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Brain anatomy: cerebral hemispheres

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The cerebral hemispheres. The cerebral cortex (consists of six lobes on each side:frontal, parietal, temporal,occipital,insular, and limbic).the underlying cerebral white matter, the basal ganglia: a complex of deep gray matter masses. . Frontal lobe. Prefrontal: PersonalityAnd adaptation of the personality to events and experiences Foresight and imaginationSense of self.
Brain anatomy: cerebral hemispheres

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1. Brain anatomy: cerebral hemispheres

2. The cerebral hemispheres The cerebral cortex (consists of six lobes on each side: frontal, parietal, temporal, occipital, insular, and limbic). the underlying cerebral white matter, the basal ganglia: a complex of deep gray matter masses.

3. Frontal lobe Prefrontal: Personality And adaptation of the personality to events and experiences Foresight and imagination Sense of self

4. Parietal lobe Principle sensory area Touch Proprioception Lesions cause sensory losses Involvement in cognition Receptive speech loss

5. Temporal lobe Cognition Emotion Memory Links to the hippocampus and the limbic system are important to both of the above Wernicke?s area (tempero-parietal) special role in auditory association and speech comprehension

6. What might be involved in speech processing?

7. Occipital lobe Vision Visual processing and visual association Involved in eye movement Hemianopia from damage Think what might be involved in visual processing?

8. The cortex is particularly well developed in humans and is responsible for many higher brain functions, including manual dexterity (eg to move the fingers individually so as to play the piano); conscious, discriminative aspects of sensation; and cognitive activity, including language, reasoning, and many aspects of learning and memory.

9. Anatomy The cerebral hemispheres make up the largest portion of the human brain. The cerebral hemispheres appear as highly convoluted masses of gray matter that are organized into a folded structure. The crests of the cortical folds (gyri) are separated by furrows (sulci) or deeper fissures. The folding of the cortex into gyri and sulci permits the cranial vault to contain a large area of cortex (nearly 2 1/2 square feet), more than 50% of which is hidden within the sulci and fissures.

10. Lateral view of L hemLateral view of L hem

11. Main Sulci & Fissures The surfaces of the cerebral hemispheres contain many fissures and sulci that separate the frontal, parietal, occipital, and temporal lobes from each other and the insula. The lateral cerebral fissure (Sylvian fissure) separates the temporal lobe from the frontal and parietal lobes. The insula, a portion of cortex that did not grow much during development, lies deep within the fissure The circular sulcus surrounds the insula and separates it from the adjacent frontal, parietal, and temporal lobes. The hemispheres are separated by a deep median fissure, the longitudinal cerebral fissure. The central sulcus (the fissure of Rolando) arises about the middle of the hemisphere, and separates the frontal lobe from the parietal lobe. The parieto-occipital fissure separates the parietal lobe from the occipital lobe.

12. Medial view of RHMedial view of RH

13. Dissected LH to show the insulaDissected LH to show the insula

14. Corpus Callosum The corpus callosum connects the two hemispheres It is a large bundle of myelinated and nonmyelinated fibers, that crosses the longitudinal cerebral fissure and interconnects the hemispheres. The corpus callosum serves to integrate the activity of the two hemispheres and permits them to communicate with each other. Most parts of the cerebral cortex are connected with their counterparts in the opposite hemisphere by axons that run in the corpus callosum.

15. Medial view of RH Note the corpus callosumMedial view of RH Note the corpus callosum

16. White Matter The white matter of the adult cerebral hemisphere contains myelinated nerve fibers of many sizes as well as neuroglia. Transverse (commissural) fibres interconnect the two cerebral hemispheres (mainly the corpus callosum) Projection fibres connect the cerebral cortex with lower portions of the brain or the spinal cord.

17. White matter continued Association fibres connect the various portions of a cerebral hemisphere and permit the cortex to function as a coordinated whole.

18. ASSOCIATION FIBERS MRI of upper headASSOCIATION FIBERSMRI of upper head

19. Areas of the cerebrum Brodmann numbers to identify functions- down to individual sulci Question localisation now that we know more about connectionism and we have amore dynamic view of the brain works

21. Medial aspect with functional associations according to BrodmannMedial aspect with functional associations according to Brodmann

22. Left lateral view showing the functions of the local areasLeft lateral view showing the functions of the local areas

23. Primary Motor Cortex The primary motor projection cortex is located on the anterior wall of the central sulcus. These cells control voluntary movements of skeletal muscle on the opposite side of the body.

