ANALYSIS OF NEURAL BURSTING - NONRHYTHMIC AND RHYTHMIC ACTIVITY IN ISOLATED SPINAL-CORD

Neuronal firing recorded from primary afferents and central spinal neu rons in isolated mammalian spinal cord in vitro was analyzed using int erspike interval histograms and Poincare maps (Return maps). Interspik e interval histograms described the time between two successive spikes . However, Poincare maps represented the interspike interval preceding a spike against the interspike interval following the spike. The vari ability in firing of neurons occurring naturally in different preparat ions was explored. In a presumptive single central spinal neuron, the firing pattern provided a single cluster. During bursting in a presump tive single primary afferent, the Poincare maps provided information o n interburst intervals. Moreover, lengthening and or shortening of int erspike intervals within bursts can be detected in the maps. The firin g of a population of neurons was modulated using a pharmacological int ervention with 4-aminopyridine and resulted in a complex Poincare map.