Articles in 2014

Corticotropin-releasing factor (CRF) and dopamine (DA) are critical for stress and motivation, respectively. The authors show that CRF is synthesized in DA neurons and released in the ventral tegmental area, where it affects GABAergic inputs to DA neurons and mediates the motivational effects of nicotine withdrawal and escalation of nicotine intake.

The counter-regulatory response (CRR) restores blood glucose levels after hypoglycemia. The authors identify a population of leptin receptor– and cholecystokinin-expressing neurons in the parabrachial nucleus of the hypothalamus that modulates the CRR. These neurons are activated by hypoglycemia, inhibited by leptin and project to the ventromedial hypothalamus.

Noonan syndrome (NS) is an autosomal dominant genetic disease that is co-morbid with cognitive deficits in a subset of patients. Using mouse models of NS, a study now shows that the synaptic plasticity and memory deficits in mouse models of NS are due primarily to the dysfunction in the MEK-Erk kinase pathways, and pharmacological intervention that alters MEK-Ras function can alleviate physiological and behavioral deficits in the mouse models of NS.

The many different behaviors mediated by the posterior parietal cortex (PPC) could arise from distinct specialized categories of neurons or from a single population of PPC neurons that is leveraged in different ways. The authors test this by studying rat PPC neurons during tasks involving multisensory decisions and conclude that a single network of neurons can support different behavioral demands.

Fragile X Syndrome (FXS) patients and the mouse model of the disease are known to have increased neocortical network excitability and hypersensitivity to sensory stimuli. The current study describes dendritic ion channel dysfunction to underlie sensory hypersensitivity in the FXS mouse model, particularly due to the reduction and dysfunction of dendritic h- and BK_Ca channels. The study also shows pharmacological rescue of cortical hyperexcitability using BK_Ca channel openers.

Training macaque monkeys with distinct sets of shapes resulted in novel domain formation in inferotemporal cortex. The localization of these domains was similar across monkeys, regardless of set-training order. The stereotyped location of the training-induced domains suggests a pre-existing architecture, and the authors explored various possible proto-architectures.

Neuregulin 1 (NRG1) type III is a key mediator of Schwann cell development and myelination and is known to undergo proteolytic cleavage to produce an intracellular fragment. In this study, the authors show that this intracellular fragment of NRG1 modulates myelination by inducing the expression of a prostaglandin synthase (L-PGDS) which, in turn, leads to prostaglandin production and activation of GPR44.

Previous work has suggested that the scaffolding protein ankyrin G is essential for the clustering of Na⁺ channels at the nodes of Ranvier. However, in this study, the authors show that, in the absence of ankyrin G, the complex of ankyrin R and βI spectrin can mediate Na⁺ channel clustering at the nodes.

In this study, the authors show that the scaffolding proteins ankyrin B and ankyrin G are expressed by Schwann cells and oligodendrocytes, respectively, and are enriched on the glial membrane at paranodal junctions where they interact with neurofascin 155. In addition, they find that ankyrins in oligodendrocytes have key roles in rapid and efficient paranode formation in the CNS.

The authors selectively modify chromatin in a specific gene in vivo to examine the link between chromatin dynamics and drug- and stress-evoked responses. They report that histone methylation or acetylation at the FosB locus in nucleus accumbens is sufficient to control drug- and stress-evoked transcriptional and behavioral responses.

Fine-scale synchrony of neural activity determines the nature of neural coding, but its underlying mechanisms are unclear. Here the authors find that coincident electrical and chemical synaptic inputs are nonlinearly integrated in overlapping retinal ganglion cell dendrites to produce synchronous spiking.

It has been suggested that astrocytes play a role in the onset and progression of neurodegenerative disorders such as ALS. In this study, the authors show that α-adducin forms a complex with α2-Na+/K+ ATPase in mutant SOD1-bearing astrocytes and that this interaction is necessary for the non-cell autonomous toxicity that induces muscle denervation, motor neuron death and decreased mortality.

This study provides causal evidence demonstrating that consuming a high flavanol diet improves dentate gyrus function and dentate gyrus–dependent cognitive functions in aged humans.

In vertebrate vision, the two types of photoreceptors, rods and cones, operate under low and bright light intensities, respectively. Here the authors show that under bright light conditions, when rods are not sensing light, they act as relay cells for cone-driven surround inhibition.

Shohamy and colleagues found that administration of a placebo can enhance learning from positive outcomes in Parkinson disease's patients. An analysis of fMRI signals recorded during behavior indicated that the drug and placebo both enhanced the representation of expected value in the ventromedial prefrontal cortex and attenuated prediction error signals in the ventral striatum. These results suggest that the mere expectation of reward can drive learning.

This study uses a combination of human fMRI and computational modeling to show that decision-making can be explained by a hierarchical model involving competition between different options at many different levels of representation. These results do not support a model where competition happens only at a final choice stage.

This recording study shows that attention can increase or decrease correlations between fluctuations in the responses of pairs of neurons, depending on task demands. These results suggest that attention can flexibly modulate such spike count correlations, independent of changes in firing rate and provide constraints on possible neuronal mechanisms.

This study uses fMRI in humans to find that prediction errors about pain are encoded in the periaqueductal gray. Modeling inter-area connectivity suggests that the ventromedial prefrontal cortex and the putamen pass on a value-related signal to this midbrain structure, which then conveys predictor error signals to prefrontal regions that regulate behavior.

Although head direction cells are known to encode information related to an organism's heading, it is unclear how the brain integrates this with information provided by fixed environmental features. In this study, the authors show that the retrosplenial complex is important for encoding heading and facing direction based on local landmarks and that this process generalizes across different environments that have similar geometry.

Radial glial progenitors (RGPs) in the developing mouse cortex generate excitatory neurons during development. This study examines the role of centriole-related protein Sas4, the mutation of which causes microcephaly in human brain, and shows that centrosome and centriole act to anchor RGPs in the ventricular zone during embryonic neurogenesis. By preventing cell death of RGPs without centrioles, the study also shows that cleavage plane orientation of cell division is not essential for radial glial progenitors' self-renewal.