Articles in 2015

In this Review, Jeanne Paz and John Huguenard examine how recent work has informed us on the function of brain microcircuitry and how different circuit types may contribute to seizure generation and/or propagation. The authors also propose the idea that these microcircuits may regulate the spread of seizures and represent new targets for therapeutic intervention.

In this Review, Jeff Noebels examines recent advances in the identification of new genes underlying the onset of epilepsy. Given their functional convergence on synaptic inhibition and rich interactive landscape, collective analysis of genes driving major network interactions—as performed in the cancer field—may help point the way forward toward better diagnostics and target prioritization.

Current treatment options are, for many patients with epilepsy, either insufficient or ineffective and, thus, new therapeutic methodologies are necessary. In this Perspective, Esther Krook-Magnuson and Ivan Soltesz look at recent advances in optogenetic-based modulation of circuit activity and seizures with an eye toward the prospect - and challenges - of utilizing these technologies for the treatment of epilepsy.

The term ‘seizure’ emphasizes the abrupt and unpredictable nature of the onset of epochs of pathological neuronal synchrony that define the disorder of epilepsy. Mechanisms of epilepsy should account for seizure transitions with these unique temporal properties. In this review, Kevin Staley discusses how combining insights from new genetic etiologies with seizure timing may begin to outline the mechanisms by which the brain becomes predisposed to seizures.

The authors use TetTag pharmacogenetics to mark neuronal ensembles activated in the preoptic hypothalamus during dexmedeotomidine-induced sedation or recovery sleep. When these ensembles were selectively reactivated, NREM sleep and the accompanying drop in body temperature were recapitulated. Thus α₂ adrenergic receptor–induced sedation and recovery sleep share circuitry sufficient for producing these states.

Temporally coordinated signals at gamma frequencies and higher are often used to study inter-regional communication in brain networks, but interpreting mechanisms from population measures can be troublesome. The authors discuss the physiological origins of gamma coherence and suggest ways to decipher its roles in neural function.

Learning of arbitrary associations depends on the hippocampus and prefrontal cortex. This learning is reflected in prefrontal cortex. The hippocampus instead provides feedback about whether trial-and-error guesses are correct or incorrect. The two areas synchronize in different frequency bands following correct vs. incorrect guesses, which may guide learning.

Human motor adaptation is often described as an automatic process insensitive to reward- or punishment-based feedback. Contrary to this hypothesis, Galea et al. show through a double dissociation that negative and positive feedback have independent effects on the learning and retention components of motor adaptation, respectively. These results promise to have significant implications for the understanding and optimization of motor adaptation.

The authors show that inhibitory neurons of the pontine reticular formation (PRF) exert powerful control over the intralaminar thalamic nuclei, a major gate of forebrain motor centers. Optogenetic activation of inhibitory PRF terminals antagonizes voluntary movements and promotes slow cortical oscillations, highlighting the contribution of brainstem ascending projections to large-scale motor circuits.

In this study, the authors report the molecular characterization of orally bioavailable and blood-brain-barrier permeable inhibitors of the nuclear export molecule Xpo1/CRM1 and define the immunomodulatory and neuroprotective effects in preclinical models of inflammatory demyelination and excitatory neurotoxicity.

Lapses of attention are commonplace, potentially because they are detected too late to be prevented. The authors use real-time fMRI to provide participants continuous access to their attentional state. Real-time feedback, particularly from frontoparietal cortex, improved sustained attention abilities and modified representations in visual cortex and basal ganglia.

Neurogliaform interneurons constitute an essential component of cortical circuits. This paper provides evidence that, during early development, superficial neurogliaform cells of the primary somatosensory barrel field cortex receive prominent innervation from the thalamus. These afferents also activate postsynaptic NR2B-containing NMDA receptors, which are essential for the neurons' proper cortical integration.

Coincidence detection is a fundamental neural operation, developed to an extreme in the computation of interaural time differences for sound localization. This study utilizes intracellular in vivo recordings and pharmacological manipulations in the medial superior olive of Mongolian gerbil to reveal that maximal coincidence is not just determined by the timing of synaptic inputs, but also by intrinsic neural properties.

Dopamine axons projecting from the ventral tegmental area to the nucleus accumbens (mesoaccumbens axons) play a role in motivation. Tthe authors show that there are distinct microdomains releasing either dopamine or glutamate within individual mesoaccumbens axons in rats and mice.

Comprehensive analysis of epigenetic regulation demonstrates a series of complex, interacting chromatin mechanisms by which chronic exposure to opiates downregulates Bdnf gene transcription in the ventral tegmental area. This regulatory cascade is also shown to play a role in controlling opiate-induced behavioral plasticity.

Insertion of AMPA receptors into the synaptic membrane is thought to be a central mechanism for controlling experience-dependent changes in synaptic strength, yet this has never been observed in real time in the intact brain. Using two-photon imaging, Zhang and colleagues were able to provide this missing piece of information by tracking the insertion of GluA1 in spines in mouse barrel cortex neurons during repetitive whisker stimulation.

The authors investigated the role of glycinergic preBötC neurons in respiratory rhythmogenesis in mice using viral delivery of Channelrhodopsin-2 (ChR2) or Archaerhodopsin (Arch) genes. They conclude that glycinergic preBötC neurons modulate inspiratory pattern and are important for reflex apneas but that the rhythm can persist after significant dampening of their activity.

This study shows that cocaine strengthens glutamatergic transmission, reduces K⁺ channel function and drives hyperexcitability in lateral habenula neurons projecting to the rostromedial tegmental nucleus. The authors also show that GluA1 trafficking mediates these cellular modifications and is instrumental in a drug-mediated depressive-like phenotype.

microRNAs control synaptic signaling through regulation of postsynaptic responsiveness. This study provides evidence that the conserved microRNAs miR-1000 and miR-137 act presynaptically via glutamate transporters to regulate glutamate release. miR-1000 expression is activity dependent, perhaps allowing activity to fine-tune the strength of excitatory synaptic transmission.