Basal Ganglia PDF

 Brain components Table 5.3 (1)Cerebral cortex Cerebral cortex Page 144 Basal nuclei (lateral to thalamus)...

 Brain components Table 5.3 (1)Cerebral cortex Cerebral cortex Page 144 Basal nuclei (lateral to thalamus) Basal nuclei Thalamus (medial) Thalamus Diencephalon Hypothalamus Hypothalamus Cerebellum Cerebellum Midbrain (Mesencephalon) Brain stem Brain stem Pons (midbrain, pons, and medulla) Medulla oblongata Spinal cord  Basal ganglia are a collection of masses of gray matter situated within the each cerebral hemisphere.  Traditional Concepts of Basal Ganglia Corpus Striatum Caudate Nucleus Neostriatum Striatum Lenticular Nucleus Putamen Globus Pallidus Paleostriatum Pallidum Corpus Amygdaloideum Archistriatum  Components of Basal Ganglia Corpus Striatum Striatum ----- Caudate Nucleus & Putamen &(Nucleus accumbens) Pallidum ----- Globus Pallidus (GP) Substantia Nigra Pars Compacta (SNc) Pars Reticulata (SNr) Subthalamic Nucleus (STN) Ventral Striatum Nucleus Accumbens Ventral Pallidum Non cholinergic portion of Substantia Innominata Central Nervous System, Noback et al, Humana Press  STRIATUM Caudate Nucleus Putamen Ventral Striatum: Nucleus Accumbens Lateral surface of basal ganglia 1. Putamen 2. Tail of caudate nucleus 3. Caudatolenticular gray bridge 4. Amygdaloid body 5. Thalamus  1. head of caudate nucelus 2. body of caudate nucelus 3. caudatolenticular gray bridge 4. putamen 5. tail of caudate nucleus 6. external segment of globus pallidus 7. internal segment of globus pallidus 8. amygdaloid body 9. nucleus accumbens septi Medial surface of basal ganglia The major parts of the basal ganglia consist of the caudate nucleus, the putamen and the globus pallidus. The basal ganglia is involved in the control of movement. Caudate Nucleus  C-shaped nucleus,  Closely related to lateral ventricle  Lateral to thalamus  Lateral to internal capsule and lentiform nucleus  Caudate Nucleus Head Anterior wall of anterior horn of lateral ventricle continues inferiorly with putamen at point of union strands of gray matter pass (striated appearance) Caudate nucleus Body It continues with head at interventricular foramen It forms part of floor of lateral ventricle It is seperated from thalamus by terminal sulcus stria terminalis, thalamostriate vein  Caudate Nucleus Tail posterior end of thalamus follows contour of lateral ventricle Roof of the inferior horn of lateral ventricle terminates in amgydala ▪ Insular cortex – extreme capsule – claustrum – external capsule – putamen – lateral medullary lamina – globus pallidus (lateral=external part) - medial medullary lamina - globus pallidus (medial=internal part) Amygdala  Corticomedial nuclear group –  Basolateral nuclear group –  Central  Through its connections, it can influence the body’s response to enviromental changes.  In case of fear, changes in heart rate, blood pressure etc. Subthalamus  Inferior to thalamus  Betweeen thalamus and tegmentum  Craniomedially hypothalamus  The subthalamus is part of the diencephalon. Subthalamus  Cranial ends of red nucleus and substantia nigra  Connection with corpus striatum, GP,SN,PPN etc  Neurons are glutamatergic (excitatory)  Control of muscle contraction  Tracts from tegmentum pass to thalamus ( medial, spinal, trigeminal leminisci) in subthalamus. Prominent bundles and nuclei in subthalamus  Forel Areas Forel Area H (ansa lenticularis) Forel Area H1 ( thalamic fasiculus) Forel Area H2 (lenticular fasiculus)  Forel Area (subthalamic fasciculus)  Subthalamic nucleus  Zona incerta  Takes part in extrapyramidal system Subthalamic nucleus  connections with corpus striatum  Control of muscle contraction  Lesion: hemiballismus Zona incerta  Elongation of reticular formation in subthalamus  Connections with tectum, tegmentum, red nucleus  Evaluates optic and vestibular impulses and send to globus pallidus Afferents Fibers of Corpus Striatum  Corticostriate fibers-  cortex to putamen and caudate nucleus  Largest input is from sensorymotor cortex  Thalamostriate fibers-  Intralaminar nuclei to caudate and putamen  Nigrostriate fibers-  SN to caudate and putamen Efferents of Corpus Striatum  Striatopallidal fibers-  Caudate and putamen to globus pallidus  Sriatonigral fibers  Caudate and putamen to SN Afferents Fibers of Globus Pallidus  Striatopallidal fibers-  caudate and putamen to GP Efferents of Globus Pallidus  Ansa lenticularis- thalamic nuclei  Fasciculus lenticularis- subthalamus  Pallidotegmental fibers-tegmentum  Pallidosubthalamic fibers- subthalamic nuclei The nucleus accumbens contains neurons that are part of the basal ganglia. Thus, this structure may play a role in the regulation of movement, including the control of complex motor activity and the cognitive aspects of motor control. In addition, this structure has been found to possibly be the area that becomes activated in situations that involve reward and punishment. The nucleus accumbens is a nucleus of the basal forebrain. It receives dopamine-secreting terminal buttons from neurons of the VTA and is thought to be involved in reinforcement and attention. Pedunculopontine Nucleus  Can be accepted as part of Basal Ganglia  It is located in mesopontine tegmentum.  Between posterior pole of substantia nigra & lateral tip of superior cerebellar peduncle  Function  Sleep  Learning, Sensation  Reaction time performance and stereotypy  Locomotion Input to Basal Ganglia- Caudate & Putamen Output of Basal Ganglia- GPi & SNr Motor Circuit  Balance between direct & indirect pathways results in measured and coordinated motor performance.  An imbalance causes disorders ; too little movements or uncoordinated, excessive movements Oculomotor Circuit  Critical in regulating gaze and orientation of the eyes  Inputs from prefrontal & posterior parietal areas to caudate  Output from Gpi & SN to thalamus(VA&DM)  VA to frontal eye field (gaze initiation)  DM (related to limbic system) direct gaze to salient & rewarding stimulus  SN to superior colliculus (coordinating & directing eye movements) Association circuit  Important in cognitive function  Input from frontal, parietal, temporal association areas to caudate & nucleus accumbens  GPi & SN to thalamus ( VA & CM)  VA to motor & prefrontal association areas  CM to cortex ( influences overall cortical arousal & function)  Planning of complex motor activity  After praticing and well learned associative circuit activity decreases and motor circuit active  Influences cognitive processes & learning  Experience and learning help to diferentiate stimuli, a goal directed behavior is developed. Limbic circuit  Regulation of emotional, motivational & affective aspects of behoviour  Motor expression of emotions (postures, gestures& facial expressions related to emotion)  Dopaminergic rich circuit – mask face  Innervation from cingulate gyrus to face (regulated by limbic circuit)