Cerebrum Ch 17 Ekman PDF

Cerebrum Ch 17 Ekman Dr. Meeyoung Kim Neuroscience Physiotherapy Dept. University of Sharjah Contents Structures Lobes White matter Lesions Cerebrum Largest portion of the brain – 80 - 83% of brain mass Responsible for complex aspects of consciousness...

Cerebrum Ch 17 Ekman Dr. Meeyoung Kim Neuroscience Physiotherapy Dept. University of Sharjah Contents Structures Lobes White matter Lesions Cerebrum Largest portion of the brain – 80 - 83% of brain mass Responsible for complex aspects of consciousness – Memory – Personality – Intelligence Containing cerebral hemispheres, subcortical structures (hippocampus, BG, olfactory bulb) Different types of cortex: Neocortex (new cortex) - 6 layers example: 1°motor and sensory cortex, Association areas Mesocortex (middle cortex) - 3-6 layers - related to limbic system - cingulate gyrus, parahippocampal gyrus Allocortex (other cortex) - 3 layers archicortex - hippocampal formation (function: memory, amnesia after lesion) paleocortex – piriform cortex (function: odor discrimination) Neocortex constitutes approximately 90% of all cortex and contains 6 identifiable cellular layers. The major neuronal types in neocortex are the pyramidal cells and granule cells. Neocortex – 6 cellular layers I. Molecular layer – mostly neuropil II. External granular layer – stellate cells III. External pyramidal layer – small pyramidal cells IV. Internal granular layer – stellate cells V. Internal pyramidal layer – large pyramidal cells VI. Multiform layer – multiple cell types Layer 4 is the recipient zone of thalamocortical axons. Layers 3, 5 and 6 are the output layers, sending axons to other cortical or subcortical targets. Layer 5 is the principal output layer to subcortical targets.  sensory association motor I II Association & Commissural III Thalamocortical afferents IV Corticofugal Efferents (pyramidal tract) V Corticothalmic VI efferents  Cerebral Cortex Areas 1. Sensory areas that deal with the perception of sensory information 2. Motor areas that control voluntary movement execution 3. Association areas that integrate complex functions Each hemisphere predominantly controls the opposite side of the body No functional area acts alone Conscious behavior requires entire cortex Brodmann Areas Area 4 = primary motor cortex Areas 3, 1,2 = primary somatosensory cortex Area 17 = primary visual cortex Areas 41, 42 = primary auditory cortex  Homunculus The primary sensory and motor areas of the cerebral cortex are precisely topographically organized. This topographic organization reflects the organization of the ascending sensory pathways and nuclei within the dorsal Sensory thalamus as well as the descending motor pathways. Specific parts of the cortex control specific motor and sensory functions on the contralateral side of the body. The amount of cortical space given to a body part varies homunculus (“little person”) MOTOR Internal Capsule Organization medial lateral Lobes of Cerebrum  Landmarks that divide the brain into lobes include the central sulcus the lateral fissure, also known as the Sylvian fissure hemisected view allows us to note the parieto- occipital sulcus separates the parietal and occipital lobes.  Further anatomical subdivisions of the medial surface of the cerebral hemisphere Parieto-occipetal fissure Cingulate gyrus Cuneate gyrus Lingual gyrus Cingulate sulcus Calcarine sulcus Locations Frontal lobe – includes the entire hemisphere rostral to the central sulcus. Parietal lobe – limited rostrally by the central sulcus, caudally by a line on the external surface corresponding in position to the parieto-occipital sulcus, and ventrally by a line which prolongs the lateral (Sylvian) sulcus in a caudal direction. Occipital lobe – located caudal to the parieto-occipital sulcus. Temporal lobe – located ventral to the frontal and parietal lobes and extending caudally up to the occipital lobe. Insula – this lobe is buried deep within the lateral fissure.  Insula can be seen by gently pulling apart the borders (opercula) of the lateral fissure. is cone-shaped portion of the cortex that is sometimes referred to as an additional lobe of the cerebral cortex.  Insula The insulae are believed to be involved in consciousness and play a role in diverse functions usually linked to emotion or the regulation of the body's homeostasis (related to visceral sensation, autonomic control). Frontal Lobe Associated with executive functions, motor performance, and production of language the precentral gyrus is the primary motor area. Prefrontal Cortex – Executive functions (e.g., personality & recognizing consequence) Primary Motor Cortex (M1): – Motor Performance (e.g., initiation of voluntary movement as well as the premotor and supplementary motor areas, which coordinate the planning and initiation of voluntary movement) Broca’s area: the left inferior frontal gyrus. – Production of language – Damage causes