Volume 14 Issue 8, August 2011

To best interpret new sensory information, populations of sensory neurons must represent the lessons of past experience. How do they do this? The same solution to this problem is now reported in two very different sensory systems, providing a classic example of computational convergence.

A study identifies mechanisms responsible for the inability to form new myelin after neonatal hypoxia. It identifies Axin2 as a potential therapeutic target for reversing the 'differentiation block' of oligodendrocyte-lineage cells.

Controversy surrounds the suggestion that recursion is a uniquely human computational ability that enables language. A study now finds this ability in a songbird and takes steps toward a model system for syntactic competence.

A study now finds early memory impairment in a mouse model of amyloid β43 (Aβ43)-overproducing familial Alzheimer's disease and suggests that this overlooked amyloidogenic Aβ species contributes to pathology.

It is thought that retinal bipolar cells do not fire action potentials, but calcium imaging in live zebrafish now reveals that in bipolar cells there are 'all or none' calcium transients that are modulated by visual stimulation.

Learning both a word list and a motor memory task in a short interval usually leads to interference between the two tasks, resulting in poorer performance. Depending on the order of the tasks, the authors were able to directly prevent interference by applying transcranial magnetic stimulation to disrupt processing in either the prefrontal or the motor cortex, which suggests that distinct mechanisms underlie memory interference.

The authors report that Hes5, a Notch effector gene, is serially activated by mammalian glial cells missing (Gcm) and later by the canonical Notch pathway. Loss of both Gcm1 and Gcm2 and subsequent lack of Hes5 upregulation in the neuroepithelium leads to impaired induction of neural stem cells.

This study demonstrates the existence of a novel retinal narrow-field amacrine cell subtype that is neither GABAergic nor glycinergic. These cells arise from a late-born glycinergic population and are specified by expression of the transcription factor Neurod6.

This study reports that CaMKIIβ is recruited to the centrosome by PCM1, where it promotes dendrite retraction and pruning via the phosphorylation and inhibition of Cdc20-APC. This effect is independent of its association with CaMKIIα.

C. elegans uses a thermotactic neural circuit to sense, move and remember temperature gradients in its surroundings. Here, Sugi and colleagues show that these responses are regulated by the heat-shock transcription factor HSF-1 and subsequent transcriptional programming in both neuronal and non-neuronal cells.

Laminin-332 is a major component of the dermo-epidermal skin basement membrane and maintains skin integrity. Here the authors find that it also suppresses a mechanosensitive current by preventing the formation of protein tethers required for current activation and exerts local control of over sensory axon branching behavior.

The authors generated a knock-in mouse line in which the MeCP2 protein cannot be phosphorylated by neuronal activity, and found that the mice exhibit superior hippocampus-dependent memory performance and enhanced synaptic plasticity by upregulating MeCP2 target genes, including BDNF, and have higher levels of excitatory synaptogenesis.

Premyelinating oligodendrocytes are vulnerable to hypoxic injuries, especially during the neonatal period. Here, Fancy et al. find that the Wnt scaffolding molecule Axin2 is crucial for normal remyelination after hypoxic injuries and demonstrate that pharmacological inhibition of tankyrase, which stabilizes Axin2 levels, can promote oligodendrocyte differentiation and recovery after hypoxic and demyelinating injuries.

The authors use transgenic mice to show that zinc modulates NMDA receptors containing the NR2A subunit, and that this interaction influences pain control in vivo.

In addition to neurotoxic Aβ42, the Aβ43 variant is also abundant in Aβ plaques in the brains of individuals with sporadic and familial Alzheimer's disease. As the functional difference between the two species of Aβ fragments are not known, Saido et al. used a presenilin-1 (PS1) mutation that increases Aβ43 production over other Aβ fragments and generated a knock-in mouse line mimicking the human PS1 mutation. They report that Aβ43 is highly amyloidogenic in this line of mice and leads to behavioral deficits.

The authors provide definitive evidence for the in vivo contribution of D₂ autoreceptors to dopamine-mediated behavior by studying mice deficient in D₂ autoreceptors. These mice lack dopamine-mediated somatodendritic responses and inhibition of dopamine release, and show supersensitivity to the psychomotor effects of cocaine.

Sniffing controls the exposure of receptors to odors. Here the authors show that mitral/tufted cells in the olfactory bulb provide precise temporal information with regard to sniff phase that can facilitate coding of odors.

Using two-photon calcium imaging in vivo and intracellular recordings in vitro, the authors find that visual stimulation only weakly modifies coactivation patterns of inhibitory neurons, whereas excitatory neuron correlations are largely stimulus dependent.

This study uses a combination of electrophysiological recordings and computational modeling to show that the properties of visual simple and complex cells (defined by the differing properties of their receptive fields) are modulated by the properties of the stimulus received by these cells. This modulation appears to serve a normalization function.

Owls accurately localize sound sources near the center of gaze, but systematically underestimate peripheral source directions. Here the authors demonstrate that this behavior is predicted by statistical inference and show that the owl's map of auditory space decoded by a population vector is consistent with the behavioral model.

The human capacity for language is unique, but other animals may have abilities in some of the domains that are required for processing language. Abe and Watanabe find that songbirds have the capacity to learn an artificial grammar and to process hierarchical structures, an ability thought to be unique to humans.

Previous work suggests that individual neurons in the lateral intraparietal area (LIP) can reflect specific learned associations. Here the authors find that individual LIP neurons can encode two completely different learned associations in two separate tasks. This suggests that LIP neurons can represent generic categorical outcomes.

This Technical Report describes an automated algorithm to trace densely labeled neurons and reconstruct their structure, thus providing a new tool in functional connectome analysis.

Two-photon calcium imaging has previously only been useful for imaging ongoing neuronal activity in the superficial cortical layers in vivo. Here the authors describe technology that enables imaging of sensory-evoked neuronal activity in layer 5 of adult mouse somatosensory cortex.