brain structure


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brain structure

  1. 1. Brain Structure and Function
  2. 2. “If the human brain were sosimple that we couldunderstand it, we would be sosimple that we couldn’t”-Emerson Pugh, The Biological Origin of HumanValues (1977)
  3. 3. Phineas Gage• September 13th, 1848• Phineas 25 years old• Rutland & BurlingtonRailroad, Cavendish, VT• Paving the way for new RR tracks• “Tamping Iron”– 1.25in x 3ft
  4. 4. • Accident– Quick Recovery• Months later: “No longer Gage”– Before: capable, efficient, best foreman, well-balancedmind– After: extravagant, anti-social, liar, grossly profane• Stint with P.T Barnum• Died 12 years laterPhineas Gage
  5. 5. Evolution of the BrainReptilian  Paleomammalian  Neomammalian
  6. 6. The Brain• Brainstem–responsible forautomatic survivalfunctions• Medulla–controls heartbeatand breathing
  7. 7. BRAINSTEM  Heartrate and breathingCEREBELLUM Coordinationand balanceParts of the BrainamygdalapituitaryhippocampusTHALAMUS Relaysmessages
  8. 8. Reticular Formation•Widespread connections•Arousal of the brain asa whole•Reticular activatingsystem (RAS)•Maintainsconsciousness andalertness•Functions in sleep andarousal from sleep
  9. 9. The Cerebellum–helps coordinatevoluntarymovement andbalance
  10. 10. The Limbic System• Hypothalamus, pituitary, amygdala, and hippocampus alldeal with basicdrives, emotions, andmemory• Hippocampus  Memoryprocessing• Amygdala  Aggression(fight) and fear (flight)• Hypothalamus Hunger, thirst, bodytemperature, pleasure;regulates pituitary gland
  11. 11. The Limbic System Hypothalamus neural structure lyingbelow (hypo) thethalamus; directs severalmaintenance activities eating drinking body temperature helps govern theendocrine system via thepituitary gland linked to emotion
  12. 12. The Limbic System
  13. 13. The Limbic System• Amygdala–two almond-shaped neuralclusters that arecomponents ofthe limbic systemand are linked toemotion and fear
  14. 14. Charles WhitmanAugust 1st, 1966
  15. 15. The Brain• Thalamus– the brain’s sensoryswitchboard, locatedon top of thebrainstem– it directs messages tothe sensory receivingareas in the cortexand transmits repliesto the cerebellum andmedulla
  16. 16. The Cerebral Cortex• Cerebral Cortex–the body’sultimate controland informationprocessingcenter
  17. 17. The lobes of the cerebral hemispheres
  18. 18. The lobes of the cerebral hemispheresPlanning, decisionmaking speechSensoryAuditoryVision
  19. 19. The Cerebral Cortex• Frontal Lobes–involved in speaking andmuscle movements and inmaking plans and judgments–the “executive”• Parietal Lobes–include the sensory cortex
  20. 20. The Cerebral Cortex• Occipital Lobes–include the visual areas, whichreceive visual information from theopposite visual field• Temporal Lobes–include the auditory areas, each ofwhich receives auditory informationprimarily from the opposite ear
  21. 21. The Cerebral Cortex• Frontal (Forehead to top)  Motor Cortex• Parietal (Top to rear)  Sensory Cortex• Occipital (Back)  Visual Cortex• Temporal (Above ears)  Auditory Cortex
  22. 22. Motor/Sensory Cortex• Contralateral• Homunculus• Unequalrepresentation
  23. 23. Sensory Areas – Sensory HomunculusFigure 13.10
  24. 24. The Cerebral Cortex Aphasia impairment of language, usually caused by lefthemisphere damage either to Broca’s area(impairing speaking) or to Wernicke’s area(impairing understanding) –see clips Broca’s Area an area of the left frontal lobe that directs themuscle movements involved in speech Wernicke’s Area an area of the left temporal lobe involved inlanguage comprehension and expression
  25. 25. Language Areas• Broca Expression• Wernicke Comprehensionand reception• AphasiasLEFT HEMISPHERE
  26. 26. Paul Broca [1800s]• Suggested localization
  27. 27. Techniques to examine functionsof the brain1. Remove part ofthe brain & seewhat effect it hason behavior2. Examine humanswho have sufferedbrain damage
  28. 28. 3. Stimulate thebrain4. Record brainactivity
  29. 29. Brain Lateralization
  30. 30. Our Divided Brains• Corpus collosum –large bundle ofneural fibers(myelinatedaxons, or whitematter) connectingthe twohemispheres
  31. 31. Hemispheric SpecializationLEFTSymbolic thinking(Language)DetailLiteral meaningRIGHTSpatial perceptionOverall pictureContext,metaphor
  32. 32. Contra-lateraldivision of labor• Right hemispherecontrols left side ofbody and visual field• Left hemispherecontrols right side ofbody and visual field
  33. 33. Split Brain Patients• Epileptic patients had corpus callosum cutto reduce seizures in the brain• Lives largely unaffected, seizures reduced• Affected abilities related to naming objectsin the left visual field
  34. 34. Brain Plasticity
  35. 35. Brain Plasticity• The ability of the brain toreorganize neural pathwaysbased on new experiences• Persistent functional changes inthe brain represent newknowledge• Age dependent component• Brain injuries
  36. 36. Environmental influences onneuroplasticityImpoverished environmentEnriched environment
  37. 37. Sensation and Perception
  38. 38. Sensation• The process by which the centralnervous system receives input fromthe environment via sensory neurons• Bottom up processing
  39. 39. Perception• The process by which the braininterprets and organizes sensoryinformation• Top-down processing
  40. 40. The psychophysics of sensation• Absolute threshold  the minimumstimulation needed to detect a stimulus with50% accuracy• Subliminal stimulation  below theabsolute threshold for conscious awareness– May affect behavior without consciousawareness• Sensory adaptation/habituation diminished sensitivity to an unchangingstimulus
  41. 41. The five major senses• Vision – electromagnetic– Occipital lobe• Hearing – mechanical– Temporal lobe• Touch – mechanical– Sensory cortex• Taste – chemical– Gustatory insular cortex• Smell – chemical– Olfactory bulb– Orbitofrontal cortex– Vomeronasal organ?
  42. 42. The sixth sense• Vestibular  balance and motion– Inner ear• Proprioceptive  relative position of bodyparts– Parietal lobe• Temperature  heat– Thermoreceptors throughout the body, sensory cortex• Nociception  pain– Nociceptors throughout the body, sensory cortexAnd the seventh…and eighth…and ninth…
  43. 43. Thresholds of the five major senses
  44. 44. The RetinaThe retina at theback of the eyeis actually partof the brain!Rods –brightnessCones – color