Localization of function psychology IB

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Localization of function psychology IB

  1. 1. T H E S T U D Y O F W H A T S T R U C T U R E S H A V E W H A T F U N C T I O N S I B L E A R N I N G O U T C O M E : E X P L A I N O N E S T U D Y R E L AT E D TO L O C A L I Z AT I O N O F F U N C T I O N O F T H E B R A I N I N I B - S P E A K T H I S M E A N S “ G I V E A D E TA I L E D A C C O U N T I N C L U D I N G R E A S O N S A N D C A U S E S ” Localization of Function
  2. 2. Why is brain function special?  The human brain is capable of carrying out different functions such as vision movement, comprehension, speech, hearing and overall body control.  Unlike other organs such as lungs or kidneys that perform the same function, different parts of the brain execute different functions.  Therefore, localization of function is relevant in the human brain.
  3. 3. But how do we find out? Methods involving alteration/change  Accidental damage – Phineas Gage (frontal cortex)  Deliberate damage/lesion (ablation)  Stimulation of the brain – electrodes inside the brain
  4. 4.  Strokes/tumors  Jill Bolte Taylor, the doctor who had a stroke in her left hemisphere.  „Tan‟ – Broca‟s patient who could only say „tan‟ because of brain damage. Broca‟s area was revealed in (postmortem) autopsy  Head trauma  Phineas Gage – had a rod go through his frontal cortex  Viral attacks  Clive Wearing – „flu‟ on his temporal lobe and hippocampus causing anterograde amnesia Accidental damage – and cases we know of
  5. 5. Ablation affects… Motivation  lesions on the hypothalamus of rats disturbed eating behavior. Aggression  removing the amygdala in animals reduces aggression. Memory  case of HM who had his hippocampus removed. Consciousness  Sperry cut Corpus Callosum in epileptic patient, who then experienced „split brain‟ Psychopathology  mental inmates were given lobotomy to control their behavior.
  6. 6. I knew you would ask about split brain!   Sperry cut the patient‟s corpus callosum to alleviate their epilepsy symptoms. This structure enables the two hemispheres to communicate.
  7. 7. Split brain – right and left are „divorced‟  The patients hemispheres were disconnected, and they experiences „split brain‟  A patient with a split brain, when shown an image in his or her left visual field, will be unable to vocally name what he or she has seen.  This is because the speech-control center is in the left side, and the image from the left visual field is sent only to the right side of the.  http://ibpsychology.wetpaint.com/page/Gazzaniga+ Key+Study - watch this clip
  8. 8. Electrical stimulation  Animal studies  Delgado stimulated areas of the limbic system to inhibit aggression in a charging bull with a remote control - while standing right in front of it!  Human studies  Penfield stimulated areas of the cortex in patient during surgery to locate areas controlling movement, hearing, sense etc.
  9. 9. Evaluation – can you evaluate the methods?  Accidental damage  Ablation  Electrical Stimulation
  10. 10. Evaluation  Accidental damage  Lack of precision – we cannot control the damage  Hard to compare before and after damage (no concrete records of „before‟)  Confounding variables – could Gage‟s behavior be caused by social relations?  Ethically good, as the damage occurs naturally in these natural experiments
  11. 11. Evaluation  Ablation  Ethical problems – not just in humans!  Animal studies – we cannot necessarily generalize  Neuroplasticity – the brain can compensate, so the missing part may not be showing  Good because there is greater control – precision of damage and therefore easier to compare
  12. 12. Evaluation  Stimulation  Less harmful than ablation  More valid – a better way of investigation „living‟ function of the brain  However, it is invasive – surgery is risky  The brain‟s interconnectedness makes it hard to know if the stimulated areas affect other areas.
  13. 13. Discussion – can we localize function? ”The brain is a highly complex, heavily interconnected system that displays non-linear properties and this is clearly a short fall of localization of function. (This means that we can argue that is is hard to localize a function to a specific structure of the brain, since the structures are interconnected)
  14. 14. Methods of localization that do not involve alteration  Direct reading of neuron activity  Very precise, but too focused. Is furthermore invasive and time-consuming.  External recording (EEG)  Non-invasive, and helpful in studying sleep, epilepsy etc.  Crude and imprecise  Scanning techniques (Still pictures – CAT, Dynamic pictures – fMRI, PET)  Detailed knowledge of structure and function in conscious patients – even while they are performing tasks  Expensive, hard to interpret, sensitive to disruption (e.g. movement), uncomfortable for patients
  15. 15. Structures and their function  We know of  Broca‟s area (language production, pt. Tan)  Wernicke‟s area (language understanding)  Frontal lobes (judgment, inhibition, pt. Phineas Gage)  Here is a more detailed description  http://ibpsychology.wetpaint.com/page/Evaluation+of+Locali sation+of+Function
  16. 16. What do we know about the hemispheres?
  17. 17. Cerebral Cortex is asymmetrical  Left  Serial processor  Linear processor  Language  Controls right side of the body  Right  Parallel processor  Holistic processor  Intuition  Controls left side of the body
  18. 18. WHAT SIDE ARE YOU ON?
  19. 19. DON‟T SAY THE WORD!
  20. 20. We will focus on the limbic system – specifically the hippocampus
  21. 21. WE WILL USE THE CASE OF HM Born in Connecticut in 1926 Suffered from severe epilepsy Had neurosurgery in 1953 Doctors removed parts of his temporal lobe to alleviate his symptoms
  22. 22. Bilateral Medial Temporal Lobe resection  Doctor‟s removed large portions of the temporal lobe from both hemispheres of the brain.  H. M.‟s condition justified drastic measures, and the surgery he underwent was extensive and radical.  Tissue was removed from the anterior (front) tips of the temporal lobes on the medial (inner) surface of the brain, extending 8cm backwards.  The resection therefore completely removed the amygdala, the entorhinal and perirhinal cortices, and about two-thirds of the hippocampus
  23. 23. Bilateral Medial Temporal Lobe resection
