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Define functional MRI. MR images of the brain measuring brain Dr. Peter J. Fiester activity during language, movement , November 14, 2012 Briefly describe fMRI image acquisition. sensory, sensation etc..
Discuss relative functional neuroanatomy.
Review clinical applications.
Briefly discuss a few examples of research applications.
Increased neuronal activity
fMRI concept builds on the earlier MRI BOLD . blood oxygen level dependent signal Blood flow Oxygen extraction scanning technology and the discovery of Normal vascular response of the brain to activation properties of oxygen‐rich blood.
i) changes in blood flow and blood Oxyhemoglobin Deoxyhemoglobin oxygenation in the brain are closely linked to neural activity.
Deoxyhemoglobin
Signal
EPI utilize gradient echo sequence. Images of the whole brain are acquired very Typically, the unwanted signal called the noise (from the scanner and random brain activity) is fast over and over. Gradient echo sequences are sensitive to local as big as the signal itself. To eliminate these, magnetic field inhomogeneities. fMRI studies repeat a stimulus presentation TR 2 seconds (low resolution, fast multiple times. Deoxyhemoglobin is paramagnetic and acquisition). The signal change is very low and cannot be decreases T2*. directly detected. Therefore, advanced Present a task and measure how signal statistical methods (general linear model, for example) must be used to identify the voxels in Areas of increased neuronal activity (less intensity in each voxel changes over time. deoxyhemoglobin) have increased signal. which the signal varies according to the paradigm.
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Acquistion time (Longer imaging time or To be useful to surgeons and clinicians in higher field strength = greater signal to interpreting fMRI images, we need to be noise). familiar with the eloquent areas of the brain including major motor and sensory pathways Post processing techniques. and language centers.
Patient preparation.
Patient monitoring.
Supplementary motor area (SMA) and premotor area are known to be activated by the motor task in addition to the primary motor area (M1).
SMA is located on the midline surface of the hemisphere just anterior to the primary motor cortex leg representation.
frontal expressive or motor area (Broca area).
posterior receptive language center (Wernicke area).
white matter fiber tract (arcuate fasciculus) interconnecting the two.
(Fukunaga M, et al Electroencephalography and Clinical Neurophysiology(suppl.) 47: 265‐269, 1996
Volume 1076, Issue 1, Brain Research. 3 March 2006, Pages 129–143
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Figure 1. Image shows language processing areas of the brain, including Broca area (blue), located in Brodmann areas (BAs) 44 and 45; and Wernicke area (yellow), located in BAs 22, 37, 39, and 40. a.g. = angular gyrus, m.t.g. = middle temporal gyrus, p.o. ...
Broca’s Aphasia ‐ effortful, nonfluent, monotonous, often agrammatic speech with phonemic paraphasias (eg, “mook” instead of “book”) and articulatory deficits. Language comprehension is reasonably good, but speech production is impaired.
Smits M et al. Radiographics 2006;26:S145-S158
©2006 by Radiological Society of North America
Wernicke’s Aphasia ‐ exhibit fluent, melodious, but Conduction aphasia ‐ fluent speech with Motor empty speech that is often distorted by semantic phonemic paraphasias and self‐corrections Language paraphasias (eg, “chair” when “table” is meant) or with reasonably good comprehension. In Sensory neologisms, with poor language comprehension. particular, the repetition of long words and . Visual, auditory sentences is disrupted. Memory Higher cortical function
Current primary clinical application of fMRI is
in presurgical planning for tumors or seizure Tapping fingers and Foot motor task. focus. wiggling toes at same time.
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Figure 4a. Areas of activation for the verbal fluency–verb generation paradigm. Figure 4b. Areas of activation for the verbal fluency–verb generation paradigm. Figure 4c. Areas of activation for the verbal fluency–verb generation paradigm.
Smits M et al. Radiographics 2006;26:S145-S158 Smits M et al. Radiographics 2006;26:S145-S158 Smits M et al. Radiographics 2006;26:S145-S158
©2006 by Radiological Society of North America ©2006 by Radiological Society of North America ©2006 by Radiological Society of North America
Figure 6a. Areas of activation for the verbal fluency–verb generation paradigm. Figure 6b. Areas of activation for the verbal fluency–verb generation paradigm. Figure 6c. Areas of activation for the verbal fluency–verb generation paradigm.
Smits M et al. Radiographics 2006;26:S145-S158 Smits M et al. Radiographics 2006;26:S145-S158 Smits M et al. Radiographics 2006;26:S145-S158
©2006 by Radiological Society of North America ©2006 by Radiological Society of North America ©2006 by Radiological Society of North America
Dementias Define functional MRI. Dyslexia Autism Briefly describe fMRI image acquisition. ADHD Several more… Discuss relative functional neuroanatomy.
ApoE4 subjects ApoE3 subjects Review clinical applications. Older adults at genetic risk for AD require more cognitive effort to achieve comparable performance on an episodic memory encoding task. Briefly discuss research applications.
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Special thanks to Dr. Bennett for sharing some of the fMRI images.
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