you have a test next week!
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You have a test next week!. Review Session Monday next week 4 – 5 Room Th 173. Parallel pathways in the visual system. Dorsal and Ventral Pathways. recall some details about visual pathways. Dorsal and Ventral Pathways. - PowerPoint PPT PresentationTRANSCRIPT
You have a test next week!
Review Session Monday next week 4 – 5 Room Th 173
Parallel pathways in the visual system
Dorsal and Ventral Pathways
• recall some details about visual pathways
Dorsal and Ventral Pathways
• Different visual cortex regions contain cells with different tuning properties represent different features in the visual field– PET study by Zeki et al.– Double dissociation of lesions
• V5/MT is selectively responsive to motion
• V4 is selectively responsive to color
What are the different roles of these pathways?
• Ventral Stream– Object identification– Awareness?
• Dorsal stream– Spatial representations
Dorsal and Ventral Pathways
• V4 and V5 are key parts of two larger functional pathways:
– Dorsal or “Where” pathway
– Ventral or “What” pathway
– Ungerleider and Mishkin (1982)
• Magno and Parvo dichotomy arose at the retina and gives rise to two distinct cortical pathways
Fusiform Gyrus: Specialized for perception of complex objects
• Ventral pathway has specialized regions for complex object identification:– Faces – Fusiform Face Area (FFA)– Word Form – Visual Word Form Area (VWFA)
Visual Word Form Area
• fMRI contrasting words with pictures
• Left inferior temporal lobe
Deheane et al. (2009) NeuroImage
Visual Word Form Area
• Exhibits invariance to surface structure of words– Table, TABLE, tAblE
are equivalent
Deheane et al. (2009) NeuroImage
Visual Word Form Area
• Possibly mediates the critical skill of overcoming mirror invariance for objects during learning
Deheane et al. (2009) NeuroImage
Visual Word Form Area
• Lesions cause Pure Alexia– Inability to read
visual input efficiently• Letter-by-letter
strategies are intact but S – L – O – W
– Words traced on the skin can be read!?
Deheane et al. (2009) NeuroImage