While this indicates that there is a biphasic situation and that piperine might or might not be a good idea, remember that our test rat (aka Ron) has had good results with his own long running experiment. Ron, correct me if I am wrong, but I seem to remember that you take somewhere around 500 mg per day sans piperine - is that right? Anyway...

1: J Biol Chem. 2008 May 23;283(21):14497-505. Epub 2008 Mar 24.

Curcumin stimulates proliferation of embryonic neural progenitor cells and
neurogenesis in the adult hippocampus.

Kim SJ, Son TG, Park HR, Park M, Kim MS, Kim HS, Chung HY, Mattson MP, Lee J.

Department of Pharmacy, College of Pharmacy and Research Institute for Drug
Development, Longevity Life Science and Technology Institutes, Pusan National
University, Geumjeong-Gu, Busan, Korea.

Curcumin is a natural phenolic component of yellow curry spice, which is used in
some cultures for the treatment of diseases associated with oxidative stress and
inflammation. Curcumin has been reported to be capable of preventing the death of
neurons in animal models of neurodegenerative disorders, but its possible effects
on developmental and adult neuroplasticity are unknown. In the present study, we
investigated the effects of curcumin on mouse multi-potent neural progenitor
cells (NPC) and adult hippocampal neurogenesis. Curcumin exerted biphasic effects
on cultured NPC; low concentrations stimulated cell proliferation, whereas high
concentrations were cytotoxic. Curcumin activated extracellular signal-regulated
kinases (ERKs) and p38 kinases, cellular signal transduction pathways known to be
involved in the regulation of neuronal plasticity and stress responses.
Inhibitors of ERKs and p38 kinases effectively blocked the mitogenic effect of
curcumin in NPC. Administration of curcumin to adult mice resulted in a
significant increase in the number of newly generated cells in the dentate gyrus
of hippocampus, indicating that curcumin enhances adult hippocampal neurogenesis.
Our findings suggest that curcumin can stimulate developmental and adult
hippocampal neurogenesis, and a biological activity that may enhance neural
plasticity and repair.