News & Views in 2004

Despite extensive study, the exact role of human anterior cingulate cortex in forming behavioral strategies is still controversial. In this issue, Williams and colleagues describe a rare opportunity to test a hypothesis about the function of this brain area in humans, by not only recording from single neurons, but also monitoring behavior immediately after surgical ablation of the area.

Neuronal networks are built from neurons with different properties and from synapses of different strengths. Modeling suggests that networks can tune these parameters to many different combinations that nonetheless produce very similar network outputs.

Relating a particular odorant to a specific behavior has proven difficult. A recent study in Nature uses clever technology to show that fruit flies possess a specialized olfactory pathway that allows them to sense, and react to, elevated levels of carbon dioxide.

Neurons that increase breathing in response to increased CO₂ have long been sought along the ventral medullary surface, but not found, until now. Exquisitely CO₂-sensitive neurons identified near this site may be the long-lost central chemoreceptors.

The perception of a stimulus can result in an emotional response, as we all know, but modulation of perception by emotion has been more difficult to demonstrate. A new study combines imaging and patient data to point to an anatomical substrate for such an effect, raising important implications regarding how sensory-processing impairments might arise in affective disorders.

In humans, recollection and familiarity represent qualitatively distinct kinds of memory. A recent study in Nature applied methods commonly used in human research to rats and suggests that their recognition memory may consist of similarly distinct components.

Newborn neurons in the cerebellum migrate along radial glial processes through a series of distinct steps. A report in this issue uses live imaging to grant us a close-up view of the cytoskeletal structures and regulating proteins involved in this migration.

The rostral cingulate zone and the orbitofrontal cortex are active when people monitor the consequences of adaptively changing behavior. A new fMRI study distinguishes their functions, implicating them in situations with different contexts and timing.

Syncytin is a viral envelope protein encoded in the human genome. New work in this issue indicates that it is activated in multiple sclerosis astrocytes and microglia, contributing to the inflammation-induced myelin destruction that causes disease symptoms.

In C. elegans, dopamine signaling regulates locomotion behavior. Chase and colleagues report that this signaling occurs through extrasynaptic and antagonistically acting receptors coexpressed in motor neurons. These results provide surprising insights into the G-protein pathways mediating this antagonism, with implications for dopamine signaling across species.

Monkeys and humans work harder for immediate than for distant rewards. How are associations between reward immediacy and sensory stimuli established in the brain? A recent study suggests a crucial role for dopamine-mediated activity in the rhinal cortex.

Many primitive movements, such as swimming or scratching, are rhythmic. An imaging study now suggests that complex discrete movements may simply be a special case of rhythmic movements, in which they are stopped after only one cycle.

Boundary cap cells of the dorsal root ganglia were thought to be limited to a structural role regulating migration into or out of the neural tube. Now a study in this issue reports that they are progenitors of small-diameter nociceptive neurons.

Glucocorticoids are important for neuronal function, but their release in conjunction with a brain injury can intensify neuronal death, causing more harm than good. A new study shows that delivery of genes that have been modified to alter glucocorticoid signaling can block the toxic effects of the hormone in vitro and in vivo, converting what was once a neuron's worst enemy into its best friend.

A new study presents the first mouse model of hereditary cerebral hemorrhage with amyloidosis–Dutch type, a disease associated with amyloid deposits in the brain's vasculature, and gives insights into Aβ deposition that may be relevant to Alzheimer disease treatment.

Thousands of active synapses on the dendrites drastically increase membrane conductance. Williams now shows that local processing is unaffected by conductance changes in distant regions, highlighting how functionally independent dendritic regions interact.

The circuitry responsible for generating orientation-specific responses in primary visual cortex remains controversial. A new study identifies an anatomical substrate for orientation selectivity and suggests the mechanism may be conserved across species.

Frequent licking and grooming by rat mothers increases the number of hippocampal glucocorticoid receptors in their pups, leading to tighter regulation of stress hormone levels. A study in this issue shows that this treatment alters DNA methylation of the glucocorticoid receptor gene and acetylation of histones early in life, providing a mechanism for these permanent changes in stress responses.

Numb is an important developmental protein that functions in fate determination, differentiation and cell maturation, but its role in mammalian neural progenitors has been controversial. A new paper uses a clever approach to attempt to reconcile the opposing views.