News & Views in 2007

A new paper reports that dopaminergic neurons initially responded optimistically in rats given free choice between two rewards, as though the animal had chosen the better reward, even on trials when it failed to do so. These findings suggest that current computational theories of dopaminergic function may need to be revised.

Brain microglia increase their numbers in response to threats. Some of these cells were thought to enter the CNS from the blood, but two new studies suggest that experimental confounds could in part account for such results.

A recent study in Nature now shows that the main olfactory bulb contains a particular zone required for innate odor aversion, indicating that olfactory receptors have behavioral as well as chemical specificity.

Maintaining a precise representation of sound frequency in auditory cortex is difficult because of converging diffuse thalamocortical inputs. A recent study demonstrates that this is accomplished via recurrent intracortical connections.

Neural activity leads to the mobilization of energy from glycogen in astrocytes. A new paper reports that neurons have an ambivalent relationship with glycogen: they can synthesize it themselves, but that synthesis induces apoptosis. Presumably for this reason, neurons normally inhibit glycogen synthesis through two redundant pathways.

Faced with the metaphorical glass, most people see it as being half full. A new study shows that activity in two limbic areas, the rostral anterior cingulate cortex and amygdala, reflects an optimistic attitude.

Receptor neurons may not encode sensory information in an efficient manner. A new paper supports the idea that the brain achieves optimal encoding downstream of sensory transduction through additional processing.

Figure-ground segmentation is a key early step in visual perception. A study now finds that V2 neurons in monkeys signal border ownership pre-attentively and that the effects of attention are predicted by the neurons' border preferences.

Maintaining balance requires the translation of a high-level command—“Keep the body's center of mass over the feet”—to low-level adjustments in individual muscles and joints. A new paper finds that a simple translation between these two levels of control provides a robust explanation for responses to several types of perturbations.

A study in this issue reports that, in mice, embryonic cortical neurons transplanted into injured adult motor cortex can rapidly and accurately reinnervate distant projections. These remarkable results urgently need to be replicated.

Despite the widespread use of functional magnetic resonance imaging, we still do not fully understand what it measures. A new study reports that oxygen-concentration changes and local field potentials are concurrent in time and space.

The identity of the tip link, which converts mechanical force to channel opening in hair cells, has been controversial, with different groups promoting cadherin 23 or protocadherin 15. A new paper in Nature shows that both proteins are involved.

Precursors in the dorsal pallium were thought to give rise exclusively to neocortex during development. A new study finds that a stream of migrating cells from this area also gives rise to a nucleus in the amygdaloid complex.

The mechanisms of sleep have been studied in Drosophila melanogaster, which show behaviors reminiscent of sleep in vertebrates. A new study identifies a growth factor signaling pathway involved in sleep regulation and consolidation in this model. Inhibiting this pathway causes a sleep pattern that is similar to insomnia in humans.

Lasting synaptic plasticity requires precise local regulation of protein expression. A recent paper reports that the postsynaptic activity–induced arc mRNA is a target for rapid degradation by the 'nonsense-mediated decay' pathway.

Memories for motor skills become resistant to interference during wakefulness within a few hours. A new study shows that such stabilization occurs faster during sleep, possibly by activating a different type of consolidation.

Central pattern generators provide the basic stepping pattern in walking, but cannot adjust for the environment. A new study of human locomotion shows a pattern of changes in independent neural controllers for left and right legs.

Pheromones influence sexual behavior and reproduction in rodents. A new report suggests that neurogenesis induced in the female mouse brain by male pheromones governs the choice of dominant males as mates.

Brain-derived neurotrophic factor (BDNF) is important in regulating synaptic plasticity in the brain areas that process reward information. A new study reports that BDNF in the nucleus accumbens, a brain area critical for the rewarding effects of cocaine, promotes persistent cocaine-seeking behaviors and heightens relapse vulnerability.