Neurological therapy devices are disclosed for the local and controlled delivery of a neurotransmitter to the brain of a subject suffering from neurotransmitter deficiency or dysfunction. In one embodiment the device includes a biocompatible, implantable, and retrievable polymeric insert including a source of neurotransmitter embedded therein. In another embodiment, the device includes a retrievable source of neurotransmitter including at least one neurotransmitter-secreting cell encapsulated within a semipermeable membrane allowing the diffusion therethrough of the neurotransmitter, and further includes a source of growth factor in close proximity to the neurotransmitter-secreting cells.