Female Carriers of the Met Allele of the BDNF Val66Met Polymorphism Develop Weaker Fear Memories in a Fear-Potentiated Startle Paradigm

The val66met polymorphism of the bdnf gene, which is associated with compromised brain-derived neurotrophic factor (BDNF) signaling, impaired synaptic plasticity, and impaired learning, may increase one’s susceptibility to stress- and anxiety-related disorders. Indeed, previous work has reported greater anxiety-related behaviors and impairments of fear conditioning and extinction in individuals who carry the met allele that results from this polymorphism. Nevertheless, findings in this area of research have been equivocal. Thus, we examined the influence of the val66met polymorphism on fear conditioning, extinction, and extinction memory testing. One hundred and twenty healthy participants completed differential fear conditioning in a fear-potentiated startle paradigm, followed by extinction and extinction memory testing 24 and 48 hr later, respectively. Participants were genotyped for the val66met polymorphism and divided into met allele carriers and non-carriers. Results revealed that, although both met-carriers and non-carriers developed conditioned fear, met-carriers exhibited significantly weaker fear acquisition than non-carriers. This difference persisted throughout extinction and extinction memory testing and, during these last two days of testing, was primarily evident in females. These results are consistent with previous work demonstrating that this polymorphism is associated with impaired amygdala-dependent fear learning and extend such findings by demonstrating that females may be more sensitive to such effects.