* Your assessment is very important for improving the workof artificial intelligence, which forms the content of this project
Download basal ganglia
Time perception wikipedia , lookup
Metastability in the brain wikipedia , lookup
Nervous system network models wikipedia , lookup
Embodied language processing wikipedia , lookup
Environmental enrichment wikipedia , lookup
Biochemistry of Alzheimer's disease wikipedia , lookup
Limbic system wikipedia , lookup
Stimulus (physiology) wikipedia , lookup
Central pattern generator wikipedia , lookup
Cognitive neuroscience of music wikipedia , lookup
Axon guidance wikipedia , lookup
Endocannabinoid system wikipedia , lookup
Neuroplasticity wikipedia , lookup
Neuroanatomy wikipedia , lookup
Perivascular space wikipedia , lookup
Development of the nervous system wikipedia , lookup
Neuroeconomics wikipedia , lookup
Channelrhodopsin wikipedia , lookup
Eyeblink conditioning wikipedia , lookup
Anatomy of the cerebellum wikipedia , lookup
Circumventricular organs wikipedia , lookup
Feature detection (nervous system) wikipedia , lookup
Optogenetics wikipedia , lookup
Molecular neuroscience wikipedia , lookup
Aging brain wikipedia , lookup
Neuroanatomy of memory wikipedia , lookup
Hypothalamus wikipedia , lookup
Neuropsychopharmacology wikipedia , lookup
Premovement neuronal activity wikipedia , lookup
Clinical neurochemistry wikipedia , lookup
Synaptic gating wikipedia , lookup
Vincenzo Perciavalle, M.D. Professor of Physiology - University of Catania BASAL GANGLIA Reproduction of plate VII of book VII of De Humani Corporis Fabrica [1543] of Andreas Vesalius (Andreas van Wesel, 1514-1564) with a rather accurate view of the basal ganglia. Bundles of white matter (E), corresponding roughly to internal capsule, are shown separating masses of grey matter (D), the lower medial one corresponding to the thalamus and the upper lateral one to the putamen. The caudate nucleus is also clearly outlined as a structure separated from the putamen by white matter. Also note, on the right side, the unmarked line separating the putamen from the globus pallidus. Vesalius A, De Humani Corporis Fabrica, Libri Septem, J. Oporinus, Basel, 1543. Reproduction of plate VIII from Cerebri anatome [1664] by Thomas Willis (16211675) that shows a dorsal view of the brainstem and basal ganglia in a sheep. The hemispheres have been removed to better illustrate the basal ganglia, and the corpus striatum on the right side has been cut in half to show its characteristic striations. Willis T., Cerebri Anatome Cui Accessit Nervorum Descriptio et Usus, Flesher, Martyn and Allestry, London, 1664. Reproduction of plate XXII from Traité d’anatomie et de physiologie [1786] by Félix Vicq d’Azyr (1746-1794) that depicts a horizontal section of the human brain. The caudate nucleus, putamen and globus pallidus are clearly singled out, but not specifically named by the author. The claustrum and the substantia nigra (locus niger crurum cerebri) are also depicted. The insert at the bottom is a drawing taken from palate XIV of Vicq d’Azyr’s treatise showing a sagittal view of the human basal ganglia, with the putamen and the inner and outer pallidal segments. Vicq d’Azyr F., Traité d’Anatomie et de Physiologie, Didot, Paris, 1786. Reproduction of plate III (book III) of Von Baum und Leben des Gehirns [1819] by Karl Friedrich Burdach (1776-1847) showing a coronal view of the right hemisphere of a human brain with the first detailed view of the basal ganglia. The Streifenhügel (caudate nucleus) is clearly separated from the Linsenkern (lenticular nucleus, consisting at this rostral level only of its Schale or envelope that Burdach called putamen) by the fiber of the innern Capseln (internal capsule). The Vormauer (claustrum) is also well delineated, with the äussern Capseln (external capsule) separating it from the Linsenkern (lentiform nucleus). Burdach K.F., Vom Baue und Leben des Gehirns und Rückenmarks, Vol. 3, Dyk, Leipzig, 1819. In strictly anatomical sense, the Basal Ganglia are constituted by three nuclei: the Caudate Nucleus and the Putamen, which constitute the Corpus Striatum, and the Globus Pallidus. Subsequently, to these three structures were added the Substantia Nigra, the Subthalamic Nucleus and, more recently, the Nucleus Accumbens. The Putamen and the Globus Pallidus are so close that in the past were called Lenticular Nucleus. Subsequently, it is seen that the Putamen has a structure similar to that of the Caudate Nucleus to which was assimilated for the characteristic striation. The Caudate Nucleus resembles a C-shape structure with a wider "head" (caput in Latin) at the front, tapering to a "body" (corpus) and a "tail" (cauda). After the body travels briefly towards the back of the head, the tail curves back toward the anterior, forming the roof of the inferior horn of the lateral ventricle. 