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functional MRI

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Chang Woo Ryu

on 21 March 2011

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Transcript of functional MRI

Functional MRI: Introduction Blood-Oxygenation-Level-Dependent (BOLD) Response MRI Increased neuronal activity results in increased MR (T2*) signal Sokoloff demonstrated that rCBF (blood flow) increases in visual cortex in proportion to photic stimulation using PET. No uncoupling of CBF and CMRO2; difference between CBF and CMRO2 lowers oxygen extraction (E) [Fick Principle]
Initial increase in blood flow increases blood volume (ballooning of venous capillary to accommodate)
1992: Ogawa and Kwong publish first functional images using BOLD signal
Blood flow increases with activity (Sokoloff, 1961)
Blood flow correlated with glucose metabolism (Sokoloff, 1981)
Demonstration of blood flow measured using MRI with an exogenous tracer (Belliveau, 1990)
Demonstration of effect of dHb on T2* contrast (Ogawa, 1990) use of blood as an endogenous tracer
fMRI is not a window on the brain Hypothesis 2: Measurement of neuronal activity fMRI is a measurement technique for measuring metabolic correlates of neuronal activity. HIgh spatial resolution Tasking and Rest Design Today.... Acquisition Preprocessing Analysis Visual stimulation Auditory Stimulation memory Langauge Attention #1. Visual Only Symptom Provocation task Trichotillomania
- hair loss from compulsive pulling or twisting of the hair until it breaks off. Department of Radiology, Chang-Woo Ryu Time Line Discovery of differential magnetic properties of oxygenated and deoxygenated hemoglobin (Pauling, 1936)
Roy and Sherrington hypothesize that local neuronal activity is related to regional changes in both cerebral blood flow and metabolism (1890).
Neuronal Activity and Blood Flow Changes Magnetic Susceptibility on T2* 100% O2 Room air Phrenology Phrenology claimed that bumps on the skull reflected exaggerated functions/traits
Nevertheless, its central idea persisted: Localization of Function
It used anecdotal, rather than scientific, evidence Wilder Penfield Korbinian Brodmann Brodmann area Hypothesis 1: Localization of Brain Functions Paul Pierre Broca (1824-1880)
Broca's or expressive aphasia: inability or difficulty speaking clear language.

Carl Wernicke (1848-1904)
Receptive or Wernicke's aphasia (unable either to understand or to express spoken language) Homunculus Different parts of the brain carry out different functions, conversely, that not all parts of the brain do the same thing. Historical & Neurophysiologic Basis Making the fMRI Subtracting the resting baseline map from the activation map Application #2. Visual and Tactile Symptom Provocation task Parkinson Disease
- Effect of acupuncture Game Perspective Ocular dominance columns High temporal resolution Functional connectivity
(in resting-state) New ocean neuroeconomics, evolutionary psychology, philosophy... Psychology Normal room air Hypoventilation Analysis of cerebral vascular reserve capacity before after Motor cortex mapping for navigation surgery Bilateral dyskinesia Rt hand movement Lt hand movement Persistent Mirror Movement Mapping before surgery Right motor Left motor Language Mapping before surgery Mapping before surgery Visual tasking fMRI measures intensity of BOLD signal. Broca's area is motor speech area. Neuronal activity results in increase of CBF.
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