This image depicts the average spectrogram during the transition from low to high states of cortical activity due to stimulation of the nucleus gigantocellularis (lower brainstem) while animals are deeply anesthetized. The low state was characterized by low-frequency activity (0.5- 4Hz), whereas a high cortical state showed a substantial predominance of frequencies between 20-50 Hz and the disappearance of low-frequencies.  

The lower panel shows the average firing rate of different neuronal cell types located within the anterior portion of the nucleus gigantocellularis (aNGC) at the time of transition. The Active aNGC neurons show an average firing rate of 19.6 ± 3.1 Hz at a high cortical state. In contrast, low active neurons display an average firing rate of 5.8 ± 1.2 Hz.