Presentation on theme: "Early discoveries of brain function and localisation"— Presentation transcript:
1Early discoveries of brain function and localisation Dr. Paul Dockree, History of Psychology: PS1203, 2009
2What is neuropsychology? “In any well-made machine one is ignorant of most of the parts – the better they work the less we are conscious of them…it is only fault that draws attention to the existence of a mechanism at all.” (Craik, K., 1943)TV set analogy:Faulty TV sets:--no sound but intact picture-no picture but intact sound-picture without colour (ie black & white pic)-colour without picture?
3What is neuropsychology? The experimental neuropsychologist asks, “What pattern of behavioural dysfunction occurs when a particular brain region is damaged or lesioned?”The clinical neuropsychologist asks, “How can normal function be restored or compensated for in the brain?”Science-Practitioner Model
4How did the field evolve? John Hughlings Jackson’s ( ) first credible human localisationist view – evidence from epileptic patients.
5Broca’s Aphasia How did the field evolve? In 1862, showing brain lesions in a stroke patient who could understand language but could not speak (could only say "tan"), he demonstrated that the left frontal lobe was responsible for articulation of speech.
6Wernicke’s Aphasia How did the field evolve? Like Broca, Wernicke investigated a similar stroke victim. But this time the patient could speak but made no sense. The damaged area was around where the temporal and parietal lobes meet in the posterior part of the left hemisphere. His findings further revived the localisationist view.Wernicke’s aphasics show deficits in language comprehension but intact articulation
7Speech content of a Broca’s and Wernicke’s aphasic How did the field evolve?Speech content of a Broca’s and Wernicke’s aphasicTo mean: "The dog needs to go out so I will take him for a walk.“a Wernicke’s aphasic patient says:“You know that smoodle pinkered and that I want to get him round and take care of him like you want before.”an Broca’s aphasic patient says:“Walk dog.”
8Function X: speech articulation Function Y: speech comprehension The logic of lesion analysisFunction X: speech articulation Function Y: speech comprehension Area A: Broca’s area Area B: Wernicke’s areaBrain functionStructures to be LesionedArea ABroca’s areaArea BWernicke’s areaFunction XSpeech articulationImpairmentCan’t speak fluentlyNo ImpairmentIn fluent speechFunction YSpeech comprehensionUnderstanding speech of othersCan’t understanding speech of others
9Function X: speech articulation Function Y: speech comprehension The logic of lesion analysisFunction X: speech articulation Function Y: speech comprehension Area A: Broca’s area Area B: Wernicke’s areaBrain functionStructures to be LesionedArea ABroca’s areaArea BWernicke’s areaFunction XSpeech articulationImpairmentCan’t speak fluentlyNo ImpairmentIn fluent speechFunction YSpeech comprehensionUnderstanding speech of othersCan’t understanding speech of others
10The logic of lesion analysis Function X (articulation of speech) depends on area A (Broca’s area) but not area B,whereas function Y (comprehending speech) depends on area B (Wernicke’s area) but not area A.Double dissociation – Gold standard of neuropsychological research
11Wilder Penfield How did the field evolve? Growing evidence for localisationist view in early 20th century – direct evidence from motor and sensory maps in the brain from early work of Wilder Penfield.Features drawn according to how much brain space they take up in somatosensory cortex.
12Wilder Penfield How did the field evolve? Stimulating the temporal lobes could he elicit meaningful, integrated responses. Physical basis for memory: an "engram.”
13How did the field evolve? Holistic approach:Karl Lashley (1935) – lesions made throughout the brain do not necessary create problems when learning a new task (e.g., maze learning in rats).A lesioned brain is like a new system, not an old system with one part missing.
14Localisation vs holistic: How did the field evolve?Localisation vs holistic:A Compromise-Complex functions (e.g., perception, memory, reasoning) cannot be accomplished by a single brain process or brain region; integration of functional neuroanatomy – holistic viewNevertheless, the simple processes themselves that are recruited to exercise complex functions are localised – localisation viewBrain damage may reveal something about the underlying organisation of the system.
