cerebral hemisphere 2.pdf

Cerebral Hemisphere- Sulci and Gyri, and Functional Areas Dr. Hussni Mubarak Alghuriri  Learning Objectives A Different lobes and surfaces of Cerebral hemisphere B. Blood supply of different regions of cerebral hemisphere C Important sulci and gyri D Different functional areas located in cereb...

Cerebral Hemisphere- Sulci and Gyri, and Functional Areas Dr. Hussni Mubarak Alghuriri  Learning Objectives A Different lobes and surfaces of Cerebral hemisphere B. Blood supply of different regions of cerebral hemisphere C Important sulci and gyri D Different functional areas located in cerebral hemisphere E. Lesions and its effects  2 Cerebrum  Largest part of the brain Heavily convoluted bilobed structure  4 Cerebral hemispheres General Appearance:  Separated by a deep midline sagittal fissure – longitudinal cerebral fissure  In the depth of the fissure, the corpus callosum connects the hemispheres across the midline  Gyri – the folds of the surface of hemispheres  Sulci – the fissures separate the gyri  5 Surfaces of Cerebral Hemisphere  Three surfaces:  Superolateral surface  Inferior surface  Medial surface  6 Lobes of Cerebral Hemispheres  Cerebral hemispheres are divided into lobes by the central, parieto-occipital, lateral and calcarine sulci  Lobes are named according to the cranial bones under which they lie  Lobes are:  Frontal  Parietal  Temporal  Occipital 8 Cerebral hemisphere the essential features can be 1 summarized by stating that:- 1. the frontal lobe lies in front of the central sulcus (1) and above 2 the lateral sulcus (2). 3 2. the parietal lobe is behind the central sulcus and above the lateral sulcus. 3. the temporal lobe is below the P lateral sulcus F 4. the occipital lobe lies below and behind the parieto-occipital O sulcus (3). T  Main sulci 1 1. Central sulcus 3 2. Lateral sulcus 3. Parito-occipital sulcus 4. Calcarine sulcus 2 5. Cingulate sulcus 6. Callsosal sulcus ( Sulcus of corpus callosum ) 7. Orbital sulcus 8. Parahippocampal sulcus 9. Collateral sulcus 5 6 10. Occipiti-temporal sulcus 4 Main sulci 1. Central sulcus 7 2. Lateral sulcus 3. Parito-occipital sulcus 4. Calcarine sulcus 5. Cingulate sulcus 6. Callsosal sulcus ( Sulcus of corpus 10 8 callosum) 9 7. Orbital sulcus 8. Parahippocampal sulcus 9. Collateral sulcus.10Occipiti-temporal sulcus.1Central sulcus 2. Lateral sulcus 3. Parito-occipital sulcus.4Calcarine sulcus 5. Cingulate sulcus 6. Callsosal sulcus ( Sulcus of corpus callosum ) 1 3 5 6 2 4.1Orbital sulcus ( NOT SHOWN / Above the orbit) !! 2. Parahippocampal sulcus 2 3. Collateral sulcus 4. Occipiti-temporal sulcus 3 4.1 Precentral Main gyri 1 2 3 2. Postcentral 3 3. Frontal (superior, middle & inferio 3 4. Parietal (superior & inferior) -5 r) 5. Temporal inferior) (superior, middle & 5 6. Callosal 5 7. Medial frontal 8. Paracentral lobule 9. Precuneus 7 8 10. Cuneus 6 11. Lingual gyrus 9 12. Orbital gyri 13. Gyrus rectus 10 14. Parahippocampal 11 15. Occipitotemporal (medial & lateral) 16. Uncus Main gyri (superior, 13 1. Precentral 2. Postcentral 12 3. Frontal (superior, midd le & inferior) 4. Parietal (superior & inf erior) 5- 5. Temporal middle inferior) 6. Callosal & 7. Medial frontal 16 8. Paracentral lobule 15 15 9. Precuneus 14 10. Cuneus 11. Lingual gyrus 12. Orbital gyri 13. Gyrus rectus 14. Parahippocampal 15. Occipitotemporal (med 16. Uncus ial & lateral)  1.1 Rectus gyrus.2 Uncus ( parahippocampus gyrus) 2.3 Hippocampal gyrus 3  9 Main sulci  Central sulcus  Indents the superior medial border of the hemisphere, 1 cm behind the mid-point  It runs downward, forward and toward the lateral sulcus across the lateral aspect of the hemisphere  The central sulcus is the only sulcus that indents the superior medial border  10 - Main sulci (Cont’d)  Lateral sulcus  Deep cleft on the inferior and lateral surfaces of the cerebral hemisphere  It consists of a short stem and three rami- Anterior