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