News & Views in 2012

Sensory deprivation can result in impaired perception in most sensory modalities owing to experience-dependent changes in neural processing. Odor perception, however, appears to be relatively immune to periods of deprivation. Work in humans now suggests that this stability may be due to robust, reversible, compensatory plasticity in cortex.

Animals often must vie with others for scarce resources, such as food, water and mates. Deciding when to engage and when to avoid such contests might critically depend on the activity of anterior cingulate cortex neurons.

Phasic bursting of dopaminergic neurons influences many behaviors. A study now finds that ATP-sensitive potassium channels mediate bursting in dopaminergic neurons of the medial substantia nigra and affect novelty-induced exploration.

Hypothalamic neurons that express agouti-related protein have been thought to regulate appetite by counteracting the melanocortin signaling pathway. Evidence now indicates that these neurons can also modulate dopamine signaling.

A study reveals that aged mice have decreased hippocampal expression of the DNA methyltransferase Dnmt3a2; re-expression in aged mice reverses memory deficits, and knockdown in young mice impairs memory formation.

Natural or artificially induced electrical activity changes can alter ion balance so as to briefly influence firing. An optogenetics study delineates one mechanism: Cl⁻ shifts causing seconds-long excitability changes after silencing.

Mice lacking NMDA receptors in the dentate gyrus and CA1 subfields of the hippocampus form spatial memories just as well as wild-type mice, but they disregard them when confounded by ambiguous local cues. Hippocampal NMDA receptors may influence spatial memory more subtly than previously thought.

The diverse population of retinal cell types has now been shown to include one that does a neat trick: an interneuron inverts the sign of the retina's response to blue light, creating the blue-Off output signal to the brain.

Changes in pupil diameter may reflect the dynamic processes in the brain that allow us to detect and rapidly adapt to hidden changes in the world. What's more, unrelated manipulations of pupil size may in turn influence these processes.

How do we feel temperature? A study now finds that a recently discovered anion channel is a temperature sensor that, like previously identified cation channels, mediates the perception of noxious hot temperatures.

Despite years of research, what regulates neurotransmitter release at synapses is still not fully understood. Physiological and ultrastructural approaches now reveal critical structural parameters of the presynaptic active zone correlating with release probability: the size of the active zone and the number of calcium channels.

A large study of impulsivity in 14-year-olds finds that substance use and ADHD symptoms are associated with different brain networks that inhibit motor responses. Genetic analysis implicates the noradrenergic system in activity levels in one of these networks, which is centered on the right frontal cortex.

By bringing mGluR1/5 and proline-directed kinases together, the scaffold protein Preso1 stabilizes the interaction between mGluR1/5 and Homer. This mechanism may attenuate calcium influx into spinal neurons and reduce pain.

How do outcomes affect future behavior? A study using precise optogenetic stimulation finds that learning from positive reinforcement is mediated by striatal pathways distinct from those that mediate learning from punishment.

A long-standing puzzle has been the seeming inconsistency between neuronal responses in primary visual cortex to colored stimuli and the elementary perceptual attributes of color vision. Nonlinear analysis resolves this paradox.

How does the brain evaluate whether the benefits of a decision outweigh the costs? A study now reveals that neurons in the anterior cingulate cortex encode costs and benefits, and altering brain activity here biases choices away from negative outcomes. These results link anterior cingulate cortex with the regulation of emotional states.

Tanycytes in the hypothalamic median eminence have now been found to form a metabolically sensitive neurogenic niche in the brain. In adult mice, tanycytes give rise to hypothalamic regulatory neurons in response to a high-fat diet.

In the developing cortex, spike timing–dependent long-term depression requires cannabinoid-induced glutamate release from astrocytes. Astrocytes may be integral to the coincidence detection that guides plasticity and map formation.

Odorants are now shown to elevate mitochondrial Ca²⁺ in sensory neurons; moreover, blocking this Ca²⁺ sequestration impairs dynamic range. Acute stimulation rapidly recruits mitochondria from the soma to the dendritic knob.