Cerebral cortex and function
- 1. CEREBRAL CORTEX (Hemispheres & Lobes) ASHARA T BOT-2018
- 2. LEARNING OBJECTIVES * CEREBRUM * CEREBRAL CORTEX *CEREBRAL HEMISPHERE * EXTERNAL FEATURES :- a- poles b-surfaces c-borders d- sulci * LOBES (function and lesions)
- 3. PARTS OF THE BRAIN
- 5. DEVELOPMENT OF BRAIN FOREBRAIN Telencephalon Diencephalon CEREBRUM THALAMUS MIDBRAIN Mesencephalon Parts of brain stem HINDBRAIN Metencephalon Myelencephalon Pons , cerebellum Medulla oblongata
- 7. CEREBRUM * Largest part of the human brain(fills the cranial cavity) * Heavily convoluted bi lobed structure * Situated in the Anterior & Mid cranial fossa of the skull * Divided into 2 parts Diencephalon (forms the central core) Telencephalon (forms the cerebral hemisphere)
- 8. * Consists of two lateral halves - left and right cerebral hemisphere * Separated by Longitudinal cerebral fissure * Cleft is complete – Ant & Post * In central part – cleft extends downward to corpus callosum (large mass of white fibers joining 2 cerebral hemispheres)
- 10. Cerebral cortex Surface layer of grey matter covering cerebral hemisphere Surface area of cerebral cortex – 2.2 sq.m Has many folds called gyri grooves in b/w folds called sulci
- 11. LAYERS OF CEREBRAL CORTEX
- 13. TYPES OF CEREBRAL CORTEX NEOCORTEX ALLOCORTEX Phylogenetically new structure of Cerebral cortex Phylogenetic ally oldest structure of Cerebral cortex Forms the major portion 90% Forms part of limbic system Structurally Thick & consists of 6 layers Also called as Isocortex/Neopallium Consists of 3 layers Divided into Archicortex & Paleocortex
- 15. CEREBRAL HEMISPHERE Each cerebral hemisphere consists of a) an outer layer of grey matter cerebral cortex b) an inner mass of white matter c) large masses of grey matter embedded in basal part basal ganglia/nuclei d) A cavity within it lateral ventricle
- 16. CHARACTERISTIC FEATURES OF HEMISPHERE Right hemisphere - Sensory stimulus and motor control from left side of the body. -Non dominant hemisphere. -Non verbal ideation. -Spatial comprehension . -Recognition of faces, places, objects. -Creative act of arts & music. -Context , perception.
- 17. Left hemisphere - Sensory and motor control from right side of the body -Dominant hemisphere - Verbal ideation -Speech -Perception of language and comprehension -Numerical skills -Writing -Recognition of words, letters, numbers
- 19. External features External features of cerebral hemisphere includes - LOBES - POLES - SURFACES - BORDERS -SULCI
- 21. POLES 1. Frontal Pole – Ant.end of hemisphere is more rounded & lies opposite to superciliary arch 2. Occipital Pole – Post.end of hemisphere is more pointed & lies at short distance to ext.occipital protuberance 3. Temporal Pole – B/w frontal & occipital poles pointed forwards & fits into ant.part of midcranial fossa
- 23. SURFACES 1. Superolateral surface – most convex & extensive,faces upwards & laterally 2. Medial surface – flat & vertical, presents corpus callosum(thick C shaped cut surface) 3. Inferior surface – irregular & divided into - Orbital surface ( small ant.part ) - Tentorial surface ( large post.part )
- 25. BORDERS 1. Superomedial border 2. Superciliary border 3. Inferolateral border 4. Medial orbital border 5.Inferomedial border 6.Medial occipital border
- 27. SULCI The sulci (or fissures) are the grooves and the gyri are the "bumps" that can be seen on the surface of the brain. The folding created by the sulci and gyri increases the amount of cerebral cortex that can fit in the skull. 1. Lateral Sulcus – b/w temporal & parietal lobe 2. Central Sulcus – b/w frontal & parietal lobe 3. Calcarine Sulcus – Caudal end of medial surface 4. Parieo-occipital Sulcus – b/w parietal & occipital
- 28. GYRUS A gyrus is a ridge-like elevation found on the surface of the cerebral cortex. Gyri are surrounded by depressions known as sulci, and together they form the iconic folded surface of the brain.
