Download - 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
You
Coronal
Axial
You
Patient
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.
Ventral “What” pathway
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
Dorsal “Where” pathway
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
David van Essen
Visual processing of information
Damage to “What” pathway
Achromatopsia, agnosia
Achromatopsia
• Complete achromatopsia- BL
area V4: Lingual/fusiform
gyri/occipitotemporal junction
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
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
Color anomia
• 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
• Inability to name colors or to point to colors given their names, which is not due to aphasia or due to defective color perception
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
Agnosia
• Topographagnosia– Inability to navigate routes using familiar landmarks -
deficit in familiar scene perception– Right lingual gyrus
• Alexia– Left (dominant lobe) fusiform/lingual areas
Lesion, left occipitotemporal region and involves parts of the lingual and fusiform gyri.
Hemi- achromatopsia , pure alexia , and category-specific visual object agnosia
Occipitotemporalgyri
Occipitotemporalgyri
Kanwisher , McDermott, and Chun, 1997
Kanwisher , McDermott, and Chun, 1997
Agnosia
• 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.