1. A method for delivery of a therapeutic neurotrophin to targeted defective, diseased or damaged neurons in a mammalian brain, the method comprising directly delivering a neurotrophic composition, comprising a neurotrophin encoding lentiviral expression vector, into one or more delivery sites within a region of the brain containing targeted neurons; wherein the neurotrophin is expressed in, or within 500 μm from, a targeted cell, and no more than about 10 mm from another delivery site; and wherein further contact with the neurotrophin ameliorates the defect, disease or damage.