Flashcards
Primary visual cortex - Columnar systems
Cards in this deck (16)
- 1What type of cells are responsible for form/contour processing (orientation selective)? Blob or inter-blob cells?Inter-blob cells
- 2What are the differences between the orientation selective cells in the vertical and horizontal columns of inter-blob cells?Verticle column cells have the same orientation preference wheras the horizontal column cells are different.
- 3What are the three sub-types of orientation-selective cells?-Simple cells (15%)
-Complex cells (75%)
-Hypercomplex cells (10%) - 4What are the features of simple cells?They resemble ganglion & LGN cells in that they are spatially distinct and have ON & OFF sub-regions but instead of them being circular, they are rectangular. They give strong responses to stationary contours and weak responses to spots of light. They have more predictable responses (linear summation) based upon the amount of light falling on subregions.
- 5What are the features of complex cells?Larger receptive fields with no spatially distinct ON & OFF sub-regions. No responses to spots of light and weak responses to stationary contours but stronger responses to moving ones (direction selectivity). It has unpredictable responses (non-linear) due to absence of sub-regions.
- 6What are the features of hypercomplex cells?They can have receptive fields like simple or complex cells but also have a silent inhibitory end-stopped region outside their main receptive field therefore their responses are influenced by stimulus size and length as well as contrast and orientation.
- 7Why do the LGN respond to a higher rang of spacial frequencies than in the cortical cells?Because of the inhibitory mechanisms within the layers of the v1 cortex.
- 8In which layer of the visual cortex are motion images processed?Layer 4b
- 9In which layer of the visual cortex are forms and contours processed?Interblob cells in layer 4c
- 10In which layer of the visual cortex are colour images processed?Blob cells of 4Cβ and blob cells from the k pathway of LGN
- 11What is in each of the 1000's of hypercolumn's in the V1 cortex?Each column represents a single point in space with a left & right ocular dominance column. Each left & right column contains a full range of orienations & spacial frequency preferences, possible direction-selective preferences in 4B, 2 CO blobs (1 for red/green and one for blue/yellow processing).
- 12What is the functional significance of the hypercolumns?Every possible stimulus is encoded by some cells in the hypercolumn regardless of form, motion or colour.
- 13What is the difference in structure between V1 and V2?They both have 6 cell layers but V2 has no subdivisions in layer 4. V2 has columns of cytochrome oxidase but they have regions of variable width and staining forms stripes. One pale stripe, thin stripe and thick stripe each around 1mm.
- 14Which part of the V1 travels to the thin stripe cells of V2?Blob cells (colour)
- 15Which part of the V1 travels to the thick stripe cells of V2?Layer 4B (motion)
- 16Which part of the V1 travels to the pale stripe cells of V2?Interblob cells (form)
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- Degree Visual science Flashcards on Primary visual cortex - Columnar systems, created by ghada.hamdi.1 on 11/11/2015.
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- ghada.hamdi.1 · Nov 2015
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- Feb 19, 2016
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