Volume 20 Issue 7, July 2017

Disruption of retinal direction selectivity reveals both peripheral and central computations contributing to direction selectivity in mouse visual cortex. These mechanisms work together to better encode motion directions and speeds.

Most thalamic research has focused on sensory transmission. Now three independent groups reveal the thalamus to be critical in behaviors linked to frontal cortex and the maintenance of persistent cortical activity during delays.

A computational model explains how memories of past rewards guide value-based choices. Incorporating behavioral and functional MRI evidence, the findings indicate that 'sampling' from individual memories of past rewards influences choices.

The authors show that in a mouse model of spinal muscular atrophy (SMA), there is a reduction in sensory synaptic drive that leads to motor neuron dysfunction and motor behavior impairments. SMA motor neurons showed a lower surface expression of Kv2.1 potassium channels and reduced spiking ability. Increasing neuronal activity pharmacologically led to the normalization of Kv2.1 surface expression and an improvement in motor function.

The authors identify programmed cell death ligand-1 (PD-L1), an immunity suppressor produced by cancer cells, as a new pain inhibitor and a neuromodulator. They report that PD-L1 is produced by melanoma and normal neural tissues and that it inhibits acute and chronic pain. Via activation of PD-1, its receptor, PD-L1 decreases the excitability of nociceptive neurons in mouse and human dorsal root ganglia.

The authors find that mammalian acid-sensing taste receptor cells, previously shown to be putative sour taste sensors, also mediate responses to water. Optogenetic activation of this population of cells in thirsty mice induced robust drinking response in the absence of water. This study shows that acid-sensing TRCs contribute to the detection of water in the oral cavity.

Most cancer patients experience loss of appetite and feelings of illness, which contribute to cancer-related deaths and morbidity. The authors demonstrate that, in mice, activation of a subset of neurons in the parabrachial nucleus mediate cancer-induced anorexia and associated sickness behaviors.

The authors provide evidence that a cerebellum-like structure at the initial stage of mammalian auditory processing (the dorsal cochlear nucleus) functions to cancel out self-generated sounds. A similar function has been established for cerebellum-like structures in electroreceptive fish, suggesting a conserved function for these structures across vertebrates.

The authors establish a critical role for somatostatin interneurons in visually induced gamma oscillations in the primary visual cortex of mice. Optogenetic manipulations in awake animals, combined with an innovative computational model with multiple interneuron subtypes, provide a mechanism for the synchronization of neural firing across the retinotopic map.

The authors monitored neuronal activity in mouse visual cortex during visual-motion stimulation and perturbed retinal direction selectivity. After perturbation, the proportion of posterior-motion-preferring cortical cells decreased, and their response at higher stimulus speeds was reduced. Thus, functionally distinct, retina-dependent and retina-independent computations of visual motion exist in mouse cortex.

Attention changes correlations between neuronal responses. In this study, Verhoef and Maunsell use multielectrode recordings in monkeys to reveal a link between normalization mechanisms, correlated neuronal activity and attention. The findings show that normalization mechanisms shape response correlations and that these correlations change when attention biases normalization mechanisms.

Although vocal learning is widely speculated to depend on motor to auditory (i.e., forward) pathways, the neurons that convey forward signals important to vocal learning remain unknown. Here the authors identify neurons that transmit signals from songbird motor to auditory regions and demonstrate their role in vocal learning.

Using pathway-specific optogenetic inhibition, the authors demonstrate that projections from the mediodorsal thalamus to prefrontal cortex support the maintenance of working memory, while prefrontal–thalamic projections support subsequent choice selection. Thalamo–prefrontal projections have a circuit-specific role in sustaining prefrontal delay-period activity, a neuronal signature required for successful task performance.

The authors demonstrate that decisions for reward can have more a complicated dependence on past experiences than previously believed. Previous models describe decisions as influenced by rewards received in similar situations. Here the authors show that experiences that share only incidental features can also reemerge to bias present choices.

To unravel structural regularities in neocortical networks, Gal et al. analyzed a biologically constrained model of a neocortical microcircuit. Using extended graph theory, they found multiple cell-type-specific wiring features, including small-word and rich-club topologies that might contribute to the large repertoire of computations performed by the neocortex.

Brain function relies on flexible communication between cortical regions. It has been proposed that changing patterns of oscillatory coherence underlie information routing. However, oscillations in vivo are very irregular. This study shows that short-lived and stochastic oscillatory bursts coordinate across areas to selectively modulate interareal communication.

No techniques exist for the precise identification of vascular pericytes. Here the authors identify and characterize a fluorescent dye that exclusively labels pericytes. Using this tool for intravital imaging of the mouse brain, the authors provide conclusive evidence that these cells are molecularly and functionally distinct from all other brain and vascular cells.