Fig. 9.

Summary of VTA neuron classifications and their properties. A: percentages of all units sorted by their respective group. In addition to the 3 main groups, a minority of unclassified units were excluded on the basis of a low response to eticlopride (low Etic response) or a long AP duration (for more details, see Fig. 6). B: electrophysiological and pharmacological properties of putative DA, high-firing/short-duration, and unidentified neurons, including basal firing rate, ISI skewness, Etic-Quin-induced firing (relative to baseline), half-AP duration, burst length (spikes per burst), and intraburst firing rate. All values are means ± SE. *P < 0.01 (2-tailed t-test).