Volume 20 Issue 1, January 2017

Recent studies reveal several groups of neurons that become activated upon anticipation or consumption of meals. These neurons constitute key components of the complex feedback system that prevents continuous feeding by mice.

A new study finds that a major population of output cells in primary motor cortex suppresses movement and behavioral engagement.

An elegant study answers a long-standing question: how do correlations arise in large, highly interconnected networks of neurons? The answer represents a major step forward in our understanding of spiking networks in the brain.

Evidence reveals that humans share remarkably similar patterns of event-specific neural activity during spontaneous spoken recall. Posterior medial cortex appears to play a key role in transforming experience into memory.

In the CNS, the primary signal initiating myelination and its cellular origin remain unclear. Goebbels et al. find that deleting PTEN from cerebellar granule cells drives radial axon growth, oligodendrocyte progenitor cell (OPC) proliferation, oligodendrocyte differentiation and de novo myelination of parallel fibers. This suggests that myelination is downstream of a neuronal PI(3,4,5)P₃-dependent signal.

The authors describe a glutamatergic septoentorhinal pathway that provides running-speed-correlated input to MEC layer 2/3. The speed signal is integrated by several MEC cell classes and converted into speed-dependent output. This speed circuit may be important for the spatial computations of MEC neurons.

In this study, the authors reveal distinct developmental programs underlying innate and learned olfactory behaviors by demonstrating that chemogenetic inactivation of neurons generated in neonatal mice impairs the behavioral response to aversive odorants, whereas inactivation of adult-born neurons impairs learning of novel food-related odors.

Auditory hair cells contain mechanotransduction channels that are activated by sound. The authors show that Piezo2, a mechanotransduction channel important for touch perception, is expressed in auditory hair cells. Surprisingly, Piezo2 is not the mechanotransduction channel essential for auditory perception and is instead observed after damage to hair cells.

Animals are sensitive to the rate of temperature change, in addition to absolute temperature. Using Drosophila larvae as a model, Luo et al. decipher the cellular and molecular mechanism controlling this behavior, which depends in part on the TRPA1 channel.

Hunger-promoting AgRP neurons and satiety-promoting POMC neurons in the arcuate nucleus mediate homeostatic regulation of hunger. Yet a rapidly acting satiety component analogous to rapidly hunger-promoting AgRP neurons has been missing. The authors identify this missing satiety signal and show that it is carried by a novel subset of arcuate glutamatergic neurons.

The authors show that a direct pathway from the dorsal hippocampus to the prelimbic cortex is necessary for contextual fear memory strengthening. Molecular analyses and functional targeting revealed that prelimbic excitatory and inhibitory synapses have a critical role in promoting memory strengthening, while inhibiting extinction.

Animals have a remarkable ability to adjust their behavioral response to the same stimulus based on the immediate behavioral context. The authors show that the nucleus basalis broadcasts a contextual signal to the auditory cortex that is then translated by inhibitory networks to regulate excitatory neuronal output and behavior.

Self-movement estimation is critical to motor control and navigation; however, the neural circuits that accurately track body motion are poorly understood. This study shows that Drosophila optic-flow-processing neurons receive three distinct locomotor-related signals that are used to encode a quantitative estimate of the fly's walking movements, even in the absence of visual stimuli.

Previous work on mammalian motor cortex has focused on the role of this region in movement generation. Here the authors demonstrate that activity of vibrissa motor cortex neurons decreases during various forms of vibrissal touch, suggesting that a primary function of vibrissa motor cortex is to suppress whisking behavior.

The strength of aversive learning is proportional to the intensity of aversive experiences, but how brain circuits set memory strength during learning is not known. The authors show that an amygdala-to-midbrain feedback circuit conveying information about future unpleasant experiences inhibits aversive processing during learning to calibrate memory strength.

The authors show that a normative approach to olfaction, Bayesian inference, reproduces much of the anatomy, physiology and behavior seen in real organisms. The model provides insight into how the olfactory system demixes odors, and, by extension, how other sensory systems extract relevant information from activity in peripheral organs.

The activity of cortical neurons is extremely noisy. This study builds a mathematical theory linking the spatial scales of cortical wiring to how noise is generated and distributed over a population of neurons. Predictions from the theory are validated using population recordings in primate visual area V1.

The authors demonstrate that activity patterns in the default network during unguided spoken recollection of real-world events were similar between individuals recalling the same specific events. Patterns were altered between perception and recall in a systematic manner across brains. These results reveal a common spatial organization for memory representations.