Basal Ganglia and Limbic System 2024-2025 PDF

University of Baghdad College of Medicine 2024-2025 Title: Basal ganglia and limbic system Grade: 2 Module: HSF2 Speaker: Dr. Zainab Zahid Date: 7/11 Basal Nuclei (Basal Ganglia) & Limbic system  Internal structures of the cerebral h...

University of Baghdad College of Medicine 2024-2025 Title: Basal ganglia and limbic system Grade: 2 Module: HSF2 Speaker: Dr. Zainab Zahid Date: 7/11 Basal Nuclei (Basal Ganglia) & Limbic system  Internal structures of the cerebral hemispheres The forebrain Telencephalon Diencephalon Cerebral hemisphere The cerebral cortex The white matter The basal nuclei Outer gray matter Below cerebral cortex Deep gray matter Basal Nuclei (Basal Ganglia) A collection of subcortical masses of gray matter situated deep within each cerebral hemisphere lateral to the thalamus The term “basal” because they lie near the base of each hemisphere Play an important role in the control of posture and voluntary movement Basal Nuclei Anatomical components of basal ganglia: o Corpus striatum o Amygdaloid nucleus o Claustrum Corpus striatum consists of: o Caudate nucleus medially Separated from each other o Lentiform nucleus laterally by internal capsule Lentiform nucleus consists of: o An outer part, the putamen o An inner part, the globus pallidus (paleostriatum) Caudate nucleus + putamen= striatum or neostriatum Striated appearance of strands of gray matter from caudate nucleus to the putamen  Coronal section Basal Nuclei Functional components of basal nuclei: Subthalamic nuclei of the diencephalon: glutaminergic and excitatory and have both way connections to the globus pallidus Substantia nigra of the midbrain: dopaminergic and inhibitory and has both way connections to the striatum (caudate and putamen) Thalami 1. The caudate nucleus Curved comma shape with a head, body and tail Closely related to the concavity of the lateral ventricle and curves around the lateral side of the thalamus and medial side of lentiform nucleus The whole length of the convexity projects into the lateral ventricle, the head lies in the lateral wall of the anterior horn of the ventricle, the body runs in the floor of the body of the ventricle and the tail runs in the roof of the inferior horn The amygdaloid situated at the end of tail of caudate nucleus Transverse section Caudate nucleus head Internal capsule Lentiform nucleus Thalamus Amygdala Caudate nucleus tail  2. The lentiform nucleus A biconvex lens shape, has two parts: the large lateral putamen and the small medial globus pallidus GP Two vertical sheets of white matter, medial and lateral medullary laminae, divide the lentiform nucleus into three parts. The medial two pale parts form the globus pallidus, internal and external globus, and the lateral dark part forms the putamen Lentiform nucleus separated from caudate nucleus and thalamus Th, by internal capsule IC, anterior limb separates lentiform from caudate and posterior limb separates globus pallidus from thalamus Sheet of white matter external to putamen, named external capsule EC, separates putamen from claustrum Lateral and medial medullary laminae  3. The amygdaloid body (or amygdala) The amygdaloid nucleus A, is so named because it resembles an almond It is groups of neurons situated anterosuperior to the tip of the inferior horn of the lateral ventricle in the medial part of the temporal lobe (near the uncus) It is located at the anterior end of the hippocampus and fused with the tip of the tail of the caudate nucleus, which passes in the roof of the inferior horn of the lateral ventricle The amygdala is functionally part of the limbic system, concerned with emotional behavior Major output pathway, Stria terminalis, runs posteriorly following the curvature of the tail of the caudate nucleus, in the roof of the inferior horn and the floor of the body of the lateral ventricle, along the lateral margin of the ventricular surface of the thalamus in a groove between caudate nucleus and thalamus, thalamostriate groove, to the septal area and anterior hypothalamus Splenium of corpus callosum Hippocampus  4. The claustrum A thin sheet of grey matter, located between the putamen medially and the insular cortex laterally. Separated from putamen by external capsule EC, and from insula by the extreme capsule The exact function of the claustrum is unknown  Function of basal nuclei It executes your target movement and posture in a proper accepted way according to the learned strategy you Exert a supraspinal control over skeletal muscle movements. They do already have not initiate muscle contraction but modify rate, range and coordination assist in learning of motor skills and help prepare for the movements This important preparatory function enables the trunk and limbs to be placed in appropriate positions before the primary motor part of the cerebral cortex activates discrete movements in the hands and feet  Plan of connections Striatum (caudate and putamen) is the main input, all its output go to globus pallidus Globus pallidus is the main output, sends inhibitory orders to the thalamus and because thalamus excitatory to motor cortex, thus globus pallidus