Brain Imaging & Imagining Final

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Neuroimaging review as therapeutic application for use in assessing interventions to relearn from traumatic memories

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Brain Imaging & Imagining Final

  1. 1. Brain Imaging & Imagining James M. DeCarli, MPH, MPA, CHES jdecarli@ph.lacounty.gov
  2. 2. Overview • Background – Review brain imaging techniques – Strengths & weaknesses of each • Neural Foundations of Imagery • Key Imaging Study – Evidence that seeing and imagining are the same to the brain • Additional Supportive Imagery Studies
  3. 3. Background • Brief Review of Imaging Techniques – Structural Imaging • X-Ray • Computerized Tomography (CT) Scan • Magnetic Resonance Imaging (MRI ) Scan – Functional Imaging • Positron Emission Tomography (PET) • Functional Magnetic Resonance Imaging (fMRI) • Single Photon Emission Computerized Tomography ( SPECT)
  4. 4. Positron Emission Tomography (PET) • PET measures emissions from radioactively labeled chemicals that have been injected into the bloodstream • Uses this data to produce two- or three-dimensional images of the distribution of the chemicals throughout the brain and body.
  5. 5. Positron Emission Tomography (PET) Strengths • Moderate accuracy of localization • Provides image of brain activity • Chemical specificity • Not subject to magnetic artifacts • Quiet -- verbal responses allowed, motion not as devastating to analysis Weaknesses • Expensive to use • Radioactive material used • Invasive • Low time resolution (>1- minute)
  6. 6. Magnetic Resonance Imaging (MRI) • MRI uses magnetic fields and radio waves to produce high-quality two- or three dimensional images of brain structures without injecting radioactive tracers
  7. 7. Magnetic Resonance Imaging (MRI) Strengths • No X-rays or radioactive material is used • Provides detailed view of the brain in different dimensions • Safe, painless, non-invasive • No special preparation is required from the patient (except the removal of all metal objects) • Patients can eat or drink anything before the procedure Weaknesses • Expensive to use • Cannot be used in patients with metallic devices, like pacemakers • Cannot be used with uncooperative patients because the patient must lie still • Cannot be used with patients who are claustrophobic (afraid of small places). However, new MRI systems with a more open design are now available
  8. 8. Functional MRI (fMRI) • Functional magnetic resonance imaging (fMRI) uses magnetic resonance imaging to measure the quick, tiny metabolic changes that take place in an active part of the brain
  9. 9. Functional MRI (fMRI) Strengths • Cheaper, more accessible • Better spatial and temporal resolution • Noninvasive • Does not require injections of radioactive isotopes • Imaging of oxygen Weaknesses • Low time resolution (around 8-seconds) • Poor anatomical definition • Movement sensitive
  10. 10. Neural Foundations of Imagery • Stephen Kosslyn (Key researcher on Imagery) – Defines Imagery as a basic form of cognition – Plays a central role in numerous human activities • Problem solving • Navigation to memory – Imagery occurs when perceptual information is retrieved from long-term memory • Results in subjective impression of “seeing with the mind’s eye” (Kosslyn, 2004)
  11. 11. Neural Foundations of Imagery • Neuroimaging techniques (PET, MRI, fMRI, etc.) provide effective methods: • Test theory of imagery on humans • Imaging studies suggest – Mental imagery draw on the same neural functions as perception – Engages similar mechanisms used in memory, motor control and emotion
  12. 12. Imagery Study • Kosslyn, et al (2004) • Assessed the degree of shared neural processing in visual mental imagery and visual perception
  13. 13. Imagery Study Methodology • Subjects: – 20 volunteers • 8 male • 12 female • Mean age 21 years – Normal or corrected- to-normal vision – Right handed – No history of neurological disease • Scanning Procedures: – Standard fMRI • Stimuli – 96 line drawings of common objects – Two sets • Imagery Scans • Perception Scans
  14. 14. Imagery Study Imagery Scan • Subjects asked to close eyes • Room lights off • Subjects presented by auditory probe, with a name of a picture – Asked to generate the corresponding visual mental image
  15. 15. Imagery Study Perception Scan • Subjects asked to keep eyes open • Room lights on • Subjects presented auditory probe with a line drawing of the named object shown on a screen after the auditory probe
  16. 16. Imagery Study Performance Results • Subjects pressed one of two keys in response to the probe, then asked not to press the key if not understood • No responses – 20.6% imagery missed – 5.2% perception missed • Responses – 96.2 imagery – 97.3 perception 0 20 40 60 80 100 120 No Response Response Imagery Perception
