Neuroanatomy Lecture Notes (004) The Cerebrum - PDF

(004) THE CEREBRUM DR. ELTON ONG | 10/14/2020 OUTLINE TWO DIVISIONS OF THE PNS...

(004) THE CEREBRUM DR. ELTON ONG | 10/14/2020 OUTLINE TWO DIVISIONS OF THE PNS o Somatic Nervous System – the nerves that convey I. DIVISIONS OF THE HUMAN NERVOUS messages from the sense organs to the CNS and from the SYSTEM CNS to the muscles and glands II. CENTRAL NERVOUS SYSTEM - Controls the voluntary muscles of the body III. CEREBRAL HEMISPHERES o Autonomic Nervous System – a set of neurons that Layers control the heart, the intestines, and other organs. - Controls the involuntary parts of the body Surfaces - Subdivided into sympathetic and parasympathetic Poles nervous system Lobes IV. SULCI ON THE LATERAL SURFACE V. GYRI ON THE LATERAL SURFACE VI. SULCI ON THE MEDIAL SURFACE VII. GYRI ON THE MEDIAL SURFACE VIII. SULCI ON THE INFERIOR SURFACE IX. GYRI ON THE INFERIOR SURFACE X. IMPORTANT CENTERS OF THE CEREBRAL CORTEX / MAIN FUNCTIONAL AREAS OF THE CEREBRAL CORTEX XI. STORAGE AND RETRIEVAL OF INFORMATION XII. MOTOR AREA A. PRIMARY MOTOR AREA B. PREMOTOR CORTEX C. SUPPLEMENTARY MOTOR AREA Figure 1. The Human Nervous System. Both the central nervous system and the D. FRONTAL EYE FIELD peripheral nervous system have major subdivisions. The closeup of the brain shows the right hemisphere. E. MOTOR SPEECH AREA (BROCA’S AREA) II. CENTRAL NERVOUS SYSTEM F. PREFRONTAL CORTEX The basic components of the CNS include the: Cerebrum (red) G. PRIMARY SOMATOSENSORY Diencephalon (green) CORTEX Cerebellum (blue) a. Ventral Posterior Nucleus Brain Stem (yellow) (VPN) Spinal Cord (orange) H. PRIMARY AUDITORY CORTEX I. SECOND MOTOR SPEECH AREA (WERNICKE’S AREA) J. PRIMARY VISUAL CORTEX K. VISUAL ASSOCIATION CORTEX XIII. TEST YOURSELF XIV. REFERENCE I. DIVISIONS OF THE HUMAN NERVOUS SYSTEM Central Nervous System – the brain and the spinal cord Peripheral Nervous System – the nerves outside the brain and spinal cord Figure 2. The basic components of the CNS (sagittal portion or medial surface of the brain) PREPARED AND EDITED BY: LIMBAUAN, J., LIVED, R., LOCQUIAO, C., LOPEZ, F., PADILLA, A., PADOLINA, J., PALAGANAS, B., PANG-AG, L  (004) THE CEREBRUM DR. ELTON ONG | 10/14/2020 REVIEW OF TERMS IN ANATOMY: Anterior (Ventral) - referring to the “front” Posterior (Dorsal) – referring to the “back” Superior (Cephalic or Cephalad)– referring to the top of the head Inferior – referring to the caudal Lateral – “away” from the middle or midline Medial – “towards” to the middle or midline III. CEREBRAL HEMISPHERES (CEREBRUM) The surface is made of ridges (gyri) and grooves (sulci) - Sulci – in between different convolutions or ridges that separates the gyri - Fissure – refers to a deeper and bigger sulcus; almost the same with sulcus but they are different in size - Tentorium cerebelli - A second horizontal fold of dura mater separates the cerebral hemispheres from the cerebellum LAYERS OF THE CEREBRUM Gray Matter – outer layer - containing neurons Figure 3. The cerebrum (lateral view of cerebrum) - composed mostly of neuron cell bodies (or nerve cells) CEREBRUM - Basal nuclei (basal ganglia) is applied to a - it is the largest part of the forebrain (largest among the three) collection of masses of gray matter situated within ○ situated in the anterior and middle cranial fossae of each cerebral hemisphere. the skull and occupying the whole concavity of the They are the: vault of the skull a. corpus striatum - it is highly developed in human (because humans think, b. amygdaloid nucleus performs judgement, calculate, talk, and have language) c. Claustrum - it is derived from the telencephalon ○ It may be divided into two parts: White Matter – fiber tracts inside the gray matter a. The diencephalon- which forms the central - inner layer core, b. The telencephalon-, which forms the - doesn’t contain any neurons; they are just fiber cerebral hemispheres. tracts of those neurons that you locate or - the two cerebral hemispheres are incompletely separated by appreciate in the gray matter the median or greater longitudinal fissure (in some books it’s - The white matter is composed of myelinated nerve called “Medial Longitudinal Fissure”) fibers of different diameters supported by neuroglia. ○ The fissure contains the sickle-shaped fold of dura - Example: corpus callosum connects hemispheres mater, the falx cerebri, and the anterior cerebral arteries -Classification of nerve fibers according to their - they are connected by the corpus callosum (connects left connections: and right