  24. 24. The surgery was a success!  It reduced his seizures to two a year!  BUT: HM was left with profound anterograde amnesia and partial retrograde amnesia.  To this day, he has no memory of anything that has happened since he underwent surgery, and cannot acquire new factual knowledge about the world around him.  He is unable to retain any kind of new information for more than several minutes.  And he cannot remember much of what happened in the decade prior to his surgery.
  25. 25. HM upon losing his hippocampi  "Right now, I'm wondering, have I done or said anything amiss? You see, at this moment everything looks clear to me, but what happened just before? That's what worries me. It's like waking from a dream. I just don't remember."
  26. 26. What Henry can and can‟t remember  Read the document, and answer these questions  What does HM‟s case teach us about the role of the hippocampus?  Which type of memory was damaged?  Which part remained intact?  What can we conclude from this natural experiment in terms of localization of function?
  27. 27. Implications/Conclusions – see point 2.4  The hippocampus is important in memory processing and particularly in the storage of new memories.  H.M. could learn a few new procedural memories so this indicates that such memories are not stored via the hippocampus.  The fact that H.M. had deficits in one part of the memory system but not in others is evidence that the brain has several memory systems and that these are supported by distinct brain regions.
  28. 28. Implications/Conclusions  Memory processes are much more complex – the hippocampus is very important in the storage of new memories it is not the only structure involved in the process.  Cortical areas are important for long-term memory, for facts and events (semantic and episodic memories), and the use of that information in daily life.  Ethical considerations in this case study. Lack of consent due to memory loss. However, the findings of the study are very important and this justifies it.  It is not usually possible to use the findings from a single case study to generalize about a larger population, but since the findings from other case studies of people with brain damage like H.M. tend to support those from this case study, it may be possible to generalize to some extent.
  29. 29. References to studies  Brenda Milner (1957) was the first to report the case of H.M. and the profound effects on memory functioning, following an operation which removed the hippocampus and adjacent areas in H.M.‟s brain.  Corkin et al. (1997) did a MRI scan of H.M‟s brain. Brain imaging was used because it allowed the researchers to get a precise picture of the brain damage. They discovered that parts of the temporal lobe, including the hippocampus and the amygdala, were missing, but also that the damage was not as extensive as previously believed.
  30. 30. 8 Tips for writing a good SAQ  Make sure you understand the command term and know the difference between explain or discuss or whatever you might be asked to demonstrate your understanding of the Learning Outcome  Define the key words in the SAQ and integrate the definitions into a “In other words…” sentence.  Make sure you use the words from the question in your answer at least two or three times. If the SAQ is about physiology use this word rather than brain or body.
  31. 31. 8 Tips for writing a good SAQ  Use studies to support your explanations. Give a brief summary of the study and then explain why this is relevant.  Take every opportunity to evaluate the study but do not just outline every strength and limitation, only the relevant ones.  For example there is no need to discuss ethical considerations with the Davidson meditation study from the BLOA, but the small sample size is relevant as it makes generalizing his finding that cognition can change brain physiology more limited.
  32. 32. 8 Tips for writing a good SAQ  Aim for a short introduction and conclusion. These can be just one sentence in length.  If you are asked about two hormones or two studies or two neurotransmitters make sure you have two body paragraphs.
  33. 33. Example of an SAQ localization of function Explain One Study Related to Localization of Function of the Brain  One study which focused on localization of function in the brain was conducted by French physician Paul Broca in the 19th Century. Broca set out to test his theory that damage to a specific part of the brain (the frontal lobe) was responsible for problems with speech.  Initially, Broca tested his theory through the use of case studies, one of which was on a patient named „Tan‟ (the only word Tan was able to say). During these case studies, Broca gathered a substantial amount of evidence including the problems each individual faced and details of any medical issues. Broca found that his patients all had two main factors in common – they understood language but had distinct problems with speech, and each patient had suffered some element of damage to the left side of their brains in earlier life. This led Broca to hypothesize that there must be a link between specific head trauma and the development of speech-based problems.  After Tan‟s death, Broca carried out a postmortem study, and found that Tan had lesions on the frontal lobe of his left hemisphere where damage had occurred earlier on in his life. Subsequent post-mortem research of several of his other patients identified that they too had specific damage to the left frontal lobe – an area now known as Broca‟s area. The research that Broca carried out during his lifetime led him to the conclusion that different parts of the brain must be responsible for specific functions. In this case, speech can be said to be localized to the frontal cortex of the left hemisphere, a finding which has been supported by recent empirical research.
  34. 34. Mark Band/Level descriptor  Zero: The answer does not reach a standard described by the descriptors below.  Low (1-3): There is an attempt to answer the question, but knowledge and understanding is limited, often inaccurate, or of marginal relevance to the question.  Mid (4-6): The question is partially answered. Knowledge and understanding is accurate but limited. Either the command term is not effectively addressed or the response is not sufficiently explicit in answering the question.  High (7-8 ): The question is answered in a focused and effective manner and meets the demands of the command term. The response is supported by appropriate and accurate knowledge and understanding of research. Where would you rate this SAQ and why? Remember the answer must observe the command term!

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