Olfactory Landmarks and Path Integration Converge to Form a Cognitive Spatial Map | bioRxiv

The convergence of internal path integration with sensory information from external landmarks generates a cognitive spatial map in the hippocampus. We have recorded the activity of cells in CA1 during a virtual navigation task to examine how mice represent, recognize and employ sparse olfactory landmarks to estimate their location. We observe that the presence of odor landmarks at multiple locations in a virtual environment greatly enriches the place cell representation and dramatically improves navigation. Presentation of the same odor at different locations generates distinct place cell representations, indicating that path integration can disambiguate two identical cues on the basis of location. The enhanced place cell representation at one cue location led to the formation of place cells at locations beyond that cue and, ultimately recognition of a second odor cue as a distinct landmark. This suggests an iterative mechanism for extending place cell representations into unknown territory. These results reveal how odor cues can serve as landmarks to guide navigation and suggest a model to explain how the convergence of landmarks and path integration participates in an iterative process that generates a cognitive spatial map.

Source: Olfactory Landmarks and Path Integration Converge to Form a Cognitive Spatial Map | bioRxiv

Recruitment of GABAergic Interneurons in the Barrel Cortex during Active Tactile Behavior: Neuron

Yu et al. measured the firing patterns of three major types of GABAergic inhibitoryinterneurons in the somatosensory cortex of mice during active tactile sensation.These cell types are recruited with distinct millisecond-scale dynamics, revealingcell-type-specific interactions and functions.

Source: Recruitment of GABAergic Interneurons in the Barrel Cortex during Active Tactile Behavior: Neuron

A global map of orientation tuning in mouse visual cortex | bioRxiv

In primates and most carnivores, neurons in primary visual cortex are spatially organized by their functional properties. For example, neurons with similar orientation preferences are grouped together in iso-orientation domains that smoothly vary over the cortical sheet. In rodents, on the other hand, neurons with different orientation preferences are thought to be spatially intermingled, a feature which has been termed “salt-and-pepper” organization. The apparent absence of any systematic structure in orientation tuning has been considered a defining feature of the rodent visual system for more than a decade, with broad implications for brain development, visual processing, and comparative neurophysiology. Here, we revisited this question using new techniques for wide-field two-photon calcium imaging that enabled us to collect nearly complete population tuning preferences in layers 2-4 across a large fraction of the mouse visual hierarchy. Examining the orientation tuning of these hundreds of thousands of neurons, we found a global map spanning multiple visual cortical areas in which orientation bias was organized around a single pinwheel centered in V1. This pattern was consistent across animals and cortical depth. The existence of this global organization in rodents has implications for our understanding of visual processing and the principles governing the ontogeny and phylogeny of the visual cortex of mammals.

Source: A global map of orientation tuning in mouse visual cortex | bioRxiv

Conserved cell types with divergent features in human versus mouse cortex | Nature

Elucidating the cellular architecture of the human cerebral cortex is central to understanding our cognitive abilities and susceptibility to disease. Here we used single-nucleus RNA-sequencing analysis to perform a comprehensive study of cell types in the middle temporal gyrus of human cortex. We identified a highly diverse set of excitatory and inhibitory neuron types that are mostly sparse, with excitatory types being less layer-restricted than expected. Comparison to similar mouse cortex single-cell RNA-sequencing datasets revealed a surprisingly well-conserved cellular architecture that enables matching of homologous types and predictions of properties of human cell types. Despite this general conservation, we also found extensive differences between homologous human and mouse cell types, including marked alterations in proportions, laminar distributions, gene expression and morphology. These species-specific features emphasize the importance of directly studying human brain.

Source: Conserved cell types with divergent features in human versus mouse cortex | Nature

Hippocampal Remapping as Hidden State Inference | bioRxiv

Cells in the hippocampus tuned to spatial location (place cells) typically change their tuning when an animal changes context, a phenomenon known as remapping. A fundamental challenge to understanding remapping is the fact that what counts as a ”context change” has never been precisely defined. Furthermore, different remapping phenomena have been classified on the basis of how much the tuning changes after different types and degrees of context change, but the relationship between these variables is not clear. We address these ambiguities by formalizing remapping in terms of hidden state inference. According to this view, remapping does not directly reflect objective, observable properties of the environment, but rather subjective beliefs about the hidden state of the environment. We show how the hidden state framework can resolve a number of puzzles about the nature of remapping.

Source: Hippocampal Remapping as Hidden State Inference | bioRxiv

Extracellular Spike Waveform Dissociates Four Functionally Distinct Cell Classes in Primate Cortex: Current Biology

Trainito et al. use a data-driven approach to robustly identify four cell classesfrom extracellular spike waveforms recorded in three cortical regions of macaque monkeys.The four cell classes are functionally distinct in terms of firing statistics, responsedynamics, and information coding.

Source: Extracellular Spike Waveform Dissociates Four Functionally Distinct Cell Classes in Primate Cortex: Current Biology

The Generation of Time in the Hippocampal Memory System: Cell Reports

Rolls and Mills describe a theory and model of how time is generated in the hippocampalepisodic memory system. Time ramping cells in the lateral entorhinal cortex producetime cells in the hippocampus using a competitive neuronal network architecture. Forwardand reverse replay are emergent properties of the system.

Source: The Generation of Time in the Hippocampal Memory System: Cell Reports

Discrete Evaluative and Premotor Circuits Enable Vocal Learning in Songbirds: Neuron

Kearney et al. used behavioral and optogenetic methods in singing birds to distinguishneural pathways that evaluate song performance from downstream premotor circuits thatare guided by these evaluations to learn new vocal behaviors.

Source: Discrete Evaluative and Premotor Circuits Enable Vocal Learning in Songbirds: Neuron

Deep Sequencing of Somatosensory Neurons Reveals Molecular Determinants of Intrinsic Physiological Properties: Neuron

Zheng et al. defined distinct intrinsic physiological properties and transcriptomeprofiles of eight somatosensory neuron subtypes and further revealed subtype-specificcontributions of differentially expressed potassium channels to the intrinsic membraneproperties in these sensory neurons.

Source: Deep Sequencing of Somatosensory Neurons Reveals Molecular Determinants of Intrinsic Physiological Properties: Neuron

Neuromodulation of Spike-Timing-Dependent Plasticity: Past, Present, and Future: Neuron

Spike-timing-dependent synaptic plasticity (STDP) is a leading cellular model forbehavioral learning and memory. Brzosko et al. discuss recent advances in our understandingof the mechanisms and functions of the neuromodulatory control of STDP in health anddisease.

Source: Neuromodulation of Spike-Timing-Dependent Plasticity: Past, Present, and Future: Neuron