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SUMMARY:The synapse-level wiring diagram of a center for learning and memo
 ry\, the insect mushroom body - Albert Cardona (None / Other)
DTSTART:20161110T110000Z
DTEND:20161110T120000Z
UID:TALK68922@talks.cam.ac.uk
CONTACT:INI IT
DESCRIPTION:Associating stimuli with positive or negative outcomes is esse
 ntial for survival\, but a complete wiring diagram of a higher-order circu
 it supporting associative memory has not been previously available. In thi
 s talk\, I will discuss our findings--in collaboration with Marta Zlatic\,
  Andreas Thum and Larry F. Abbott--on circuits for associative memory base
 d on the full reconstruction at synaptic resolution of one such circuit\, 
 the insect mushroom body (MB)\, as mapped in the larva of Drosophila. Our 
 results provide single-animal cross-hemispheric evidence that Kenyon cells
  (KCs)--the parallel fibers--integrate random combinations of stimuli\, bu
 t we also found a set of KCs that are wired in an ordered way to relay sig
 nals from single projection neurons (PNs).   &nbsp\; We show that combinin
 g these two kinds of KCs maximizes the dimension of the odor representatio
 n. Memories are formed when co-activation of KCs and modulatory neurons (m
 ostly dopaminergic\, DAN) alters the strength of KC synapses onto MB outpu
 t neurons (MBONs) within discrete MB regions known as compartments.&nbsp\;
  We found a novel canonical circuit in these compartments with previously 
 unpredicted connections: a reciprocal KC-to-DAN connection and a DAN-to-MB
 ON connection\, suggesting multiple potential sites of synaptic plasticity
 .&nbsp\; Counting of individual synaptic connections allowed us to assess 
 the relative contributions of olfactory\, non-olfactory\, modulatory and e
 xtra-MB signals onto each MBON\, providing evidence that MBONs contextuali
 ze associative memories with a variety of other information. We also found
  a stereotyped MBON-MBON circuit with reciprocal inhibition among MB compa
 rtments of opposing valences suggestive of competitive interactions that c
 ould enhance the selection of learned response. Finally\, feedback connect
 ions from MBONs to neuromodulatory neurons provide a possible mechanism fo
 r existing memories to affect the formation of new ones. The complete circ
 uit map of the MB should guide future functional studies of this center of
  learning and memory.  <br><br><br><br>
LOCATION:Seminar Room 2\, Newton Institute
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