Articles in 2009

Akt signaling has been implicated in a number of diseases, but its role in brain disorders is less clear. Here, the authors report that CTMP, an endogenous inhibitor of Akt, is critical in the neurodegeneration that is associated with stroke. Blockade of CTMP in a stroke model rescues hippocampal neurons.

Mechanically sensitive transducer channels are responsible for the detection of sound-induced hair cell vibrations. However, the location of these channels in the stereociliary bundle has been unclear. Using high-speed calcium imaging, this study demonstrates that there are no transduction channels in the tallest row of stereocilia in the mammalian cochlea. Instead, these channels are more likely to be present in the bottom stereociliary rows.

The authors identify motoneurons selectively vulnerable and resistant to motorneuron disease longitudinally in vivo. Their data suggests that subtype-selective ER stress responses influence disease pathology and the progressive manifestations of weakening and paralysis.

Oxidative damage contributes to loss of nervous system function in age as well as a result of degenerative disease. But how exactly can oxidation impair neuronal function? In the worm C. elegans, this study shows that the potassium channel KVS-1 is subject to oxidation at a particular cysteine residue. Mutation of this residue led to preservation of chemosensation in aging worms.

Phosphodiesterase (PDE) activity in olfactory sensory neuron cilia is thought to be responsible for degrading odor-induced signaling, resulting in rapid response termination. However, disrupting the variety of PDE found only in cilia unexpectedly turns out not to result in a rapid response termination deficit. Only eliminating both cilia-localized and cell body–localized varieties of PDEs resulted in prolonged termination.

The balance of excitation and inhibition across large populations of spiking neurons has been suggested to be important. Here the authors model the effects of a more detailed balance between incoming excitation and local inhibition on the transmission of signals through a neural network.

The organization of the olfactory bulb has been extensively studied, but much less is known about downstream areas. The authors compare activity patterns in the zebrafish olfactory bulb and two of its targets. They find that the subpallial area has overlapping odor representations, whereas those in the area homologous to the olfactory bulb are more sharply tuned.

This study shows that the microRNA miR-124 is required for neuronal differentiation of adult neural progenitors in vitro and in vivo. The transcription factor Sox9 opposes neuronal differentiation and is suppressed by miRNA-124.

The authors use patch-clamp recordings and two-photon microscopy to characterize monosynaptic connections between Purkinje cells of the juvenile cerebellum. They then construct a network model that generates traveling waves of activity between connected Purkinje cells and validate their model with observations in juvenile cerebellar cortex.

Sonic hedgehog (Shh) functions as both a mitogen and a patterning agent during development. Looking mainly at the developing mouse cerebellum, this study shows that the mitogenic activity, but not the patterning role, requires Shh to interact with proteoglycans.

In the cochlea, ribbon synapses are used to transmit acoustic information from inner hair cells to spiral ganglion cells. Here the authors find that the properties of these synapses vary along the tonotopic axis, providing a candidate presynaptic mechanism for modulating the dynamics of ganglion cell spiking.

This study shows that the transcription factor SRF, expressed in neurons, crucially affects oligodendrocyte maturation and myelination through a non–cell autonomous mechanism. SRF appears to act, at least in part, by repressing transcription of the paracrine growth factor CTGF. Overexpression of CTGF reduced oligodendrocyte differentiation.

People can form opinions of others during an initial encounter. Neuroimaging results suggest that these first impressions are mediated by the amygdala and posterior cingulate cortex.

Active somatosensory perception requires the integration of signals arising from both external stimuli and motor activity. The authors found a population of neurons in rat somatosensory cortex that responded to touch only when contact occurred at a specific phase in the whisk cycle, providing information about the position of the object relative to the rat's face.

Previous work has implicated prefrontal and parietal cortex in time perception and the temporal domain in decision making. Single-cell recordings in monkeys performing an interval-generation task now reveal that neurons in the medial motor areas can also represent the passage of time.

The release of stress hormone from the hypothalamic paraventricular nucleus (PVN) is regulated by nearby GABAergic input. This study shows that behavioral stress affects chloride ion homeostasis and thus tapers GABAergic inhibition, thereby suggesting disinhibition of the PVN as a mechanism for stress response initiation.

The frontal lobes are critical for cognitive control over both abstract actions and motor plans. On the basis of the behavioral deficits of lesions patients, the authors report that there is a hierarchical organization of cognitive control, with rostral areas being required for decisions about more abstract actions and caudal areas being required for decisions about more concrete actions.

Although the receptor tyrosine phosphatase LAR is known to regulate the devolvement of excitatory synapse and to direct proper guidance of axons, the extracellular ligand for its activation has remained unknown. This study identifies postsynaptic netrin G-ligand 3 (NGL-3) as the trans-synaptic adhesion ligand of LAR and demonstrates a bidirectional regulation of excitatory synapse formation by the LAR/NGL-3 interaction.

TARPs, which are associated with AMPA-type glutamate receptors and which regulate their properties and trafficking, have not been shown to specifically regulate calcium-permeable AMPARs. In this study, the authors report that the stargazin-related protein g-5, which is expressed in Bergmann glia, preferentially regulates calcium-permeable AMPARs.

Childhood abuse or neglect alters the hormonal stress response and increases the risk for suicide. Analysis of hippocampal samples from human suicide victims with a history of child abuse indicated changes in the expression of the NC3R1 gene that did not occur in suicide victims with no childhood abuse or in people who died of other causes.