is inhibitory to cerebral cortex Substantia nigra has both way communication with striatum (caudate and putamen), it is inhibitory. Subthalamic nucleus has both way communication with globus pallidus, it is excitatory. There is no direct connection between basal ganglia & spinal cord It receives input from most cortical areas and send output via thalamus, to cortical areas involved with planning of movement Basal ganglia regarded as one of the extrapyramidal system It sends projection to most extrapyramidal systems; red nucleus, tectum, reticular formation and vestibular nuclei; thus exerting its control upon lower motor nuclei  Basal nuclei lesion Disorders of the basal nuclei are of three types: 1. Hyperkinetic disorders result in excessive and abnormal Mask face movements 2. Hypokinetic disorders result in a lack or slowness of movement 3. Both hyper and hypokinetic disorder like in Parkinson disease, its the most common disease of basal nuclei Tremor characterized by tremor (hyperkinesia), rigidity and abnormal slowness of movements (hypokinesia); there is a decrease of dopamine in the nigrostriatal pathway (from substantia nigra to corpus striatum) Manifestations: Tremor (usually at rest) Rigidity Bradykinesis; difficulty in initiating new movements Mask face + slurred speech Postural disturbances; short steps & inability to stop No weakness  Blood supply of basal nuclei Medial and lateral striate branches (lenticulostriate artery) from middle cerebral artery Anterior choroidal artery from internal carotid artery Recurrent artery of Heubner from anterior cerebral artery  The Limbic System Limbic means border or margin. Includes a group of cortical and subcortical structures with the cortical ones lie on the medial rim or border of the cerebral hemisphere Concerned with regulating behaviors related to the objectives of primitive life (food, shelter and sex), controlling behaviors of seeking food, mating, housing, rage, aggression, emotions, mood and memory Areas included fall into two categories: ✓ Areas are portions of the cerebral cortex (cortical structures) ✓ Areas are subcortical structures The Limbic System Limbic lobe Cortical regions that are involved in the limbic system include: The hippocampal formation (Parahippocampal gyrus, hippocampus) The insular cortex Orbital frontal cortex Subcallosal gyrus (below rostrum of corpus callosum) Septal and piriform areas of cerebral cortex, near the lamina terminalis (anterior boundary of the third ventricle Cingulate gyrus (above corpus callosum) These components of cortex has been termed the "limbic lobe" because it makes a rim surrounding the corpus callosum, following the lateral ventricle Subcortical structures of the limbic system include: The olfactory bulb Mammillary body (hypothalamus) The amygdala The septal nuclei The anterior thalamic nucleus  Hippocampal Formation Hippocampal formation Located in the temporal lobe of each cerebral cortex, medial to the inferior horn of the lateral ventricle Consists of: Hippocampus Subiculum Dentate gyrus Inf. Horn of lat. ventricle Parahippocampal gyrus At the inner side of parahippocampal gyrus there is hippocampal sulcus The parahippocampal gyrus lies between hippocampal sulcus and collateral sulcus The transitional zone between the parahippocampal gyrus and the hippocampus is the subiculum  The hippocampus Coronal section Superior view It is enfolding of the inferomedial part of the temporal lobe in to the lateral ventricle, along the line of the choroid fissure so that it appears as an elevation of gray matter that extends temporal lobe throughout the entire length of the floor of the inferior horn of temporal the lateral ventricle lobe In lateral view, it appears to consists of a head, body and tail (like sea horse). The head is the anterior part and appears like the knuckles of the clenched fist, hence called the pes hippocampus. The body is more cylindrical in shape, and the tail tapers posteriorly Sagittal plane  Coronal section Coronal plane The hippocampus In the coronal plane, the hippocampus and parahippocampal gyrus form Temporal lobe an S-shaped configuration that also resembles a seahorse The hippocampus itself has spiral shape, consists of two interlocking C- Hippocampus shaped gyri: hippocampal gyrus or Ammon’s horn (cornu ammonis) and Parahippocampal gyrus dentate gyrus Ammon’s horn The dentate gyrus Is a narrow, notched band of gray matter that lies between the hippocampus and the parahippocampal gyrus The term dentate gyrus comes from the beaded or toothed appearance of this structure resulting from the many small blood vessels that penetrate the dentate gyrus Posteriorly, the gyrus accompanies the fimbria almost to the splenium of the corpus callosum and becomes continuous with the indusium griseum The indusium griseum is a thin, vestigial layer of gray matter that covers the superior surface of the corpus callosum Anteriorly, the dentate gyrus is continued into the uncus Coronal view Superolateral view Fornix Indusium griseum Dentate gyrus Splenium of Corpus callosum Amygdala  White matter output of hippocampus A thin layer of white matter called the alveus lies along medial