Figure 6.

Rapidly firing DA neurons typically exhibit burst firing activity. A: In this DA neuron recorded in vivo in the substantia nigra of a rat, the spike activity is showing the characteristic pattern of burst firing in DA neurons: bursts of 3–10 spikes with comparatively brief interspike intervals (e.g., 80–160 msec) separated by extended periods of post-burst inactivity. The DA neuron in this example is discharging at 7.2 Hz. B: Plotting the spike discharge pattern in the form of an interspike interval histogram reveals the multimodal form of this activity. The initial peak at 40 to 60-msec intervals represents the interspike intervals within the burst events, whereas the long intervals illustrate the intervals between the termination of one burst and the onset of the subsequent event. C: In rats in which an electrolytic lesion of the subthalamic nucleus had been performed, DA cells located in the lateral portions of the substantia nigra often exhibited pacemaker-like discharge patterns. This DA cell is discharging at a rate (i.e., 7.0 Hz) comparable to that observed in A. D: As revealed in the interspike interval histogram for this neuron, the intervals between spikes in this neuron show a much narrower distribution. (From ref. 65, with permission.)

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published 2000