Articles in 2016

Human intracranial amygdala recordings reveal fast-latency responses to broad and low, but not high, spatial frequency components of fearful, but not happy or neutral, faces, which are not observed with unpleasant scenes. Amygdala fearful face responses are faster than in fusiform cortex, supporting a phylogenetically old, subcortical pathway to human amygdala.

Using in vivo spinal cord two-photon calcium imaging, the authors provide the first comprehensive characterization of the representations of temperature in the spinal cord and reveal that spinal neurons encode temperature change for cold and absolute temperature for heat.

The acquisition of a new skill or motor program is thought to be mediated by changes in neuronal plasticity at early stages of learning, which is later stabilized by new myelin generated by oligodendrocytes. In this study, the authors show that oligodendrocyte precursors exist in a ‘primed’ state, which allows them to contribute to early stages of motor learning.

Feedforward and feedback synaptic pathways shape how neural activity evolves across cortical areas, but they are difficult to monitor using traditional methods during behavior. The authors use pathway-specific and cellular-resolution in vivo imaging to quantify sensory and decision-related neural activity both within and propagating between two cortical areas critical for touch perception.

Social encounters are associated with varying degrees of stress. The authors show that modulation of stress system components in the medial amygdala alters preference for familiar vs. novel conspecifics. Inhibition of the relevant circuit in a group of familiar mice kept under semi-natural conditions increased pro-social behavior.

Infantile amnesia is the forgetting of memories in young children. In this paper, the authors show that in rats early life memories are not lost but rather stored in a latent form that can be retrieved later during adult life following exposure to appropriate reminders. The formation of these early memories requires the hippocampus and is subject to a developmental critical period that depends on mechanisms similar to those underlying critical periods in sensory systems.

Mutations in MECP2 cause Rett syndrome. The authors show that a MeCP2-HDAC3 complex positively regulates a subset of neuronal genes through FOXO recruitment and deacetylation, and that HDAC3 loss contributes to cognitive and social deficits in mice. Rett-patient-derived cells exhibited similar HDAC3-FOXO-mediated transcriptional impairments and were rescued by gene editing.

Control of action selection in the brain must be stable yet flexible. Using two-photon calcium imaging, the authors find distinct population activity states in secondary motor cortex for different stimulus–response contingencies and show that transitions between these states occurred earlier when mice were required to abort a repetitive action and use a conditional rule.

Long-term depression at synapses between L4 and L2/3 neurons in somatosensory cortex is thought to require presynaptic NMDARs. In contrast, the present work finds that genetic deletion of postsynaptic but not presynaptic NMDARs blocks LTD and that the action of postsynaptic NMDARs appears to be metabotropic rather than ionotropic.

The authors mapped thalamocortical connectivity in local networks of excitatory neurons in mouse visual cortex. They found that interconnected neurons in layer 4 and translaminar pairs of connected L4–L2/3 neurons receive common inputs from the thalamus.

Neurotransmission is regulated by glial cells; however, the underlying mechanisms are not fully understood. Sun and colleagues provide evidence that Lrp4 in astrocytes facilitates glutamatergic transmission by controlling ATP release. Their results provide insight into the interaction between neurons and astrocytes for synaptic homeostasis and/or plasticity.

The authors show that downregulation of SHANK3 in the VTA induces cell specific changes in DA and GABA neurons that converge to generate social behavioral deficits. Administration of a positive allosteric modulator of the type 1 metabotropic glutamate receptors (mGluR1) ameliorates synaptic, circuit and behavioral deficits.

Cells respond to mechanical signals during development and after injury. Poitelon et al. report for the first time that myelin-forming glia activate the Hippo pathway effectors Yap and Taz in response to mechanical stimuli, and that they are required for Schwann cell development and myelination in vivo.

The neural mechanisms of subjective choice are largely unknown. Here the authors show that neural activity in orbitofrontal cortex alternates rapidly between the values of available options in patterns that predict choice behavior. These dynamics may provide a neural mechanism for deliberation and optimal decision-making.

The circuit mechanisms underlying temporal coding in hippocampal area CA1 are poorly understood. The authors demonstrate that genetically removing CA3 input to CA1 disrupts temporally compressed ensemble-wide theta sequences in CA1 while sparing single-cell place coding, suggesting a crucial role for CA3 input in organizing the ensemble code for space.

Cocaine and morphine produce similar addiction-related behaviors, but different adaptations at accumbens synapses. The authors explain this paradox, showing that both drugs generate silent synapses in distinct neuronal types: cocaine in D1 type and morphine in D2 type. Withdrawal strengthens cocaine-generated silent synapses and weakens morphine-generated ones, producing common circuit effects.

Developmental nicotine exposure increased cortical dendritic complexity, levels of Ash2l and Mef2c (components of a histone methyltransferase complex), and H3MeK4 trimethylation at promoters of genes involved in synapse maintenance. Knockdown and overexpression experiments in utero showed that Ash2l and Mef2c regulate nicotine-mediated dendritic remodeling and changes in passive avoidance behavior.

Hippocampal place cells encode the animal’s position within the environment. Using flying bats navigating either by vision or echolocation, the authors found that hippocampal spatial maps changed completely between vision and echolocation. This suggests the hippocampus does not contain a single abstract map for a given environment, but rather multiple maps for different sensory modalities.

In fish, prostaglandin F_2α is a female hormone regulating ovulation, but it is also a pheromone that triggers male reproductive behavior. In this study, the authors identified an olfactory receptor for prostaglandin F_2α, which, when mutated, leads to impaired courtship behavior in male zebrafish.

During evolution, the neocortex has expanded dramatically and folded in certain species, providing superior sensorimotor and cognitive abilities. Expansion of neural progenitors called bRGs and IPCs plays key roles in expansion and folding of the neocortex. Using mouse models, comparative genomics and human cerebral organoids, this study shows that Shh signaling expands bRG and IPC populations, leading to neocortical expansion and folding.