Volume 25 Issue 10, October 2022

Learning requires new oligodendrogenesis, but how myelin patterns change during learning is unclear. Bacmeister et al. show that motor learning induces phase-specific changes in myelination on behaviorally activated axons that correlate with motor performance, suggesting myelin remodeling is involved in learning.

Although axonal GABA_A receptors are thought to cause presynaptic inhibition, we show that instead they often facilitate sodium channel activation at nodes of myelinated axons. This facilitation determines which branches of sensory axons conduct action potentials to motor neurons, enabling computation at the level of the node to regulate sensory feedback.

Frontal cortex activity contains a mixture of signals for different behavioral and cognitive processes. Analysis of 20,000 frontal cortical neurons during a tactile decision-making task revealed functional clusters encoding specific behavioral variables. By manipulating the inputs to frontal cortex, we attributed the origin of their activities to inputs from the thalamus.

This Review organizes models of cognitive maps into a clear ontology. This ontology reveals parallels between existing empirical results and implies new approaches to understand hippocampal–cortical interactions and beyond.

Oligodendrocyte precursor cells (OPCs) have functions beyond oligodendrogenesis. Here the authors show that OPCs can engulf thalamocortical presynapses in response to sensory experience in mice.

This genome-wide association study identified 12 novel loci for opioid use disorder, a common, potentially fatal condition. Analyses implicated the CNS, with gene expression enriched in brain regions associated with addiction.

This study shows that, rather than causing inhibition, axonal GABA_A receptors often facilitate sodium channel activation and prevent spike propagation failure at branch points of myelinated spinal cord sensory neuron axons.

The authors show how myelination is altered on learning-activated cortical neurons during motor learning in mice. They propose that learning-induced circuit-specific myelin plasticity may contribute to information encoding during learning.

Samborska et al. trained mice on a set of problems with the same structure but different physical layouts to study generalization. Neurons in prefrontal cortex generalized across problems, whereas those in hippocampus were more problem specific.

Filipchuk et al. show that when awake mice perceive sounds, the auditory cortex produces sound-specific neuronal assemblies distinct from its ongoing activity, whereas under anesthesia sound-evoked assemblies are indistinguishable from ongoing activity.

Frontal cortex contains a complex mixture of signals reflecting distinct behavioral and cognitive processes. An analysis of 20,000 neurons during decision-making revealed distinct functional clusters and their activities are driven by the thalamus.

Duffy et al. profiled mRNA translation in 73 human prenatal and adult cortex samples and identified thousands of previously unknown translation events, including small open reading frames that give rise to human-specific and/or brain-specific microproteins.

The authors generated the largest epigenome atlas of postmortem brains with Alzheimer’s disease. They reported regulatory genomic signatures associated with AD, including variability in open chromatin regions, transcription factor networks and cis-regulatory domains.

Colombo et al. build a morphological spectrum of over 40,000 microglia across development and disease with a topological data analysis approach that allows mapping of new conditions along these sex-region-specific and brain-region-specific atlases.