horizontal , anterior ascending and posterior  11 Main sulci (Cont’d(  Parieto-occipital sulcus:  Begins on the superior medial border of the hemisphere, about 5 cm anterior to the occipital pole  It passes downward and anteriorly on the medial surface to meet the calcarine sulcus Main sulci (Cont’d) Calcarine Sulcus- Medial surface  Insula portion of the cerebral cortex folded deep within the lateral sulcus. Play a role in consciousness and emotions The cortical area overlying the insula toward the lateral surface of the brain is the operculum (meaning lid.) The opercula are formed from parts of the enclosing frontal, temporal, and parietal lobes. Insulaa is surrounded by circular sulcus ( arrow) !! Superior surface of temporal operculum presents anterior and posterior transverse temporal gyri  BROADMANS AREAS AND FUNCTIONAL AREAS OF CEREBRAL HEMISPHERE  Specific Sulci/Fissures: Central Sulcus Longitudinal Fissure Sylvian/Latera l Fissure Transverse Fissure  Frontal Lobe - Cortical Regions  Primary Motor Cortex Brodmann,s area 4  Precentral Gyrus – it control all voluntary movements of the contralateral side of th body  Site where movements of the various parts of the body are initiated  Recieves sensory input from cerebellum and thalamus  The body is represented upside down along the precentral gyrus  Investigation (Phineas Gage) Primary Motor Cortex/ Precentral Gyrus Broca’s Area Orbitofrontal Cortex Olfactory Bulb Modified from:  secondary motor area/6,8,44 and 45  Precentral gyrus,sup,middle,inf frontal gyri  It programs the activity of the PMA  Stronger stimulation is required to produce the same degree of movement  Broca’s Area –44,45  Inf.frontal gyrus  Brings about the formation of words.  Located on Left Frontal Lobe  Broca’s Aphasia – Results in the ability to comprehend speech, but the decreased motor ability (or inability) to speak and form words Frontal eye field ,8 Middle frontal gyrus Voluntary eye movements towards opposite side and the accomodation pathway also controls eyelid movements Prefrontal cortex9,10,11,12 Concerned with the makeup of the individual,s personality Head rotation area Parietal Lobe - Cortical Regions  Primary sensorymotor Cortex 1,2,3(Postcentral Gyrus) – Site involved with processing of tactile and proprioceptive information. Somatosensory Association Cortex -5,7 sup parietal assists with the integration and interpretation of sensations. Primary Gustatory Cortex 43 Inferior part of the post central gyrus– Primary site involved with the interpretation of the sensation of Taste. Primary Somatosensory Cortex/ Postcentral Gyrus Somatosensory Association Cortex Primary Gustatory Cortex Occipital Lobe – Cortical Regions  Primary Visual Cortex – This is the primary area of the brain responsible for Vision Visual Association Area – Interprets information acquired through the primary visual cortex. Primary Visual Cortex Visual Association Area Temporal Lobe – Cortical Regions  Primary Auditory Cortex –41,42 mostly hidden in the lateral sulcus  Responsible for hearing  Its anterior part recieves low freq sounds  Post part –high freq sounds  Sec. Auditory Cortex 22  Interpretation of sounds Temporal Lobe – Cortical Regions Primary Olfactory Cortex – sense of smell (Not visible on the superficial cortex) Wernicke’s Area superior and middle temporal gyri Understanding of speech - Wernicke’s Aphasia – Words and sentences are not clearly understood, and sentence formation may be inhibited. Primary Auditory Cortex Wernike’s Area Primary Olfactory Cortex (Deep) Conducted from Olfactory Bulb dominant hemisphere  95-left  Broca  90% right handed BLOOD SUPPLY  Anterior and middle cerebral artery (internal carotid artery)  Posterior cerebral artery (basilar artery) Physiological information about brain Left hemisphere is dominant in Which hemisphere 90% of the right handed and 64% of the left handed is dominant!? Righ hemisphere is dominant in 