Brain-derived neurotrophic factor (BDNF), like nerve growth factor (NGF), neurotrophin-3 (NT-3), and neurotrophin-4 (NT-4), is a member of the NGF family of neurotrophins, which are required for the differentiation and survival of specific neuronal subpopulations in both the central and the peripheral nervous systems (Minichiello and Klein; Minichiello et al.). BDNF binds with high affinity to the tropomyosin receptor kinase B (TrkB), and activates AKT and ERK pathways (Mattson et al.). It is expressed in the hippocampus, cortex, and synapses of the basal forebrain. BDNF acts as a survival factor for human embryonic stem cells when plated on either feeder cells or Corning® Matrigel® (Pyle et al.). BDNF regulates synaptic transmission and plasticity at adult synapses in the central nervous system, and contributes to adaptive neuronal responses including long-term potentiation, long-term depression, certain forms of short-term synaptic plasticity, and homeostatic regulation of neuronal excitability (Reichardt). It also has a role in neurogenesis by promoting survival and growth of dorsal root ganglion cells, and hippocampal and cortical neurons (Binder and Scharfman). BDNF, together with glial cell line-derived neurotrophic factor (GDNF) and other supplements, is commonly used to differentiate human pluripotent stem cell (hPSC)-derived neural progenitor cells into neurons (Brafman).