hemisphere) - each hemisphere has a cavity called the lateral ventricle. (1) Commissural fibers - connect ○ Each ventricle is a roughly C-shaped cavity lined corresponding regions of the two with ependymal cells and filled hemispheres, with cerebrospinal fluid. ○ The lateral ventricle may be divided into a body, (2) Association fibers - are nerve fibers which occupies the parietal lobe, and from which that essentially connect various cortical anterior, posterior, and inferior horns extend into the regions within the same hemisphere and frontal, occipital, and temporal lobes, respectively may be divided into short and long groups , and (3) Projection fibers - afferent and efferent nerve fibers passing to and from the brainstem to the entire cerebral cortex. PREPARED AND EDITED BY: LIMBAUAN, J., LIVED, R., LOCQUIAO, C., LOPEZ, F., PADILLA, A., PADOLINA, J., PALAGANAS, B., PANG-AG, L  (004) THE CEREBRUM DR. ELTON ONG | 10/14/2020 B Figure 5. (a) The three surfaces of the hemisphere (b) The closer look of the inferior surface of the hemisphere Figure 4. Cerebrum showing corpus callosum and lateral ventricle POLES Each hemisphere has Frontal pole 3 surfaces Occipital pole 3 poles Temporal pole 4 borders 4 lobes LOBES Frontal lobe (most anteriorly located part) - occupies the area anterior to the central sulcus and superior to SURFACES the lateral sulcus Lateral or Superolateral o Divided by three sulci: o Convex and related to the skull vault a. Precentral sulcus, o Away from the middle b. Superior and c. Inferior frontal sulci Medial o Flat and vertical and related to the falx cerebri and oAnd four gyri: median longitudinal fissure a. Precentral gyrus, Inferior b. Superior frontal gyrus, o Divided into orbital and tentorial parts by the stem of c. Middle frontal gyrus and the lateral sulcus d. Inferior frontal gyrus) o Has more anteriorly located orbital surface that are Temporal lobe (below the frontal and parietal lobe) - actually part of the frontal lobe and more posteriorly occupies the area inferior to the lateral sulcus located tentorial surface which is actually the inferior portion of the temporal lobe o Three gyri: a. superior, b. middle, and c. inferior temporal gyri by o Two Sulci: a. superior and b. middle temporal sulci Parietal lobe (back of the frontal lobe) - occupies the area posterior to the central sulcus and superior to the lateral sulcus; it extends posteriorly as far as the parieto-occipital sulcus o Lateral surface is divided by two sulci (postcentral sulcus and intraparietal sulcus) into three gyri (postcentral gyrus, superior parietal gyrus, and inferior parietal gyrus) Occipital lobe (the most posterior portion) - occupies the A small area behind the parieto-occipital sulcus PREPARED AND EDITED BY: LIMBAUAN, J., LIVED, R., LOCQUIAO, C., LOPEZ, F., PADILLA, A., PADOLINA, J., PALAGANAS, B., PANG-AG, L  (004) THE CEREBRUM DR. ELTON ONG | 10/14/2020 Pre-central Sulcus o A finger breadth anterior and parallel to the central sulcus o Runs parallel to the central sulcus Post-central Sulcus o A finger breadth behind and parallel to the central sulcus Superior and Inferior Frontal Sulci o Frontal lobe has two horizontally oriented sulci: superior frontal sulcus and the inferior frontal sulcus o Extending anteriorly from the precentral sulcus Superior and Inferior Temporal Sulci o Temporal lobe has two horizontally oriented sulci: superior temporal sulcus and the inferior temporal sulcus o Superior and middle temporal sulci run parallel to the posterior ramus of the lateral sulcus and divide the temporal lobe into the superior, middle, and inferior temporal gyri Interparietal sulcus o Parietal lobe has only one sulcus and that is the Interparietal Sulcus o Running posteriorly from the middle of the post-central sulcus is the intraparietal sulcus Lunate sulcus o The occipital lobe has only one sulcus called the Lunate Sulcus Figure 6. The three poles (top) and the four lobes of the cerebrum (bottom) IV. SULCI ON THE LATERAL SURFACES Lateral sulcus or fissure o Separates the frontal and parietal lobes from the temporal lobe o It consists of a short stem that divides into three rami. The stem arises on the inferior surface, and on reaching the lateral surface, it divides into the anterior horizontal ramus, anterior horizontal ramus and continues as the posterior ramus Lateral sulcus or Sylvian Fissures – important because it separates the brain into upper portion of the temporal lobe o The central and parieto-occipital sulci and the lateral and calcarine sulci are boundaries