Neuroscience
-
Training inhibitory control, the ability to suppress motor or cognitive processes, not only enhances inhibition processes, but also reduces the perceived value and behaviors toward the stimuli associated with the inhibition goals during the practice. While these findings suggest that inhibitory control training interacts with the aversive and reward systems, the underlying spatio-temporal brain mechanisms remain unclear. We used electrical neuroimaging analyses of event-related potentials to examine the plastic brain modulations induced by training healthy participants to inhibit their responses to rewarding (pleasant chocolate) versus aversive food pictures (unpleasant vegetables) with Go/NoGo tasks. ⋯ The electrophysiological results also revealed an interaction between reward responses and inhibitory control plasticity: we observed different effects of practice on the rewarding vs. aversive NoGo stimuli at 200 ms post-stimulus onset, when the conflicts between automatic response tendency and task demands for response inhibition are processed. Electrical source analyses revealed that this effect was driven by an increase in right orbito-cingulate and a decrease in temporo-parietal activity to the rewarding NoGo stimuli and the reverse pattern to the aversive stimuli. Our collective results provide direct neurophysiological evidence for interactions between stimulus reward value and executive control training, and suggest that changes in the assessment of stimuli with repeated motoric inhibition likely follow from associative learning and behavior-stimulus conflicts reduction mechanisms.
-
Review
The Control of Neuronal Calcium Homeostasis by SNAP-25 and its Impact on Neurotransmitter Release.
The process of neurotransmitter release is central to the control of cell-to-cell communication in brain. SNAP-25 is a component of the SNARE complex, which, together with syntaxin-1 and synaptobrevin, mediates synaptic vesicle fusion with the plasma membrane. ⋯ Consistently, reduced levels of the protein affect presynaptic calcium homeostasis and result in pathologically enhanced glutamate exocytosis. The SNAP-25-dependent alterations of synaptic calcium dynamics may have direct impact on the development of neuropsychiatric disorders where the Snap-25 gene has been found to be involved.
-
Synaptosomal Associated Protein-25 kilodaltons (SNAP-25) is an integral member of the SNARE complex. This complex is essential for calcium-triggered synaptic vesicular fusion and release of neurotransmitters into the synaptic cleft. In addition to neurotransmission, SNAP-25 is associated with insulin release, the regulation of intracellular calcium, and neuroplasticity. ⋯ We believe investigation of SNAP-25 is important for understanding both normal behavior and some aspects of the pathophysiology of behavior seen with psychiatric disorders. The wealth of information from both animal and human studies on SNAP-25 offers an excellent opportunity to use a bi-directional research approach. Hypotheses generated from genetically manipulated mice can be directly tested in human postmortem tissue, and, conversely, human genetic and postmortem findings can improve and validate animal models for psychiatric disorders.
-
Vti proteins are conserved from yeast to humans and regulate intracellular membrane trafficking by providing one specific SNARE domain, the Qb SNARE, to the four helical SNARE bundle that drives membrane fusion. Two mammalian Vti genes, Vti1a and Vti1b are reported to regulate distinct aspects of endolysosomal trafficking and retrograde transport to the Golgi, but have also been implicated in synaptic vesicle secretion. ⋯ We propose that, despite some unique aspects, the two mammalian VTI genes have largely redundant functions in neurosecretory cells and recycle molecules required for the sorting of regulated cargo to the Golgi. Defects in this recycling also lead to defects in synaptic transmission and dense core vesicle secretion.
-
SNARE-complexes drive the fusion of membrane-bound vesicles with target membranes or with each other (homotypic fusion). The SNARE-proteins are subdivided into Qa, Qb, Qc and R-SNAREs depending on their position in the four-helical SNARE-bundle. Here, we review the SNAP-25 protein sub-family, which includes both the Qb and Qc SNARE-domains within a single protein. ⋯ SNAP-29 is present on intracellular membranes and performs functions in autophagosome-to-lysosome fusion, among others. An overlapping function for SNAP-47 was described; in addition, SNAP-47 mediates postsynaptic AMPA-receptor insertion. Overall, the presence of two SNARE-domains confers members of this family the ability to associate to different Qa and R-SNAREs and drive diverse membrane fusion reactions; one member of the family, SNAP-25, has been devoted entirely to Ca2+-triggered fusion and has taken on a number of additional, regulatory roles.