- 30. *Cerebral cortex is demarcated into large no.of areas Which differ from structure as well as function . * Brodmann (1909) divided the cerebral cortex into 52 areas & indicated each of them by number . TYPES 1. Motor areas ( motor function ) 2. Sensory areas ( sensory function ) 3. Association areas ( integrative , cognitive function) FUNCTIONAL AREAS OF BRAIN
- 31. Areas 1, 2, 3 Primary somatosensory cortex (postcentral gyrus) Area 4 Primary motor cortex (precentral gyrus) Area 5 Somatosensory association cortex Area 6 Area 8 Premotor and supplementary motor cortex Area 9 Dorsolateral/anterior prefrontal cortex (motor planning, and organization) Area 10 Anterior prefrontal cortex (memory retrieval) Area 17 Area 18 Primary visual cortex Area 22 Primary auditory cortex Area 37 Occipitotemporal (fusiform) gyrus Areas 22, 39, 40 Wernicke's area (language comprehension) Areas 44, 45 Broca's area (motor speech programming
- 33. • Lies anterior to Central sulcus & above posterior ramus of lateral sulcus Functions -Initiation of voluntary movement , intelligence, problem solving, judgement, language, conjugate movements of eyeball. -plays higher mental function such as motivation, planning, social behaviour and speech production. FRONTAL LOBE
- 34. • Hemiplegia :- disease or injury to the motor centers of the brain. • Broca’s Aphasia :- “EXPRESSIVE APHASIA” characterised by partial loss of ability to produce language although comprehension remains intact. • Emotional instability • Bilateral hemiparesis • Apraxia • Contralateral gaze paresis:- Inability to produce conjugate eye movements in one or both directions. • Apathy LESION
- 35. • Lies behind the central sulcus & below bounded by posterior ramus of lateral sulcus Functions - Cutaneous sensation , spatial recognition (2 point discrimination, Tactile, localization,stereognosis) - processing of sensory information, understanding spatial orientation and body awareness. PARIETAL LOBE
- 36. • Poverty of movement • Visuospatial disorders :- IPSILATERAL GAZE PARESIS.(complete gaze impairment) • Apraxia :- Inability to perform a movement or task when asked despite having the desire and physical capability to carry it out • Loss of tactile localization • Anosognosia :- deficit of self awareness. LESION
- 37. PARIETAL LOBE SYNDROME *Lesion involving primarily the right (non dominant) parietal cortex. *impaired proprioception and some degree of mental confusion *Sensory inattention may persist indefinitely *Anosognosia *Hemisomatopagnosia :- denies the very existence of paretic side .
- 38. • Lies below the posterior ramus of lateral sulcus & separated from the occipital lobe Functions - Auditory perception The temporal lobe is involved in primary auditory perception, such as hearing, and holds the primary auditory cortex (area 22). The primary auditory cortex receives sensory information from the ears and secondary areas ( rostally in the temporal lobe and contains broadmann area 42) process the information into meaningful units such as speech and words. TEMPORAL LOBE
- 39. • Wernicke’s aphasia ( Deafness ):- sensory aphasia • Visual agnosia :- impairment in recognition of visually presented objects. • Right temporal damage:- loss of inhibition of talking. • Left temporal damage :- impaired memory for verbal material. Auditory ,visual , gustatory & olfactory hallucination. Dreamy states. LESIONS
- 40. TEMPORAL LOBE EPILEPSY Complaints of unpleasant smelling odors, unpleasant taste Lost ability to speak Sense of depersonalization Lip smaking and chewing movement,followed by generalized seizure. Experience dejavu
- 41. • Lies behind the vertical line joining parieto-occipital sulcus & preoccipital notch • Functions - Visual perception - The occipital lobe is the visual processing area of the brain. It is associated with visuospatial processing, distance and depth perception, colour determination, object and face recognition, and memory formation. OCCIPITAL LOBE
- 42. * Homonymous hemianopia( contralateral/left/right) * Visual agnosia * Blindness partial/complete *Loss of perception of colour LESIONS
- 43. CORTICAL BLINDNESS AND ANTON’S SYNDROME The inability to see because of bilateral injury to the occipital lobe . Brains ability to process visual information. In rare condition cortical blindness patient insist they can see and confabulate when asked to describe objects in the environment – Anton’s syndrome
- 44. FRONTOTEMPORAL DEMENTIA Atrophy involving predominantly the frontal and temporal cortices (and thus different from the distribution changes in the alzhimer’s or lewy body dementia ). Abnormal tau proteins can be identified in nerve cells and glia.
- 45. GERTMANN’S SYNDROME Area of acute infraction in the region of the left posterior temporal and parietal region characteristic features are finger agnosia, left right confusion, dysgraphia , dyscalculation.
- 46. BALINT’S SYNDROME It is an uncommon disorder caused by bilateral injury to parietal and occipital cortices Symptoms:- optic ataxia inability to recognize more than one object in the visual field. inability to change the visual fixation. dysmetria
- 47. * Textbook of Clinical Neuroanatomy – Vishram Singh,3rd Edition, chapter 12- Cerebrum, pg.no.138-151 * Adams & Victor’s Principles of Neurology – Allan Ropper, Joshua Klein 10th edition, chapter 22- Neurological lesions, pg.no.472-478 * Gray’s clinical Neuroanatomy – Eliot L.Mancall,David G Brock,2nd edition,pg.no 279- 312 *Clinical Neuroanatomy - Richard S.Snell,7th edition,chapter 7, pg.no.252-271 *BD Chaurasia’s Brain-Neuroanatomy – Volume 4,7th edition,chapter 4, pg.no 58-73 * Essentials of Medical Physiology- Sembulingam,6th edition,Section 10 Cerebral cortex,pg.no.884-898 REFERENCES