Articles in 2008

This study combines transcranial magnetic stimulation (TMS) and electroencephalography (EEG) and finds that TMS over frontal eye fields affects EEG over more posterior areas. This effect was modulated by the task and attentional preparation and provides causal evidence for the existence of a prefrontal top-down control signal.

The normal physiological function of the prion protein PrP^C remains unknown. Here, the authors report that PrP knockout mice show altered behavior in two olfactory tasks and that PrP deficiency affects oscillatory activity in the olfactory bulb. Both the behavioral and electrophysiological phenotypes could be rescued by transgenic neuronal-specific expression of PrP^C.

Previous work links hyper-responsive threat detection to anxiety. Using fMRI, this study finds that highly anxious individuals had reduced prefrontal cortex activity and slower target identification during a response conflict task when the task did not fully use up their attentional resources. Trait anxiety is therefore linked to less prefrontal attentional control, even when there are no threatening stimuli.

The retinal degeneration disease retinitis pigmentosa is characterized by an initial loss of rod photoreceptors followed by a progressive loss of cones. Providing a mechanism behind the long delay of cone death in retinitis pigmentosa, Punzo et al. identify and characterize the involvement of an insulin/mTOR pathway, indicating that cell starvation of cones can partially account for the nonautonomous photoreceptor death in retinitis pigmentosa.

Tiling describes the arrangement of neuronal processes in a pattern with little or no overlap with those of neighboring neurons. It is unclear how this is mediated in the vertebrate retina, whose mosaic cell body distribution of horizontal cells is accompanied by extensively overlapping dendrites. A study by Huckfeldt et al. now shows that the nonrandom distribution of the horizontal cells is correlated with repulsive homotypic interactions between developmentally transient processes, leading to the development of initial territories of horizontal cell.

The authors report that the population of lateral habenula neurons responds most strongly for the most unpleasant outcome in a particular context: either the absence of reward when rewards are available or the presence of punishment when punishments are feared.

Liu and Davis identify a GABAergic neuron, the anterior paired lateral neuron, that innervates the mushroom body neuropil and elaborate on the reciprocal relationship between GABA signaling and Drosophila olfactory memory.

By simultaneously recording spikes and local field potentials (LFPs) in cat and monkey visual cortex, the authors demonstrate that the magnitude and spread of LFP waves from the originating spike are reduced with increasing stimulus contrast. This suggests that visual cortex functional connectivity is not fixed, but is instead modulated by stimulus contrast.

In sedated and whisking rats, the authors show that motor cortex activity enhances sensory processing through a cortico-cortico-thalamic feedback circuit. In whisking rats, however, inhibitory brainstem input to the thalamus was also enhanced, leading to a net suppression of thalamic sensory responses.

The nervous system produces accurate movements by adapting to environmental changes. The authors construct a probabilistic model that compensates for motor errors and estimates their sources, finding that if the motor system used such a strategy, it would explain many previously observed movement-generalization phenomena.

It has been proposed that neurons in the intraparietal cortex gradually accumulate evidence supporting different response options. Here the authors show that this model generalizes to arbitrary stimulus-response associations in humans.

The authors here show that two completely different classes of spinal premotor interneurons drive motoneurons during slow and fast swimming of zebrafish larvae. As the fish accelerate, the 'slow' interneurons are progressively silenced, while the 'fast' interneurons take over, and vice versa.

Genetic ablation of β-catenin in the embryonic ventral forebrain restricted proliferation of neural precursors in the medial ganglionic eminence, resulting in fewer cholinergic projection neurons in basal forebrain and fewer calbindin- and somatostatin-positive interneurons in the cortex. This work suggests a crucial role for canonical Wnt signaling in ventral forebrain neurogenesis.

The authors report that fMRI responses in human foveal retinotopic cortex contain information about objects presented in the periphery. This information is position invariant and correlated with perceptual discrimination accuracy.

Adenosine receptor A_2AR is known to antagonize dopaminergic signaling in the striatum and its malfunctions have been implicated in various striatum-related diseases. Flajolet et al. show that A_2AR and fibroblast growth factor receptor interact to synergistically activate ERK1/2 pathway and that such interaction modulates the morphological changes of cultured neurons and synaptic plasticity of cortico-striatal synapses.

Hippocampal GABAergic synapses are excitatory during the early postnatal period and can undergo spike timing-dependent modifications of synaptic strength. Xu and colleagues demonstrate that this plasticity can be modulated bidirectionally by frequency and that it depends on the action of GABA_B receptors.

Recent work has suggested a role for astrocyte dysfunction in the etiology of amyotrophic lateral sclerosis (ALS) caused by mutations in superoxide dismutase (SOD1). Lepore et al. show here that transplantation of astrocyte-restricted progenitors in fact improves survival of rats expressing a human ALS-associated SOD1 allele. The rescue effect required the astrocytic glutamate transporter GLT1.

Neural systems adapt to changes in stimulus statistics. The authors find that neocortical pyramidal neurons adapt with a time scale that depends on the time scale of changes in stimulus statistics, and that for individual neurons the firing is a fractional derivative of slowly varying stimulus parameters.

The contribution of fatty acids to Alzheimer's disease pathogenesis is unclear. The authors identify an increase in arachadonic acid and its metabolites in a mouse model for Alzheimer's disease and show that amyloid-beta (Aβ) affects phosphorylation of an isoform of phospholipase A₂ (GIVA-PLA₂). Inhibiting activation of GIVA-PLA₂ protected against Aβ-induced toxicity and prevented some Aβ-induced deficits in learning and memory.

The authors analyze gene coexpression relationships in microarray data generated from specific human regions. They identify modules of coexpressed genes that correspond to neurons, oligodendrocytes, astrocytes and microglia, demonstrating that cell type-specific information can be obtained from whole brain tissue without isolating homogenous populations of cells.