used for the division of the Figure 7. Sulci on the Lateral Surfaces cerebral hemisphere into frontal, parietal, temporal, and occipital lobes V. GYRI ON THE LATERAL SURFACES Central sulcus o Central Sulcus of Rolando or Rolandic Sulcus Pre-central gyrus – between central and precentral sulci o Divides the cerebrum into an anteriorly located frontal Postcentral gyrus – between central and post-central sulci lobe and a posteriorly located parietal lobe o Running posteriorly from the middle of the o Begins from the superomedial border ½ inch behind the postcentral sulcus is the intraparietal sulcus Superior, Middle & Inferior Frontal Gyri midpoint between the frontal and occipital poles o It descends downward and forward making an angle o The inferior frontal gyrus is divided into 3 smaller about 70° with the vertical line portions: o It stops slightly above the lateral sulcus a. Triangular o the gyrus that lies anterior to it contains the motor cells b. Opercular that initiate the movements of the opposite side of the c. Orbital gyri. body; posterior to it lies the general sensory cortex that d. receives sensory information from the opposite side of the o The superior frontal gyrus lies superior to the body superior frontal sulcus, the middle frontal gyrus lies PREPARED AND EDITED BY: LIMBAUAN, J., LIVED, R., LOCQUIAO, C., LOPEZ, F., PADILLA, A., PADOLINA, J., PALAGANAS, B., PANG-AG, L  (004) THE CEREBRUM DR. ELTON ONG | 10/14/2020 between the superior and inferior frontal sulci, and VI. SULCI ON THE MEDIAL SURFACE the inferior frontal gyrus lies inferior to the inferior frontal sulcus Callosal sulcus o Just above the corpus callosum Superior, Middle & Inferior Temporal Gyri o Separates cingulate gyrus from the corpus callosum o Frontal and Temporal lobes are called Gyrus or Gyri Cingulate sulcus o You will only see the inferior temporal gyrus at the o One inch above and parallel to the callosal sulcus inferior surface of the cerebrum. o Separates the cingulate gyrus from the superior frontal Superior & Inferior Parietal Lobules gyrus o Parietal lobes are called lobules Parieto-occipital sulcus o The inferior parietal lobule has two subdivisions: o Begins in the upper border 4cm in front of the occipital more anteriorly located supramarginal gyrus and pole more posteriorly located angular gyrus. o It ends at the meeting of calcarine and postcalcarine Angular Gyrus sulci Lateral Occipital Gyri – found at the occipital lobe; at the most o Separates in the medial aspects of the cerebrum the lateral portion of the cerebrum. parietal lobe and the occipital lobe Calcarine o Begins below the splenium then passes backwards and upwards to meet the parieto-occipital sulcus then continuous as the postcalcarine sulcus. o Between the collateral sulcus and the calcarine sulcus is the lingual gyrus. Post calcarine sulcus o It is an extension of the calcarine Figure 8. Gyri on the Lateral Surfaces Figure 10. Sulci on the Medial Surface VII. GYRI ON THE MEDIAL SURFACE Cingulate Gyrus o Between the callosal and cingulate sulci o begins beneath the anterior end of the corpus callosum and continues above the corpus callosum until it reaches its posterior end Paracentral lobule o It is the continuation of the precentral and postcentral gyri Precuneus o Behind the paracentral lobule o is an area of cortex bounded anteriorly by the upturned posterior end of the cingulate sulcus and posteriorly by Figure 9. Gyri on the Lateral Surfaces the parieto-occipital sulcus. PREPARED AND EDITED BY: LIMBAUAN, J., LIVED, R., LOCQUIAO, C., LOPEZ, F., PADILLA, A., PADOLINA, J., PALAGANAS, B., PANG-AG, L  (004) THE CEREBRUM DR. ELTON ONG | 10/14/2020 Cuneus o Between the parieto-occipital and postcalcarine sulci o Cuneus and Linugal Gyrus belong to Occipital lobe. o is a triangular area of cortex bounded above by the parieto-occipital sulcus,inferiorly by the calcarine sulcus, and posteriorly by the superior medial margin Figure 12. Sulci on the Inferior Surface Figure 11. Gyri on the Medial Surface IX. GYRI ON THE INFERIOR SURFACE Gyrus rectus o Medial to the olfactory sulcus VIII. SULCI ON THE INFERIOR SURFACE Orbital gyri o Separates Anterior, posterior, medial, and lateral orbital Olfactory sulcus gyrus o Close and parallel to the medial orbital margin o Lateral to the olfactory sulcus o On the inferior surface of the frontal lobe, the olfactory Lateral occipitotemporal gyrus bulb and tract overlie a sulcus called the olfactory sulcus o Lateral to occipitotemporal sulcus Orbital sulcus Medial occipitotemporal