The Neuroscience for Kids website has created an online exhibition of neuroscience-themed stamps that depict everything from drugs to brain scans.
They also include the wonderful Swedish set displayed on the left that include a series of impossible shapes.
Unfortunately, the stamps aren’t dated. Rather surprisingly, Portugal put Egas Moniz, inventor of the frontal lobotomy, on their stamps, and it would be interesting to know when they were in circulation.
To be fair, he did win the Nobel Prize, although these days the mention of his award tends to make people shuffle their feet and mutter things like “well, of course, it wouldn’t happen in this day and age…”
Link to neuroscience stamp exhibition.
Mind Hacks 
Regarding the stamps they where issued 16 February 1983 by the Swedish postal service. They where named “Isometriska Perspektiv”. No translation necessary. 😉