Volume 15 Issue 10, October 2012

Not only can the sleeping brain perceive sensory information, it can learn from this information, leading to changed behaviors the next day: it can come to associate a sound with a pleasant or unpleasant odor and react, both while still asleep and after waking, with a deeper or shallower breath. But classic ‘sleep learning’ remains just a dream.

Pathological alterations in Alzheimer's disease disrupt neuronal network function. An in vivo imaging study using a fluorescent reporter of neuronal activity finds dysfunction specifically in those neurons near amyloid plaques.

During brain injury, mechanical injuries to neural cells initiate an apoptotic cascade through cardiolipin oxidation. Mitochondrially targeted electron scavenger compounds block this process, suggesting new therapeutic avenues.

Sleep consolidates memory. By cuing specific memories during sleep, a study now links this consolidation of memory to the replay of neuronal ensemble activity that occurs in the hippocampus during slow-wave sleep after learning.

Many comparisons between obesity and drug addiction have been made in recent years. In this review, the authors critically compare the behavioral responses to food and drugs of abuse, as well as the neural circuitry involved in each, pointing out key differences between the two.

Energy balance is maintained by neuronal populations throughout the central nervous system, but is primarily localized in the mediobasal hypothalamus. In this review, the authors discuss recent work examining plastic changes in hypothalamic circuits in response changes in nutrient availability and long-term energy status.

This review discusses what we have learned about the neural regulation of feeding from genetic studies, both from studies in mutant mice and more recent genome-wide association studies in humans.

Circuits have been described in the hypothalamus and brainstem involved in regulating feeding and energy balance. In this review, the authors discuss the many peripheral signals that influence these central circuits to affect feeding behavior and energy balance.

By examining natural behavioral variation of an outbred strain of mice on a Pavlovian-to-instrumental transfer task, the authors show that the level of polysialylated neural cell adhesion molecule (PSA-NCAM) in the ventromedial prefrontal cortex (vmPFC) can predict the extinction and cue-induced reinstatement of alcohol seeking. The study also shows that depleting endogenous PSA-NCAM in the vmPFC in mice confers resistance to the extinction of alcohol seeking.

Alcoholism and post-traumatic stress disorder are frequently co-morbid. The authors show that chronic intermittent exposure to ethanol impairs extinction of fear conditioning in mice. In vivo recordings showed that extinction encoding was impaired in infralimbic medial prefrontal cortical (mPFC) neurons, which are associated with downregulation of the NMDA receptor subunit GluN1 in mPFC.

Noise-induced sensorineural hearing loss selectively worsens peripheral temporal coding in noisy compared with quiet conditions reports this study in chinchillas. This may explain why noisy conditions are particularly difficult for hearing-impaired people.

Neurons in the parietal cortex have been shown to encode position in external reference frames. This work demonstrates that parietal cortex neurons can simultaneously register spatial information in multiple external reference frames. The form this takes suggests a mechanism for encoding relationships between parts and the whole that they compose.

Optogenetic manipulations of behavior in primates have largely been unsuccessful. Here, the authors report that monkeys reliably shift their gaze toward the receptive field of optically driven channelrhodopsin-2–expressing V1 neurons.

This paper reports that there are substantial differences in DNA methylation patterns between nurses and forager caste phenotypes in honeybees, and that reverting foragers back to nurses reestablishes methylation levels for a majority of genes.

In this paper, Bessereau and colleagues identify MOLO-1 as an auxiliary subunit for levamisole-sensitive acetylcholine receptors (L-AChRs) present at the neuromuscular junction of C. elegans. MOLO-1 is the first auxiliary subunit ever found for a member of the Cys-loop receptor superfamily.

Expression of GluN2 subunit of NMDA receptor (NMDAR) in rodents is developmentally regulated such that GluN2B expression is high during early postnatal period but is replaced by GluN2A in adulthood, thus conferring different NMDAR channel properties and kinetics. This study identifies a molecular mechanism for GluN2A/B switch that is mediated by the transcriptional repressor REST. This process is also shown to be affected by postnatal stress induced by maternal deprivation, leading to long-lasting effects on NMDAR-subunit composition in the hippocampus.

Leptin regulates energy balance. The authors show that Rho-kinase 1 (ROCK1) regulates leptin signaling by increasing activation of signaling molecules downstream of leptin receptor. Deletion of ROCK1 from POMC or AgRP neurons leads to obesity and reduced leptin sensitivity.

This work shows that ephrin-B2 from astrocytes provides a critical niche signal for cell fate determination in adult mouse hippocampus, in part by directing neuronal differentiation of adult neural stem cells through EphB4-dependent juxtacrine signaling.

The authors show that traumatic brain injury can induce peroxidation of cardiolipin, leading to accumulation of numerous oxygenated species and the induction of neuronal cell death. This accumulation of cardiolipin and the associated toxicity can be ameliorated by mitochondria-targeted delivery of an electron scavenger.

The pathology in Parkinson's disease is known to extend beyond mesencephalic dopaminergic neurons, but it is unclear why. Here the authors show that vulnerable neurons in the dorsal motor nucleus of the vagus have similar physiological features, including basal mitochondrial oxidant stress, providing an insight into the distributed disease pathology.

The immediate-early gene Arc mediates synaptic plasticity and long-term memory formation. Whether Arc is dysregulated by amyloid-beta or in Alzheimer's disease is controversial. Here, a study used a reporter mouse line expressing destabilized fluorescent protein Venus under the control of the Arc promoter to show that Arc induction pattern, brain regional difference and precise location of active neurons with respect to senile plaque are major determinants of differential Arc response in a mouse model of Alzheimer's disease.

Dentate mossy cells in hippocampal slice can temporarily store stimulus information from the perforant path with persistent up-state–like activity. Here, Hyde and Strowbridge show that hippocampal dentate hilar cells can store several distinct patterns of information simultaneously for several seconds and that the activity of the local network in the dentate gyrus can predict which input conveyed the stimulus information and what temporal sequence of stimuli was presented.

The authors report that, during sleep, a task-related auditory cue biases hippocampal reactivation events towards replaying the spatial memory associated with that cue. These results indicate that sleep replay can be manipulated by external stimulation, and provide further evidence for the role of hippocampal replay in memory consolidation.

Path integration allows animals to track their body position in planar space by relying on both external cues and internal cues. For monitoring internal cues, head direction cells in the anterodorsal thalamic nucleus are one of the best candidates for the neural mechanism underlying path integration. This study shows that head-direction cells in rats act as a mediator of path integration such that their firing matches the level of movement trajectory heading errors in a cumulative manner, and that head-direction cells correct their firing when internal error is corrected by external cues.

Here the authors test the proposal that premotor circuits participate in sensory learning for imitation using convergent approaches in the juvenile zebra finch, including optogenetic disruption and in vivo multiphoton imaging. Their findings provide evidence that premotor circuits help to encode sensory information prior to shaping and executing imitative behaviors.

Although it is well-known that sleep can strengthen existing memories, this study demonstrates that people can acquire completely new associations (between distinct tones and pleasant/unpleasant smells) during sleep, which are preserved during the awake state.

The increasing prevalence of obesity has added a degree of urgency to research into how and why humans overeat and become obese. Although obesity and metabolic syndrome are often seen as diseases of the body, the central nervous system plays an important role in regulating feeding behavior and metabolism. Neuroscience research has provided insight into the role the central nervous system plays in the regulation of feeding behavior, and how disruption of such regulation might lead to obesity. Nature Neuroscience presents a special focus issue including reviews examining how central regulation of feeding is influenced by genetics, peripheral factors, and previous experience, and how reward circuits affect feeding behavior.