Parkinson's disease and depression: evidence for an alteration of the basal limbic system detected by transcranial sonography. - Becker,T.; Becker,G.; Seufert,J.; Hoffmann,E.; Lange,K.W.; Naumann,M.; Lindner,A.; Reichmann,H.; Riederer,P.; Beckmann,H.; Reiners,K. (J Neurol Neurosurg Psychiatry, 1997)