Reviews & Analysis

A new study shows that amyloid plaques tagged with fluorinated ligand can be detected with ¹⁹F MRI in transgenic mice. The superior signal to noise of this technique is a major step toward visualizing the histopathology of Alzheimer disease in living patients.

A report in Nature describes a physiological screen used to identify a previously unknown chemical signal in mouse urine. The chemical's selective response in the olfactory bulb raises interesting questions for how socially relevant odors are encoded.

A new model by Machens et al. proposes a mechanism by which prefrontal cortex neurons can do two jobs that are normally thought to occur independently. In a stimulus comparison task, these model neurons both cast votes for a stimulus and make decisions.

The outer photoreceptors of Drosophila project to their targets in an extremely intricate pattern. Prakash et al. in this issue show that homophilic adhesion via N-cadherins is an essential part of the axon guidance mechanism in this system. The new results suggest that axons respond to the level of N-cadherins, and not to any combinatorial cadherin code, as had been postulated previously.

A new paper quantifies the dependence of synaptic transmission on transient local changes in internal calcium, examining the equilibrium dynamics of the calcium sensor for exocytosis and its contribution to short-term changes in synaptic strength.

A recent study of an Olig1 knockout mouse concludes that remyelination after injury may occur by a different mechanism from myelination during normal development, but another report suggests that this mouse model should be interpreted cautiously.

In a technical tour de force, Okhi et al. image the activity of thousands of visual cortical neurons in vivo at a single-cell resolution, and examine their orientation and direction selectivity. Their results show that cortical maps can be built with single-cell precision.

How activity-dependent synaptic plasticity shapes the development of inhibitory synapses has remained unclear. In this issue, Gillespie et al. show that in the developing rat auditory system, inhibitory synapses transiently co-release glutamate. The consequent activation of postsynaptic NMDA receptors may be critical for the plasticity mechanisms that determine tonotopic sharpening.

Having control over a stressful situation can reduce its negative physiological and cognitive consequences. In this issue, a new study in rats suggests that descending inputs from the prefrontal cortex to the serotonergic midbrain signal the controllability of stress.

Stem cells transplanted after spinal cord injury mostly generate astrocytes, which can promote aberrant sprouting of sensory neurons, leading to allodynia. Making cells produce more oligodendrocytes reduces allodynia and improves functional recovery.

Despite 20 years of study, the mechanism underlying the cochlear amplifier remains contentious. In this issue, a novel in vitro cochlear preparation implicates calcium current–driven active stereocilia motion in generating amplification.

Voltage-gated ion channels shape the integration of synaptic input in dendrites. Forebrain-restricted deletion of the hyperpolarization-activated channel HCN1 enhances spatial learning, demonstrating a behavioral role for an active dendritic conductance.

Comm downregulates the Slit receptor Robo on commissural axons, thereby enabling midline crossing. Elegant new experiments show that Comm functions by diverting Robo to the endosomal pathway, preventing its delivery to the growth cone.

Neurons in the mammalian master clock can maintain circadian rhythms in isolation, but must synchronize to function as a time-keeping system. A new study finds that gap junctions between neurons promote synchronous electrical activity and rhythmic behavior.

Moving stimuli evoke a response from a large number of neurons in cortical area MT. A new study investigates how perceptual decisions may arise from that population response, with important implications for theories of neural coding.

Amyotrophic lateral sclerosis is an incurable paralyzing disorder caused by the death of motor neurons in the spinal cord and brainstem. Patients typically die within three to five years. In this issue, Storkebaum and colleagues offer new evidence for VEGF action in motor neuron survival and new hope for direct delivery of VEGF into the nervous system as a therapy for ALS.

In a technical tour de force, whole-cell patch clamp in tiny C. elegans touch receptor neurons in vivo is used to directly record currents in response to mechanical force, providing the first direct evidence that specific proteins are mechanotransducers.