049 Vision - Central Vision Pathways 2 Flashcards
What are the 3 levels of hierarchy in Hubel and Wiesels model?
Simple cells -> direction and orientation selective
Complex cells -> only orientation selective
Hypercomplex cells -> flanked by inhibitory regions with same orientation selectivity. Extension into this region will inhibit cells. Respond to more complex combinations of simple features e.g. two edges at right angles.
What are the 3 independant channels for basic cortical module?
Color, shape, motion
What do layers II and III in V1 contain?
Parvocellular and konio cells
Blobs are for color processing
Interblobs are for high resolution processing
What does layer IVB do in V1?
Magnocellular input for moetion and sterostopia.
Which outward projections does layer IVB project to?
Sends outward input to V5 (motion) and layers II and III.
Describe the structure of V2?
Contains thick stripes that receive from area IVB
Contains thin stripes that receive from area II and III
Describe the two streams from V1?
Dorsal stream: V1 –> V2 –> MT –> MST (parietal cortex)
Ventral stream: V1 –> V2 –> V3 –> V4 –> IT (temporal cortex)
Which pathway does magnocellular neurons go through from V1, where is it located, and what occurs when this pathway is damaged?
Magnocellular neurons go through the dorsal stream in the parietal cortex. When this is damage, there will be deficits in visual guided behaviour and motion vision.
Which pathway do parvocellular neurons go through from V1, where is it located, and what occurs when this pathway is damaged?
Parvocellular neurons go through the ventral stream in the temporal lobe. Damage will result in inability to identify objects (agnosia).
What does lesions in the occipital and temporal cortices result in?
Associative visual agnosia
Inability to identify what you are looking at
You can copy pictures but cannot recognise what you are copying.
Which area of the brain would lesions result in optic ataxia?
Superior parietal cortex because of the ventral stream.
What is construction apraxia?
Mixing of both optic ataxia and associative visual agnosia. They cannot construct. and the concept is also not understood.
What would occur with inferior parietal cortex lesions?
Hemispatial neglect, particularly in left field because it is usually loss in right side that causes this. Angular gyrus is critical region that can be destroyed by this
Where would lesions take place to result in prosopagnosia?
Fusiform face area in lingual and fusiform gyrus in temporal lobe.
What deficit in neurons do dyslexic subjects show?
Magnocellular neurons
