Volume 12 Issue 11, November 2009

During early development, rats show the unlikely behavior of becoming attracted to the very stimulus that they should avoid. A new study shows that this occurs as a result of a complex interplay of glucocorticoid secretion and dopaminergic tone in the amygdala.

The α₂δ-3 auxiliary subunit of voltage-dependent calcium channels promotes the formation of synaptic boutons in Drosophila neuromuscular junction independently of its role in channel localization.

Cholinergic neurons in the basal forebrain enable alert and attending brain states. A study now shows how basal forebrain activity increases coding abilities of cortical neurons and at what stages these changes occur.

Contrary to previous findings, this study finds that ablation of microglia, the resident macrophages of the brain, does not affect amyloid plaque or neuritic pathology in two mouse models of Alzheimer's disease.

Tonic pain, a chief clinical problem, is difficult to study in rodent models that measure threshold changes of evoked reactions to acutely applied stimuli. These authors used conditioned place preference to assess tonic pain in rats and measure the efficacy of agents that relieve it.

The instinctual attachment of young animals to their mothers is crucial for survival. Demonstrating the overriding importance of attachment, very young rat pups learn to prefer an odor coupled to electrical shock if the mother is present. This paper shows that low amygdalar dopamine signaling in very young pups is essential for their paradoxical response to odor/shock conditioning.

Although previous work has shown that extensive training in the complex visuo-motor skills involved in juggling results in adult gray-matter changes, it is unclear whether such practice can produce similar changes in adult white matter. This paper now uses diffusion tensor imaging to demonstrate structural white-matter changes when adults practice juggling.

Smad-interacting protein 1 (Sip1) is a transcriptional repressor that acts in the TGF-β signaling pathway. This study finds that Sip1 is involved in a feedback signaling mechanism in which newly generated postmitotic cells in neocortical layers instruct progenitor cells for proper cell-fate switch and proliferation.

The authors show that the LIM homeodomain transcription factor Lhx2 is responsible for the fate decision of cortical progenitors to generate neocortex or olfactory cortex. Conditional deletion of Lhx2 in telencephalic progenitors refated them to generate three-layer cortex resembling olfactory cortex, rather than lateral neocortex.

The authors report the conditional deletion of the alpha and beta forms of glycogen synthase kinase 3 (GSK-3) in mouse neural progenitors. This deletion is associated with dysregulations in β-catenin, Sonic Hedgehog, Notch and fibroblast growth factor signaling pathways and leads to markedly increased proliferation of neural progenitors.

Here, Chen et al. describe the role of the G protein–coupled receptor GPR17 in oligodendrocytes and show that it acts as a negative regulator of oligodendrocyte maturation and myelination.

This study shows that the kinase Mst3b is required cell-autonomously for axon regeneration of both retinal ganglion cells and peripheral sensory neurons in vitro and in vivo.

The main function of the α₂δ-3 calcium channel subunit is thought to be facilitation of the pore-forming subunit delivery to presynaptic terminals. Kurshan et al. now show that this subunit has other, independent synaptogenic functions and that it is important for shaping the architecture of the synapse.

The authors found considerable preparation-to-preparation variability in the strength of two identified synapses, the amplitude of a modulator-evoked current and the expression of six ion channel genes in the pyloric circuit of the crab stomatogastric ganglion. These parameters correlated with circuit performance. Circuits produced similar outputs because of compensatory and coordinated changes among the parameters.

Using endogenous circadian oscillators, Drosophila can anticipate diurnal light on/off transition and behave accordingly. Here, the authors show that the fly evening oscillator circuit can synchronize to light cycle through the visual system and the molecular components of morning oscillator.

Silva et al. show that CREB modulates allocation of fear memory to specific cells in the lateral amygdala. Reversibly inactivating a subset of CREB-expressing neurons disrupted memory for tone conditioning. Neurons with higher CREB levels were more excitable than their neighbors and showed larger synaptic efficacy changes following tone conditioning.

The nucleus basalis is thought to regulate arousal and attention via release of acetylcholine in the cortex. Here the authors report that nucleus basalis stimulation in rats results in a decorrelation between visual cortical neurons as a result of activation of cortical muscarinic receptors and an increase in the reliability of responses to natural scenes as a result of more distributed changes along the visual pathway.

A feeding leech ignores incoming stimuli that would normally cause an avoidance response. This study found that synaptic transmission from mechanosensory neurons to postsynaptic partners was reduced in feeding leeches. This presynaptic depression by feeding could be mimicked by serotonin and was antagonized by a blocker of an unusual serotonin-gated chloride channel.

Monkeys were trained to switch rapidly between two category boundaries when classifying the speed of a moving dot pattern. Neurons in the frontal eye field changed their activity when the boundary changed and a subset of these neurons were used to classify the stimuli nearly as accurately as the monkeys' behavioral performance.

Activity in the frontal eye fields (FEF) is important for visuospatial processing and is thought to code information in retinal coordinates. This fMRI study finds FEF activity even for auditory locations behind the head, suggesting that extra-retinal space is also coded in this area.

When our actions conflict with our prior attitudes, we often change our attitudes to be more consistent with our actions, a phenomenon that is known as cognitive dissonance. Here the authors report that activity during cognitive dissonance in the dorsal anterior cingulate cortex and anterior insula predicts subsequent attitude changes.