|DATE:||Wednesday, September 22nd, 1999|
|TITLE:||Non-Random Patterns of Synaptic Connectivity in Neuronal Networks.|
|SPEAKER:||Dr. Danny Baranes, Department of Anatomy and Cell biology, McGill University|
Neuronal networks, the basic information processing units in the brain, specify their function by unique assembly of their synaptic connections into patterns of connectivity during development. We have identified a novel mechanism of neuronal connectivity in vivo and in vitro, which may play a key role in fashioning the circuitry within neuronal networks.
Neurites, neuronal processes through which information is transmitted between neurons (dendrites - receiving information; axons - transmitting information) predominantly grow through intersections between other neurites. This results in the formation of multi-neurite intersections (MNIs) at frequencies higher than those in simulated neuronal networks where neurons are positioned randomly. The system is reinforced by activity-mediated addition of neurites to the existing MNIs. This behavior gives rise to highly organized geometrical shapes, or polygon-like spaces, between bundles of neurites connected through MNIs. Axons involved in these gigantic intersections cluster their synaptic connections at the points of intersection.
In addition, they make multi-synaptic connections with several of the intersecting dendrites and occasionally switch targets at intersections. Thus, wiring of neurons through MNIs increases and patterns synaptic connectivity in the neuronal network.