Broca’s aphasia  Frontal Executive function Lobe Mental processes (executive functioning skills ) that help you set and carry out goals. You us e these cognitive skills to solve problems, ma ke plans and manage emotions. Top-down processing by definition is when behavior is guided by internal states or intentions. Examples: planning, attentional control, organizational skills, etc… Wisconsin Card Sorting Test (WCST). Parietal Lobe Associated with integrating sensory information, contains the spatial orientation system, and is involved in the comprehension of language Postcentral gyrus – located posterior to the central sulcus. – is the primary somatosensory area (processing of proprioceptive and tactile stimuli) Two-point discrimination – through touch alone without other sensory input (e.g. visual) Graphesthesia – recognizing writing on skin by touch alone Wernicke’s area: – Located partially in the parietal lobe – Involved in recalling, recognizing, and interpreting words and other sounds in the process of using language. speech perception angular and supramarginal gyri  Parietal Lobe - Posterior parietal cortex (PPC) receives somatosensory and visual input, which then, through motor signals, controls movement of the arm, hand, and eyes. - Visuospatial processing: PPC is the dorsal stream of vision both the "where" stream (as in spatial vision) and the "how" stream (as in vision for action).  IMPORTANT! Parietal The dorsal stream and ventral stream Lobe are shown. They originate from primary visual cortex. Dorsal (green) = "Where Pathway" or "How Pathway", is associated with motion, representation of object locations, and control of the eyes and arms, especially when visual information is used to guide saccades or reaching. Ventral (purple) = "What Pathway", is associated with form recognition and object representation. Temporal Lobe Contains the primary auditory cortex and part of Wernicke’s area anterior transverse temporal gyrus (Heschl’s gyrus) - the largest of these gyri and the site of the primary auditory area. Medial parts of the temporal lobe are involved in aspects of memory and learning  Occipital Lobe Primary visual cortex (V1) is composed of the upper and lower banks of the calcarine cortex. V2: secondary visual cortex Limbic System (not a true lobe) involves with Cingulate gyrus -connect sensory input to emotion Hippocampus- short term memory Amygdala- fear, aggression, mating (Trigger of Fight-Flight response) Fornix - pathway to hypothalamus Hypothalamus- ANS control (Carry out of fight-flight: message to adrenal glands to release stress hormone)  intracortical White Matter intercortical projection fibers  Much of the cerebral hemispheres is occupied by subcortical white matter, which is anatomically organized. There are three types of fibers in the subcortical white matter: 1) projection fibers - leave the hemisphere for subcortical targets 2) commissural fibers - interconnect the two hemispheres, L-R and R-L 3) association fibers (2 types) - intrahemispheric connections, L-L and R-R Commissural Fibers Anterior Commissure Inf. & mid. temporal gyri, olfactory areas Posterior Commissure Preoptic nuclei (vision) Corpus Callosum Connects hemispheres Rostrum, genu, body & splenium  Association Fibers Short fibers – connect adjacent gyri Long fibers Superior longitudinal fasc. Arcuate fasciculus: connecting 2 language centers. Inferior longitudinal fasc. Cingulum – septal area, cingulate and parahippocampal gyri Uncinate fasc. – orbital frontal gyri to temporal pole Association fibers do not leave the cerebral hemisphere and can be classified as either long or short. Projection Fibers  Lesions of cerebrum Remember name of lesion with damaged area  Apraxia (Error in execution of learned movements without coexisting weakness) Damage to dominant parietal, premotor, and supplementary motor areas Dominant hemisphere association areas Parietal - integrates motor sequences with vision and somatic sensory info Frontal lobe - execution of act  Aphasias-Sensory Wernicke’s Dominant (left usually) hemisphere Fluent, paraphasias, poor comprehension, Naming, repetition, reading and writing impaired Less aware and less frustrated than motor aphasias  Agnosia-impaired perception or recognition with OK vision, hearing, sensation , attention, intelligence Visual: colors, faces, letters Auditory: tunes, spoken words, pure word deafness Somatosensory - stereognosis, graphesthesia May not have other signs: aphasia, apraxia Atrophy or metastatic disease Disconnections of specific sensory association areas Corpus callosum, deep white matter near main sensory areas  Contralateral Neglect Right parietal Right side is dominant for attention - do not attend to opposite side, ie. Dressing apraxia Severe - failure to recognize one’s opposite limb Impaired visuospatial ability (drawing, copying, 3D, manipulate objects in space) Fail to appreciate humor Any questions?