Figure 1

Proposed components of the limbic system. Red: Major structures of the classical circuit of Papez (937) defining a loop from the dentate gyrus (DG) of the hippocampus (HP) via the fornix (FX) to the mammillary body (MB) and via the mammillothalamic tract (MT) to the ANT. Light red: Extended concept of the limbic system as proposed by MacLean¹⁰⁸ by incorporating both the Papez circuit and Yakovlev’s view¹⁰⁹ of an amygdala–orbitofrontal network into a concept of the ‘visceral brain.’ Light green: Primary optic pathway. Dark blue: Mesencephalon. Abbreviations: AC anterior commissure, ACC anterior cingulate cortex, ACF anterior column of the fornix, AG amygdala, AR acustic radiation, ANT anterior nuclear group, AP ansa peduncularis, ATP anterior thalamic peduncle, BST bed nucleus of the stria terminals, CF crus fornicis, CB cingulum bundle, CG cingulate gyrus, DG dentate gyrus, FX fornix, Hb habenula, HP hippocampus, HIP habenulo-interpeduncular tract, HT hypothalamus, IC inferior colliculi, ILF inferior longitudinal fasciculus, IP nucleus interpenducularis, ITL inferior temporal lobe, LGN lateral geniculate nucleus, MB mammillary body, MD mediodorsal nucleus, MFB medial forebrain bundle, MGN medial geniculate nucleus, MPC medial prefrontal cortex, MLF medial longitudinal fasciculus, MT mammillothalamic tract, MTT mammillotegmental tract, NA nucleus accumbens, NC nucleus caudatus, OC optic chiasm, OFC orbito-frontal cortices, OT optic tract, PC parietal cortex, PFX Precommisural Fornix, PG postcentral gyrus, PAG periaqueductal grey, PHG parahippocampal gyrus, RN raphe nuclei, RSC retrosplenial cortex, SB subiculum, SC superior colliculi, SCA subcallosal area, SI substantia innominata, SM stria medullaris, SP septum, SCP superior cerebellar peduncle, SCT spinocerebellar tract, SPN septal nuclei, ST stria terminalis, STP superior thalamic peduncle, TH thalami nuclei, TO tectum opticum, UF uncinate fasciculus, VC visual cortices, VTG ventral tegmental nucleus of Gudden.