News & Views in 2006

Defining the connections between the cells of the mammalian retina remains a major challenge. A new study shows how two types of cone photoreceptors selectively connect with the multiple types of postsynaptic bipolar cell.

Orbitofrontal cortex damage impairs decision making. A recent article in Nature shows that this brain region is critical for computing the subjective value of an outcome and using this value signal to make choices

Antidepressants take a few weeks to act, and their effects can extend for months after the drugs are discontinued. Tsankova et al. suggest a possible molecular basis for these effects, by showing that stress and the antidepressant imipramine induce modifications of chromatin to produce more or less repressive states for gene expression.

Both menthol and cool temperatures activate the cation channel TRPM8, but whether they do so via distinct domains was unclear. A new paper shows that activation of TRPM8 by these two stimuli can be separated.

Neurons born in the adult subventricular zone migrate a long way to their destination. A new study suggests that signals from the corticospinal fluid, in particular the chemorepellent Slit2, guide adult neuroblast migration.

A Bayesian model of visual motion perception describes how the brain combines assumptions with evidence. A new study in this issue tests and expands the model, building connections between perception, the environment and neural responses.*

Traditional learning theory suggests that animals do not understand that actions cause their consequences. A new paper uses sophisticated behavioral experiments to conclude that rats are capable of causal reasoning.

Many neurons, particularly inhibitory neurons in motor areas, express ion channels that cause them to fire rapidly and regularly without input. A paper now presents evidence that an inherited ataxia due to mutation in a P/Q-type calcium channel gene results from compromised pacemaking in cerebellar Purkinje neurons, suggesting a possible therapy.

The suprachiasmatic nucleus is the main circadian pacemaker. Another oscillator entrains behavior to food availability, but its location has been a mystery. A new study suggests the dorsomedial hypothalamic nucleus as a possibility.

Stem cells are defined by their ability to self-renew. Adult brain stem cells divide slowly, and it is unclear how their division is regulated. A new study identifies PEDF as a growth factor that promotes adult stem cell self-renewal.

Activity in early visual processing areas is often thought to reflect physical input from the retina, rather than conscious perception. A new study now finds that activity in V1 corresponds to perceived rather than actual object size.

The exact embryonic origins of forebrain oligodendrocytes have been unclear. A new study addresses the question with elegant genetic fate mapping, and concludes that oligodendrocytes are generated in three distinct waves. Oligodendrocytes from later waves eventually replaced those generated in earlier waves, but if one wave was lost, the other waves could compensate.

Alpha-fetoprotein binds estrogens in the developing brain. A new paper shows that inhibiting estrogen rescues the brain masculinization found in female mice lacking this gene, suggesting that alpha-fetoprotein inhibits estrogen activity in females.

The Cav1.3 calcium channel is found on striatopallidal neurons expressing the D2 dopamine receptor. A new study finds that in an animal model of Parkinson disease, this channel is involved in degeneration of dendritic spines on striatal projection neurons.

Visual attention in primates is influenced by microstimulation of the frontal eye fields. A study in Nature now reports similar effects on auditory information processing after microstimulation of a region of the forebrain that controls gaze direction in barn owls.

Increased local blood flow in response to neural activity is critical for brain function and the basis for functional imaging. Takano et al. now show that in vivo, astrocytes are central in translating neural activity into vasodilation via a mechanism involving COX1 metabolites.