border of hippocampus The alveus consists of nerve fibers that have originated in the hippocampus, and these converge medially to form a bundle called the fimbria The fimbria, a bundle formed from convergence of alveus on the medial border of the hippocampus, breaks free from the hippocampus as crus of the fornix (posterior column) on each side, posteriorly beneath the splenium of the corpus callosum Fornix Mammillary bodies  Fornix The fornix is “C” shaped tract, efferent pathway from the hippocampus Begins as the alveus, then fimbria then crus or posterior column of the fornix, beneath the splenium of the corpus callosum and around the posterior surface of the thalamus Both sides crura join its fellow in the commissure of the fornix or the hippocampal commissure fibers pass to contralateral hippocampus= 1st path of hippocampi communication Continue as body of the fornix beneath the corpus callosum which reaches the anterior commissure, in front of the anterior poles of the thalami Body of fornix Body diverge as the anterior column on both sides, forming the Anterior columns of fornix anterior margins of the interventricular foramina and ends in Interventricular foramen mammillary bodies Anterior commissure Fibers from the anterior column of the fornix pass to septal nuclei, Mammillary body hypothalamus, thalamus and mamillary body Some fibers from the fornix pass through anterior commissure to the contralateral hippocampus= 2nd path of hippocampi communication Two crura of fornix body of the fornix Two anterior columns Connecting Pathways of the Limbic System The connecting pathways of different parts of the limbic system are: Alveus Fimbria Fornix Mammillothalamic tract Stria terminalis Cingulum The structures of limbic system not only are interconnected but also send projection fibers to many different parts of the nervous system Hypothalamus regarded as the major output pathway of the limbic system Hypothalamus Hippocampus  The major output pathways from the limbic system to Hypothalamus: 1. Papez circuit In 1937, James Papez proposed that the neural circuit connecting the hypothalamus to the limbic lobe was the basis for emotional expression Papez circuit involves various structures. It begins and ends with the hippocampal formation Papez circuit goes through the following neural pathways: Hippocampal formation → fornix → mammillary bodies (hypothalamus)→ mammillothalamic tract → anterior thalamic nucleus → cingulum → hippocampal formation Papez circuit The major output pathways from the limbic system to Hypothalamus: 2. Stria terminalis Emerges from amygdala and runs as a bundle of nerve fibers posteriorly in the roof of the inferior horn of the lateral ventricle on the medial side of the tail of the caudate nucleus It follows the curve of the caudate nucleus and comes to lie in the floor of the body of the lateral ventricle Separates thalamus from caudate in thalamostriate groove Cary fibers to the septal nuclei, hypothalamic, and thalamic areas and back to amygdala (afferent and efferent) caudate thalamostriate groove with stria terminalis hippocampus thalamus Inferior horn of lateral ventricle  Mammillary bodies Pair of small round bodies, part of the diencephalon (hypothalamus) Related to the limbic system They are located at the ends of the anterior columns of the fornix Receives output of hippocampus through fornix, being part of Papez circuit Mammillothalamic tract From the mamillary body, fibers pass in the lateral wall of the third ventricle as the mammillo-thalamic tract to the anterior nucleus of the thalamus Here, they relay and the thalamic neurons send their fibers to the cingulate gyrus, which send connecting fibers through cingulum to parahippocampal gyrus and then to hippocampus It is part of Papez circuit  Septum pellucidum A thin partition connecting the rostrum, genu and front of the body of the corpus callosum to the fornix, composed of two adherent layers. The two layers may be separated by the small cavity of the septum between them Anterior Corpus callosum Caudate Thalamostriate groove Corpus callosum Fornix Hippocampus Fornix Choroid plexus Thalamus Posterior  Function of limbic system Process and regulate emotion and memory, dealing with sexual stimulation and learning, behavior, motivation, and long-term memory Linked to the endocrine and autonomic nervous systems through hypothalamus, therefore, plays a significant role in our body’s reaction to stressful situations and visceral responses to reactions of fear, anger and sexual behavior Hippocampus is concerned with converting recent memory to long term memory A lesion of the hippocampus results in inability to store long-term memory for the events occurring after the lesion (anterograde amnesia). Memory of remote past events before the lesion is unaffected Blood supply of limbic system Blood supply of limbic system comes from anterior and posterior cerebral arteries and from internal carotid Internal carotid artery artery Vessels supplying hippocampal formation: ✓ Anterior choroidal artery from internal carotid artery (mainly) ✓ Posterior choroidal artery from posterior cerebral artery Posterior cerebral artery