Volume 24 Issue 11, November 2021

Grid cells produce exceptionally regular firing patterns as animals navigate in 2D spaces. Two new studies show that in flying and climbing animals, the activity patterns of these cells in 3D space are irregular. These results reveal an unexpected way in which the brain represents spatial location.

Positive and negative valence are encoded in specific neural populations of the basolateral amygdala, but only few of these populations have been characterized. A new study identifies a novel population, defined by the molecular marker Fezf2, and demonstrates that two of its output pathways differentially encode emotional valence.

Myelin is traditionally perceived as inert and immutable, but this notion is now being challenged. de Faria et al. discuss how myelin changes throughout life and in response to experience, and consider the functional implications of these changes.

A novel study led by scientists in Lübeck, Germany, shows that SARS-CoV-2-infected brain endothelial cells undergo cell death due to the cleavage of NEMO by the viral protease M^pro, potentially causing cerebral COVID-19 and ‘long COVID’ symptoms.

Magen et al. discovered new miRNA-based biomarkers in the blood of patients with ALS. miR-181 levels alone or in combination with an established protein biomarker predict ALS severity and prognosis and might enhance the power of clinical trials.

By developing a long-term ALS/FTD patient-specific iPSC-derived organoid model that recapitulates mature cortical cell types, the authors pinpoint early selective molecular pathologies at single-cell resolution and a druggable neuronal vulnerability.

By recording from the Drosophila mushroom body during active odor navigation, Zolin et al. reveal that dopaminergic reinforcement pathways encode rewards and goal-directed actions through similar patterns of neural activity and dopamine release.

Grieves et al. show that when rats explore a 3D space, grid cells in the entorhinal cortex exchange their usual spatially regular firing patterns for more irregular ones, suggesting that 3D space is mapped differently than previously thought.

Grosmark et al. use simultaneous calcium imaging and electrophysiology to track the formation and long-term evolution of hippocampal memory traces in mice and uncover a role for post-learning reactivation in the formation of spatially uniform cognitive maps.

Zhang et al. report that the BLA contains ‘hardwired’ positive-valence and negative-valence neurons, which each express Fezf2 but have distinct connectivity. These neurons separately drive learning and expression of avoidance or approach behavior.

Markovic et al. demonstrate in rodents that anhedonia-like states in inflammatory pain are mediated through increased inhibitory control and subsequent diminished activity of mesolimbic dopamine neurons.

By manipulating the rhythmicity of neural activity in entorhinal cortex and hippocampus, Quirk et al. show that memory is impaired by aberrant oscillatory activity during the encoding phase, but not during retention or retrieval phases.

This study shows that visual areas pass information to the amodal semantic system through semantically selective channels aligned at the border of visual cortex. This architecture might support the integration of visual perception and semantic memory.