Artichoke extract contains a number of bioactive compounds, among which is luteolin, a known PDE4 inhibitor.
PDE4 inhibition in animal models has been shown to enhance object memory, and reverse deficits to learning, working and reference memory.
The primary means by which PDE4 inhibitors are believed to improve learning and memory is by lengthening the duration during which the secondary messenger cyclic-adenosine monophosphate (cAMP) is present in cells where it can activate CREB and thus increase CREB'S gene transcription activities in the nucleus and mitochondria.
No significant adverse side effects have been observed. Artichoke extract interacts with DNA, so it's possible there is a safe upper limit, but this has yet to be elucidated by the evidence.