Volume 16 Issue 4, April 2013

A study reporting spatiotemporal stimulation and inhibition of synaptic activity is made possible by the development of synaptically targeted, light-controlled G protein–coupled receptors.

To be become long-lasting, short-term memories must be transformed into more permanent forms. mTORC2 has now been found to be crucial for the molecular reorganization of the cytoskeleton needed for memory consolidation.

A study finds that sound textures are stored in auditory memory as summary statistics representing the sound over long time scales; specific events are superimposed, forming a 'skeleton of events on a bed of texture'.

Stress reduces motivation to work for rewards. The authors show that corticotrophin releasing factor (CRF) acts in the ventral tegmental area (VTA) to reduce the motivation to work for food rewards. CRF in the VTA inhibited dopamine release occurring in response to reward delivery, but not to reward-predictive cues.

Patients with obsessive-compulsive disorder (OCD) have attenuated reward anticipatory activity in the nucleus accumbens (NAc), and deep brain stimulation (DBS) of the NAc is used to treat OCD. The authors show that NAc DBS normalizes NAc activity, reduces connectivity between NAc and prefrontal cortex, and decreases frontal low-frequency oscillations in OCD patients.

Here the authors demonstrate that the long-term behavioral expression of fear memory can be predicted from neural patterns at the time of learning by applying multi-voxel pattern analysis to single-trial functional magnetic resonance imaging data.

When sleep followed implicit training on a motor sequence, children showed greater gains in explicit sequence knowledge after sleep than adults. Measurements of slow-wave sleep and hippocampal activation suggest that the children's superior performance could be a result of enhanced reprocessing of hippocampal memory representations during slow-wave sleep.

This study shows that Parkinson's disease–associated mutant forms of leucine-rich repeat kinase 2 (LRRK2) impair chaperone-mediated autophagy in neurons, thereby reducing degradation of α-synuclein by this pathway and contributing to the accumulation of this protein observed in brain tissue from patients with Parkinson's disease.

In this study, the authors show that, in newborn cortical neurons, the TrkB and TrkC receptors are transactivated by the EGF receptor, rather than by their traditional ligands, BDNF and NT-3. This transactivation appears to be involved in the migration of these neurons from the ventricular zone to the cortical plate.

In embryonic development, epithelial-mesenchymal transition (EMT) is the process whereby epithelial cells delaminate from the epithelial sheet and adopt a mesenchymal phenotype in cell motility and migration. This study shows that the Snail superfamily transcription factors Scratch 1 and 2 regulate an EMT-like process in newborn neurons derived from neuroepithelial cells in the developing mouse cortex. This process affects subsequent initiation of radial migration and ultimately neuronal cell positioning.

Neurofibromatosis type 2 (NF2) is caused by inactivation of the NF2 gene, which encodes merlin. NF2 patients develop peripheral neuropathies. The authors show that NF2 inactivation decreases axonal integrity in mice and NF2 patient tissue. Their data suggest that merlin activates RhoA and promotes neurofilament heavy chain phosphorylation to maintain axonal integrity.

The authors show that reducing histone deacetylase 1 expression or activity in the nucleus accumbens increases global levels of histone acetylation but also increases histone methylation, leading to reduced cocaine-induced changes in behavior. This effect is mediated in part by decreased GABA_A receptor expression and decreased inhibitory tone on nucleus accumbens neurons.

Memory and associated plasticity mechanisms span different timescales, from fleeting to enduring. This study shows that, across species, mTORC2's control of actin dynamics is critical for long-term forms of memory and synaptic plasticity.

Trovò and colleagues find that aging is accompanied by a decrease in the levels of the phosphoinositide PI(4,5)P₂, PLCγ activity and the PI(4,5)P₂-clustering molecule MARCKS in mouse hippocampal synaptic membranes. Moreover, increasing MARCKS levels in old mice corrects some of the synaptic plasticity and memory deficits associated with aging.

The endocannabinoid 2-AG is produced by the enzyme diacylglycerol lipase (DGL). The authors show that DGLα is phosphorylated and inhibited by calcium/calmodulin–dependent protein kinase II (CaMKII). Inhibition of CaMKII activity increases striatal DGL activity and basal 2-AG amounts, and augments short-term retrograde endocannabinoid signaling at striatal glutamatergic synapses.

The authors find that serotonin, acting through 5-HT_1B receptors, potentiates temporoammonic pathway–to–CA1 cell excitatory synapses in the hippocampus. Chronic unpredictable stress increased the magnitude of this potentiation, and chronic treatment with fluoxetine restored normal levels of this potentiation, a process that was required for the behavioral effects of chronic fluoxetine.

The brain selects stimuli for preferential processing on the basis of both their physical salience and their relevance to behavior. Recording from the midbrain of the barn owl, the authors show that a single inhibitory circuit is critical for both physical salience-driven (exogenous) and internally driven (endogenous) control of stimulus selection.

To facilitate decisions between distinct options, goal values could be represented using a common currency. Here the authors find that a region of medial prefrontal cortex contains a distributed goal-value code that is independent of stimulus category. However, in the medial orbitofrontal cortex, they also find unique category-dependent distributed value codes.

Research on event perception has focused on transient elevations in predictive uncertainty or surprise as the primary signal driving event segmentation. Here the authors report behavioral and neuroimaging evidence that suggests that event representations can emerge even in the absence of such cues. They propose that this learning occurs in a manner analogous to the learning of semantic categories.

Sensory signals are transduced at high resolution, but their structure must be stored in a more compact format. Here the authors show that the auditory system summarizes the temporal details of sounds using time-averaged statistics. Such statistical representations produce good categorical discrimination, but limit the ability to discern temporal detail.

Using whole-transcriptome RNA sequencing at single-nucleotide resolution, this Resource article describes the mRNAs, RNA editing, splice variants and exon-intron boundaries of expressed genes in the cerebral cortex of embryonic and adult mice.

This Technical Report describes light-activatable metabotropic glutamate receptors based on synthetic photoswitchable tethered ligands, and demonstrates optogenetic control of G protein–coupled receptor activity in neurons in vivo and ex vivo.