gyrus o Irregular H-shaped lateral to olfactory sulcus o Medial to occipitotemporal sulcus Stem of Lateral sulcus o Extends from the occipital pole to the temporal pole.It is o It divides the inferior surface into orbital and tentorial parts bounded medially by the collateral and rhinal sulci and Rhinal sulcus laterally by the occipitotemporal sulcus o A short sulcus on the temporal pole Parahippocampal gyrus Collateral sulcus o Medial to collateral sulcus o Behind the rhinal sulcus and extends to the occipital pole o Anterior to lingual gyrus o situated on the inferior surface of the hemisphere Lingual gyrus Occipitotemporal sulcus o Between collateral and calcarine sulci o Lateral to the collateral sulcus Uncus o It extends from temporal to occipital poles o Anterior end of the parahippocampal gyrus o It is the smell cortex o Hooklike PREPARED AND EDITED BY: LIMBAUAN, J., LIVED, R., LOCQUIAO, C., LOPEZ, F., PADILLA, A., PADOLINA, J., PALAGANAS, B., PANG-AG, L  (004) THE CEREBRUM DR. ELTON ONG | 10/14/2020 Frontal lobe (Motor) – most anterior portion of the cerebrum – the only lobe that serves a motor function (efferent in nature, which allows action) Figure 13. Gyri on the Inferior Surface X. IMPORTANT CENTERS OF THE CEREBRAL CORTEX / MAIN FUNCTIONAL AREAS OF THE Figure 14. Illustration showing the important centers of the cerebral cortex. CEREBRAL CORTEX The cerebral cortex is important for: XI. STORAGE AND RETRIEVAL OF INFORMATION - Conscious awareness o Consciousness requires the person to fulfill of two Information is elaborated to the association cortex, (at the components: meeting of the parietal, temporal and occipital) for (1) must be awake (wakefulness is contributed by identification n by touch, sight and hearing the brainstem) The limbic system (medial part of cerebrum): enable storage (2) must be aware of what is happening to its body and retrieval of the information processed in the posterior or environment (awareness is contributed by the cortex. cerebral cortex) - Thought - Memory - Intellect The cerebral cortex is organized into vertical units or columns of functional activity measuring about 300 to 600 um wide. Most sensory modalities ascend to the cortex from the thalamus, perceived and interpreted in the light of the previous experience. Posterior part of the cerebrum receives sensory information in the sensory modality lobes (afferent in nature): 1. Parietal lobe (Somatosensory) – posterior of central sulcus – gathers information/sensation from the body (e.g. skin, muscle, fascia) 2. Occipital lobe (Vision) – most posterior portion of the cerebrum 3. Temporal lobe (Hearing) – inferior to the lateral sulcus/Sylvian fissure Figure 15. Limbic lobe (shaded), the hippocampus, and amygdaloid nucleus PREPARED AND EDITED BY: LIMBAUAN, J., LIVED, R., LOCQUIAO, C., LOPEZ, F., PADILLA, A., PADOLINA, J., PALAGANAS, B., PANG-AG, L  (004) THE CEREBRUM DR. ELTON ONG | 10/14/2020 - The principal subcortical afferent to PMC is from Lateral ventral nucleus (LVN) of thalamus. XII. MOTOR AREA - Lateral Ventral Nucleus (LVN)- receives its input form The frontal lobe (anterior part of cerebrum) concerned with globus pallidus dentate. the organization of movement: - LESION leads to hemiparesis or weakness of one side of 1. Primary motor area the body, specifically on the contralateral side. 2. Premotor area - Upper 1/3 and paracentral lobule: leads to affection of 3. Supplementary motor area voluntary control in lower limb and perineum of the 4. Prefrontal area (guidance of complex motor behaviour) opposite side - Lower 2/3rds: affection of voluntary control of the head, neck and upper limb on the opposite side. o APRAXIA (Inability to perform skilled complex voluntary movement in spite of absence of muscle paralysis) Figure 16. The motor area of the Cerebellum A. PRIMARY MOTOR CORTEX - In precentral gyrus and anterior part of the paracentral lobule. o In the frontal lobe, The precentral area is situated in the precentral gyrus and includes the anterior wall of the central sulcus and the posterior parts of the Figure 17. Primary motor complex (highlighted in red) in the cerebrum superior, middle, and inferior frontal gyri o The precentral area is divided into the posterior B. PREMOTOR CORTEX/PREMOTOR AREA region, which is referred to as the motor area/ - Lies anterior to the primary motor cortex. primary motor area/Brodmann area 4, and anterior - Brodmann’s area #6 region which are premotor area/ secondary motor - It includes the posterior parts of: Superior, Middle, Inferior area/Brodmann