Volume 14 Issue 5, May 2011

A study this issue by Truccolo et al. analyzing extended recordings of single-neuron activity in human neocortical epilepsy, demonstrates that, even in areas remote from the seizure focus, neuronal firing patterns alter minutes before seizure onset, are heterogeneous during seizures, and change homogeneously at seizure offset.

Synapse density and patterning must be tightly regulated to ensure proper circuit formation and function. A new report finds that postsynaptic L-type calcium channels control the pattern and differentiation of developing synapses.

A study now identifies a new progenitor subtype in the developing mouse cortex, similar to the outer radial glia progenitors described previously in human, ferret and other mammals with larger, folded brains.

The molecular mechanisms of itch, particularly histamine-independent itch, are unclear. Wilson et al. report that TRPA1, an ion channel critical for pain sensation, also functions as an essential component of itch transduction.

Goals are represented in prefrontal cortex and modulate sensory processing in visual cortex. A new study combines TMS, fMRI and EEG to understand how feedback improves retention of behaviorally relevant visual information.

Amyloid-β is known to inhibit hippocampal long-term potentiation (LTP), but the underlying molecular mechanisms are only partially understood. In this capacity, Jo and colleagues report the involvement of a signaling pathway comprised of caspase-3, Akt1 and glycogen synthase kinase-3β.

Homeostatic plasticity is mostly thought be a global event that affects all synapses of the same neuron. Here, Deeg and Aizenman finds sensory pathway–specific homeostatic plasticity in the Xenopus optic tectum.

This study uses subjects with newly removed congenital occlusions to demonstrate that object matching between touch and vision is not innate. Formerly blind subjects, when they had their sight restored, were initially unable to visually match an object to a sample they had previously touched, but rapidly developed such cross-modal matching.

The authors report that radial glia–like (oRG) progenitor cells are present in the mouse embryonic cortex and that these cells arise from asymmetric divisions of radial glia. In turn, they undergo asymmetric divisions to generate neurons.

Secreted frizzled-related proteins (SFRPs) are putative Wnt antagonists. Here, Esteve et al. show that SFRPs during eye development can also serve as inhibitors of Notch signaling by acting on ADAM10 metalloprotease activity.

Developing skeletal muscle fibers are intrinsically pre-patterned prior to motor neuron innervation. Chen and colleagues show that a functional skeletal muscle dihydropyridine receptor (DHPR) is required for muscle pre-patterning during neuromuscular junction development. DHPR is an L-type calcium channel and its regulation of muscle pre-patterning requires calcium influx.

People with nonsyndromic congenital retinal nonattachment (NCRNA) are blind from birth. The authors show that NCRNA is caused by a deletion spanning a remote cis regulatory element upstream from ATOH7 (Math5), a transcription factor gene required for retinal development. The deleted region is a conserved secondary transcriptional enhancer of ATOH7.

Chen and colleagues show that visual deprivation drives structural remodeling of the dendritic branch tips of cortical layer 2/3 interneurons in an input-specific manner. Neighboring pyramidal cells show a corresponding loss of inhibitory inputs. This decreased inhibition seems to be permissive for the subsequent addition of new synapse-bearing branch tips.

Previous work has shown that two members of the Mas-related GPCR family, MrgprA3 and MrgprC11, mediate histamine-independent itch signaling. Here, Wilson et al. demonstrate that TRPA1 is a downstream target of both of these receptors in sensory neurons and is required for Mrgpr-evoked itch.

This study demonstrates that D-serine released from Bergmann glia can act as a ligand for Δ2 glutamate receptor to regulate long-term depression at parallel fiber–Purkinje cell synapses in immature cerebellum.

This study presents a new assay for investigating alcohol reward in Drosophila. Flies learned to associate cues with ethanol intoxication and developed a long-lasting attraction for the ethanol-paired cue. Dopamine neurons were necessary for expression of this conditioned preference. Mutations in a regulator of Notch signaling disrupted the formation of this memory.

Midbrain dopaminergic neuron activity is associated with reward signaling and aversive stimuli. Using genetic models in which excitatory response of dopaminergic neurons are reduced, the authors find that the imbalance of dopaminergic neuronal response following aversive stimuli is manifested in generalized anxiety.

Brief and synchronous inter-ictal events can occur between seizures. Using human tissue samples and electroencephalography, this study shows that the transition from pre-ictal discharge to ictal discharge involves distinct temporal and spatial characteristics as well as glutamatergic mechanisms.

Epileptic seizures are traditionally considered to reflect hypersynchronous neuronal activity arising from runaway excitation. Here the authors analyze spike train patterns of single neurons during seizures in human epilepsy patients, finding that spiking activity during seizure initiation was highly heterogeneous in small cortical patches and across the network.

Perceptual learning has been proposed to result from improvements either in early sensory processing or at the later stage of sensory decoding. Here the authors show that altering the feedforward connectivity in a recurrent neural network so as to improve probabilistic inference in early visual areas results in both modest changes in tuning curves and reduced noise correlations.

Previous work suggests that occipital pole areas corresponding to the central retina can be driven by retinal activity elsewhere when the central retina is lesioned. This fMRI study in individuals with macular degeneration with retinal lesions finds no evidence for such remapping of activity, suggesting that plasticity in adult visual cortex is limited.

This study uses a combination of TMS, fMRI and EEG to provide causal evidence for the role of the prefrontal cortex in the modulation of selective attention. Participants with greater decrement in visual association cortex modulation when TMS was used to knock out the prefrontal contribution had greater working memory performance decline.

The use of brain machine interfaces for neuroprosthetic control is known to change the tuning properties of neurons directly projecting the interface. Here the authors report that there are also tuning changes to indirectly projecting neurons, which are stable, but relatively small when compared with changes in the directly projecting neurons.