Volume 18 Issue 2, February 2015

A study reports for the first time on the importance of post-translational modification by neddylation in postnatal brain development. In particular, it is critical to synapse maturation and stability, and thus to cognition.

Glutamate transporters influence the kinetics of synaptic transmission by acutely buffering synaptically released glutamate. In addition to high synaptic density of EAAT2, the transporter's high mobility contributes to function.

Spatial hearing in birds and mammals is more alike than previously thought in its patterns of developmental plasticity, physiological responses, and the computations employed to interpret binaural cues and map the environment.

Harris and Shepherd review our knowledge of input and output patterns for different classes of cortical cells. They propose that cortex, like other parts of the body, has a serially homologous organization, featuring area- and species-specific variations on a basic theme, that allows different types of function to emerge.

Microdeletions of chromosome 16p11.2 can cause autism, but the pathogenic mechanisms remain unclear. Here the authors show that in a 16p11.2 mouse model, mGluR5 synaptic plasticity and protein synthesis are altered and that a modulator of mGluR5 reverses the cognitive deficits.

This study shows that auditory development is guided by multiple adaptive processes. This flexibility can help maintain accurate perception in different environments and provides a more unified account of developmental plasticity across species. The adaptive plasticity observed also provides insight into the nature of distributed neural representations underlying spatial hearing.

Anxiety symptoms may arise from an overgeneralization of negative memories to include more neutral ones. Here the authors show that the tuning of amygdala neurons for a conditioned stimulus broadens and matches the behavioral generalization to innocuous stimuli.

Autism spectrum disorders (ASDs) are characterized by both phenotypic and genetic heterogeneity. Here the authors find that ASD functional genetic networks are enriched for genes expressed in deep layer cortical neurons, that mutations in females impact more highly expressed genes as compared to males and that intellectual scores reflect the severity of mutations.

Better analytical methods are needed to extract biological meaning from genome-wide association studies (GWAS) of psychiatric disorders. Here the authors take GWAS data from over 60,000 subjects, including patients with schizophrenia, bipolar disorder and major depression, and identify common etiological pathways shared amongst them.

Here, the authors imaged calcium response in the mouse olfactory bulb in vivo to show that the calcium transients in astrocytic processes—but not cell bodies—are tightly coupled to neuronal activity and precede functional hyperemia.

The authors find that glutamate release increases the diffusion of the astrocytic glutamate transporter GLT-1 in the plasma membrane. This activity-dependent increase in mobility facilitates glutamate clearance from the synaptic cleft, which influences the kinetics of excitatory post-synaptic events in rat hippocampal neurons.

In amyotrophic lateral sclerosis (ALS), some motor neuron types are more vulnerable to disease pathology. Here the authors show that resistant subtypes express the ER chaperone SIL1. Disease-associated loss of SIL1 impairs ER homeostasis and worsens ALS pathology, whereas its expression improves pathology and survival in an ALS mouse model.

The authors report that neddylation is required for dendritic spine development and stability, and loss of neddylation in excitatory forebrain neurons leads to synaptic loss, impaired neurotransmission, and learning and memory deficits. The roles of neddylation in spine maturation and synaptic transmission could be attributed to neddylation of PSD-95.

Rapid developmental changes in the response properties of neurons in visual cortex enhance motion discriminability following eye opening. Here the authors show that increases in direction selectivity are accompanied by reductions in the density of active neurons and variability in their responses and levels of noise correlation, changes that depend on the nature of visual experience.

The authors find that behavioral habituation to the repeated presentation of visual stimuli, measured as reduced occurrence of a brief motor response called a 'vidget', depends on primary visual cortex in mice and is accompanied by a potentiation of layer 4 responses to visual stimuli. Local manipulations indicate that this form of recognition memory is stored in primary visual cortex.

Due to their volatility, olfactory inputs are spatially and temporally dynamic. Here the authors find that, in contrast to previous studies, mitral/tufted cells of the olfactory bulb can sum inputs linearly across odors and time.

Wang and colleagues find that weakening hippocampal theta in a familiar environment reduces the performance of rats in a spatial memory task, decreases the number of theta sequences and degrades internally generated hippocampal episode cell firing, while leaving place cell firing intact. The same weakening of theta also prevents the formation of a precise spatial representation in a novel environment unless proximal cues are present. Together these results suggest that the mechanisms underlying internally generated hippocampal sequences of activity are crucial for episodic memory.

During a single theta cycle, discrete groups of hippocampal place cells can produce a distributed series of spikes called a theta sequence. Such sequences represent the time-compressed trajectory of an animal running in its environment and usually extend ahead of the current position. Here, Wikenheiser and Redish find that the ‘look-ahead’ distance of rat theta sequences can predict the imminent choice of the animal in a value-guided decision making task.

Donahue and Lee identify prefrontal neurons that integrate task-relevant information about past and current stimulus features and past action outcomes across trials during a probabilistic reversal task. The activity of these neurons is sensitive to past rewards and is predictive of imminent behavioral choices, suggesting that they dynamically contribute to the selection of actions that maximize reward during decision making under uncertainty.

Previous studies have reported both increased and decreased functional brain connectivity in individuals with autism spectrum disorder (ASD). The authors find that instances of such over- and underconnectivity in adults with high-functioning ASD point to a deeper principle of increased individual variation (idiosyncrasy) of functional connectivity in individuals with ASD.

In this technical report, Khodagholy and colleagues find that NeuroGrid, a planar, scalable and highly conformable electrode array, allows recordings of local-field potentials and stable single-unit activity from the surface of the rat cortex or hippocampus. The authors also validate NeuroGrid across species by showing that that it can capture LFP-modulated spiking activity intraoperatively in surgical patients, thus demonstrating its utility as tool for fundamental research on the human brain and in the clinic.