Volume 21 Issue 1, January 2018

New studies provide compelling evidence that the number and length of myelin sheaths generated by oligodendrocytes in the CNS are controlled by local calcium levels, linking axonal activity to individual myelin sheath formation.

Both nucleus accumbens and orexin play clear roles in motivated behavior, but the functions of orexin projections to accumbens are poorly understood. Blomeley et al. show that this pathway, via specific orexin excitation of dopamine D2 receptor–expressing neurons, can inhibit reward seeking and exploratory drive when danger is perceived.

Super-resolution optical imaging of presynaptic terminals shows that a protein essential to all known forms of neurotransmitter release is clustered in small assemblies that likely correspond to release sites for synaptic vesicle fusion.

The medial entorhinal cortex contains spatially selective grid cells, whose lattice-like firing patterns are proposed to support path-integration-based navigation. However, direct behavioral evidence has been lacking. Gil et al. disrupt grid cells in a targeted manner, establishing a clear link between grid cell codes and navigation.

The glial scar plays critical but divergent roles during regeneration of the mammalian CNS. Here the authors propose that in-depth analysis of the functionally heterogeneous populations of reactive glia within the scar is needed to fully understand the glial scar’s dual nature.

A genome-wide association study of delay discounting (DD) on 23,127 subjects found that genotype accounted for 12% of variance in DD; the DD genetic signature overlapped with ADHD, schizophrenia, depression, smoking, personality, cognition and weight.

The authors live-image zebrafish myelin sheath Ca²⁺ activity in vivo and find that high-amplitude long-duration Ca²⁺ transients precede calpain-dependent sheath retractions while frequent low-amplitude short-duration transients drive sheath growth.

Myelin formed by oligodendrocytes enables rapid, energy-efficient information transmission in CNS, but its development is unclear. The authors show that the rate of intracellular calcium transients regulates elongation of developing myelin sheaths.

Most species exhibit instinctive risk-avoidance, e.g., lab mice avoid predator smells despite having never encountered predators. Here the authors show how innate risk-avoidance arises from accumbal dopamine receptor neurons tuned by orexin signals.

Synaptotagmin-1 (Syt1) controls synaptic vesicle–membrane attachment activities via its C2B domain. These correlate with release synchronization and synaptic short-term facilitation, revealing a mechanism for Syt1-mediated synchronous release.

The authors show that Munc13-1 molecules form multiple supramolecular self-assemblies that serve as vesicular release sites. Having multiple Munc13-1 assemblies affords a stable synaptic weight, which confers robustness of synaptic computation.

Long-lasting synaptic plasticity is regarded as a mechanism for learning and memory. Using genetically engineered mice in which the C-terminal domains of AMPA receptor subtypes are switched, the authors reveal that GluA1 and GluA2 differentially regulate synaptic plasticity and contribute to different forms of learning.

The mosquito-borne ZIKA virus triggers microcephaly in human newborns. The authors report that the microcephaly results from induction of endoplasmic stress that interferes with generation and survival of projection neurons in the cerebral cortex.

Apicco and colleagues show that reducing TIA1 inhibits tau-mediated neurodegeneration and improves survival in a mouse model of tauopathy. This rescue occurs with a transition in tau aggregation from oligomeric to fibrillar forms of tau. These findings suggest a key role for RNA binding proteins in the pathophysiology of tau.

Grid cell activity may subserve path integration, but a direct link is lacking. The authors selectively disrupt retro-hippocampal region grid cell activity and show that disrupted grid cell firing impairs performance in a path integration task.

The authors investigate grid cell dynamics after removal of a border between two environments. Near the transition between environments, grid fields changed location, resulting in local spatial periodicity and continuity between the original maps.

Humans can deliberately control the timing of their actions but the neural mechanisms underlying such control are largely unknown. In this article, Wang, Narain and their colleagues report that such flexibility emerges in rhesus monkeys from the ability of their brain to flexibly control the speed at which cortical responses unfold in time.

Like all terrestrial mammals, humans emit body odors that subtly communicate emotions. This study suggests that adults with autism may be misreading these chemical signals and that this may explain a portion of their social difficulties.

Using single-cell RNA-sequencing, the authors record snapshots of the dynamic sensory-experience-dependent transcriptome across all cell types of the visual cortex in mice exposed to a light stimulus. The authors note diverse cell-type-specific programs in pyramidal neuron subtypes and robust non-neuronal responses that may regulate experience-dependent neurovascular coupling and myelination.

The protein composition of excitatory synapses differs in the areas of the human neocortex controlling language, emotion and other behaviors. This neocortical postsynaptic proteome data resource can be used to link genetics to brain imaging and behavior.

The authors present a new computational approach to automatically annotate, analyze, visualize and easily share whole-brain datasets at cellular resolution, based on a scale-invariant and interactive mouse brain reference atlas. The authors applied this framework to define the organization and cocaine-induced activity of corticostriatal circuits.