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We derived attention response functions for different cortical areas by plotting neural activity (measured by fMRI) as a function of attentional load in a visual tracking task. In many parietal and frontal cortical areas, activation increased with load over the entire range of loads tested, suggesting that these areas are directly involved in attentional processes. However, in other areas (FEF and...
We perceive motion when presented with spatiotemporal changes in contrast (second-order cue). This requires linear signals to be rectified and then summed in temporal order to compute direction. Although both operations have been attributed to cortex, rectification might occur in retina, prior to the ganglion cell. Here we show that the Y ganglion cell does indeed respond to spatiotemporal contrast...
The mechanisms involved in mossy fiber LTP in the hippocampus are not well established. In the present study, we show that the kainate receptor antagonist LY382884 (10 μM) is selective for presynaptic kainate receptors in the CA3 region of the hippocampus. At a concentration at which it blocks mossy fiber LTP, LY382884 selectively blocks the synaptic activation of a presynaptic kainate receptor that...
Mechanisms composing Drosophila's clock are conserved within the animal kingdom. To learn how such clocks influence behavioral and physiological rhythms, we determined the complement of circadian transcripts in adult Drosophila heads. High-density oligonucleotide arrays were used to collect data in the form of three 12-point time course experiments spanning a total of 6 days. Analyses of 24 hr Fourier...
RNA granules are a macromolecular structure observed in neurons, where they serve as motile units that translocate mRNAs. Isolated RNA granules are highly enriched in Staufen protein and ultrastructurally contain densely packed clusters of ribosomes. With depolarization, many mRNAs, including those involved in plasticity, rapidly shift from the RNA granule fraction to polysomes. Depolarization reorganizes...
Emotionally loaded visual stimuli have shown increased activation in visual and cortex limbic areas. However, differences in visual features of such images could confound these findings. In order to manipulate valence of stimuli while keeping visual features largely unchanged, we took advantage of an “expressional transfiguration” (ET) effect of faces. In addition, we used repetition effects, which...
Netrins are bifunctional guidance molecules, attracting some axons and repelling others. They act through receptors of the DCC and UNC5 families. DCC receptors have been implicated in both attraction and repulsion by Netrins. UNC5 receptors are required only for repulsion. In Drosophila, Netrins are expressed by midline cells of the CNS and by specific muscles in the periphery. They attract commissural...
To reduce the information gap between human neuroimaging and macaque physiology and anatomy, we mapped fMRI signals produced by moving and stationary stimuli (random dots or lines) in fixating monkeys. Functional sensitivity was increased by a factor of ∼5 relative to the BOLD technique by injecting a contrast agent (monocrystalline iron oxide nanoparticle [MION]). Areas identified as motion sensitive...
The organizing centers and molecules that pattern the cerebral cortex have been elusive. Here we show that cortical patterning involves regulation of the Lhx2 homeobox gene by the roof plate. Roof plate ablation results in reduced cortical size and Lhx2 expression defects that implicate roof plate signals in the bimodal regulation of Lhx2 in vivo. Bimodal Lhx2 regulation can be recapitulated in explants...
Increasing NR2A subunit expression and the associated shortening of the NMDA-EPSC are thought to underlie the loss of diverse types of sensory cortical plasticity. Lu and colleagues (Lu et al., 2001 [this issue of Neuron]) now report that mice lacking the NR2A subunit display normal duration of critical periods of barrel cortex plasticity. Shortening of the NMDA-EPSC is therefore not responsible for...
In voltage-gated K+ channels (Kv), an intracellular gate regulates access from the cytoplasm to the pore by organic channel blockers and by chemical modifiers. But is ion flow itself controlled instead by constriction of the narrow selectivity filter near the extracellular surface? We find that the intracellular gate of Kv channels is capable of regulating access even by the small cations Cd2+ and...
Kainate receptor agonists depress transmitter release at several synapses in the hippocampus. Distinct mechanisms appear to underlie this phenomenon at different synapses. Recently, it has emerged that presynaptic kainate receptors can also potentiate the release of both GABA and glutamate and that axonal kainate receptors can trigger ectopic action potentials in interneurons. Because synaptically...
Essential to nerve and muscle function, little is known about how potassium leak channels operate. KCNKØ opens and closes in a kinase-dependent fashion. Here, the transition is shown to correspond to changes in the outer aspect of the ion conduction pore. Voltage-gated potassium (VGK) channels open and close via an internal gate; however, they also have an outer pore gate that produces “C-type” inactivation...
What is the moving part that switches an ion channel's current on and off? In this issue of Neuron, del Camino and Yellen (2001) exploit scanning cysteine mutagenesis and sulfhydryl reagents to show that the intracellular end of the S6 helices forms a mechanical gate for the Shaker potassium channel.
When hippocampal synapses in culture are pharmacologically silenced for several days, synaptic strength increases. The structural correlate of this change in strength is an increase in the size of the synapses, with all synaptic components—active zone, postsynaptic density, and bouton—becoming larger. Further, the number of docked vesicles and the total number of vesicles per synapse increases, although...
The regulation of NMDA receptor (NMDAR) subunit composition and expression during development is thought to control the process of thalamocortical afferent innervation, segregation, and plasticity. Thalamocortical synaptic plasticity in the mouse is dependent on NMDARs containing the NR2B subunit, which are the dominant form during the “critical period” window for plasticity. Near the end of the critical...
To visualize odorant representations by receptor neuron input to the mouse olfactory bulb, we loaded receptor neurons with calcium-sensitive dye and imaged odorant-evoked responses from their axon terminals. Fluorescence increases reflected activation of receptor neuron populations converging onto individual glomeruli. We report several findings. First, five glomeruli were identifiable across animals...
The carboxyl terminus of presenilin 1 and 2 (PS1 and PS2) binds to the neuron-specific cell adhesion molecule telencephalin (TLN) in the brain. PS1 deficiency results in the abnormal accumulation of TLN in a yet unidentified intracellular compartment. The first transmembrane domain and carboxyl terminus of PS1 form a binding pocket with the transmembrane domain of TLN. Remarkably, APP binds to the...
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