An extract of the water hyssop plant called Bacopa monnieri has shown to enhance connections between neurons in the brain, but this has only been directly shown in animals. The purpose of this research was to determine if this effect can be captured in healthy adults as well, and in healthy adults that are undergoing sustained cognitive activity. This is because keeping cognitively active positively alters the brain to perform better, while Bacopa monnieri could act as an important supplement to enhance these alterations, by increasing the connections between neurons.

What was the study?

28 healthy adults between the age of 57–78 years were asked to complete cognitive training over a 12-week period. 15 participants took Bacopa monnieri and 13 took a placebo during this period. At the start and after 12 weeks, participants were tested on their cognitive ability and their brains were scanned using Magnetic Resonance Imaging (MRI).

What were the cognitive results?

There was a difference in the pattern separation task between groups. This task requires participants to discriminate between previously presented and very similar pictures (distractors). Those who took Bacopa monnieri were slower at responding to distractor pictures, but they were more accurate at correctly identifying them than those who took the placebo. 

The increase in reaction time may indicate there was an accuracy/speed trade-off — those who took Bacopa monnieri favoured precision over speed, while those who took the placebo were less cautious and their responses reflected this. Previous research has shown that accuracy specifically on the pattern separation task declines with increasing age (figure 1) and in those with Alzheimer’s (figure 2), indicating Bacopa monnieri may help improve aspects of cognition affected by the ageing brain.

What were the neuroimaging results?

When we talk about the connections between neurons in the brain, we are referring to the synapse. Synapses interconnect multiple neurons to facilitate the communication and transmission of information between functional areas in the brain. This is similar to a web, where there is an intricate network of silk connecting and intersecting with one another. These ‘silk’ connections within a brain network are called neurites.

The results from the neuroimaging analysis showed that those who took Bacopa monnieri had neurites that become more dispersed over the 12-week period. This indicates that there was an increase in the complexity of the web, as there was a larger proportion of neurites that were spread in multiple directions and orientations. 

The neuroimaging results may also indicate the brain became more ‘malleable’ as the increased dispersion suggests the neurites were more spread out in space and therefore able to ‘reach’ new connections more readily. 

Were there any side effects?

The Bacopa monnieri tablets were well tolerated. There were no serious side effects — a mild side effect reported was some digestive symptoms (bloating, increased bowel movements) and increased tiredness. There were no side effects reported in those who took the placebo.

What else should I know about this study? 

Despite these results, it is important to recognise this study was exploratory and had a small sample size. This makes the outcomes vulnerable to differences between participants, particularly if the differences are large enough in one participant to affect the average change seen within a group, that in turn affects the change comparison seen between groups. This is important to take into consideration when weighing up the relative importance of these results and what they may mean for you. Unfortunately, due to the expense of using MRI, a small sample size like in this study is not uncommon in neuroimaging research. 

The data from this study is a good start, however, particularly as this is the first time a combination of cognitive training and Bacopa monnieri has been tested using neuroimaging methods. This allows the linkage between treatment and brain structure that has not been conducted before in humans. The observation that older adults’ brains change after taking Bacopa monnieri in this study provides some support that it may improve some aspects of brain health and helps inform directions for future larger research projects.

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Grace McPhee

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