_h is an excitatory inward current at subthreshold voltages, but enhancing I_h in CA1 pyramidal neurons leads to inhibition of action potential firing. A report in this issue suggests activation of the potassium current I_M underlies this paradox.

A recent study in Nature shows that sister neurons of the same lineage are preferentially interconnected to each other, thereby suggesting a local guidance mechanism using chemospecific markers.

This perspective illustrates some of the problems involved in analyzing the complex data yielded by systems neuroscience techniques, such as brain imaging and electrophysiology. Specifically, when test statistics are not independent of the selection criteria, common analyses can produce spurious results. The authors suggest ways to avoid such errors.

How can the multifunctional factor Sonic Hedgehog (SHH) elicit specific responses from its target cells? A study now pinpoints proteoglycans as crucial anchors and modulators of SHH signaling, eliciting a proliferation response.

Neural stem cells transition through several progenitor stages before finally generating postmitotic neurons. New work shows that one of these steps, the generation of neuroblasts from transient amplifying precursors in the adult subventricular zone, requires downregulation of the transcription factor Sox9 by the microRNA miR-124.

What controls the functional connections between sending and receiving neurons? A new model suggests that each receiver circuit has a local switch that is controlled by the balance between excitation and inhibition.

A subset of neurons in rat barrel cortex integrate information about the object a whisker contacts with the motion of the whisker at the time of contact, setting the stage for a highly specialized object localization system.

Recent work suggests that endoplasmic reticulum stress in myelinating cells is important in the pathogenesis of various disorders of myelin, including multiple sclerosis. In this review, Lin and Popko review our current understanding of the role of endoplasmic reticulum stress in myelinating cells.

Rat models implicate epigenetic regulation of hippocampal glucocorticoid receptor expression in mediating the effects of early life experience on adult behavior. A report now suggests that the same mechanism might also be at work in humans.

Rett syndrome (RTT) is caused by mutations in the X-linked gene encoding methyl CpG–binding protein (MeCP2). The loss of MeCP2 function in neurons was thought to cause the disease. A study now challenges this assumption by showing that MeCP2 is expressed in glia and that MeCP2 loss in glia causes abnormalities in neighboring neurons.

The ependymal cells lining the lateral ventricles are not stem cells, but a study now shows that they can be activated to generate neuroblasts in a stroke model, and mature olfactory bulb neurons when Notch signaling is disrupted.

Previous studies have attempted to decode functional imaging data to infer the perceptual state of an observer, but the level of detail has been limited. A new decoding study reconstructs accurate pictures of what an observer has seen.

Brain development requires precise control of progenitor proliferation and differentiation. PML appears to be a crucial regulator of cortical progenitors, limiting proliferation and promoting the generation of committed neuronal precursors.

Many sensory brain areas are characterized by a specific spatial organization, with neurons being ordered according to their similarity in receptive field properties. A surprising new study provides evidence that the organization of glomeruli in the olfactory bulb violates this anatomical principle, suggesting that olfaction might work by a different set of rules.

ProBDNF has been proposed to alter synaptic plasticity, but whether it is normally released from neurons has been a matter of contention. New work suggests that proBDNF is indeed secreted from central neurons.

The floor plate can generate neurons, but does so only in the midbrain. New work shows that Shh suppresses floor plate neurogenesis, and that in the midbrain, Wnt downregulates Shh expression via canonical signaling through β-catenin.

The in vitro reconstitution of vesicular glutamate transport reveals that the transporter itself antiports chloride ions and suggests that extracellular chloride concentrations may determine neurotransmitter refilling and quantal size.

Cortical and thalamic contribution to V1 neuron response properties is thought to be fixed. New work overturns this assumption, showing that the spread of corticocortical activation can be strongly modulated by stimulus strength.

Research indicates that sleep influences learning, but little is known about the mechanisms involved. A recent article suggests that sleep modifies the firing patterns of sensorimotor neurons before there is improvement in performance.