Reviews & Analysis

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.

In the adult brain, new neurons are generated from neural stem cells residing in the subventricular zone. Newborn neuroblasts release the transmitter GABA, which reduces the proliferation of stem cells—and thereby neurogenesis—by a nonsynaptic mechanism.

Object identification improves with repeated presentation, but neural activity decreases. In a new study, disrupting inferior frontal activity with transcranial magnetic stimulation during initial exposure to an object blocks later behavioral and neural changes.

Neurofibrillary tangles, composed of tau protein, are a central feature of Alzheimer disease. A new paper challenges the idea that these tau inclusions alone cause disease by showing that they can be dissociated from memory impairment and neuronal loss.

Choosing to accept enough risk, but not too much, is an important survival skill, and depending on the circumstances, animals may either seek or avoid risk. Given the choice between a sure bet and a larger but uncertain reward, a paper in this issue reports macaques consistently take the riskier option, and posterior cingulate cortex neurons represent the riskiness of those choices.

Voluntarily paying attention to one object in a crowded scene enhances perception of that object and increases the activity of neurons representing it. Attention can also be drawn involuntarily by salient objects—for example, by the sudden onset of a bright stimulus. A study now shows how this involuntary type of attention may mediate competition between representations in human visual cortex.

Aβ peptide is linked to Alzheimer pathology, but its toxic mechanism remains unclear. New work shows that Aβ leads to internalization of NMDA receptors, reducing their availability at synapses. The authors also suggest a molecular mechanism for this endocytosis.

Cerebral cortex size in individuals and species is determined by cortical progenitor mitosis and death during embryogenesis. EphA signaling—important in axon guidance and patterning—also seems to be critical in regulating the survival of cortex progenitors.

A new paper shows that the transcription factor Dlx1, known to be involved in neuronal migration, is also necessary for interneuron survival. Mice lacking Dlx1 show subtype-specific loss of interneurons, a reduction in inhibitory currents and generalized seizures.

Reward-sensitive neurons are present throughout the brain. A report in Science now shows that a subset of thalamic neurons respond selectively to the smaller of two rewards, as opposed to just reflecting reward magnitude, as do neurons in other brain areas.

Empathy refers to our ability to share emotions and sensations such as pain with others. Imaging studies on pain showed that the affective but not sensory component of our pain experience is involved in empathy for pain. In contrast, a new study using transcranial magnetic stimulation highlights for the first time the role of sensorimotor components in empathy for pain in other people.

Although we hear sounds throughout their duration, studies on anesthetized animals have suggested that auditory cortex neurons primarily detect changes in sound. New evidence in a report in Nature from awake animals is forcing us to reconsider this view.