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In addition to the neurotropic role of brain-derived neurotrophic factor (BNDF) in cortical circuit plasticity, there is a good positive correlation between the cortical expression level of BDNF and developmental changes in visual acuity. Here, the authors find that directly impairing BDNF signaling using transgenic methods causes visual impairment by affecting the systems level control on contrast gain.
A hallmark of Huntington's disease is the accumulation of polyglutamine-expanded huntingtin (htt) protein in striatal neurons. The removal of cytosolic mutant htt is known to be mediated by the macroautophagy-lysosomal system. Here the authors specifically identify the defective step of autophagy in Huntington's models, in which autophagosomes fail to recognize mutant htt as a cargo destined for degradation.
An et al. visualized complexin, a cytosolic protein implicated in synaptic vesicle fusion, during real-time single exocytic events in live cells. They find that complexin is recruited to a SNARE complex prior to fusion and directly regulates the dynamics of fusion pore dilation.
The authors report that inactivating the protein kinase isoform PKMζ in the amygdala impairs fear conditioning in rats and that PKMζ maintains long-term memory by trafficking GluR2-containing AMPA receptors.
5-HT2 and corticotrophin releasing factor (CRF) receptors both regulate stress responses and anxiety behavior; however, potential cross-talk between the two pathways is poorly understood. Magalhaes et al. find that CRF receptor activation causes cell-surface recruitment of constitutively internalized 5-HT2 receptor and that this mechanism is relevant to anxiety-related behaviors.
Odors, via the olfactory AWC neurons, trigger food searching in C. elegans. This study shows that the peptide NLP-1, co-released with glutamate from AWC neurons, acts to limit searching locomotion through a feedback loop that involves activation of the receptor NPR-11 on AIA interneurons and release of another peptide, INS-1, from the AIA neurons.
Dendritic distortion is problematic for neurons using temporal coding strategies, such as medial superior olivary neurons, which encode microsecond differences in binaural auditory input. Mathews et al. find that both the specific activation properties and spatial distribution of Kv1 channels compensate for passive cable filtering, helping to preserve binaural synaptic timing.
Silver et al. demonstrate that Magoh, a component of the RNA-binding exon junction complex (EJC), controls mouse cerebral cortical size by regulating neural stem cell division. A critical function of Magoh is controlling levels of the microcephaly-associated protein Lis1. This work shows a novel role for the EJC in neurogenesis.
Using transcranial magnetic stimulation, the authors report that the left lateral prefrontal cortex is critical for choosing between immediate and delayed rewards. As the LPFC has previously been implicated in self-control, these results suggest that self-control may be important for intertemporal choice.
A traditional way of inducing reconsolidation of associative fear memory is to present the conditioning stimulus (CS), which reactivates the memory trace. The current study shows that an unconditioned stimulus (US)—often stronger in perceptual intensity than CS—on its own can trigger memory reconsolidation that is specific for the sensory properties of the US.
Luna et al. examined the strength of interneuron-to–pyramidal cell connections across the rat anterior piriform cortex. Surprisingly, they found a gradient of increasing inhibition across the rostro-caudal axis of the cortex.
The authors show that myelin, signaling through the receptor p75NTR and its downstream effectors, prevents aberrant sprouting of basal forebrain cholinergic axons in the adult mouse brain.
Although most inhibitory synapses are homeostatically scaled down after chronic inactivity, Kim et al. report that chronic inactivity specifically strengthens a subset of hippocampal GABAergic synapses that express cannabinoid receptors. This local tuning effect is mediated by enhanced degradation of anandamide, which reduces basal cannabinoid receptor activation, augmenting GABA release probability.
Overeating can be compulsive, resembling drug addiction. This paper reports that in rats, developing diet-induced obesity correlates with decreasing sensitivity of the brain's reward system. Knockdown of the striatal dopamine receptor D2 led to rapid loss of reward function and to compulsive overeating undeterred by conditioned aversive foot shocks.
Using two-photon imaging in a transgenic mouse model of Alzheimer's disease, the authors find that microglia, the resident macrophages of the brain, surround neurons prior to nerve cell death. They also find that inactivation of the microglial chemokine receptor CX3CR1, which is critical in neuron-microglia communication, prevents neuron loss.
The authors devised a method for detecting the bioluminescent Ca2+ sensor GFP-Aequorin in freely behaving zebrafish larvae. To demonstrate the efficacy of the technique, they targeted the sensor to a genetically specified population of hypothalamic neurons. The resulting neuroluminescence reveals patterns of neuronal activity that are associated with distinct swimming behaviors.
Psychopathy is a disorder that has typically been considered to result from a primary deficit in fear or empathy. Here the authors find that impulsive-antisocial psychopathic traits are correlated with hyper-reactivity of the dopaminergic reward system as measured with positron emission tomography and functional magnetic resonance imaging.
The immediate early gene Arc has been implicated in many forms of synaptic plasticity. This report finds that in mice lacking Arc, the visual cortex remains unmodified by deprivation or experience, suggesting that Arc expression is among the mechanisms that are critical for experience-dependent plasticity.