area 6 and parts of areas 8, 44, and frontal gyri 45 - FUNCTION: programming and preparing for movement and - It corresponds to Brodmann’s area 4 control of posture. - Body is represented upside down. The premotor area- receives numerous inputs from o Homunculus – representation of the different parts the sensory cortex, the thalamus, and the basal of the body in the cerebrum (such that the head is ganglia. located at the lower portion of the cerebrum, and the -The function is to store programs of motor activity lower extremities are located in the medial portion). assembled as the result of past experience. Thus, the - Size of the functional area is directly proportional to the premotor area programs the activity of the primary skilled movement, not the size of the muscle. motor area. - It is here that actions are conceived and initiated. -Particularly involved in controlling coarse postural Primary Motor Area- is to carry out the individual movements through its connections with the basal movements of different parts of the body. ganglia. - It receives numerous afferent fibers - It receives its afferent from the ventral anterior nucleus of from the premotor area, the sensory thalamus. cortex, the thalamus, the cerebellum, and - Isolated lesions of the premotor cortex lead to APRAXIA. the basal ganglia. Primary motor cortex- not responsible for the design of the pattern of movement but is the final station for conversion of the design into execution of the movement. PREPARED AND EDITED BY: LIMBAUAN, J., LIVED, R., LOCQUIAO, C., LOPEZ, F., PADILLA, A., PADOLINA, J., PALAGANAS, B., PANG-AG, L  (004) THE CEREBRUM DR. ELTON ONG | 10/14/2020 D. FRONTAL EYE FIELD - it lies in posterior part of the middle frontal gyrus - corresponding to Brodmann’s area #8 - controls conjugate movement of the eye, especially toward the opposite side. - unilateral damage to AREA 8 causes conjugate deviation of the eyes to the side of the lesion. The frontal eye field is considered to control voluntary scanning movements of the eye and is independent of visual stimuli. The involuntary following of moving objects by the eyes involves the visual area of the occipital cortex to which the frontal eye field is connected by association fibers. Figure 18. Premotor complex (yellow) in the cerebrum C. SUPPLEMENTARY MOTOR CORTEX - Medial aspect of the primary motor and premotor cortex - The principle subcortical input to premotor and supplementary motor cortex is the ventral anterior nucleus of the thalamus. - This nucleus receives its afferent from the globus pallidus & substantia nigra. - Stimulation of the SMC results in movements of the contralateral limbs, but a stronger stimulus is necessary than when the primary motor area is stimulated. Removal of the supplementary motor area produces no permanent loss of movement. Figure 20. Frontal Eye field E. MOTOR SPEECH AREA (BROCA’S AREA) - In the inferior frontal gyrus in the dominant (usually left hemisphere) - Brodmann’s areas #44 and #45 - It has connections with ipsilateral temporal, parietal, occipital lobes that share in language function. - Two components of language: (1) Understanding (Wernicke’s Area) (2) Expression (Broca’s Area) - Brings about the formation of words by its connections with the adjacent primary motor areas; the muscles of the larynx, mouth, tongue, soft palate, and the respiratory muscles are appropriately stimulated - LESION: o LEFT MIDDLE CEREBRAL ARTERY - expressive of motor aphasia (acquired language problem); patients could understand what they hear, but unable to express thought, answer or writing inspite of a normal comprehension. Figure 19. Supplementary motor complex PREPARED AND EDITED BY: LIMBAUAN, J., LIVED, R., LOCQUIAO, C., LOPEZ, F., PADILLA, A., PADOLINA, J., PALAGANAS, B., PANG-AG, L  (004) THE CEREBRUM DR. ELTON ONG | 10/14/2020 Figure 22. Bodmann’s areas G. PRIMARY SOMATOSENSORY CORTEX - The primary somesthetic area (primary somatosensory cortex SI) Figure 21. Motor Speech area/Broca’s Area - In the postcentral gyrus and posterior part of paracentral lobule. - It corresponds to Brodmann’s areas #1, #2 and #3 F. PREFRONTAL CORTEX - Here thalamocortical neurons terminate (3 rd order neuron) - Lies anterior to premotor area - Input comes from ventral posterior nucleus (VPN) of the It includes the greater parts of the superior, middle, and inferior thalamus frontal gyri; the orbital gyri; most of the medial frontal gyrus; - Within the somatosensory cortex the contralateral half of the and the anterior half of the cingulate