15Psychometric testing: database of standardised scores What are the methods used in neuropsychology?Psychometric testing:database of standardised scoresClinical patients vs. healthy controlsClinical observation:DiagnosisAssessmentRehabilitationNeuroanatomy:Connectional studies in animal studiesprojection maps (e.g., LGN to visual cortex)
16What are the methods used in neuropsychology? Lesion analysis:selection of animals or humans with discrete brain damage to areas thought to be essential in a particular processing chain.one of the oldest methods for studying brain function in humans and animals.single most informative technique available for understanding the neural bases of behaviour.
17What are the methods used in neuropsychology? Types of lesions:cerebrovascular accidents (CVA; stroke); occurs when blood flow to the brain is disrupted;
18penetrating head injuries, from gunshot or other incidents; What are the methods used in neuropsychology?Types of lesions:penetrating head injuries, from gunshot or other incidents;
19What are the methods used in neuropsychology? Types of lesions:Following traumatic brain injury (TBI), diffuse white matter damage typically co-occurs with more focal lesions or hematomas (blood clots) and contusions (bruising) damaging the dense collections of cell bodies (grey matter)
20What are the methods used in neuropsychology? Types of lesions:Neurodegeneration: widespread area of tissue death or abnormal cell functioning due to neuropathology (AD, PD);healthy older personPt with AD
21Deliberate lesions - on experimental animals. What are the methods used in neuropsychology?Deliberate lesions - on experimental animals.tissue excision, where tissue is deliberately removed (usually by aspiration);tissue destruction, tissue is destroyed electrolytically or chemically (e.g., MPTP, a chemical agent to create an animal model of Parkinson’s disease);
22What are the methods used in neuropsychology? tissue deactivation, where tissue is reversibly deactivated via injections of local anaesthetic or through chemical cooling;tissue disconnection, where brain areas are left intact but fibre tracts which communicate between these areas are permanently cut or temporarily interrupted (by anaesthetic or cooling);
23What are the methods used in neuropsychology? Neurosurgery is often conducted on humans in order to relieve conditions such as drug-resistant epilepsy (patient H.M.), relief from intractable pain or brain tumours.
24The Wada test: sodium amytal technique LateralityThe Wada test: sodium amytal techniqueSodium amytal is injected into one hemisphere at a timeThe effect is to shut down any language and/or memory function in that hemisphere in order to evaluate the other hemisphere ("half of the brain").Then the patient is engaged in a series of language and memory related tests
25Broca and aphasia therapy (1865) NeurorehabilitationBroca and aphasia therapy (1865)Broca concluded that the patient, “could recognize a word as one would a face or landscape, the details of which had never been analysed”it deosn't mttaer waht oredr the ltteers in a wrod are, the olny iprmoetnt tihng is taht the frist and lsat ltteres are at the rghit pclae. The rset can be a tatol mses and you can sitll raed it wouthit a porbelm. Tihs is bcuseae we do not raed ervey lteter by it slef but the wrod as a wlohe.
26NeurorehabilitationWW1- German rehabilitation (Popplereuter, Goldstein)Cologne and Frankfurt centresWWII – Alexandra Luria: theoretical perspective from which to predict recoveryRestoration of function via:De-inhibitionTransfer to opposite hemisphereReorganisation of the systemLuria stressed the importance of premorbid personality and motivation
27Is there any point to lesion analyses now? A reading of the last fifteen years of the functional imaging literature - imaging literature largely concerned with the high-tech confirmation of the preceding one hundred and fifty years of careful neuropsychological analysis.PET and fMRI studies do not provide a definitive conclusion about whether or not a particular area is absolutely required in a processing chain.The only way to definitively decide if function X is dependent on area A is to remove that area from the processing chain.
28Is there any point to lesion analyses now? Lesion analysis complements functional imaging by identifying necessary and contributing components of the processing chain; functional imaging also allows the identification of specific components of the processing chain.Overall one strategy complements and underlines the other.nb: All of the above techniques require that you get the psychology right - if you do not have a good functional theory, applying technology will not get you a meaningful answer.Further understanding of lesions and their functional role is key for targeted rehabilitation of function and the guided recovery of patients.