D-cell speculation of schizophrenia is an essential hypothesis to interface the NSC brokenness theory to the DA theory. In brains of schizophrenia patients, dysfunction of neural stem cells in the subventricular zone of lateral ventricle causes the decrease of D-neurons in the striatum and nucleus accumbens. This leads to the decrease in the amounts of trace amines in the nuclei, though direct evidences have not yet been demonstrated. Enlargement of the lateral ventricle, a usual finding documented in brain imaging studies of schizophrenia, is possibly due to dysfunction of neural stem cells of the subventricular zone