Articles in 2015

Using optogenetic manipulations and bioluminescence imaging of suprachiasmatic nucleus (SCN) firing rate, this study examines the interaction between molecular, electrical and behavioral circadian rhythms in mice. The study shows that alteration of clock neuron firing can reset molecular and behavioral circadian rhythms, and this effect required neuronal network interaction within the SCN. Thus, clock neuron spiking is fundamental to circadian pacemaking as both an input to and output of the neuronal network responsible for circadian behavior.

The hippocampus, a structure critical for memory and navigation, contains both place and episodic cell assemblies. Synchronous input from the medial septum is crucial for inducing spatial and temporal neural sequences. These sequences are, in turn, necessary for constructing episodic cells and, in the absence of sensory input, place cells.

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.

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.

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.

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.

The authors recorded spiking activity in the sensorimotor striatum of rats performing a motor sequence in an automatic manner. They report continuous and integrative representation of contextual and kinematic information. Reversible perturbation of these representation increased execution variability, suggesting a strong contribution in constraining the execution motor habits.

The authors show that astrocytes produce high levels of the adenosine receptor A2A in Alzheimer brains. Reducing the levels of astrocytic A2A boosted memory in young and aging mice and mouse models of Alzheimer disease, whereas activating a related molecular pathway impaired memory. Thus, astrocytes regulate memory and abnormal receptor activity in these cells may contribute to memory disorders.

Combining single-neuron recordings and a multistep economic choice task in monkeys, the authors find activity in amygdala neurons that predicts the value and length of an internally planned choice sequence leading to future reward. Prospective amygdala activity appears to encode components of an internal plan and guide behavior over several steps towards self-defined, distant goals.

Enhanced NMDA receptor function and social interaction deficits are observed in mice lacking the excitatory postsynaptic scaffolding protein IRSp53. Reducing NMDAR activity by pharmacological methods rescues the impaired social interaction observed in these mice. This suggests that enhanced NMDA receptor function may be associated with social deficits.

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.

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.

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.

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.

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.

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.

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.

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.

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.

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.