Articles in 2011

Using a multisensory cue-conflict task, the authors report that monkeys employ the optimal strategy of weighting each cue in proportion to its reliability, and that population decoding of neural responses from area MSTd predicts behavioral cue weighting. This behavior is further linked to the specific computations by which single neurons combine their inputs, consistent with recent theories of optimal probabilistic neural computation.

Heidenreich et al. show that KCNQ4—a gene encoding a K⁺ channel whose mutation is linked to progressive human deafness—is expressed in a subset of dorsal root ganglion neurons and mechanosensory touch neurons that serve tactile sensation. The authors show that KCNQ4 loss of function in mice causes a specific tactile dysfunction owing to altered touch sensitivity. The study also finds that human subjects with KCNQ4 mutations and progressive deafness are hypersensitive to tactile information and are able to discern minute high-frequency tactile vibrations.

The authors show that rats trained with overlapping complex odorant mixtures have improved behavioral discrimination ability and enhanced cortical ensemble pattern separation. Training to disregard normally detectable differences between overlapping mixtures impairs cortical pattern separation and behavioral discrimination. These results show that the balance between pattern separation and completion is experience dependent.

Polarized transport to axons and dendrites is critical for neuronal function, but the molecular mechanisms and cytoskeletal cues for asymmetry are incompletely defined. Here the authors show that Caenorhabditis elegans CRMP (UNC-33) acts early in neuronal development, together with ankyrin (UNC-44), to polarize microtubule organization and kinesin-dependent axon-dendrite sorting.

After its release, the endocannabinoid anandamide is taken up from the synaptic cleft by internalization by neurons and astrocytes. Although several lines of evidence suggest that the anandamide uptake itself is a carrier-mediated diffusion process, the molecular identity of the transporter was unknown until now. Here Fu et al. show that anandamide uptake is mediated by a novel protein named FAAH-like anandamide transporter (FLAT) that is generated as an alternative splicing product of the fatty acid amide hydrolase-1 (Faah) mRNA.

Development of eye-specific segregation and binocularity in the superior colliculus, dorsal lateral geniculate nucleus and primary visual cortex is partly attributed to the timing of spontaneous retinal waves, in which bursts of activity are thought to act through a Hebbian learning rule to guide circuit refinement. This study uses the latest optogenetic tools to provide definitive evidence for the binocular activity timing rule—and the specific temporal features of activity—in dictating binocularity development in the mouse visual system.

The authors report that prolonged inhibition of nicotinic acetylcholine receptors in Drosophila CNS results in a homeostatic increase in the α7 receptor, which then induces an increase in the A-type K⁺ current carried by Shal/Kv4 channels. This increase in Shal activity stabilizes postsynaptic potentials.

C. elegans show a dispersal behavior called nictation. The authors show that this is regulated by the ciliated neuron IL2 and requires cholinergic transmission.

The authors developed an assay using optogenetic stimulation of dopaminergic neurons as a reference stimulus to measure the reward value of nutrients. They found that fasting increases and leptin decreases the reward value of sucrose.

Polarization of a neuron begins with the appearance of the first neurite. The authors study Drosophila neurons in vivo and find that the mechanisms of polarization appear to be defined at the precursor stage.

The authors show that the Drosophila gustatory receptor Gr64e is necessary and sufficient for neuronal and behavioral response to glycerol. They find that species of Drosophila that are predicted to carry pseudogenes of Gr64e have reduced glycerol sensitivity.

Patches in primary visual cortex (V1) rich in cytochrome oxidase were thought to contain unoriented, color-opponent neurons. Here the authors measure orientation tuning in V1 neurons using acutely implanted 100-electrode arrays. Patch cells were nearly as well tuned as those in interpatches, suggesting that processing of form and color is not strictly segregated in primate V1. Patch cells had higher mean discharge rates, consistent with their enhanced metabolism.

The authors report that, in the extended amygdala, 2-arachidonoylglycerol and anandamide mediate retrograde short-term depression and long-term depression, respectively, via different signaling pathways. In contrast, in the striatum, 2-arachidonoylglycerol and cannabinoid receptor 1–mediated retrograde signaling mediated both forms of plasticity.

Here the authors identify NCKX4, a potassium-dependent Na⁺/Ca²⁺ exchanger as being necessary for rapid response termination and proper adaptation of vertebrate olfactory sensory neurons. They also report that Nckx4^−/− mice have a reduced ability to locate an odorous source and have lower body weights.

The authors report that GABA transporter 1 (GAT-1) cation currents directly increase GABAergic neuronal excitability and synaptic GABA release in the periaqueductal gray (PAG), and that these GAT-1 changes contribute to PAG-mediated signs of opioid withdrawal.

Loss of FMR1 gene function results in fragile X syndrome. Here, the authors demonstrate that the Drosophila fragile X homolog dFMR1 is involved in the RNA editing pathway via interaction with the enzyme dADAR and suggest that proper NMJ synaptic architecture requires modulation of dADAR activity by dFMR1.

The orbitofrontal cortex (OFC) has been hypothesized to carry information regarding the value of expected rewards. Such information could be used for generating instructive error signals conveyed by dopamine neurons. Here the authors report that this is indeed the case. However, contrary to the simplest hypothesis, OFC lesions did not result in the loss of all value information. Instead, lesions caused the loss of value information derived from model-based representations.

This study reports a double dissociation in the neuronal correlates of value-based decision making in monkey prefrontal cortex, with orbitofrontal cortex neurons encoding choice value relative to recent choice values, while anterior cingulate cortex neurons flexibly encode multiple decision parameters and reward prediction errors using a 'common valuation currency'.

This study examines the contribution of a specific phosphatidylinositol 3-kinase (PI3K) isoform, namely PI3Kγ, to hippocampal synaptic plasticity and behavior. The authors find that the loss of PI3Kγ can specifically impair NMDA receptor–mediated long-term depression and cognitive functions that rely on behavioral flexibility.

The authors find that the Avpr1a gene, encoding the vasopressin-1A receptor, is responsible for strain-dependent pain sensitivity of mice to formalin and capsaicin. In humans, a single nucleotide polymorphism in AVPR1A was found to affect capsaicin pain and desmopressin analgesia. In both species, the effects were male specific and dependent on stress levels at the time of testing.