Reviews & Analysis

Manipulation of the neurons required for a specific behavior can be difficult, but is required for proof of causality. A clever technique now allows inactivation of only the subset of neurons that have been recently active.

How are volatile molecules entering the nose converted to odor percepts in the brain? A fMRI study finds that distributed patterns of activity in the human posterior piriform cortex code the perceived category of odorants. This categorization of odors into objects is independent of their chemical structure.

A study shows that the histone deacetylases HDAC1 and HDAC2 stimulate oligodendrocyte differentiation by antagonizing the inhibitory action of Wnt signaling, linking genetic and epigenetic control of oligodendrocyte development.

A recent study shows that GABA switches from stimulating to inhibiting interneuron motility during neocortical development. This change in response is gated by the expression of the chloride transporter KCC2.

How different frontal brain regions contribute to goal-directed behavior is not fully understood. A study now suggests a parallel functional architecture in medial and lateral prefrontal cortex for motivating and selecting behavior.

Mitochondria are considered to be the main source of reactive oxygen species during glutamate excitotoxicity. Data now support a prominent role in this process for NADPH oxidase, the enzyme that neutrophils use to kill bacteria.

A study in this issue uses a new technique to show that synaptic vesicles released spontaneously and those released in response to action potentials are drawn from distinct, non-overlapping pools that coexist in presynaptic terminals.

The orientation of the mitotic spindle determines whether divisions of the polarized neural progenitors in the ventricular zone cause their expansion or lead to neurogenesis. A guanine nucleotide exchange factor for the small GTPase RhoA is now shown to tip this balance in favor of neurogenesis.

The olfactory bulb is densely innervated by serotonergic fibers. A study now shows that serotonin activates periglomerular interneurons, which release GABA to reduce transmitter release from olfactory sensory neurons.

Projections from the amygdala to the ventral striatum are important for learning. A study finds that fleeting epochs of coherent gamma oscillations between these brain areas may be important for reinforcement learning.

This perpective offers an evolutionary perspective on the advantages of binaural hearing, and discusses the many different strategies for such hearing that animals have evolved. Authors discuss how these strategies might inform future work on auditory prosthetics.

Primary auditory cortex is usually thought to be directly analogous to primary visual cortex, with stimulus physical properties being represented at this level. This perspective argues that the auditory system has unique operating principles that make it different from the visual system, such as considerably greater subcortical processing.

In this perspective, the authors discuss recent advances in the development of cochlear implants and elucidate the implications of implant-induced plasticity for future technology.

As language is unique to humans, it is usually thought that work in other animals has made limited contributions to understanding it. Authors here review work on species-specific vocalizations in nonhuman primates to arrive at a new model for how human speech is processed.

This review describes how the genetic causes of the many forms of human deafness have provided insight into the molecular mechanisms of auditory transduction. In combination with mouse models, these genetic studies have elucidated the mechanisms behind the formation and functioning of the hair bundle as a mechanical transducer.

Whereas birds can generate new auditory neurons even in adulthood, mammals cannot. This perspective suggests that factors such as increasing life span expose a deficit in cochlear self-regeneration that was irrelevant for most of mammalian evolution, resulting in hearing loss. Authors discuss various approaches aimed at regenerating hair cells to ameliorate such hearing loss.

This review summarizes recent work in auditory brainstem nuclei to demonstrate that developing brain stem circuits are subject to experience-dependent synaptic refinement. This is in contrast to the traditional view, which interprets the early development of brain stem tonotopy as indicative of a 'hard-wired' mechanism.

Playing action-based video games has been shown to improve attentional processing. A study now finds that it also induces long-lasting improvements in contrast sensitivity, a basic visual function that commonly deteriorates with age. These improvements do not happen for an equivalent group who played a non-action video game.

A study now demonstrates that the transduction channel responsible for converting sound to neural signals in the mammalian cochlea is excluded from the tallest row of stereocilia and is instead more likely in the bottom row.