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Psy 123_Lec 5

Echo planar imaging epi one rf echoes back and forth

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Unformatted text preview: ces takes 80 seconds.! Extremely high spatial resolution! Echo Planar Imaging (EPI)! One RF echoes back and forth through the plane. One slice can be scanned in 40 ms, 25 slices can be scanned in 2 seconds. ! Whole brain very quickly, but not as high spatial resolution and not as stable.! EPI is much less stable than conventional imaging, and not as fine resolution. But the trade-off is worth it in the end b/c can collect data very quickly. Physiological issues of the BOLD signal! Physiological issues of the BOLD signal: Basic layout of how the BOLD signal occurs. All these areas have increased in activity when they are not… Physiological issues of the BOLD signal! Sensitive, Motor, or Cognitive Task! Localized increase in neuronal activity! Increased metabolic rate! Local vasodiliation! Increased Blood Volume! (small compared to blood flow) ! Increase in Blood flow is greater than the increase in metabolism. This increase in OC occurs in .5 sec and at the same time there is an increase in CBF, and thus CBF will exceed the OC increase. When the brain is rest, there is still metabolism and a baseline level of increasing bloodflow and OC. Increased Blood Flow! We are measuring at the end the MR signal, so it is a very indirect measure of the n...
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  • Fall '11
  • Staff
  • Magnetic resonance imaging, Functional magnetic resonance, neural activity, BOLD Signal, Functional magnetic resonance imaging

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