The thin, terminal dendrites of CA1 neurons receive thousands of synaptic inputs arriving at varying times and locations and integrate these into a string of transient somatic voltage deflections. This process has traditionally been viewed as a passive, antenna-like funneling of electrical signals to the cell body. However, recent evidence suggests that dendritic integration is actually a complicated interplay between active ion conductances and passive cable properties. Our previous data supports a view of the terminal dendrite as an isolated compartment, capable of branch-wide activation. We now propose that terminal dendrite activation can change dynamically. This dynamicity endows the dendrite with greater computational power, but also makes it vulnerable to pathological states of excitability. We hypothesize that the compartmental behavior of terminal dendrites will vary according to: 1) The specific intensity, location, and timing of inputs; 2) The current electrical state of the dendritic arbor; and 3) Previously experienced plasticity. We will test these hypotheses by using novel methods of multi-focal glutamate photolysis, combined with patch recordings and optical calcium imaging, to record dendritic behavior in each circumstance.
