I don't know about taurine, just my subjective experience with that during short periods of taking it makes me think it's both stimulating and relaxing. It certainly does something with cognition, to some extent, not sure what the effect would be long term.
But yeah there's a lot of substances people on this forum and other places have taken that basically shift the balance of inhibition versus stimulation, everything from racetams (which to my mind are stimulating in the vague sense, e.g. can cause headaches, muscle tension, brain fog, irritability, increased amount of intelligent thoughts, "creativity", etc) to pure GABA antagonists (I don't know if anyone seriously used the heavy stuff to improve their IQ or mental performance, but certainly things like ginkgo biloba).
IQ is probably a bit weird and complicated but in a more broad sense of improving performance, yeah cranking up the dial of brain activity on your brain (so to speak) is perhaps not the definition of improving mental performance, but one of the obvious ways it could and can be done. AFAIK it's well established prescription stimulants (methylphenidate, d-amphetamine) at low doses can have some mild or moderate effect on things like working memory in healthy individuals.
Cerebrolysin I believe is a positive allosteric modulator of GABA-b receptors (e.g. on the other hand benzodiazepines are that on GABA-a receptors), or something close to that, at least in some particular circumstance, maybe it was a test-tube study I don't remember. (It also has some other potential actions relating to anxiety, that are very interesting and perhaps unique. I haven't read the paper summarizing cerebrolysin in a long time, but it mentioned an enzyme that basically trains (or un-trains) phobias and fear responses, and cerebrolysin having something to do with that.) Meanwhile it also has some more stimulating effects (due to CNTF, IGF-1, BDNF etc. type properties). (IME cerebrolysin certainly is relaxing to a small degree, also stimulates thought and alleviates dysthymia for me, the best thing tho is that it seems to produce long-lasting effects. Only potentially bad thing is I can't drink coffee any longer, maybe due to all the cerebrolysin I've been using or maybe due to something else like benzo withdrawal years ago. Coffee makes me way too stimulated these days, even tho my overall state is much lower anxiety than ~10 years ago when I could drink lots of coffee.).
Edited by Keizo, 10 July 2019 - 07:54 AM.