10% of righ handed and 20% of left handed In the remaining 16% of left handed both hemispheres are dominant.. Speech areas in brain usually in the dominant hemisphere !! ( OF CLINICAL IMPORTANT) Brodmann areas Motor areas of cortex 1- primary motor area :- - MSI area ( precentral gyrus ) MSII - MSII area ( Anterior part of MSI paracentral lobule ) -2secondary motor area –Posterior parts of frontal gyri extending medially Primary motor area Broadmann area 4 The area Msl is where movements of the various parts of the body MSII are initiated, Afferent :- receives its main inputs MSI from the cerebellum and thalamus. Efferent :- the corticonuclear and corticospinal (pyramidal) tracts. MSII area receives many fibres from the basal nuclei and is concerned with postural mechanisms, but this area is not yet clearly understood. Motor homunculus the body is represented upside down along this cortex, although the face itself is represented the right way up. The face lies lowest, then the hand (a very large area), then arm, trunk and leg. The leg and perineum areas overlap the superior border and extend down on the medial surface of the hemisphere Blood supply-: -1middle cerebral artery -2anterior cerebral a. ( leg area) Primary motor area Lesions to this area produce contralateral paralysis !! Organs that supplied bilaterally are the less affected… Secondary motor area Or supplementary motor area Broadmann are 6 Location :- Posterior parts of frontal gyri extending medially The function of the secondary motor area: 1- To store programs of motor activity resulted from past experience -2 Controls sequence of movements -3 Controls spatial & postural orientation movements. -4Controls bimanual movements. Blood supply: Middle & anterior cerebral arteries secondary motor area Lesions-: Apraxia (inability to execute learned purposeful movements despite having the desire and the physical capacity to perform them.) There is no or little loss of strength Boca's area The motor (anterior) speech area (of Broca, areas 44 and 45) is usually situated in the inferior frontal gyrus on the left side (in right-handed and in most left- handed people), below and in front of the face area and centred on the pars triangularis between the anterior and ascending rami of the lateral fissure. Damage to it produces motor aphasia — difficulty in finding the right words, but not paralysis of laryngeal musculature. Blood supply :- Middle cerebral a. Wernicke's area The posterior speech area (of Wernicke) is in the posterior parts of the superior and middle temporal gyri and extends into the lower part of the parietal lobe. -It is connected to the Broca’s, visual & auditory cortex Function: To understand the written and spoken language Its integrity is necessary for the understanding of speech. Lesion … Receptive dysphasia; the patient responds by intact, but irrelevant speech! Blood supply: Middle cerebral artery Prefrontal cortex The prefrontal cortex is an extensive area that lies anterior to the precentral The prefrontal area is concerned with.1 the makeup of the individual’s personality..2 regulator of the person’s depth of feeling. 3. It also exerts its influence in determining the initiative and judgment of an individual. Prefrontal cortex Lesions-: It is now generally agreed that destruction of the prefrontal region does not produce any marked loss of intelligence Tumour or traumatic destruction of the prefrontal cortex result in the person’s losing initiative and judgment. Emotional changes that occur include a tendency to euphoria. The patient no longer conforms to the accepted mode of social behavior and becomes careless of dress and appearance. Bipolar disorders Schizophrenia Sensory areas -1Primary somatosensory area - The postcentral gyrus 1 - Posterior part of paracentral 2 lobule - Recieves primary from thalamus - Sensations from the oral region, pharynx, larynx & perineum are received bilaterally -2 Secondary ( or association ) somatosensory area. - Occupies the superior parietal lobule Primary sensory area Sensory homunculus: The amount of the cortex for a particular part of the bod is related to its functional importance & number of receptors ( not to its size) Blood supply: - Middle cerebral artery - Anterior cerebral artery (leg area) Primary sensory area Lesions-: Lesions of the primary somesthetic area of the cortex result in contralateral sensory disturbances, which are most severe in the distal parts of the limbs. Crude painful, tactile,and thermal stimuli often return,but this is believed to be due to the function of the thalamus. The patient remains unable to judge degrees of warmth, unable to localize tactile stimuli accurately, and unable to judge weights of objects. Loss of muscle tone may also be a symptom of lesions of the sensory cortex. Secondary somatosensory area Function: - Receive different sensory modalities & relate them to past experience. e.g; object recognition without vision. - Lesions = asterognosis!! - Inable to identify things without see them… Primary visual cortex Broadmann area 17 Functions: - Receives fibers from the opposite field of vision - It also excludes & modulates unwanted images! Blood supply: - Posterior cerebral artery Lesions-: Crossed homonymous hemian opia Secondary visual cortex Brodmann area 18,19 Surrounded by the primary visual cortex… Functions to relate the visual information to past experiences Lesions produce … Visual agnosia; loss of ability to recognize objects seen in the opposite field of vision WHY don't we see everything upside-down? -Brain makes images 'easier' to see by: -1Combining the two images of the two eyes (in corpus callosum.) -2Make images right-side-up (in the visual cortex.) It does this because your brain is so USED to see things upside-down that it eventually adjusts to it (it's easier to flip the image than to try using hands and legs with an upside-down world) For the first days, babies see everything upside-down! Primary auditory area Broadmann area 41,42 In the inferior wall of lateral sulcus Afferent: Principally from the medial geniculate body Blood supply: - Middle cerebral artery - Lesions produce … Partial deafness in both ears with inability to locate sound. - The greater loss being in the opposite ear - (cochlear nuclei send 2nd order to the olivary nucleus & nuclei of trapezoid body bilaterally) Auditory pathway Explaning why greter loss of inability to hear on the opposite site!!! Cochlear n. send fibers more to the other side than the same side… Secondary auditory area Broadmann area 22 Lies posterior to the primary auditory area Function: -To interpret sounds and associate the auditory input with other sensory information. Blood supply: Middle cerebral artery Lesions : auditory agnosia!! The dominant angular gyrus This part is often considered a part of the Wernicke area Lesion here results in inability to read (alexia) or write (agraphia.) Aphasia Alexia Sensory aphasia Agraphia Motor aphasia A lesion resulting in a nonfluent expressive aphasia would most likely be found in the (A) temporal lobe (B) parietal lobe (C) frontal lobe (D) occipital lobe Alexia without agraphia and aphasia would most likely result from occlusion of the (A) left anterior cerebral artery (B) right anterior cerebral artery (C) left middle cerebral artery (D) left posterior cerebral artery (E) right posterior cerebral artery A patient is asked to bisect a horizontal line through the middle, to draw the face of a clock, and to copy a cross. The patient bisected the horizontal line to the left of the midline, placed all of the numerals of the clock on the right side, and did not complete the cross on the left side. The most likely lesion site for this deficit is the (A) left frontal lobe (B) right parietal lobe (C) left parietal lobe (D) right temporal lobe (E) left occipital lobe THANK YOU