Figure 11.
Model for auditory cortical population responses to sustained tones. In synchronized states (top), population activity consists of discrete packets separated by periods of global silence. Tone onset reliably induces an activity packet, but packets also occur sporadically throughout the sustained and spontaneous periods. Within each packet, neurons fire with a stereotyped sequential pattern. Presentation of a neuron's preferred tone causes it to fire at higher rates during activity packets, but not to fire outside packet periods. In desynchronized states (bottom), population activity does not show long periods of silence, but temporal relationships between neurons are similar to those in the synchronized state. This can be explained by a model in which many packets, individually similar to those seen in the synchronized state, are superimposed to produce a firing pattern that exhibits smaller fluctuations in global activity but retains a fine temporal structure.