BDNF Gene Polymorphisms and Motor Cortical Plasticity in Healthy Humans: When Should We Consider It

Background: The brain-derived neurotrophic factor (BDNF) gene is involved in mechanisms of synaptic plasticity in the brain and has been demonstrated to also play a role in influencing brain plasticity induced by transcranial magnetic and electrical stimulation. Objective and methods: This is an update of a previous study from our laboratory. We retrospectively analysed the data of 115 healthy subjects participating in 130 experimental sessions, measuring the amplitude of motor evoked potentials (MEPs) before and after transcranial stimulation of the primary motor cortex (M1). We explored whether BDNF polymorphism shapes the effects of excitatory theta burst stimulation (iTBS, n=23), anodal (n=32) and cathodal (n=19) transcranial direct current (tDCS), random noise (tRNS, n=33) and alternating current (tACS, n=13) stimulation. Results: Although a trend toward altered plasticity was observed in Val- 66Met allele carriers to stimulation with regard to all protocols compared with the response of Val66Val individuals, no significant GENOTYPE x TIME interaction was found. Conclusions: The BDNF polymorphism is suggested to have an impact on transcranial stimulation-induced plasticity in humans, which differs according to the mechanism of plasticity induction. However, according to our data, we suggest that genotyping in general, in transcranial stimulation studies including small number of subjects and at least when the M1 is stimulated, is not necessary. Nevertheless, the impact of BDNF on plasticity inducing protocols might be taken into account for e.g. in cognitive studies, when the prefrontal cortex is stimulated.