Dear Users Today (YNiC open plan from 4.30 pm) there will be a talk by Roger Traub, from Columbia University Medical Center, on "Cellular mechanisms of epilepsy: chemical synapses and gap junctions". Abstract: During brief epileptic bursts, principal neurons fire together for tens to hundreds of milliseconds, producing a large extracellular potential ("field"). Superimposed on this large field are high-frequency oscillations, from ~100 to several hundred Hz. Two distinctive means of coupling between neurons cooperate to generate the event. Recurrent excitatory synaptic connections shape the overall event, but gap junction coupling (between pyramidal cells) produces the fast oscillations. I will describe the dissection of the cellular mechanisms via in vitro experiments (on rodent and human tissue) and via computer modeling and network theory. Experimentally, the fast oscillations can be evoked alone, during blockade of chemical synapses; but blockade of gap junctions abolishes BOTH the fast oscillations and the larger burst. Other lines of evidence pointing toward a critical role for gap junctions in epilepsy-related very fast oscillations are these: a) large-scale spatial patterns of cortical fast oscillations, resembling an excitable medium; b) the existence of "glissandi" (~30 to >150 Hz) oscillations in epileptic tissue, with chemical synapses blocked; c) recent data showing that fast ripples (>250 Hz) in resected human tissue persist without chemical synapses. These data suggest that a targeted manipulation of selected gap junctions might prevent certain seizure events. Everyone is welcome to attend and refreshments will be provided afterwards. Best wishes Rebecca -- ************************************************************************ Dr. Rebecca E. Millman Science Liaison Officer York Neuroimaging Centre The Biocentre York Science Park Heslington YO10 5DG Tel: +44 (0) 1904 567614 Fax: +44 (0) 1904 435356