24. Homunculus Map of motor control Reflects the body Sizes indicate the amount of ?brain? needed for various functions Note vast area for the face- why?

25. Motor homunculus drawn on a coronal section through the precentral gyrus. The location of cortical control of various body parts is shown. Motor homunculus drawn on a coronal section through the precentral gyrus. The location of cortical control of various body parts is shown.

26. Figure 10-16. Motor activity in the cerebral cortex, visualized with functional magnetic resonance imaging. Changes in signal intensity, measured using a method called echoplanar magnetic resonance imaging, result from changes in the flow, volume, and oxygenation of the blood. This study was performed on a 7-year-old boy. The stimulus was repetitive squeezing of a foam-rubber ball at the rate of two to four squeezes per second with the right or left hand. Changes in cortical activity associated with squeezing the ball with the right hand are shown in black. Changes in cortical activity associated with squeezing the ball with the left hand are shown in white. (Reproduced, with permission, from Novotny EJ, et al: Functional magnetic resonance imaging (fMRI) in pediatric epilepsy. Epilepsia 1994;35(Supp 8):36.) Figure 10-16. Motor activity in the cerebral cortex, visualized with functional magnetic resonance imaging. Changes in signal intensity, measured using a method called echoplanar magnetic resonance imaging, result from changes in the flow, volume, and oxygenation of the blood. This study was performed on a 7-year-old boy. The stimulus was repetitive squeezing of a foam-rubber ball at the rate of two to four squeezes per second with the right or left hand. Changes in cortical activity associated with squeezing the ball with the right hand are shown in black. Changes in cortical activity associated with squeezing the ball with the left hand are shown in white. (Reproduced, with permission, from Novotny EJ, et al: Functional magnetic resonance imaging (fMRI) in pediatric epilepsy. Epilepsia 1994;35(Supp 8):36.)

27. Primary Sensory Cortex The primary sensory projection cortex for sensory information received from the skin, mucosa, and other tissues of the body and face is located in the postcentral gyrus and is called the somatesthetic area, This area receives fibers that convey touch and proprioceptive (muscle, joint, and tendon) sensations from the opposite side of the body. A relatively wide portion of the adjacent frontal and parietal lobes can be considered a secondary sensory cortex because this area also receives sensory stimuli. The cortical taste area is located close to the facial sensory area.

28. Sensory homunculus drawn overlying a coronal section through the postcentral gyrus. The location of the cortical representation of various body parts is shown. Sensory homunculus drawn overlying a coronal section through the postcentral gyrus. The location of the cortical representation of various body parts is shown.

29. How do areas compare on the homunculous?

30. Primary Visual Cortex The primary visual receptive cortex is located in the occipital lobe. In primates, an extensive posterior portion of the occipital pole is concerned primarily with high-resolution macular vision; the more anterior parts are concerned with peripheral vision. The visual cortex in the right occipital lobe receives impulses from the right half of each retina, The left visual cortex receives impulses from the left half of each retina. The upper portion of area 17 represents the upper half of each retina, and the lower portion represents the lower half.

31. Primary auditory cortex The primary auditory receptive area is located in the superior temporal gyrus toward the lateral cerebral fissure. The auditory cortex on each side receives the auditory radiation from the cochlea of both ears, and there is point-to-point projection of the cochlea on the acoustic area. Wernicke's area (in the posterior third of the superior temporal gyrus in the dominant (usually left) hemisphere, is involved in high-order auditory discrimination and speech comprehension. When is it on the L? What about in L handers? Discuss why cerebral dominance s a useful concept?When is it on the L? What about in L handers? Discuss why cerebral dominance s a useful concept?

32. Basal ganglia The term basal ganglia are masses of gray matter deep within the cerebral hemispheres. The term is debatable because these masses are nuclei rather than ganglia Anatomically, the basal ganglia include the caudate nucleus, the putamen, and the globus pallidus. Together they are called the corpus straitum Functionally, the basal ganglia and their interconnections and neurotransmitters form the extrapyramidal system.

33. Extrapyramidal system Influences motor instructions sent to the periphery Has a role in stabilising the large and complicated systems that control movement Helps to direct action and interpret sensory information

34. Basal ganggliaBasal gangglia

35. Basal ganglia connectionsBasal ganglia connections

36. Horizontal section through headHorizontal section through head

37. About the hemispheres Why have they evolved? Why do we need them? Why are they so big?


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