Figure 4.

Identified dopaminergic neuron activity during two different brain states. A, Activity of an identified dopaminergic neuron (DA Unit) during SWA in the cortex (ECoG). Unit activity was irregular as shown by a flat AC. B, During the same recording session, and recording from the same neuron as in A, the firing pattern became markedly more regular during a spontaneous shift to an activated brain state [defined by the absence of the large ∼1 Hz cortical slow oscillation; see power spectra (pECoG)]. Note that peaks appeared in the AC at a similar time scale to the mean firing rate. C, Population analyses confirmed that neurons recorded during the activated brain state (n = 30) fired in a significantly more regular manner (lower CV) than neurons recorded during SWA (n = 44, *p < 0.001, Mann–Whitney U test), whereas the firing rate did not change. Calibration in A also applies to B. Data in C are means ± SEMs.