Local thickening in the embryonic ectodermal layer in the early embryo. The cells of the placed ordinarily constitute a primordial group from which a sense organ (e.g., lens placode) or neurons of sensory ganglia will be derived. Other parts of these ganglia arise from the neural crest.
See Brain-derived neurotrophic factor (BDNF), Ectoderm, Ganglia, Neural crest