Bacopa Monnieri extract may be able to increase memory formation by the enzyme Tryptophan Hydroxylase (TPH2) and increasing the expression of the serotonin transporter (SERT).[28] Bacopa does appear to have some interactions with the serotonin system, and may have downstream effects on the cholinergic system through this.[29][30]
Additionally, dendritic intersections and branching points in neurons have been noted to be proliferated with Bacopa Monnieri supplementation after 4 and 6 weeks, but failed to have any changes at 2 weeks.[31] This neuronal growth effect occurs in adult rats[32] and younger rats undergoing growth spurts,[33] and occur in areas of the brain known to be involved with memory, such as the hippocampus[31] and the basolateral amygdala.[33][32] These changes coincide with memory enhancement seen in human studies, where usage for under 2 weeks is not associated with any cognitive enhancement but additional usage is; implicating dendritic enhancement as a probable explanation for memory enhancement.
Mechanism of memory enhancement has not been completely solidified, but appears to be related to either enhancing neuronal transmission (via enhancing dendritic proliferation) or through interactions with the serotonergic system (which then influence acetylcholinergic transmission). These effects do not appear to require cognitive decline or the elderly to work, and thus suggest Bacopa can benefit all ages
Enhancing neuronal transmission and proliferating dendrites may enhance memory map formation
Bacopa, in healthy persons, has been successful in beneficially affecting the retention of learned information. It may be able to reduce the rate of short term forgetting (ie. increase encoding of information)[34] while increasing retention speeds.[35] In addition to rate of learning, Bacopa Monnieri shows some promise at 300mg daily for improving memory, verbal learning and delayed recall.[36] This has been repeated in healthy persons between 18 and 60 with two doses of 150mg daily.[37]
In regards to persons with impaired memory, low dose Bacopa (125mg daily) appears to be somewhat effective.[38] Bacopa has also been implicated in helping children aged 6-12 with ADHD, but this study used a blend of other herbs (Melissa Officinalis, Centella Asiatica, Paeoniae Alba, Ashwaghanda, and Spirulina Platensis) and causation cannot be placed on any in isolation.[39] These two studies are less able to be extrapolated to healthy persons, but should still be noted.
Not all research is conclusively solid, as some studies do note no difference from placebo at therapeutically relevant dosages,[40] although this study was critiqued on suggesting that the null results were due to 'low doses'.[41] The former study was conducted at 300mg Bacopa and 120mg Gingko for 2-4 weeks, which is shorter in time to other studies but at a similar dosage. Beyond this study, one other study has noted no effects with a single administration, suggesting that longer term supplementation is needed.[42]
Many of these studies have been subject to Meta-Analysis, where it was concluded that Bacopa shows preliminary efficacy in improving general memory (9 out of 17 measured parameters) with little influence on other parameters of cognition.[43] In a study analyzing the comparative effect sizes of Bacopa, Panax Ginseng, and Modafinil it was found that although Modafinil and Bacopa were both potent they were at different parameters; Modafinil increasing speed of information processing much better than Bacopa, which tended to reliably increase cognition after chronic dosing.[44]
There is a surprising amount of human interventions on Bacopa Monnieri for being an Ayurvertic herb, and the majority of them note positive results. No longer term studies have been done, but the evidence at the time is very promising and is in line with the traditional claims of Bacopa Monnieri being a memory enhancer
Beyond enhancing memory, Bacopa has been implicated numerous times in reducing amnesia (memory loss due to stressor) via a collection of mechanisms.[29][30][45][46][47]