Recognition of temporally structured activity in spontaneously discharging neurons in the somatosensory cortex in waking cats

We describe a method to automate the detection and analysis of structured neuronal activity obtained in relatively non-restrictive experiments in awake animals. Several different, regularly occurring, discharge patterns consisting of groups of spikes were identified in extracellular recordings from the somatosensory cortex of awake cats. The introduction of an interspike interval threshold made it possible to segregate these bursts from single spikes. The threshold interval was obtained from the modal interval in high-resolution autocorrelograms (up to 0.1 ms/bin) of the spontaneous neural activity. Single spikes were those separated by intervals greater than the threshold, while those within the group were of less than threshold value. When intervals were arranged and averaged according to their order of occurrence within the burst, four distinctive burst patterns were observed. These four patterns occurred in both normal and deafferented cortex and we believe them to be characteristic of particular cell types, a feature that will be useful for studying such cells in intact cellular networks.