The effect of Pyrroloquinoline quinone (PQQ) on cognition was tested in 41 healthy elderly subjects. Subjects were given 20 mg of PQQ or placebo for 12 weeks. In the group with the lowest initial score on visual-spatial cognitive function (via laptop tablet Touch M), scores were significantly increased after PQQ supplementation. Researchers also noted that PQQ administration led to increased cerebral blood flow in the prefrontal cortex, as measured by near-infrared spectrometry.
Nakano M, Kawasaki Y, Suzuki N, Takara T. (2015). Effects of pyrroloquinoline quinone disodium salt intake on the serum cholesterol levels of healthy Japanese adults. J Nutr Sci Vitaminol (Tokyo). 61(3): 233-40