lecture03

lecture03 - Watching the brain remember Neuroimaging...

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Watching the brain remember Neuroimaging techniques for studying learning and memory David A. Ziegler Wednesday, Sept 12, 2007 Outline • Imaging brain anatomy – Structural magnetic resonance imaging (MRI) • Imaging brain function – Positron emission tomography (PET) – Functional MRI (fMRI) – Magnetoencephalography (MEG) – Strengths and limitations of each method Please interrupt me if you have questions! 1 Image removed due to copyright reasons. Cartoon.
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Functional neuroimaging techniques: spatial and temporal resolutions Spatial resolution 2 Images removed due to copyright restrictions. Three brain scan images of increasing resolution quality. Patch-clamp recording Single-unit recording Animal optical techniques Human intracranial ERPs Brain Gyrus Voxel(fMRI) Cortical column Neuron Axon (diameter) Synapse Temporal resolution Spatial resolution 1yr 1 wk 1 day 1 hr 1 min 1 s 100 ms 10 ms 1 ms 0.1 μ m 1 μ m 10 μ m 100 μ m 1 mm 1 cm 10 cm 1 m Drug manipulations Lesion (human) Lesion (animal) Scalp ERPs Human optical fMRI PET EEG TMS Figure by MIT OpenCourseWare.
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MRI then and now First MRI of a human chest 3 Images removed due to copyright restrictions. Photographs of original and modern MRI machines. Images removed due to copyright restrictions. First MRI, of a human chest; photograph of man in first MRI machine; handwritten notes describing these results.
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Basic modern MRI setup • A superconducting magnet creates static magnetic field (B 0 ) • B 0 is aligned along head-toe axis • How do we generate images of the brain? 4 Illustration of human insertion into MRI machine. Figure removed due to copyright restrictions. Image removed due to copyright restrictions. Please see http://easymeasure.co.uk/principlesmri.aspx .
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Low energy B 0 High energy excitation pulse T1 relaxation time Based on Huettel et al. (2004) Radiofrequency excitation & relaxation time Energy state Low High Low High excitation pulse B 0 Low High 5 Images removed due to copyright restrictions. Please see http://easymeasure.co.uk/principlesmri.aspx .
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Following excitation, the amount of dephasing differs depending on the tissue type, leading to different T1 relaxation times Typical T1 relaxation times at 1.5 Tesla: White matter = 787 ms Gray matter = 921 ms CSF = 2650 ms Nitz & Reimer (1999) Anatomical contrast Huettel et al. (2004) 6 Images removed due to copyright restrictions. MRI image with illustrative diagrams of white matter and CSF molecular dephasing activities. Figure from: Nitz, W.R., and P. Reimer. "Contrast Mechanisms in MR Imaging." Eur Radiol 9 (1999): 1032–1046. Images removed due to copyright restrictions.
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This note was uploaded on 11/11/2011 for the course BIO 9.07 taught by Professor Ruthrosenholtz during the Spring '04 term at MIT.

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lecture03 - Watching the brain remember Neuroimaging...

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