Limbic system Semmelweis University Department of Anatomy, Histology and Embryology 2nd year Kocsis Katalin 2016.10.13.

General view of the limbic brain mammalian brain organized on the base of two major basic theories 1) Modularity theory -specialised functions localized to different brain areas 2) Neuronal network theory complex functions, features - learning, memory, intelligence personality - functional integration - processing of information is in neuronal networks, scattered brain areas

Functions of the limbic system Complex human functions: -personality, behaviour, learning, memory, emotions Basic functions -reproduction, stress, autonomic functions

Pierre Paul Broca (1878) – French neuroanatomist „Limbic lobe” – ring shaped cortical area on the medial surface of hemispheres: - parolfactory area (subcallosal area) - uncus - subcallosal gyrus (paraterminal gyrus) - parahippcampal gyrus - hippocampus - cingulate gyrus („limbic gyrus”) Smell is the main function of the limbic lobe Pierre Paul Broca

-emotional feeling and expression Papez presumed at first (1937): limbic lobe - functions related to the behaviour and emotions , emotions and motivated activity - localized in distinct brain structures Papez proposed: -cingulate gyrus and hippocampus are connected with hypothalamus, anterior thalamic nuclei (limbic thalamus) through neuronal pathways: Papez- circuit -emotional feeling and expression -interconnections constitute a harmonious mechanism -cingulate gyrus is a receptive region for experiencing of emotion Subcortical structures are connected to the limbic lobe: Diencephalon mamillary bodies thalamic nuclei medial and lateral habenular ncll. James Papez (1883-1958) American anatomist

Components of limbic system Cortical areas gyrus cinguli gyrus subcallosus prefrontal cortical areas – anterior part of frontal lobe (rostral to motor areas) piriform cortex –parahippocampal g. anterior part, including uncus, lat. olf. stria entorhinal cortex – parahippocampalis g. hippocampus dentate gyrus subiculum - pre/parasubiculum parahippocampal gyrus Subcortical limbic areas Diencephalon habenula mamillary body(hypothalamus) anterior thalamic nuclei (limbic thalamus) Telencephalon olfactory bulb anterior olfactory nucleus nucleus of the lateral olfactory tract septum nucleus tractus diagonalis nucleus accumbens (ventral striatum) amygdala nucleus stria terminalis Mesencephalon interpeduncular n., raphe dorsalis and medianus n. ventral tegmental nucleus, centr. gray matter

Nomenclature Parolfactory area (subcallosal area) -a small area of cortex on the medial surface of the frontal lobe, immediately in front of and below the subcallosal (=paraterminal) gyrus Gyrus subcallosus = gyrus paraterminalis Septal nuclei -in the septum pellucidum: only a few scattered neurons - nuclei of „true septum” (septum verum) are ventral to the septum pellucidum - extend into the subcallosal gyrus Piriform cortex (olfactory cortex)= rhinecephalon = olfactory brain=nose brain - olfactory bulb, tract, lat. olfactory stria, ant. perf. substance, ant. part parahippocampal gyrus, uncus, amygdala (dorsomed) -paleopallium, oldest part of hemisphere – projections to enthorinal cortex Entorhinal cortex -behind the ant. part of parahippocampal gyrus (piriform cortex) -projections to hippocampal formation (archicortex) Rhinal sulcus (16) -minor sulcus in the parahippocampal gyrus on the ventral-medial margin of the anterior temporal lobe -the rhinal sulcus continuous with the collateral sulcus along the lateral margin of parahippocampal gyrus Isthmus of cingulate gyrus (9) -connects the neocortical cingulate gyrus to parahippocampal gyrus paleocortex archicortex transitional BrainInfo (2007), Neuroscience Division, National Primate Research Center, University of Washington, http://www.braininfo.org.

