Cerebrum Ch 17 Ekman PDF

Cerebrum Ch 17 Ekman Dr. Meeyoung Kim Neuroscience Physiotherapy Dept. University of Sharjah Contents Structures Lobes White matter Lesions  biggest part of the brain each lobe hav...

Cerebrum Ch 17 Ekman Dr. Meeyoung Kim Neuroscience Physiotherapy Dept. University of Sharjah Contents Structures Lobes White matter Lesions  biggest part of the brain each lobe have diff functions Cerebrum outside cortex matter -> inside cream is white matter pathway of ascending and descending Largest portion of the brain – 80 - 83% of brain mass Responsible for complex aspects of consciousness – Memory – Personality – Intelligence Containing cerebral hemispheres, some part is in cerebrum and some is in midbrain functional unit subcortical structures (hippocampus, BG, olfactory bulb) memory no input cranial nerve 1 short term  surface of cerebrum Different types of cortex: Neocortex (new cortex) - 6 layers in the primary motor and sensory cortex and association cortex area example: 1°motor and sensory cortex, Association areas Mesocortex (middle cortex) - 3-6 layers - related to limbic system - in other area of cerebrum 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. some input and some output areas 3, 5, 6 are sending info out -> descending tract (motor pathway) which are input and which are output is imp Neocortex – 6 cellular layers I. Molecular layer – mostly neuropil II. External granular layer – stellate cells 3 and 5 has III. External pyramidal layer – small pyramidal cells pyramidal cells IV. Internal granular layer – stellate cells receiving (triangular info from outside -> shape of ascending tract (sensory pathway) the initiation V. Internal pyramidal layer – large pyramidal cells) they are area 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 neocortex thick layer 3, 5, 6 layer 4 of motor is very tiny (thickest in sensory) remember I which layers are input and output II 3 output layers 3,5,6 and 5 is Association & the main one because they Commissural have large pyramidal cells (origin of III corticospinal Thalamocortical tract) afferents input layer IV Corticofugal Efferents (pyramidal tract) V Corticothalmic VI efferents  from central sulcus, anterior is motor posterior is sensory 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  can make sound but cant talk -> problem in Broca's area not understand but able to talk, there is fluency in talking-> lesion in Wernicke area only left side of hemisphere partially in the parietal and partially in the temporal lobe limbic system - emotion includes cortex area just above corpus callosum -> cingulate gyrus fluency of talking -> broca's area (motor language) sensory language understanding the language -> wernicke area Brodmann Areas remember only these Area 4 = primary motor cortex Areas 3, 1,2 = primary somatosensory cortex Area 17 = primary visual cortex Areas 41, 42 = primary auditory cortex  Homunculus left hemisphere - there is one sensory and 1 motor little person homunculus resp for right side sensation 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”) A homunculus is a visual representation of how the brain's sensory and motor cortex is organized to control different parts of the body. The brain areas responsible for motor control and sensation are mapped in a way that corresponds to the body, but not equally. Some parts of the body, like the hands and face, have a much larger area of the brain dedicated to them because they require more precise movements and sensitivity. This organization reflects how the brain controls the opposite side of the body (contralateral control). The term homunculus means "little person," symbolizing this distorted but MOTOR organized map of the body in the brain.  The internal capsule is a bundle of nerve fibers in the brain that acts as a major pathway for signals traveling between the cerebral cortex and other parts of the central nervous system, including the brainstem and spinal cord. part of cerebral cortex Internal Capsule Organization organization: * Motor fibers (descending) control voluntary movements and run through the posterior limb of the internal capsule. * Sensory fibers (ascending) carry information from the body to the brain and also pass through the posterior limb. * The anterior limb carries fibers involved in cognitive and emotional processes, connecting the frontal lobe with deeper brain structures. medial side of the thalamus is responsible for the face while the lateral part is for LL medial lateral Damage to the internal capsule can result in motor and sensory deficits on the opposite side of the body (contralateral).  Lobes of Cerebrum some questions about each lobe differences aphasia is involving brocas area and wernicke area broca area in frontal lobe wernicke area in parietal and temporal lobe connect this with cerebral artery BROCA AREA - MCA she gives lesion, we tell which part is involved  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 cortex area just above the corpus callosum is Parieto-occipetal fissure the cingulate gyrus Cingulate gyrus Cuneate gyrus Lingual gyrus Cingulate sulcus Calcarine sulcus in the middle of occipital dividing 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.  