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The Brain in MRI and CT

The Brain in MRI and CT. MRI are taken by a rotating magnetic field CT scans are taken by rotating X-ray source. Always Your Right is the Patient’s Left. Coronal. Axial. Patient. You. Patient.

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The Brain in MRI and CT

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  1. The Brain in MRI and CT • MRI are taken by a rotating magnetic field • CT scans are taken by rotating X-ray source

  2. Always Your Right is the Patient’s Left Coronal Axial Patient You Patient In axial MRI , you looking from down to top, as if you look to the patient from the feet “see demonstration” In coronal MRI, you looking to the patient face to face. You

  3. Ventral “What” pathway

  4. Ventral “What” pathway • Carries information about static object properties such as colour, luminance, stereopsis and pattern recognition. • Slow pathway from P-ganglion cells (through laminae 3-6 of LGN, V1) to V2, V4 and inferior temporal cortex

  5. Dorsal “Where” pathway

  6. Dorsal “Where” pathway • Information about dynamic object properties- motion and spatial relationships • Fast pathway for transient visual signals • Pathway to V1, V2, MT, medial superior temporal and parietal lobe

  7. David van Essen

  8. Visual processing of information

  9. Damage to “What” pathway Achromatopsia, agnosia

  10. Achromatopsia • Complete achromatopsia- BL area V4: Lingual/fusiform gyri/occipitotemporal junction

  11. Color agnosia • Color agnosia: loss the ability to retrieve color knowledge • cannot name colors for objects but can sort • Remembering the color of object • Color composition Left or bilateral occipitotemporal region Inferior temporal , fusiform and right lingual

  12. Color anomia • Inability to name colors or to point to colors given their names, which is not due to aphasia or due to defective color perception

  13. Color anomia • Inability to name colors or to point to colors given their names, which is not due to aphasia or due to defective color perception • Usually associated with left mesial occipitotemporal region • hence usually affect the visual cortex or optic rediation leading to right hemianopia , and also associated with alexia

  14. The Neural Basis of Visual Perception • Visual agnosia is the inability to recognize objects despite satisfactory vision. • Caused by damage to the pattern pathway usually in the temporal cortex. • For words : Alexia

  15. Agnosia • Topographagnosia • Inability to navigate routes using familiar landmarks - deficit in familiar scene perception • Right lingual gyrus • Alexia • Left (dominant lobe) fusiform/lingual areas

  16. Lesion, left occipitotemporal region and involves parts of the lingual and fusiform gyri. Hemi- achromatopsia , pure alexia , and category-specific visual object agnosia

  17. Occipitotemporal gyri

  18. Occipitotemporal gyri

  19. Kanwisher , McDermott, and Chun, 1997

  20. Kanwisher , McDermott, and Chun, 1997

  21. Prosopagnosia- Inability to recognize or learn faces Identify people by other cues- gait, mannerisms or facial features- spectacles, gait Aware of defect BL lingual and fusiform gyri of medial occipitotemporal cortex. Agnosia

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