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Research Methods.docx

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University of Guelph
PSYC 2410
Elena Choleris

Methods for Visualizing Human Brain 9172012 73200 PMMACK 120 Monday 330530How to Get into Graduate School Research MethodsMeasuring the activity of the nervous systemMeasuring behaviour o In humans o In animalsMethods of Visualizing the Living Human BrainStructure o Conventional xrays o Contrast xrays o Xray Computed Tomography CT o Magnetic Resonance Imaging MRIFunction o Positron Emission Tomography PET o Functional MRI fMRI o Magnetoencephalography o Transcranial Magnetic StimulationConventional Xray PhotographyXray beam passed through an object then onto photographic plateStructures that absorb xrays differently show up different on filmOnly works when there is high contrast o Bones vs soft tissue guns vs clothesNot good for brain scans because various structures of brain differ only slightly from on another in absorption of xrays o Essentially cannot see the brainContrast Xray PhotographyInjection of a contrast medium eg a radio opaque dye o Absorbs xrays less than or more than surrounding tissuesEnhanced structure to background different in xray absorption o Still cannot see the brain o Eg angiographyUses infusion of radio opaque dye into a cerebral artery to visualize the cerebral circulatory system during xray Used for vascular damage and tumours displacement of blood vessels can be indicatorXray Computed Tomography CTVisualize brain and other internal tissues in living organismRotating xray tube takes multiple images2D images are combined to create 3D image810 scans per session that are put together to create 3D imageFirst approach used to see the brain o White blobstumoursMagnetic Resonance Imaging MRIWidely used in 80s and 90sRadio waves passed through tissueRadio frequency waves align hydrogens in water molecules o Water molecules all over brain Aligned hydrogens emit measureable magnetic signalBoth 2D and 3D imagesClearer than CTHigh spatial resolution ability to detect and represent differences in spatial locationPositron Emission Tomography PETFirst brain technique to provide images of brain activity rather than structureRadioactive compound is injected eg 2deoxyglucose aka 2DG o Injected into carotid artery artery at back of neck o Similar to glucose main energy of neurons 2DG is recognized and carried into neuron by active cells but cannot be used in metabolism instead 2DG accumulates o The more active the neuron the more 2DG is being picked up by neurons2DG degrades slowly o Accumulates in active cells o Radioactive signal of active cells is greater than that of non active cells o PET scans can measure activation of brain areasredvery activebluenot very active o Do not have scan of brain must overlap images from CT scan or MRI scan to see which areas are being lit upMerely a coloured map o Other radioactive tracersspecific systemsEg LDOPA for Parkinsons diagnosisChemical precursorSee how much LDOPA neurons are bringing in and how active they areAs disease progresses less neurons pick up LDOPA
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