taste 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 physically close to limbic system to emotion or the regulation of the body's homeostasis (related to visceral sensation, autonomic control). broca and wernicke area is only in the left hemisphere!! right side hemiplegia will most likely have aphasia 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 MCA feeds most of lateral part and base (feeds Broca's area) – Damage causes Broca’s aphasia ACA goes top and the frontal broca's area: responsible for speech production, language expression, and controlling the muscles involved in speaking. damage results in Broca's aphasia (non-fluent aphasia), where a person has difficulty speaking. speech is slow, broken, and effortful. broca's area  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).  remmeber which information they are processing Parietal Lobe space 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 very important Parietal Lobe integration area is PPC - 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). Visuospatial processing involves how we interpret visual information in relation to space, primarily handled by the posterior parietal cortex (PPC), which is part of the dorsal stream of vision. it handles the "where" and "how" stream -> where tells about the location of object and distance, How uses visual information to guide the movement  IMPORTANT! Parietal The dorsal stream and ventral stream Lobe start from the visual cortex, comes to the side ventral stream -> "what" recognition "how" where" is v imp to decide the motor reaction so combination of dorsal and ventral stream gives it 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. saccades - rapid, jerky movements of the eyes that allow us to quickly shift our focus from one point to another. The dorsal stream helps you know where things are and how to interact with them (motion and spatial relations). The ventral stream helps you know what things are by identifying objects based on visual characteristics. 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 calcarine cortex Limbic System (not a true lobe) involves with which structures are involved know each structure and their function esp amygdala and hypothalamus Cingulate gyrus -connect sensory input to emotion Hippocampus- short term memory Amygdala- fear, aggression, mating (Trigger of Fight-Flight response) triggering area where we feel the fear Fornix - pathway to hypothalamus Hypothalamus- ANS control (Carry out of fight-flight: message to adrenal glands to release stress hormone)  intracortical White Matter intercortical passing both hemisphere - commissural passing one hemisphere - association going inside to out - projection fibers projection fibers going out  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 intercortical 3) association fibers (2 types) - intrahemispheric connections, L-L and R-R intracortical Commissural Fibers Anterior Commissure Inf. & mid. temporal gyri, olfactory areas of both hemispheres Posterior Commissure Preoptic nuclei (vision) Corpus Callosum biggest one Connects hemispheres Rostrum, genu, body & splenium  Association Fibers remember only highlighting one Short fibers – connect adjacent gyri Long fibers Superior longitudinal fasc. Arcuate fasciculus: connecting 2 language centers. without this cannot understand and talk 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 connecting the cerebral cortex to other parts of the central nervous system looks like fan shape thats why named corona radiata  Lesions of cerebrum Remember name of lesion with damaged area name, meaning plus which site is related to the lesion  inability to perform purposeful movements or gestures despite having the desire and physical capability to do so. Apraxia (Error in execution of learned not only for speech multiple areas movements without coexisting weakness) involved Damage to dominant parietal, premotor, and supplementary motor areas Dominant hemisphere association areas Parietal - integrates motor sequences with vision and somatic sensory info ppc function Frontal lobe - execution of act motor understanding of language is fine but difficulty in articulation is speech apraxia  Aphasias-Sensory aphasia motor - motor area effected aphasia global - both Wernicke’s Dominant (left usually) hemisphere Fluent, paraphasias, poor comprehension, Naming, repetition, reading and writing impaired Less aware and less frustrated than motor aphasias means you dont know Agnosia-impaired perception or recognition with OK vision, hearing, sensation , attention, intelligence sensation intact Visual: colors, faces, letters can see, hear, and feel normally but are unable to recognize or interpret these Auditory: tunes, spoken words, pure word deafness stimuli. 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 regions effected ask pt to imagine flower and draw it, they will only draw the right part (left hemiplegia pt) right lesion -> left neglect 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?