Increasing the firing rate of prefrontal cortical neurons via agonism of serotonin receptors with LSD looks like this (All credit to reddit!)
For further information:
Effects of LSD on EEG (from 1960, when reserach was still legal)
The Pharmacology of Lysergic Acid Diethylamide: A Review
Review in Nature Reviews Neuroscience
Serotonergic Modulation of the Prefrontal Cortex: From Neurons to Brain Waves.pdf