Reviews & Analysis

Reward-related events activate dopamine and other neurons in many brain areas. A report in Nature, however, now suggests that neurons in the lateral habenula signal to dopamine neurons when no reward is expected.

Contrary to the synaptic homeostasis theory, new work finds that reactivating memories during slow-wave sleep enhances learning and hippocampal activation. This may be useful for treating post-traumatic stress disorder.

Sensory cortex area 3a contains a map of the body. A new paper reports the location of eye position signals in this map, which should allow researchers to test the functions of eye position signals and visual gain fields in more detail.

Amyotrophic lateral sclerosis (ALS) is characterized by the selective degeneration of motor neurons. Two independent studies in this issue show that astrocytes expressing a mutation in the enzyme superoxide dismutase can exacerbate motor neuron death, supporting previous suggestions that non-neuronal cells contribute to ALS pathogenesis.

Transient receptor potential (TRP) channels participate in many diverse neuronal functions. A study in this issue now shows that TRPC-dependent calcium fluxes are also crucial to neurotrophin-induced cell survival signaling.

Damage to the insula enables some smokers to quit easily and without relapse, reports a recent paper. The lesion may disrupt a a representation of internal bodily urges that is normally cued by learned drug associations.

Neurosteroids generally reduce anxiety, but a new paper shows that they promote anxiety in female mice around puberty via the selective desensitization of extrasynaptic GABA_A receptors made up of α4β2δ subunits. This change increases input resistance and excitation of hippocampal pyramidal neurons, thus promoting anxiety.

The timing of thalamocortical excitation and inhibition is critical to local microcircuits. Two new papers shed light on the development and performance of a somatosensory microcircuit that regulates the integration of thalamic inputs.

Jordan and colleagues report that activity causes the shuttling of a synaptic protein AIDA-1d from dendritic spines to the nucleus. This work sheds light on how nuclear protein synthesis is regulated in response to synaptic activity.

Two independent groups in this issue report synaptic communication between callosal axons and the NG2-positive glial precursors in the brain. Activity-dependent vesicular glutamate release from axon collaterals triggers AMPA-type currents in the precursors. This phenomenon might be involved in regulation of oligodendrocyte differentiation or remyelination.

Astrocytes modulate synaptic strength. This effect occurs, reports a new paper, because ATP-dependent vesicular release of astrocytic glutamate acts on presynaptic neuronal NMDA receptors to increase synaptic efficacy.

Sensory neurons express sets of ion channels that contribute to pain transmission. A new study finds that a sensory neuron–specific exon encodes a molecular switch that recruits other signaling pathways to N-type Ca²⁺ channels.

In the adult hippocampus, a brain region that is important for memory, new neurons are generated continuously. A study now shows that these newly generated neurons are preferentially activated during learning and recall of new memories.

A new study shows that the identity of olfactory sensory neurons in flies is regulated by Notch signaling, which divides the neurons into two classes that express specific sets of olfactory receptors and project to distinct glomeruli.

The primate prefrontal cortex is associated with cognitive operations linked to intelligence. A study in Nature now shows that prefrontal neurons represent movement sequences at an abstract level, even when not required for the task.

Humans engage in complex social interactions, including altruism. A study in this issue finds that watching a computer perform an altruistic act, earning money for charity, is sufficient to activate a brain region that has been implicated in the evaluation of others' motives and goals, suggesting that this area may be involved in detecting agency in other creatures.