BDNF and neurodegenerative disease: BDNF is a synaptic growth factor that is secreted in response to excitatory synaptic activity and serves as a key mediator of neuroplasticity in the brain, including somatosensory and visual cortex.51–56 BDNF promotes neurogenesis and synaptic plasticity and its expression and release can be decreased by various factors, such as pro-inflammatory cytokines, advanced age, chronic stress, mental and neurodegenerative diseases.57–63