  17. 17. Imagery Study fMRI Results • Various brain regions activated – visual perception – visual imagery • Pattern of activation in both imagery and perception were similar – However similarity was not uniform across brain regions • Similarity – Greatest • Frontal & parietal cortex – Smallest • Occipital cortex
  18. 18. Imagery Study Imagery & Perceptual Activation Results in Frontal Cortex Reliable Activation (Positive Changes) Negative Activation (Negative Changes) Overlap •Inferior frontal gyrus •Middle frontal gyrus •Superior frontal gyrus •Medial frontal gyrus •Insular cortex •Precentral gyrus •Anterior cingulate gyrus •Medial frontal cortex •Superior frontal cortex •Anterior cingulate •In all frontal areas
  19. 19. Sagital View: Illustrates position of each section Grey area: (Z score) Significant overlap Activation Map: Coronal sections of the brain
  20. 20. Imagery Study Imagery & Perceptual Activation Results in Parietal Cortex Reliable Activation (Positive Changes) Negative Activation (Negative Changes) Overlap •Left angular gyrus •Supramarginal gyrus –Inferior parietal lobule •Superior parietal lobule •Precuneus •Postcentral gyrus •Middle cingulate •Posterior cingulate •Right supramarginal gyrus • Precuneus •Left angular gyrus •Supramarginal gyrus •Inferior parietal lobule •Superior parietal lobule •Postcentral gyrus
  21. 21. Sagital View: Illustrates position of each section Grey area: (Z score) Significant overlap Activation Map: Pattern of similarity in parietal & temporal regions
  22. 22. Imagery Study Imagery & Perceptual Activation Results in Temporal Cortex Reliable Activation (Positive Changes) Negative Activation (Negative Changes) Overlap •Fusiform gyrus •Parahippocampal gyrus •Inferior temporal gyrus •Middle temporal gyrus •Superior temporal gyrus •Transverse temporal gyrus •Right middle temporal gyrus •Right superior temporal gyrus • Transverse temporal gyrus •Superior temporal gyrus •Left middle temporal gyrus
  23. 23. Sagital View: Illustrates position of each section Activation Map: Pattern of similarity in parietal & occipital regions Grey area: (Z score) Significant overlap
  24. 24. Kosslyn’s Conclusion • Results suggest that visual images & visual perception draw on similar neural regions • Overlap is not uniform: – “Visual imagery & visual perception appear to engage frontal and parietal regions” more similarly than occipital and temporal regions • Indicates that “cognitive control processes function similarly in both imagery and perception”
  25. 25. Additional Brain Imaging & Imagery Studies • Preston, et al (2002) • Investigated neural substrates of cognitive empathy by using emotional imagery paradigm • Subjects: 11 • Procedure: PET • Stimuli: Subjects imagined an emotional experience (fear of anger) from their past or a hypothetical situation form another subject • Results: Similar brain activation between personal and hypothetical imagery
  26. 26. Additional Brain Imaging & Imagery Studies • O’Craven & Kanwisher (2000) • Tested if specific regions of the extrastriate cortex activated during mental imagery depend on the content of the image • Subjects: 8 • Procedure: fMRI • Stimuli: Photographs of faces and familiar places via imagery & perception scans • Results: – Imagery and perception share common processing neural mechanisms – Specific brain regions activated during mental imagery depend on the content of visual image
  27. 27. Additional Brain Imaging & Imagery Studies • Downs, et al (1999) • Examined neural mechanisms involved in imagined self-rotation in a task that involved spatially updating the positions of objects • Subjects: 10 • Procedure: fMRI • Stimuli: – Before scanning: Memorize positions of 4-objects – During scan: • 1) no visual input, • 2) test question-“rotate 90?, what’s on the right?” • 3) Control question-“rotate 0?, what’s on the right” • Results: Imagined self-movement involves many of the same brain areas as physical-movement
  28. 28. Summary • Function imaging techniques, such as PET and fMRI have made it possible to demonstrate that specific brain regions are activated similarly between: – Visual imagery & visual perception – Fear & hypothetical emotions – Imagined rotations of self & objects • Application – While Stephen Kosslyn studies find that 90% of the brain regions used for imagining visual images are the same ones used in actually seeing them: • Therapeutic application (due to many psychological approaches integrating visualization as a way of healing): – Relearning from traumatic memories – Flooding to heal phobias

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