1 – 3 caudate nc. 4 – putamen 5 – globus pallidus 6 - amygdala The substantia nigra (SN) is a brain structure located in the midbrain and is divided into two parts: the pars reticulata (SNpr) and pars compacta (SNpc). The SNpr bears a strong structural and functional resemblance to the internal part of the globus pallidus. The two are sometimes considered parts of the same structure, separated by the white matter of the internal capsule. Like those of the globus pallidus, the neurons in pars reticulata are mainly GABAergic. The SNpc is formed by dopaminergic neuron. In humans, these cells are coloured black by the pigment neuromelanin; they degree receive striatal information and send their axons along the nigrostriatal pathway to the striatum where they release the neurotransmitter dopamine. The subthalamic nucleus (STN) is a small lens-shaped nucleus in the brain where it is, from a functional point of view, part of the basal ganglia system. It was first described by the French neurologist Jules Bernard Luys (1928-1897), and the term Corpus Luysi or Luys' body is still sometimes used. The STN receives GABAergic, inhibiting inputs from the external part of globus pallidus and excitatory, glutamatergic inputs from the cerebral cortex. The efferent axons of STN are glutamatergic (excitatory) and reach the inner segment of globus pallidus. The nucleus accumbens (nucleus accumbens septi; latin for nucleus adjacent to the septum) is a region in the basal forebrain rostral to the preoptic area of the hypothalamus. Major inputs to the nucleus accumbens include the prefrontal cortex, basolateral amygdala, ventral tegmental area (VTA) and hippocampus. The output neurons of the nucleus accumbens send axon projections to the ventral pallidum, VTA, substantia nigra, and the reticular formation of the pons. Excitatory (red) and inhibitory (black) connections forming the corticostrio-pallido-thalamocortical circuit. It can be seen that the Striatum (Caudate + Putamen) act on the internal segment of Globus Pallidus either directly (direct pathway) that by means of its external segment and the Subthalamic Nucleus (indirect pathway). The direct pathway exerts an excitatory effect on the thalamus and, therefore, on the cerebral cortex. In the motor cortex the induced effect is a facilitation of movements and a reduction of muscular tone. The indirect pathway exerts an inhibitory effect on the thalamus and, therefore, on the on the cerebral cortex. In the motor cortex the induced effect is an increase of muscular tone and a reduction of movements . Distribution of corticostriatal neurons in cortical layers Large dots – striatum Small dots - thalamus Neurons of the basal ganglia Basal Ganglia Loops Convergence – large dendritic trees – decreasing cell number 150,000,000 30,000 Cortex Striatum 100 GPe 1 GPi/ SNr 500:1 300:1 100:1 Dopaminergic cells of Substantia Nigra pars compacta send their axons the striatal medium spiny neurons from which originates both the direct and the indirect strio-pallidal pathways. On striatal medium spiny neurons of origin of the direct pathway. dopamine binds receptors D1-type, while on those of origin of the indirect pathway binds receptors D2-type. Activation of receptor D1-type induces an increase of cAMP, whereas the activation of receptor D2-type produces a decrease of cAMP. Therefore, nigrostriatal dopaminergic neurons activate the direct pathway and inhibit the indirect one. THE DOPAMINERGIC PATHWAYS PARKINSON’S DISEASE Parkinson's disease (PD) is a neurodegenerative disorder mainly affecting the motor system. The motor symptoms of PD result from the death of dopamine-generating cells in the substantia nigra. The early symptoms include shaking, rigidity, slowness of movement and difficulty with walking and gait. Later, thinking and behavioral problems may arise, with dementia and depression commonly occurring in the advanced stages of the disease. Other symptoms include sensory, sleep and emotional problems. PD is more common in older people, with most cases occurring after the age of 50. In 2013 PD resulted in about 103,000 deaths globally, up from 44,000 deaths in 1990 HUNTINGTON’S DISEASE Huntington's disease (HD) is a neurodegenerative genetic disorder that affects muscle coordination and leads to mental decline and behavioral symptom. The most characteristic initial physical symptoms are jerky, random, and uncontrollable movements called chorea exhibited as general restlessness, small unintentionally initiated or uncompleted motions, lack of coordination, or slowed saccadic eye movements. Physical symptoms usually begin between 35 and 44 years of age. The disease is caused by an autosomal dominant mutation in either of an individual's two copies of a gene called Huntingtin. The most prominent early effects damage the caudate nucleus and putamen, so compromising the functioning of the indirect pathway. HYPO-FUNCTIONING OF INDIRECT PATHWAY Athetosis is a symptom characterized by slow, involuntary, convoluted, writhing movements of the fingers, hands, toes, and feet and in some cases, arms, legs, neck and tongue. Lesions to the Corpus Striatum are most often the direct cause of the symptoms. Hemiballismus is a very rare movement disorder, caused in most cases by a decrease in activity of the Subthalamic Nucleus, resulting in the appearance of flailing, ballistic, undesired movements of the limbs. The Basal Ganglia are involved not only in motor functions, but also in cognition and emotion.