Reviews & Analysis

White people who have difficulty implicitly pairing black names with positive words also tend to be impaired on tasks requiring cognitive control after interacting with a black experimenter. A new functional imaging study finds that such subjects also show more activity in brain regions associated with cognitive control when looking at black faces that are irrelevant to their task.

Presynaptic inhibition of cutaneous afferents influences sensory-motor responses in the spinal cord. In-vivo recordings in monkeys now show that this process suppresses the transmission of cutaneous signals generated during volitional movement.

Confusing results from gene deletion experiments have left the importance of doublecortin (DCX) during brain development unclear. A report in this issue establishes a definitive function for DCX and highlights limitations of gene knockout approaches.

A recent study in Nature shows that the columnar fate of motor neurons in the embryonic spinal cord is imposed by cross-repressive patterns of Hox-c expression. This Hox expression is in turn controlled by graded FGF signaling.

The auditory cortex, once thought to be a passive detector, is now caught in the act of reshaping the frequency sensitivity of its neurons to intercept target sounds that are significant for a behavioral task, suggesting tuning properties can change 'on-line'.

New findings reveal that people sniff when imagining odors and that sniffing can modify the pleasantness or unpleasantness of the mental image. The work parallels findings in other systems and suggests common neural principles for mental imagery.

How does the brain orchestrate the integration of new neurons into mature circuitry, without disrupting those circuits in the process? Mizrahi and Katz provide a new perspective on how the brain manages this dilemma, by showing that the dendritic backbone of mitral/tufted cells in the adult olfactory bulb is remarkably stable despite learning and neuron turnover.

A new study in this issue demonstrates that two GABAergic motor neurons in C. elegans are excitatory at target muscles because GABA activates a ligand-gated cation conductance, which is structurally similar to several other ligand-gated channels.

In C. elegans, social and solitary feeding behavior can be determined by a single amino acid change in a G protein–coupled receptor. A new study identifies ligands for this receptor and suggests how changes in behavior evolve at the molecular level.

A homeostatic control mechanism that monitors and reacts to the need for sleep has been thought to function independently of the brain's circadian clock in previous studies. Now simultaneous recordings of sleep stages and electrical activity in the suprachiasmatic nucleus in behaving animals reveal feedback from sleep centers to the circadian pacemaker.

Corticotropin releasing factor (CRF) is a critical integrator of the central stress response. A new study now provides conclusive evidence that CRF-mediated forebrain activation underlies the behavioral response, such as anxiety, to stress.

HIV-associated neurodegeneration likely involves release of signals from activated glial cells. A new study reveals that matrix metalloproteinase from HIV-1-infected macrophages or microglia cleaves the chemokine SDF-1 to generate a potent neurotoxin.

How is synaptic facilitation mediated? New work suggests that a calcium-sensing molecule, neuronal calcium sensor-1 (NCS-1) transduces a residual calcium signal into an enhancement of transmitter release at excitatory synapses in the hippocampus.

After exocytosis, synaptic vesicles must be retrieved and refilled with neurotransmitter to supply the needs of an active neuron. A new report finds that synaptic activity, through the retrograde action of nitric oxide (NO), regulates the rate of this synaptic vesicle recycling. These findings suggest that NOmight enhance the synaptic strength of coincidentally active neurons.

The unusual case of a man who regained his sight after 40 years of blindness allows researchers to examine the neural and behavioral effects of losing visual experience on the establishment and maintenance of visual system function in humans.

Temporal integration, in which transient inputs shift neurons between stable firing rates, is thought to require neural networks. A new modeling study now proposes that single neurons could perform this calculation via intracellular calcium release dynamics.

Repeated imaging of the same individual neuron for over a year in mice allows the authors of a new study in this issue to show that presynaptic axon terminals become progressively more stable as the animals age, changing little after 6 to 12 months.