Articles in 2009

Sensory signals for movement planning originate in multiple reference frames. Here the authors present a model in which the statistical properties of sensory signals and the transformations needed to compare them determine their effect on movement planning. Their results account for known patterns of movement planning errors and suggest that maintaining multiple reference frames is actually an optimal use of available sensory information.

The authors combine electrophysiology and behavioral assays to show that the duration of cocaine-induced synaptic plasticity in the VTA of mice is gated by mGluR1. The lack of mGluR1 in vivo made VTA potentiation persistent and led to synaptic plasticity in the NAc, which is important for relapse.

It is well established that monkey middle temporal area and the human middle temporal complex (MT+) mediate two-dimensional motion perception. Here, the authors use functional magnetic resonance imaging to demonstrate that MT+ carries signals that are also critical for three-dimensional motion perception.

The role of feedforward inhibition onto Purkinje cells during learning is still not well understood. Here, the authors report that selective genetic removal of GABA_A receptor–mediated inhibition onto Purkinje cells modulates fine-scale patterns of Purkinje cell activity. These patterns may mediate the induction of downstream plasticity and, ultimately, the consolidation of cerebellar motor learning.

Breathing relies on a respiratory rhythm generator, which depends on activity of the pre-Bötzinger complex (preBötC) and the parafacial respiratory group. The authors characterize an early emerging group of Phox2b-expressing parafacial oscillatory cells that entrain and couple with the preBötC at the onset of fetal breathing.

Some neurites in developing C. elegans interneurons are eventually pruned. Which exact neurites are subject to pruning appears to be random, suggesting an ongoing local competition between pro- and anti-pruning signals. Hayashi and colleagues show that Wnt signaling through the transmembrane receptor kinase CAM-1/Ror protects developing neurites from being pruned.

Ethanol activates G protein-gated inwardly rectifying K⁺ (GIRK) channels, but it is unclear how. This study identifies an alcohol-binding pocket located in the cytoplasmic domains of GIRK2. A leucine residue in this pocket was crucial for GIRK2 activation by alcohols, but was not involved in the alcohol inhibition of related, but constitutively active, K⁺ channels.

The authors examine the effect of increased synthesis of AMPAR subunits on their subcellular distribution in hippocampal neurons. Virally expressing AMPARs caused an accumulation in cell bodies with little effect on dendritic amounts. Stargazin coexpression enhanced dendritic GluR1 levels by protecting it from lysosomal degradation but didn't increase surface or synaptic GluR1 levels.

Memories can be reconsolidated when reactivated. However, reconsolidation does not occur under certain boundary conditions. The authors show that these boundary conditions can be transient and that strong auditory fear memories in rats that initially did not undergo reconsolidation eventually did over time. Moreover, they find that the hippocampus is necessary for preventing reconsolidation from occuring in the amygdala, and that NR2B subunits, normally required for induction of reconsolidation in the amygdala, are downregulated when strong memories do not undergo reconsolidation.

Young birds rely on auditory feedback when learning to imitate the songs of adult birds. Here the authors find that, as with humans, birds use auditory feedback to correct vocal errors in adulthood. This suggests that lifelong error correction may be a general principle of learned vocal behavior.

Orr and colleagues identify a molecular pathway in microglia that converts ATP-dependent process extension into process retraction during inflammation. This reversal is dependant on A_2A adenosine receptor upregulation and P2Y₁₂ downregulation.

Hippocampal replay is thought to be essential for the consolidation of event memories. Sleep replay involves the reactivation of stored representations in the absence of specific sensory inputs, whereas awake replay is thought to reflect input from the current environment. Here the authors find that the hippocampus consistently replays past experiences during brief pauses in waking behavior, suggesting a role for waking replay in memory consolidation and retrieval.

PolyQ-Htt inhibits fast axonal transport in cellular and animal Huntington's disease models. Here, the authors show that this effect is a result of the activation of JNK3. PolyQ-Htt–activated JNK3 reduces kinesin-1 binding to microtubules.

Although the role of Notch signaling in CNS glial development is well established, its participation in peripheral glial development is still unclear. This paper shows that Notch signaling regulates the differentiation of Schwann cell precursors and the proliferation of Schwann cells, and acts as a break on myelination of peripheral nerves.

Previous work has suggested that the histone deacetylase HDAC1 promotes and canonical Wnt signaling antagonizes oligodendrocyte differentiation. Here, Ye et al. show that HDAC1/2 directly interferes with canonical Wnt signaling in oligodendrocyte precursors by competing with β-catenin for interaction with the transcriptional co-factor TCF7L2. TCF7L2 itself is shown to be crucial for oligodendrocyte development.

The authors use high-resolution total reflection fluorescence microscopy to study the mechanisms of AMPA receptor synaptic delivery. They report that palmitoylation of the GluR1 subunit modulates phosphorylation by PKC. This enhances protein 4.1N binding to GluR1, thereby facilitating GluR1 insertion.

NMDA-induced superoxide production, which can lead to cell death at excessive levels, is widely believed to originate from mitochondria. Here, the authors find that, in both cultured neurons and mouse hippocampus, NADPH oxidase is actually the primary source of NMDA-induced superoxide production.

Using functional magnetic resonance imaging, the authors investigate how the prefrontal cortex (PFC) combines the motivation and selection processes underlying cognitive control. They find that these functions are physically separable, represented in different areas of the PFC, and that these areas may subserve the integration of motivation and cognitive control for decision making.

During sleep, neural patterns reflecting previously acquired information are replayed in the hippocampus. Here, the authors report that there is reactivation of learning-related patterns of activity in the medial prefrontal cortex during sleep following rule acquisition that coincided with hippocampal sharp wave/ripple complexes.

Lee and colleagues demonstrate that actin depolarizing factor (ADF)/cofilin regulates, and is required for, the insertion of acetylcholine receptors (AChRs) into the postsynaptic membrane at neuromuscular synapses. ADF/cofilin also appears to stabilize membrane AChRs; it associates with AChR clusters and disappears before the clusters themselves disassemble.