Dynamics of leech heart interneurons: how is bursting activity generated
by neurons?
Gennady S. Cymbalyuk
Department of Biology, Emory University, Atlanta, GA
Abstract: Bursting behavior is an oscillatory activity consisting
of intervals of repetitive spiking separated by intervals of quiescence.
Brain functions such as motor control, information rocessing
and memory formation frequently involve bursting activity of neurons.
Our study is focused on determining basic mechanisms underlying
bursting activity. The heartbeat motor pattern in leeches is based on the
activity of two mutually inhibitory pairs of heart interneurons,
which generate alternating bursting activity. Experiments and dynamical
system analysis were combined to study bursting and other dynamic
behaviors of heart interneurons both as single cells and in the mutually
inhibitory half-center oscillator configuration. This analysis revealed
general biophysical mechanisms that underlie such behaviors as equilibrium,
plateau, spiking behavior, slow oscillatory behavior and bursting
behavior. This study indicates that the half-center configuration enhances
robustness of oscillations making them less susceptible to
changes in membrane parameters, while endogenous capability to produce
bursting behavior ensures bursting behavior if the strength
of mutual inhibition is weakened.