gyrus (Brodmann areas body is represented upside down. 9, 10, 11, and 12) - Although most sensations reach the cortex from the - It has rich connections with the parietal, temporal and contralateral side of the body, some from the oral region go occipital cortex. to the same side, and those from the pharynx, larynx, and - Serves all the higher cortical functions: perineum go to both sides. o Intellect o Judgement - Secondary somesthetic area o Prediction (secondary somatosensory cortex S2)- is in the superior o Motivation lip of the posterior limb of the lateral fissure. o Planning of behavior - It has been shown that the neurons respond - The prefrontal cortex is concerned with the makeup of the particularly to transient cutaneous stimuli, such as individual’s personality. As the result of the input from many brush strokes or tapping of the skin. cortical and subcortical sources, this area plays a role as a regulator of the person’s depth of feeling. It also exerts its - Somesthetic association area- occupies the superior influence in determining the initiative and judgment of an parietal lobule extending onto the medial surface of individual. the hemisphere (Brodmann areas 5 and 7). -This area has many connections with other sensory areas of the cortex -Its main function is probably to receive and integrate different sensory modalities. -For example, it enables one to recognize objects placed in the hand without the help of vision. PREPARED AND EDITED BY: LIMBAUAN, J., LIVED, R., LOCQUIAO, C., LOPEZ, F., PADILLA, A., PADOLINA, J., PALAGANAS, B., PANG-AG, L  (004) THE CEREBRUM DR. ELTON ONG | 10/14/2020 H. PRIMARY AUDITORY CORTEX - Lies in the superior bank of the middle of the superior temporal gyrus. - Hidden within the lateral fissure - Brodmann’s 41, 42 - This is closely associated with Wernicke’s Area, which aids in the understanding of language. - Precise location is marked by small transverse temporal gyri (HESCHL’S convolutions) - Input to primary auditory cortex is from medial geniculate nucleus (MGN) of the thalamus - Auditory radiation undergoes partial decussation in the brain stem before it reaches the MGN. - Lies behind the primary auditory cortex. - Continuous posteriorly with the second motor speech (Wernicke’s) area - Here the heard sounds or words are interpreted - LESION: o SENSORY APHASIA – inability to recognize the meaning of sounds or words with hearing unimpaired Figure 23. Primary somatosensory complex a. VENTRAL POSTERIOR NUCLEUS (VPN) -receives: 1. MEDIAL LEMNISCUS - fine touch & proprioception 2. SPINAL LEMNISCUS - coarse touch & pressure 3. SPINOTHALAMIC TRACT - pain &temperature 4.TRIGEMINOTHALAMIC TRACT -general sensation from head Figure 25. Primary auditory complex SECONDARY AUDITORY CORTEX or AUDITORY ASSOCIATION CORTEX: o situated posterior to the primary auditory area in the lateral sulcus and in the superior temporal gyrus (Brodmann area 22) o Could hear but could not understand o receives impulses from the primary auditory area and from the thalamus. o The secondary auditory area is thought to be necessary for the interpretation of sounds and for the association of the auditory input with other sensory information. I. SECOND MOTOR SPEECH (Wernicke’s area) - Also known as the “Language Area” - Brodmann’s 21, 22 - Lies in dominant hemisphere (refers to part of the cerebrum that contains the language center, usually the left hemisphere) Figure 24. Illustration of different ventral posterior nucleus PREPARED AND EDITED BY: LIMBAUAN, J., LIVED, R., LOCQUIAO, C., LOPEZ, F., PADILLA, A., PADOLINA, J., PALAGANAS, B., PANG-AG, L  (004) THE CEREBRUM DR. ELTON ONG | 10/14/2020 - Lies in the inferior parietal lobule and auditory association -Function is to relate the visual information area received by the primary visual area to past visual - Connected with Broca’s Area through a fiber tract, called experiences, thus enabling the individual to Arcuate fasciculus recognize and appreciate what he or she is seeing. - LESION: o SENSORY RECEPTIVE APHASIA – lack of - Occipital eye field- is thought to exist in the secondary comprehension of words by vision or hearing visual area in humans. -Stimulation produces conjugate deviation of the - Receives fibers from the visual cortex in the occipital lobe and eyes, especially to the opposite side. the auditory cortex in the superior temporal gyrus. -The function of this eye field is believed to be reflex - Permits understanding of written and spoken language and and associated with movements of the eye when it