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The International Brain Laboratory presents a brain-wide electrophysiological map obtained from pooling data from 12 laboratories that performed the same standardized perceptual decision-making task in mice.

Tracing of projection neuron axons from the primary visual cortex to their targets shows that these neurons often project to multiple cortical areas of the mouse brain.

Brain-wide recordings in mice reveal that prior expectations are distributed through recurrent loops across all levels of cortical and subcortical processing.

A study of mouse visual cortex relating patterns of excitatory synaptic connectivity to visual response properties of neighbouring neurons shows that, after eye opening, local connectivity reorganizes extensively: more connections form selectively between neurons with similar visual responses and connections are eliminated between visually unresponsive neurons, but the overall connectivity rate does not change.

In complex networks of the cerebral cortex, the majority of connections are weak and only a minority strong, but it is not known why; here the authors show that excitatory neurons in primary visual cortex follow a rule by which strong connections are sparse and occur between neurons with correlated responses to visual stimuli, whereas only weak connections link neurons with uncorrelated responses.

The connectivity of cortical neurons relates to the way in which they encode sensory features, and integrate them with behavioural context; these factors are discussed in relation to recent research, the major questions still to be addressed, and emerging techniques that may help to answer these.

Brain-wide recordings in mice show that learning leads to sensory evidence integration in many brain areas simultaneously, allowing sensory input to drive global movement preparatory dynamics, which collapse upon movement onset.

Experiments in mice show that a cortico-thalamic circuit generates prediction-error signals in primary visual cortex that amplify visual input that deviates from animals’ expectations.

Two studies show how electrical coupling between sister neurons in the developing cerebral cortex might help them to link up into columnar microcircuits that process related sensory information. See Letters p.113 & p.118

Three studies in visual and auditory cortex show that intracortical excitatory inputs amplify incoming sensory signals, as their sensory tuning is closely matched to that arriving from the sensory thalamus.

Khan et al. simultaneously measured activity from excitatory cells and three classes of inhibitory interneurons in visual cortex and show that learning differentially shapes the stimulus selectivity and interactions of multiple cell classes.

Clancy et al. investigated the relationship between individual neuron activity and cortex-wide dynamics. Neurons were diversely coupled to distal areas, and locomotion affected how neurons in different areas coupled with distal activity.

Noel et al. show aberrant updating of expectations in three distinct mouse models of autism spectrum disorder. Brain-wide neurophysiology data suggest this stems from excess units encoding deviations from prior mean and a lack of sensory prediction errors in frontal areas.

Dendritic spine morphogenesis is sensitive to experience-dependent plasticity, but whether or not experience-induced structural changes outlast the experience itself is unknown. This paper reveals that long-lived spine density increases in response to monocular deprivation that persist beyond the duration of time the eye was closed. Subsequent deprivation fails to induce further spine density increases, suggesting initial experience may provide a structural experience 'trace' that could be utilized in response to further functional shifts.

Using two-photon calcium imaging in vivo and intracellular recordings in vitro, the authors find that visual stimulation only weakly modifies coactivation patterns of inhibitory neurons, whereas excitatory neuron correlations are largely stimulus dependent.

To study long-term changes in neuronal circuits at single-cell resolution, a Troponin C–based Ca²⁺ indicator protein has been reengineered to increase the signal strength. This allows repeated measurements, over days and weeks, of orientation selective neurons in mouse visual cortex. Hasan et al., also in this issue, describe the use of a similar sensor for recording neuronal activity in vivo.

Experiments in mice alternating between a visual working memory task and a task that is independent of working memory provide insight into the neural representation of working memory and the distributed nature of its maintenance.

Thermostable antibodies called SPEARs enable rapid immunostaining with improved tissue penetration.

Mice generalize complex task structures by using neurons in the medial frontal cortex that encode progress to task goals and embed behavioural sequences.

Following a retinal lesion, it is known that extensive topographical remapping occurs in visual cortex. To examine the dynamics of this plasticity, Keck et al. combined chronic intrinsic and two-photon imaging to follow both the functional and structural modifications of the affected cortical region. They observed close to a complete turnover of spines on the functionally relevant cells, suggesting that a massive rewiring had occurred, producing new circuits.

Lightning Pose is an efficient pose estimation approach that requires few labeled training data owing to its semi-supervised learning strategy and ensembling.

RNA-sequencing analysis of cells in the human cortex enabled identification of diverse cell types, revealing well-conserved architecture and homologous cell types as well as extensive differences when compared with datasets covering the analogous region of the mouse brain.

A modular architecture for managing and sharing electrophysiology, behavior, colony management and other data has been built to support individual laboratories or large consortia.

Exploring the relationship between population coupling and neuronal activity reveals that neighbouring neurons can differ in their coupling to the overall firing rate of the population, the circuitry of which may potentially help to explain the complex activity patterns in cortical populations.