Research articles

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.

Neuronal response selectivity and perceptual discrimination can be affected by acoustic experience during development. Here the authors show that intensive discrimination training in adult animals can restore normal cortical response patterns.

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.

Transgenic expression of microbial channelrhodopsins in neurons allows direct light activation of ionic currents. Here, the authors describe a modified channelrhodopsin that remains open for seconds once it is activated by light and can be 'switched off' by a second light flash, thereby obviating the need for constant illumination during an experiment.

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.

Attention is thought to select nonspatial features later than spatial location. This study uses ERPs to show that color-based attention effects manifest themselves as early as 100 ms, similar to spatial attention effects.

Prosopagnosics have impaired face recognition, but make relatively normal responses to face stimuli in core brain regions for face recognition. The authors now report that it is the connectivity among these regions that is being disrupted in the disorder.

The striatum receives projections to a number of cortical and subcortical areas. The authors report here that fiber tracts from prefrontal cortex are correlated with individual differences in reward dependence and that tracts from the hippocampus, amygdala and ventral striatum are correlated with individual differences in novelty seeking.

Activation of GABA_A receptors can depolarize specific neuronal compartments, causing excitation. The authors report that hippocampal interneurons hyperpolarize pyramidal cells, irrespective of the location of their synapses, along the entire somato-dendritic axis.

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.

No two roses smell exactly alike, but our brain accurately bundles these variations into a single percept 'rose'. The authors now report that although olfactory bulb neurons decorrelate odor mixtures that are quite similar, piriform cortex neuronal responses show pattern completion and predict olfactory perception.