Volume 19 Issue 2, February 2016

A previously unknown mechanism contributes to dysfunction of the neurogenic niche during CNS autoimmunity. Natural killer cells are retained specifically in the subventricular zone in chronic disease, killing stem cells and promoting pathology.

Connections between a specific thalamic structure and the neocortex convey mismatches between internal perceptions and external events. These findings help to define the circuits controlling contextual modulation of visual-motor processing.

The most complete single-neuron transcriptome database of the mouse visual cortex was performed using a large collection of reporter mouse lines. Results highlight the unmatched neuronal diversity of the cerebral cortex.

The role of transient elevations of the intracellular concentration of calcium in astrocytes is controversial. Some neuroscientists believe that, by triggering the release of 'gliotransmitters', astrocyte calcium transients regulate synaptic strength and neuronal excitability, while others deny that gliotransmission exists. Bazargani and Attwell assess the status of this rapidly evolving field.

Dynamic membrane transformations are not exclusively controlled by cytoskeletal rearrangement, but also by biophysical constraints, adhesive forces, membrane curvature and compaction. Recent technological advances have helped clarify longstanding controversies concerning myelination, from target selection to axon wrapping and membrane compaction. Chang et al. review these findings and discuss how understanding these processes provides insight into myelination-centered mechanisms of neural plasticity.

Stuber and Wise review the role of the lateral hypothalamic area (LHA) in generating motivated behaviors related to feeding and reward processing. Classic experiments demonstrate that the LHA is critical for reward processing, and more contemporary approaches are beginning to elucidate the cells types and circuits required for these behaviors.

Central melanocortinergic signaling via the melanocortin-4 receptor is both a culprit in and a target for obesity. The authors review our understanding of this evolutionarily conserved system in the regulation of mammalian energy homeostasis.

Neuropathic pain poses a major healthcare burden. The authors show that a specific set of neurons in the nucleus accumbens, a region long associated with affect, were changed in a mouse model of neuropathic pain. A pharmacotherapy that is well tolerated in man reversed these adaptations and alleviated pain.

Impairment of cognitive function is a common feature of many neurodevelopmental disorders. Systems genetics analysis in the brain uncovered a convergent gene network for both cognition and neurodevelopmental disorders. As the network does not recapitulate known pathways, this finding represents a new basis for understanding factors influencing normal and disordered cognition.

GABA_B receptors are the most abundant inhibitory G protein–coupled receptors in the mammalian brain. Using high-resolution proteomics, the authors show that native GABA_B receptors are macromolecular complexes with previously unknown complexity in subunit composition. This molecular diversity in structure and assembly encodes the diversity of GABA_B physiology in the CNS.

Natural killer (NK) cells are retained and reside in the vicinity of neural stem cells (NSCs) in the brain subventricular zone during the chronic phase of multiple sclerosis in humans and its animal model in mice. In this study, the authors show that these NK cells limit NSCs' reparative capacity following brain inflammation, while NSCs promote NK survival via an interleukin-15-dependent mechanism.

The authors find that Kif1a has sequential roles during cortical development. Kif1a inhibition blocks basal nuclear migration in radial glial progenitor cells, resulting in a persistent proliferative state. Kif1a inhibition subsequently disrupts neuronal migration at the multipolar-to-bipolar transition, with a massive non-cell-autonomous arrest of surrounding neurons. These effects are phenocopied by Dcx RNAi and rescued by BDNF, a Kif1a cargo protein.

Adult-born neurons are already contributing to learning and memory at immature developmental stages. Heigele et al. show that during the first 3 weeks after mitosis, the young cells fire action potentials generated by excitatory GABAergic synapses. Strong GABAergic synaptic activity, however, inhibits spiking, thereby generating a well-defined GABAergic excitation window.

The serotonergic raphe nuclei modulate neuronal function typically over minutes or hours. The authors report that raphe nuclei affect odor responses in output neurons of the olfactory bulb at sub-second time scales. These effects are mediated through multiple neurotransmitters and are distinct depending on the type of output neuron.

Animals can fear specific objects with no previous experience. For example, naive mice are innately afraid of cats. Here the authors employed optogenet­ics and behavioral assays to determine the neural circuit mechanisms involved in mediating olfactory cue–induced innate fear in mice.

The authors identify a new arousal circuit in the mammalian brain. They provide correlative and optogenetic evidence indicating that a subset of hypothalamic cells drive awakening from non-rapid eye movement (slow-wave) sleep and emergence from anesthesia by exerting a strong inhibitory tone onto reticular thalamic neurons.

Current models of active vision emphasize the role of intracortical feedback projections. The authors report that thalamocortical projections, in particular from the higher order lateral posterior nucleus, provide an alternative pathway by which contextual sensory and motor information, as well as putative visuomotor error signals, are conveyed to primary visual cortex.

The authors measured the orientation tuning of ∼28,000 thalamic boutons and ∼4,000 neurons in layers 1–5 of awake mouse V1. With adaptive optics allowing accurate measurement of deep tissue activity, around half of the boutons in layer 4 were found to carry orientation and direction information.

The authors used two-photon imaging to measure the orientation tuning of thalamic boutons and neurons in mouse V1. They found that a smaller fraction of thalamic boutons in layer 4 than in superficial cortical layers carried orientation and direction information.

Several prominent theories propose that, in situations affording more than one possible action, the brain prepares, in parallel, multiple competing movements before selecting one. The authors provide evidence for this idea, showing that individuals simultaneously specify distinct feedback gains, a critical component of control, for competing target options.

The authors propose that deciding where to look and reach depends on how neurons in the posterior parietal cortex communicate with each other. They find that ‘dual-coherent’ neurons, which tend to fire spikes timed to neural activity within and across the banks of the intraparietal sulcus, predict look-reach choices before neurons without this property.

Mammalian cortex comprises a variety of cells, but the extent of this cellular diversity is unknown. The authors defined cell types in the primary visual cortex of adult mice using single-cell transcriptomics. This revealed 49 cell types, including 23 GABAergic, 19 glutamatergic and 7 non-neuronal types.