Synaptic vesicles have been divided into distinct pools based on their release kinetics. Fast-releasing and slowly releasing pools were initially detected using stepwise increases in intracellular calcium, but this week Sakaba examined vesicular release in response to more physiological stimuli: action potential-like depolarizations of rat calyx of Held neurons. Using a deconvolution method, the author estimated the quantal release rate and separated synchronous and asynchronous release populations. The analysis suggested that 80% of the fast-releasing and 60% of slowly releasing vesicles were released during a 100 Hz train. Presynaptic capacitance measurements supported these estimates. By blocking the calcium/calmodulin-dependent recovery of the fast-releasing pool, the author was able to examine the slow-releasing pool of vesicles in isolation. Synchronous release primarily consisted of fast-releasing vesicles, whereas asynchronous release was carried mainly by slowly releasing vesicles. It took a 300 Hz train to deplete both vesicle populations.

2. Stroke Recovery and the Contralateral Hemisphere
Martin Lotze, Jochen Markert, Paul Sauseng, Julia Hoppe, Christian Plewnia, and Christian Gerloff

Recovery after a brain injury such as a hemispheric stroke can involve not only both local recovery and repair but perhaps compensation from distant regions, including the contralateral hemisphere. This week, Lotze et al. examined a group of patients with a history of an ischemic stroke involving the internal capsule. These patients initially had significant movement impairment in the affected hand but then recovered almost fully. The authors used functional magnetic resonance imaging to compare activation of motor areas in the damaged and contralateral hemispheres during a fingertapping task. Cortical ctivation ipsilateral to the moving hand (contralateral to th
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Contact: Tracey Somers
tsomers@sfn.org
202-962-4000
Society for Neuroscience
30-May-2006