A new study has revealed that a variant of the gene BDNF can affect an individual’s response to brain stimulation.
Stimulating brain activity
Transcranial magnetic stimulation (TMS) is a non-invasive method of brain stimulation. It uses magnetic fields to cause an electric current at a specific area of the brain, which then stimulates nerve cells. Repetitive TMS (rTMS) is occasionally used as a treatment for depression.
However, recent studies have revealed significant variation between individuals in their responses to rTMS. Scientists have suggested that there is a genetic basis to the variation. Specifically, they have implicated variants of the gene BDNF. BDNF encodes the brain-derived neurotrophic factor (BDNF). BDNF is a key protein in our brains and is associated with several processes related to memory and brain plasticity. It also supports the survival and growth of neurones.
Therefore, the team behind a new study, published in Scientific Reports, used neuroimaging techniques to understand how BDNF was influencing the effect of TMS on the brain.
Analysing memory
The scientists studied the brain activity of 43 male participants. All participants underwent genotyping analysis of the genetic variant BDNF Val66Met, causing a valine (Val) to methionine (Met) amino acid substitution at codon 66. Results revealed that 19 participants were Met carriers, whilst the remaining 24 were homozygous for the Val allele.
The participants undertook cognitive tasks, such as memory tasks, whilst receiving rTMS. The cognitive performances of the Met carriers were then compared to that of the Val carriers. The team found that during memory-related activities, the homozygous Val individuals showed greater brain activity. Interestingly, under control conditions there were no significant differences in memory between Val and Met carriers. This suggests that rTMS was stimulating homozygous Val carriers to have greater brain activity related to memory. Further imaging analyses confirmed that rTMS was stimulating areas of the brain specifically associated with memory functions – but only in individuals homozygous for Val in BDNF.
Future work
Altogether, the results in this study suggest that genetic variants of the gene BDNF play a role in how rTMS affects neural processes. However, researchers will need to carry out further studies to confirm these findings. It is important to note that in the current study, all the participants were male. Investigations done in a more diverse study cohort will be required in the future.
Despite those limitations, we now understand more about how a genetic variant can affect brain stimulation. Knowing which individuals are more sensitive to TMS may help shape future therapies for conditions such as depression or for methods to enhance cognitive function.