enables a person to read a sentence, understand it, and say is following an object. it out loud. - Because the Wernicke area represents the site on the cerebral cortex where somatic, visual, and auditory Other Cortical Areas association areas all come together, it should be regarded as an area of very great importance. - Taste area- is situated at the lower end of the postcentral gyrus in the superior wall of the lateral sulcus and I n the adjoining area of the insula (Brodmann J. PRIMARY VISUAL CORTEX area 43). - Lies on the medial surface of the occipital lobe. - In close relation to the calcarine sulcus - Vestibular area- is believed to be situated near the part of - It extends to the occipital pole the postcentral gyrus concerned with sensations of - Brodmann’s area 17 the face. - Receives optic radiation from lateral geniculate nucleus -Its location lies opposite the auditory area in the (LGN) of the thalamus superior temporal gyrus. - Each lateral half of the visual field is represented in the visual -The vestibular area and the vestibular part of the cortex of the contralateral hemisphere inner ear are concerned with appreciation of the - LESION: positions and movements of the head in space. o HOMONYMOUS HEMIANOPIA -Through its nerve connections, the movements of the eyes and the muscles of the trunk and limbs are influenced in the maintenance of posture. - Insula- is an area of the cortex that is buried within the lateral sulcus and forms its floor. -This area is thought to be important for planning or coordinating the articulatory movements necessary for speech. Figure 26. Primary visual cortex K. VISUAL ASSOCIATION CORTEX - Brodmann’s area #18, #19 - Interpretive to the visual image - LESION: o VISUAL AGNOSIA – inability to recognize a seen object - Secondary visual area (Brodmann areas 18 and 19)- surrounds the primary visual area on the medial and lateral surfaces of the hemisphere. -This area receives afferent fibers from area 17 and other cortical areas as well as from the thalamus. Figure 27. Visual Association cortex PREPARED AND EDITED BY: LIMBAUAN, J., LIVED, R., LOCQUIAO, C., LOPEZ, F., PADILLA, A., PADOLINA, J., PALAGANAS, B., PANG-AG, L  (004) THE CEREBRUM DR. ELTON ONG | 10/14/2020 1. Example: corticospinal tract, spinothalamic tract 2. Example: corpus callosum 3. Example: arcuate fasciculus Figure 28. Additional illustrations and diagrams of the cerebral cortex PREPARED AND EDITED BY: LIMBAUAN, J., LIVED, R., LOCQUIAO, C., LOPEZ, F., PADILLA, A., PADOLINA, J., PALAGANAS, B., PANG-AG, L  (004) THE CEREBRUM DR. ELTON ONG | 10/14/2020 TEST YOURSELF 4. The following statements concern the primary somesthetic area: Directions: Each of the numbered items in this section is followed by answers. Select the ONE lettered answer that (a) It occupies the lower part of the precentral gyrus. is CORRECT. (b) Histologically, it contains large numbers of 1. The following statements concern the cerebral pyramidal cells and few granular cells. cortex: (c) The opposite half of the body is represented (a) The cerebral cortex is thinnest over the crest inverted. of a gyrus and thickest in the depth of a sulcus. (d) Although most sensations reach the cortex from (b) The largest giant pyramidal cells are found in the the contralateral side of the body, sensations from the postcentral gyrus. hand go to both sides. (c) In the visual cortex, the outer band of Baillarger is (e) The area extends onto the anterior part of the thin and can only be seen under a microscope. paracentral lobule. (d) The molecular layer is the most superficial layer of 5. The following statements concern the visual areas the cerebral cortex and is composed of the small cell of the cortex: bodies of the granular cells. (a) The primary visual area is located in the walls of (e) From a functional point of view, the cerebral cortex the parieto-occipital sulcus. is organized into vertical units of activity. (b) The visual cortex receives afferent fibers from the 2. The following statements concern the precentral medial geniculate body. area of the frontal lobe of the cerebral cortex: (c) The right half of the visual field is represented in the visual cortex of the right cerebral hemisphere. (a) The anterior region is known as the primary motor area. (e) The superior retinal quadrants pass to the inferior portion of the visual cortex. (b) The primary motor area is responsible for skilled movements on the opposite side of the body. (e) The secondary visual area (Brodmann areas 18 and 19) is surrounded by the primary visual area on (b) The function of the primary motor area is to store the medial and lateral surfaces of the hemisphere. programs of motor activity, which are conveyed to the premotor area for the execution of movements. 