Articles in 2011

A study now reports the genome-wide profiling of 5-hydroxymethylcytosine, an alternate epigenetic state of DNA modification, of the mouse brain across development, aging and in a neurodevelopmental disease model.

A1 adenosine receptor is antagonized by caffeine and is highly expressed in the CA2 layer of rodent hippocampus. This study now shows that caffeine can induce CA2 synaptic potentiation in a dosage-dependent manner.

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.

Recent work in a number of species has emphasized the role of orbitofrontal cortex in value-based decision-making. However, discrepancies have arisen when comparing the findings from animal models to those from humans. In this review, the author examines several possibilities that might explain these discrepancies.

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 the two main types of adult-born neurons in the mouse olfactory bulb show experience-dependent plasticity long after maturation and integration into the network.

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.

This technical report describes a 360-channel flexible multi-electrode array with high spatial resolution, wide coverage area and minimal damage to the recorded neural tissue. Among other descriptions of multiunit in vivo neuronal recording in cats, the authors also use the electrode array to show spiral-patterned spread of epileptic neural activity in the neocortex.

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.

Reversal learning requires cognitive flexibility and is mediated by multiple brain regions, including the prefrontal cortex and the dorsal striatum. This study examines how environmental factors such as stress can affect prefrontal cortex–dorsal striatum interactions and reversal learning.

Deficits in prefrontal cholinergic function have been implicated in cognitive impairment in many neuropsychiatric diseases. Here, the authors report that monkeys with lesions of cholinergic input to prefrontal cortex were impaired on a spatial working memory task, but not on other tests of cognitive function that also require intact prefrontal cortex.

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.