Volume 15 Issue 4, April 2012

Extracts from the Cannabis plants, or cannabinoids, bind to the same receptors as do endogenous cannabinoids. Although usually found on nerve terminals, where their activation inhibits transmitter release, cannabinoid receptors are now reported to exist on mitochondria, where their activation by endocannabinoids regulates energy metabolism.

How do sensory systems encode prolonged stimuli? A study reveals molecular and circuit mechanisms by which C. elegans interprets oxygen concentration to produce both transient and long-lasting behaviors.

A study now demonstrates how dendritic architecture and differential synaptic innervation can account for functional heterogeneity of dopaminergic neurons in the substantial nigra.

A drug that promotes cell death in cancer cells prevents cell death in post-ischemic neurons. These contrasting effects stem from the distinct actions of the anti-apoptotic protein Bcl-x_L and its cleavage product, ΔN-Bcl-x_L.

Neuroscience seeks to understand how neural circuits lead to behavior. However, the gap between circuits and behavior is too wide. An intermediate level is one of neural computations, which occur in individual neurons and populations of neurons. Some computations seem to be canonical: repeated and combined in different ways across the brain. To understand neural computations, we must record from a myriad of neurons in multiple brain regions. Understanding computation guides research in the underlying circuits and provides a language for theories of behavior.

This perspective describes how neural oscillations are likely to play an important role in speech processing, particularly in creating a discrete neural code.

This review surveys the latest advances in the intrinsic regulatory programs directing the development and maintenance of vertebrate serotonin neurons. A new model of the regulatory program comprising a dynamic network of transcription factors is presented. The authors discuss the potential importance of network regulatory dysfunction in neuropsychiatric disorders.

This review discusses human neuroimaging as well as cellular studies to describe how learning sculpts the brain.

Using optical imaging and two-photon microscopy in awake mice, the authors show that natural odorants at their native concentrations can elicit dense activation of glomeruli in the olfactory bulb. The authors show that both anesthesia and odorant concentration can modulate the density of glomerular activation.

This study uses fMRI to demonstrate that the retinotopic representation of an afterimage in primary visual cortex is dependent on its perceived size, not the size of retinal image. This provides a neural underpinning for the well known Emmert's law of size constancy.

The death of oligodendrocytes has been hypothesized to trigger the anti-myelin immunity observed in multiple sclerosis. In a mouse model, the authors show that diffuse oligodendrocyte death alone or in conjunction with immune activation does not initiate any anti-CNS immunity.

Following axonal injury in C. elegans, the growth factor SVH-1 and its cognate receptor tyrosine kinase, SVH-2, act to promote axonal regeneration via activation of the JNK-MAPK pathway.

The authors show that the type-1 cannabinoid receptor (CB₁) is present in mouse neuronal mitochondrial membranes. They show that mitochondrial CB₁ receptors regulate cellular respiration and energy production in the brain and may contribute to synaptic plasticity in the hippocampus.

The authors show that the voltage-dependent proton channel Hv1 is required for NADPH oxidase (NOX)-dependent generation of reactive oxygen species in microglia in mice. Hv1^−/− mice were protected from NOX-mediated neuronal death and brain damage in a model of ischemia.

Inhibition of Bcl-2 and Bcl-x_L by ABT-737 is known to enhance tumor cell death. Here the authors find that it is actually protective against neuronal death in an animal model of ischemia via blockade of Bcl-x_L–induced mitochondrial channel activity. These findings point to Bcl-x_L as a potential therapeutic target.

Using optogenetic and physiological imaging tools, Busch et al. show that C. elegans sensory neurons that detect ambient oxygen concentration are tonic receptors and modify behavior in a persistent manner.

Aversive long-term memory is formed after multiple conditioning sessions spaced by a rest interval. The authors identify specific dopaminergic neurons that display oscillatory calcium activity and are required during the rest interval to allow the formation of long-term memory in the mushroom body, the olfactory memory center.

This study describes the properties of dendritic electrogenesis in rat hippocampal CA3 pyramidal neurons and distinguishes the functional differences between proximal dendrites and distal dendrites, which receive differential inputs from the mossy fibers and the perforant pathways, respectively.

In this report, the authors demonstrate unique membrane potential dynamics of somatostatin-expressing (SOM) GABAergic neurons in layer 2/3 primary somatosensory barrel cortex of awake behaving mice. SOM neurons hyperpolarized and reduced action potential firing rates during sensorimotor processing, thereby reducing dendritic inhibition in nearby excitatory neurons during active neocortical computation.

With a combination of ultrastructural analysis, juxtacellular/immunolabeling reconstruction and in vivo recording of dopaminergic neurons in the substantia nigra pars compacta, this study finds that the structural differences of dopaminergic neurons underlie heterogeneous dopaminergic response to aversive stimuli.

Thalamic activity is strongly inhibited by pallidal inputs from the basal ganglia, but the role of excitatory inputs from cortex is unclear. Recording from presynaptic pallidal axon terminals and connected postsynaptic thalamocortical neurons in zebra finches, the authors find that pallidal inputs control thalamic spike timing, whereas cortical inputs may be the principle drivers of thalamic activity during singing.

It has been proposed that the center-surround receptive fields encountered in the early visual system serve to reduce the redundancy that is always present in natural scenes. The authors test this idea by recording from salamander retinal ganglion cells. They find strong decorrelation that is primarily a result of non-linear processing in the retina, rather than center-surround interactions. These nonlinearities serve to enhance efficient coding in the presence of noise.

This study used fMRI to find that the dorsal visual area (V3B/KO) combines information about binocular disparity and relative motion cues to work out depth information.