Gyrus parahippocampalis Gyrus uncinatus Uncus Limbus Giacomini Gyrus intralimbicus Gyrus parahippocampalis B

limbic system scheme: afferentation nucl. ant. thalami limbic system scheme: afferentation

Papez circle

limbic system scheme: Papez circle nucl. ant. thalami limbic system scheme: Papez circle

limbic system scheme: efferentation nucl. ant. thalami limbic system scheme: efferentation

Prefrontal cortex - human Complex functions: -working memory, attention, cognition, emotion -executive control -regulates behavioral inhibition -jugdment, foresight Prefrontal cortex - human Dorsomedial prefrontal cortex -extensive connections with sensorimotor and association neocortex (contemporary and past sensory experiences) Orbitofrontal cortex -strong connections with amygdaloid complex -project heavily to subcortical limbic structures: hypothalamus and septum influences on behavioral and autonomic functions Reciprocal relationship between dorsal and ventral prefrontal cortex cognitive - emotional interactions

Amygdaloid complex Basolateral nuclei (younger) Extraordinarily complex Involved in many aspects of behavior but: there is no single high level function Swanson and Petrowich: „neither a structural nor a functional unit” Amygdaloid complex -implicated in emotional processing -critically involved in mediating the stress on hippocampal memory processes – amygdalo-hippocampal interactions Basolateral nuclei (younger) -extensive reciprocal relations: sensory assotiation cortex (parietal, temporal), frontal lobe and ventral striatum (putamen, and caudate n. ventral parts) n. accumbens, Meynert’s n. basalis, dorsal thalamus -projections from olfactory bulb, entorhinal cortex, cingulate gyrus, subcallosal area Corticomedial nuclei (older) -descending pathways to n. dorsalis n.vagi, brainstem cardiovascular centers, locus coeruleus, n. raphe dorsalisventral tegmental nucleus -peptidergic neurons(enkephalin, CRH, somatostatin, cholecystokinin) -HYPOTHALAMUS – tractus amygdalo-hypothalamicus ventralis + stria terminalis - reciprocal Many authors have attempted to divide this complex into clear functional units, largely without succes corticomediális, basolaterális subnuclei

Nucleus accumbens (limbikus striatum) N. accumbens functional aspects: -responsible for motivated, goal-directed behaviors -(compulsive drug seeking in cocaine addicts) -interface between limbic and motor system Normally descending projections from prefrontal cortex to n. accumbens, as well as other limbic regions, exert inhibitory control over reward-seeking behaviors

Hippocampal formation: hippocampus, gyrus dentatus, subiculum

Hippocampus afferents somatic, visual, auditory, olfactory and motor information from: regio entorhinalis, olfactory cortex, neocortex other hippocampus (comm. fornicis/hippocampi) gyrus cinguli thalamus (anterior and lateral dorsal nuclei) septal region corpus amygdaloideum hypothalamus

Hippocampus efferents Fornix Hypothalamusba (Corpus mamillare) Septum region Papez-circuit Thalamus (nucl. ant. thalami) Gyrus cinguli Gyrus parahippocampalis (regio entorhinalis, subiculum)

Hippocampal formation: hippocampus, gyrus dentatus, subiculum G. dentatus Ammon-horn Subiculum Fimbria Alveus Sulcus hippocampi G. parahippo- campalis

Hippocampal formation: hippocampus, gyrus dentatus, subiculum

Hippocampus connections I. Papez-circuit Cingulum Nucl. anterior thalami Fasc. mamillothalamicus (Vicq-d’Azyr-köteg Fornix

Hippocampus connections II. Commissura hippocampi (fornicis) G. cinguli Cingulum Fornix Frontallappen MD Nucl. ant. thalami Nuclei habenulae Stria med. thalami Fasc. mamillothalamicus Septumregion C. mamillare Hypothalamus Hippocampus Stria terminalis+ Broca-Diagonalband G. parahippocampalis Temporallappen Area entorhinalis Amygdala

Hippocampal formation function memory short term long term memory processing functions (learning) from short term to long term rational memory - hippocampus, Papez-circle emtional or autonomic - amygdala motor memory - sensory and motor cortex areas through the thalamus anger, motivation, consciousness, agression

References