A neural substrate of sex-dependent modulation of motivation

While there is emerging evidence of sex differences in decision-making behavior, the neural substrates that underlie such differences remain largely unknown. Here we demonstrate that in mice performing a value-based decision-making task, while choices are similar between the sexes, motivation to engage in the task is modulated by action value more strongly in females than in males. Inhibition of activity in anterior cingulate cortex (ACC) neurons that project to the dorsomedial striatum (DMS) preferentially disrupts this relationship between value and motivation in females, without affecting choice in either sex. In line with these effects, in females compared to males, ACC-DMS neurons have stronger representations of negative outcomes and more neurons are active when the value of the chosen option is low. By contrast, the representation of each choice is similar between the sexes. Thus, we identify a neural substrate that contributes to sex-specific modulation of motivation by value.

Three-dimensional ultrastructure of the brain pericyte-endothelial interface

Pericytes and endothelial cells share membranous interdigitations called "peg-and-socket" interactions that facilitate their adhesion and biochemical crosstalk during vascular homeostasis. However, the morphology and distribution of these ultrastructures have remained elusive. Using a combination of 3D electron microscopy techniques, we examined peg-and-socket interactions in mouse brain capillaries. We found that pegs extending from pericytes to endothelial cells were morphologically diverse, exhibiting claw-like morphologies at the edge of the cell and bouton-shaped swellings away from the edge. Reciprocal endothelial pegs projecting into pericytes were less abundant and appeared as larger columnar protuberances. A large-scale 3D EM data set revealed enrichment of both pericyte and endothelial pegs around pericyte somata. The ratio of pericyte versus endothelial pegs was conserved among the pericytes examined, but total peg abundance was heterogeneous across cells. These data show considerable investment between pericytes and endothelial cells, and provide morphological evidence for pericyte somata as sites of enriched physical and biochemical interaction.

A Comparison of Dopaminergic and Cholinergic Populations Reveals Unique Contributions of VTA Dopamine Neurons to Short-Term Memory

We systematically compare the contributions of two dopaminergic and two cholinergic ascending populations to a spatial short-term memory task in rats. In ventral tegmental area dopamine (VTA-DA) and nucleus basalis cholinergic (NB-ChAT) populations, trial-by-trial fluctuations in activity during the delay period relate to performance with an inverted-U, despite the fact that both populations have low activity during that time. Transient manipulations reveal that only VTA-DA neurons, and not the other three populations we examine, contribute causally and selectively to short-term memory. This contribution is most significant during the delay period, when both increases and decreases in VTA-DA activity impair short-term memory. Our results reveal a surprising dissociation between when VTA-DA neurons are most active and when they have the biggest causal contribution to short-term memory, and they also provide support for classic ideas about an inverted-U relationship between neuromodulation and cognition.

Specialized coding of sensory, motor and cognitive variables in VTA dopamine neurons

There is increased appreciation that dopamine (DA) neurons in the midbrain respond not only to reward¹ and reward-predicting cues^1,2, but also to other variables such as distance to reward³, movements^4–9, and behavioral choices^10,11. Based on these findings, a major open question is how the responses to these diverse variables are organized across the population of DA neurons. In other words, do individual DA neurons multiplex multiple variables, or are subsets of neurons specialized in encoding specific behavioral variables? The reason that this fundamental question has been difficult to resolve is that recordings from large populations of individual DA neurons have not been performed in a behavioral task with sufficient complexity to examine these diverse variables simultaneously. To address this gap, we used 2-photon calcium imaging through an implanted lens to record activity of >300 midbrain DA neurons in the ventral tegmental area (VTA) during a complex decision-making task. As mice navigated in a virtual reality (VR) environment, DA neurons encoded an array of sensory, motor, and cognitive variables. These responses were functionally clustered, such that subpopulations of neurons transmitted information about a subset of behavioral variables, in addition to encoding reward. These functional clusters were spatially organized, such that neighboring neurons were more likely to be part of the same cluster. Taken together with the topography between DA neurons and their projections, this specialization and anatomical organization may aid downstream circuits in correctly interpreting the wide range of signals transmitted by DA neurons.