Research articles

The authors use in vivo two-photon calcium imaging to examine the responses and network dynamics of layer 2/3 neurons in the primary auditory cortex of mice in response to pure tones. They find that local populations in A1 are heterogeneous, but, despite this, there was a higher than average noise correlation.

The authors report that the mRNA for myo-inositol monophosphatase-1, an enzyme that regulates the inositol cycle and the main target of lithium in neurons, is localized to axons. They identify a novel NGF-responsive localization element within the 3′ UTR that directs this targeting and local translation.

Using two-photon calcium imaging, the authors found that although tonotopy was present in mouse auditory cortex at a coarse scale, it was fractured on a fine scale. Intensity tuning appeared to have no topography at all, but subthreshold responses revealed that there was some clustering of neurons with similar response properties.

SNAP-23 has previously been implicated in exocytosis regulation in non-neuronal cells. Here the authors report that SNAP-23 is also important in neurons, where it is responsible for functional regulation of postsynaptic glutamate receptors.

The authors develop a model of synaptic plasticity that can account for a large body of experimental data on connection patterns in the cortex. This model uses multiple parameters, including presynaptic spike interval and postsynaptic membrane potential.

The signals ensuring maintenance of the myelin sheath on peripheral nerves are distinct from those instructing myelination and are largely unknown. Here, the authors report that neuronal expression and regulated proteolysis of the prion protein are essential for myelin maintenance.

It is hard to dissociate the time taken for purely perceptual processes from motor reaction times when making responses to stimuli. Using a combination of a novel task design and computational modeling, this study dissociates these two processes and finds that monkeys can discriminate perceptual color information in as little time as 30 ms.

During refinement of inhibitory inputs to the lateral superior olive (LSO), terminals in the medial nucleus of the trapezoid body express VGLUT3 and co-release glutamate with glycine or GABA. Using mice lacking VGLUT3, the authors show impaired refinement of inhibitory inputs to the LSO and degraded tonotopic precision.

Hägglund et al. have generated a transgenic mouse line that expresses channelrhodopsin2 selectively in cells expressing vesicular glutamate transporter 2. Using these mice, they find that activation of glutamatergic neurons in spinal cord is critical for initiating or maintaining locomotor-like activity.

Glutamate-induced kainate receptor activation can inhibit or facilitate inhibitory synaptic transmission. This study demonstrates that it is the concerted activity of presynaptic CB1 receptors and kainate receptors that together mediate short-term depression of inhibitory synaptic transmission.

Channelrhodopsins such as ChR2 can drive spiking with millisecond precision. However, when ChR2 is highly expressed, a single light pulse can produce extra spikes, and ChR2 does not allow sustained spike trains above about 40 Hz. Rapid ChR2-driven spike trains can also cause plateau potentials. Here, the authors report an engineered opsin gene, ChETA, that overcomes these limitations and allows sustained spike trains up to 200 Hz.

Light makes migraines worse. The authors show that this effect can be mediated by intrinsically photosensitive retinal ganglion cells projecting onto thalamic neurons that also receive nociceptive input from the dura mater.

Loss of function of the tuberous sclerosis complex, which leads to overactive mTOR signaling, disrupts EphA-dependent repulsive guidance of retinal axons. Growth cone collapse and repulsion by ephrin-A correlates with and requires the downregulation of mTOR signaling.