Fig. 1

Schematical drawing and fiber reconstructions of the medial forebrain bundle. Schematical drawing (a) and fiber reconstruction based on diffusion imaging of a healthy control (b) illustrating the main projections of the fasciculus telencephali (medial forebrain bundle, MFB) are shown. Further, individual MFB reconstructions, with the corresponding electrode position for only the left side are shown for patient 1 (c sagittal-, d axial-, e coronal sections), patient 2 (f, g, h) and patient 3 (i, j, k). The activated contact is marked in red. The MFB consists of thin, loosely arranged ascending and descending fibers extending from septal area (SP) to the mesencephalic tegmentum. Along this route it traverses the lateral hypothalamic area (ALH) and splits into a smaller medial and larger lateral stream at transitional zone of diencephalon and midbrain. The medial stream (mSTR) passes through the parts of the mesencephalic and rhombencephalic tegmentum, connecting the hypothalamic centers with raphe nuclei and medial reticular formation. On the other hand, ascending serotonergic fibers from the dorsal (DR) and medial raphe (MnR) nuclei reach the ALH and a variety of diencephalic and telencephalic centers. The lateral stream (lSTR) connects the central nucleus of the amygdala (CeA) and hypothalamic areas with different brain stem areas in pons and medulla oblongata. It further comprises fibers ascending from dopaminergic ventral tegmental area (VTA) and substantia nigra pars compacta (SNc), but also fibers from noradrenergic fields like the locus coeruleus (LC) reaching cortical and limbic regions like hippocampus (HPC), amygdala (AMY) and nucleus accumbens (NAc). MOB—main olfactory bulb, SNr—substantia nigra pars reticulata, CN—cingulate gyrus