Volume 23 Issue 2, February 2020

Rewards direct behavioral adaptation through midbrain dopamine signaling, though the timing of those effects is often ambiguous. Lee and colleagues find that different subpopulations of dopamine neurons obey similar constraints, indirectly regulating reward-related behavior through learning mechanisms restricted to a brief time window following reward.

Framed around the potential use of microglia as new cellular therapies for brain disease, Bennett and Bennett review new discoveries about the effects of developmental origin and environmental signals on brain macrophage identity and function.

Kodama et al. show that microglia from male and female adult mice have distinct microRNA profiles and that loss of microglial microRNAs leads to sex-specific changes in the microglial transcriptome and tau pathology.

Arc, a master regulator of synaptic plasticity, can mediate intercellular RNA transfer. Arc evolved from retrotransposon genes. Erlendsson et al. present structures of retroviral-like Arc capsids as a basis to understand their function.

Maes et al. use second-order conditioning, blocking and optogenetic inhibition to show that cue-evoked dopamine transients function as temporal-difference prediction errors rather than reward predictions.

Rees et al. show that de novo mutations in the gene SLC6A1, and more broadly across evolutionary constrained genes and genes implicated in neurodevelopmental disorders, increase the risk for developing schizophrenia.

In this study of protein-coding de novo mutations in schizophrenia, researchers found only a small contribution toward overall risk, coming predominantly from genes under negative selection and highly expressed in the brain.

Microglia in the aging hippocampus accumulate lipid droplets, and are functionally impaired and inflamed. Lipid droplet formation in microglia is regulated by genes linked to neurodegeneration such as progranulin.

In mice that have undergone Pavlovian reward conditioning, dopaminergic neurons regulate conditioned movements in a temporally restricted manner, consistent with a primary contribution to associative learning rather than online movement generation.

Gao et al. provide evidence that two major classes of neurons exist in the paraventricular thalamus. One of these, termed type II PVT neurons, belongs to a previously ignored cell population that relays arousal information to the infralimbic cortex.

Shuman et al. report that epileptic mice harbor desynchronized hippocampal interneuron activity and unstable spatial representations, revealing that precise intrahippocampal synchronization is critical for spatial coding.

Munn et al. provide evidence that medial entorhinal speed signals scale to reflect the geometry of the environment, whereas entorhinal head direction signals reflect learned information about the geometric symmetry of the environment.

Yoo and colleagues find that while pursuing virtual prey, monkeys predict the prey’s upcoming movements, and neurons in the dorsal anterior cingulate cortex tracked prey position, velocity and acceleration to facilitate these predictions.

Gallego, Perich et al. report that latent dynamics in the neural manifold across three cortical areas are stable throughout years of consistent behavior. The authors posit that these dynamics are fundamental building blocks of learned behavior.

This resource comprises ultra-high-resolution MRI datasets and corresponding gray and white matter atlases of the marmoset brain to facilitate brain connectivity studies and the development of tractography algorithms in the primate brain.

A chemogenetic approach was developed for cell-type-specific drug-inducible protein synthesis inhibition in mice. It was used to show that consolidation of long-term aversive memories requires rapid neuronal protein synthesis in the amygdala.