Reviews & Analysis

Dendritic spines confine activity-dependent changes to the affected synapses. A paper in this issue reports that retarded diffusion in dendrites of aspiny interneurons may create dendritic biochemical compartments without spines.

Macrophages near neuronal cell bodies can promote regeneration in an otherwise inhibitory environment. Now Yin et al. identify oncomodulin as a factor secreted from macrophages that promotes extensive regeneration of lesioned optic nerve axons when applied together with elevated cyclic AMP (cAMP) and mannose.

Visual cortex neurons are arranged into maps according to their response selectivity. Ocular dominance and orientation selectivity maps can develop without visual experience. Unexpectedly, the direction selectivity map requires visual input during a critical period, as later visual experience cannot rescue the direction selectivity map in dark-reared ferrets.

Many forms of LTP involve insertion of new postsynaptic AMPA receptors. Plant et al. now report transient insertion of Ca²⁺-permeable AMPA receptors after LTP induction, and find their activation is required for LTP maintenance.

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.