Articles in 2014

Using in vivo recording of neuronal activities in rat secondary motor cortex and devising a novel task of waiting before performing an action, Murakami et al. show a neural correlate of voluntary action initiation. The study also shows population activity and computational modeling data that correspond to action timing of voluntary action that are consistent with integration-to-bound theories of decision making.

The authors devised a new behavioral task to study cooling perception in head-fixed mice. Using whole-cell recordings from layer 2/3 neurons in the somatosensory cortex, they reveal that the same neurons that respond to mechanical stimulation of the skin also respond to its cooling. In addition, they find that both the perception of cooling and the cooling responses in S1 are eliminated in TRPM8 knockout mice.

Oligodendrocyte precursor cells (OPCs) retain their proliferative/differentiation capacity throughout life. This study uses in vivo and ex vivo imaging to show a specific temporal window between OPC division and oligodendrocyte differentiation in the postnatal mouse brain that is modulated by the microenvironment. The latency between OPC division and differentiation is shortened by myelin damage, while sensory deprivation reduces the survival of divided OPCs undergoing differentiation.

Using the Drosophila system, this study shows that rewarding and motivational properties of water are mediated by different subsets of dopaminergic neurons. The study also shows a satiety state–dependent effect in which thirst can change water avoidance behavior into water-seeking behavior and demonstrates that water wanting versus liking versus learning are separable at the level of behavior and the underlying neural circuit.

Neurofibromatosis type 1 (NF1) is associated with social dysfunction in children. Here the authors show that Nf1 heterozygous mice have deficits in social memory associated with alterations in amygdala plasticity and Map kinase signaling. Global deletion or amygdala-specific pharmacological inhibition of Pak1 rescued social deficits in Nf1 heterozygous mice.

This study describes the segregated neural representations at single cell level and in whole brain when mice are presented with positive and negative emotional stimuli given in succession. Using a newly developed technique called tyramide-amplified-immunohistochemistry–fluorescence in situ hybridization (TAI-FISH) to label multiple neuronal populations, the authors demonstrate specific overlap and divergence of neuronal activation pattern to different emotional stimuli.

During adaptation, neocortical responses change as a result of repeated sensory stimulation, but it's unclear how this affects perception. Here the authors use optogenetics to mimic sensory evoked cortical responses with or without adaptation. They find adaptation impairs frequency discrimination but enhances change detection during whisker stimulation.

The ventral tegmental area (VTA) and lateral habenula (LHb) are reciprocally connected. Here the authors show, using electron microscopy, tract tracing and optogenetics in rodents, that the majority of VTA neurons innervating LHb release both GABA and glutamate at the same synaptic terminals.

In this study, the authors describe the subset of activity-regulated enhancers that modulate transcription in cultured neurons and that participate in the regulation of synaptic maturation. In addition, they demonstrate Fos binding to these enhancers is essential for this activity-dependent regulation of transcription.

Using chronic microelectrode arrays in monkeys, this study finds that progressive learning on a visual task is largely explained by changes in the response of primary visual cortex neurons. The decoding accuracy of a linear classifier trained on V1 aggregate responses suggests that as learning proceeds, the primary visual cortex codes more task-relevant information.

Correlations of noise in neural population activity are thought to limit the amount of information contained in such population activity, whereas decorrelation is suggested to increase information content. Here the authors show that decorrelation does not imply an increase in information, and only certain types of correlations limit information content.

Axonal maintenance is known to rely, in part, on non-cell-autonomous support from myelinating glia, but the mechanisms are still unclear. In this study, the authors show that loss of the serine/threonine kinase LKB1 in Schwann cells leads to changes in nerve metabolism and axonal degeneration, even in the absence of demyelination.

Theta oscillations are thought to propagate unidirectionally along the hippocampal circuitry, from CA3 to CA1 and the subiculum. In this paper, Jackson and colleagues demonstrate that, in the intact rat hippocampus, theta activity can also flow in reverse from subiculum to CA3, and find that this phenomenon depends on long-range GABAergic inhibition.

The lateral intraparietal area (LIP) in monkeys plays an important role in decision-making. Here the authors use a statistical approach to decode the activity of LIP spikes and find multiplexed and temporally heterogeneous signals. This provides a framework for studying complex coding in higher brain areas.

It is known that the primary sensory neurons that mediate tactile sensation exhibit elaborate receptive fields because of dendritic branching in the skin. In this study, the authors show that such branching allows neurons that innervate the human fingertips to extract geometric features of touched objects and signal them via both temporal and intensity codes.

Sox10 and Nuclear Factor I-A (NFIA) are transcriptional regulators of oligodendrocyte and astrocyte generation in the mammalian brain, respectively. This study describes reciprocal antagonism between these transcription factors whereby NFIA directly antagonizes Sox10 regulation of myelin gene expression in oligodendrocytes, and Sox10 negatively regulates NFIA during astrocyte differentiation. The work also demonstrates this mutual antagonism being involved in tumorigenesis, particularly during oligodendroglioma to astrocytoma conversion.

In the visual system, familiarization to an image results in reduced neural responses to it. Here the AUs find that with dynamic visual displays, neurons in the inferotemporal cortex respond more strongly to familiar than novel images. This indicates that familiarization sharpens the response dynamics of neurons in extrastriate visual cortex.

Uptake of the neurotransmitter GABA by transporters called GATs is known to influence neuronal GABAergic tone. Here Muthukumar et al. show that the wave of synaptogenesis in Drosophila brains occurs during the second half of pupal development in an astrocyte-dependent manner. The study also shows that the upregulation of GAT during this process requires astrocytic metabotropic GABA receptors, and this pathway mediates mechanosensory-induced seizure activity in GABAergic mutants with hyperexcitable neurons.

The synchronization of fast-spiking cortical interneurons (FS) produces gamma-like oscillations or ‘FS-gamma’. In this study, Siegle and colleagues found that the induction of FS gamma in the primary sensory cortex of mice performing a tactile task could enhance their detection of less salient stimuli.

Alzheimer's disease (AD) is a chronic neurodegenerative disorder characterized by progressive neuropathology and cognitive decline. Here the authors describe an epigenome-wide association study (EWAS) of human post-mortem brain samples across multiple independent AD cohorts. They find consistent hypermethylation of the ANK1 gene associated with neuropathology.