6. The following statements concern the superior temporal gyrus: (c) lndividual skeletal muscles are represented in the primary motor area. (a) The primary auditory area is situated in the inferior wall of the lateral sulcus. (e) The area of cortex controlling a particular movement is not proportional to the skill involved. (b) The main projection fibers to the primary audi tory area arise from the thalamus 3. The following statements concern the motor speech area of Broca: (c) The sensory speech area of Wernicke is localized in the inferior temporal gyrus in the dominant (a) In most individuals, this area is important on the left hemisphere. or dominant hemisphere. (d) A unilateral lesion of the auditory area produces (b) The Broca speech area brings about the formation complete deafness in both ears. of words by its connections with the secondary motor area. (e) The secondary auditory area is sometimes referred to as Brodmann areas 41 and 42. (c) It is not connected to the sensory speech area of Wernicke. 7. The following statements concern the association areas (d) It is located in the superior frontal gyrus between of the cerebral cortex: the anterior and ascending rami and the ascending and posterior rami of the lateral fissure. (a) They form a small area of the cortical surface. (e) Brodmann areas 34 and 35 represent the motor (b) The prefrontal area is concerned with the makeup speech area. of the individual’s personality. PREPARED AND EDITED BY: LIMBAUAN, J., LIVED, R., LOCQUIAO, C., LOPEZ, F., PADILLA, A., PADOLINA, J., PALAGANAS, B., PANG-AG, L  (004) THE CEREBRUM DR. ELTON ONG | 10/14/2020 10. The neurologist made the following likely (c) They are concerned with the interpretation of motor conclusions except: experiences. (a) The diagnosis of left hemiasomatognosia (loss of (d) Appreciation of the body image is assembled in the appreciation of the left side of the body) was made. anterior parietal cortex, and the right side of the body is represented in the left hemisphere. (b) This condition probably resulted from a lesion of the left parietal lobe. (e) The association areas have only four layers of cortex. (c) In addition, the patient exhibited left hemi akinesia (unilateral motor neglect). 8. The following statements concern cerebral dominance: (d) A lesion was likely in areas 6 and 8 of the medial and lateral premotor regions of the right frontal lobe. (a) The cortical gyri of the dominant and nondominant hemispheres are arranged differently. (e) The failure to look toward the left side (visual extinction) suggested a lesion existed in the right (b) More than 90% of the adult population is right parieto-occipital lobes. handed and, therefore, is left-hemisphere dominant (c) About 96% of the adult population is right- REFERENCE hemisphere dominant for speech. (d) The nondominant hemisphere interprets Snell, Richard S. (2010) Clinical neuroanatomy. handedness, perception of language, and speech. Philadelphia : Wolters Kluwer Health/Lippincott Williams & Wilkins (e) After puberty, the dominance of the cerebral hemispheres becomes fixed. Directions: Each case history is followed by questions. Read the case history, then select the ONE BEST lettered answer. A 54-year-old woman was seen by a neurologist because her sister had noticed a sudden change in her behavior. On questioning, the patient stated that after waking up from a deep sleep about a week ago, she noticed that the left side of her body did not feel as if it belonged to her. Later, the feeling worsened, and she became unaware of the existence of her left side. Her sister told the neurologist that the patient now neglects to washthe left side of her body. 9. The neurologist examined the patient and found the following most likely signs except: (a) The patient did not look toward her left side. (b) She readily reacted to sensory stimulation of her skin on the left side. (c) On being asked to move her left leg, she promptly did so. (d) Muscular weakness of the upper and lower limbs on the left side was evident. (e) On being asked to walk across the examining room, she tended not to use her left leg as much as her right leg. Answers: 1.E 2.B 3.A 4.C 5.D 6.A 7.B 8.B 9.D 10.B PREPARED AND EDITED BY: LIMBAUAN, J., LIVED, R., LOCQUIAO, C., LOPEZ, F., PADILLA, A., PADOLINA, J., PALAGANAS, B., PANG-AG, L