Lecture 30- Extrastriate Cortices Flashcards
Which visual field do cells on the superior bank of the clacarine sulcus respond to?
Cells on the superior bank of the calcarine sulcus respond to signals in the lower visual field (inverted)
Where is the “stripe of Gennari” located within the cortex?
layer 4B
What accounts for the white stripe seen in the primary visual cortex?
the presence of large amounts myelin in layer 4B of the cortex
Where do the visual inputs from the lateral geniculate nucleus (LGN) project to in the primary visual cortex?
Layer 4 of the Striate (primary visual cortex)
Where do neurons from layer 4 of the striate cortex project?
back to the LGN
Where do neurons of layer 5 of the striate cortex project?
superior colliculus
What happens if the entire primary visual cortex on one side is lesioned?
homonymous hemianopia- unable to detect or respond to stimuli in the contralateral visual field
What accounts for the blindsight phenomenon seen in patients with destruction of the primary visual cortex?
ascending projection from the superior colliculus to the pulvinar nuclueus of the thalamus that allow for detection of large and moving stimuli
What are the two types of cells of the primary visual cortex?
parvocellular and magnocellular
What are parvocellular ganglion cells of the primary visual cortex also known as?
midget cells
What are magnocellular cells of the primary visual cortex known as?
parisol cells
What types of stimuli are parvocellular (midget) cells more receptive to?
color, high contrast detail
What types of stimuli are magnocellular (parasol) cells more receptive to?
quick changes/movement
Where do the magnocellular LGN neurons project?
the upper part of layer 4C (4C alpha)
Where do the parvocellular LGN neurons project?
the lower part of layer 4 C (4C beta)
Which layer of the striate cortex do cells of the LGN project to?
4C (Magnocellular-4C alpha, Parvocellular-4C beta)
What must a brain area have to be considered an extra striate area?
an extrastriate area must have its own representation of the visual field
What type of stimuli is the ventral pathway in charge of?
the “what”->color/form
What type of stimuli is the dorsal pathway in charge of?
the “where”-> motion
What type of stimuli do the cells in V4 respond to? Where is it located?
V4-color temporal lobe (ventral pathway)
What type of stimuli do the cells in V5 respond to? Where is it located?
V5- motion parietal lobe (dorsal pathway)
What do lesion of V4 in the temporal lobe result in? What is this called?
V4 lesions result in achromatopsia- loss of color vision
What is the fusiform face area associated with?
recognition of faces
What brain area is involved in recognizing faces?
fusiform face area
What is prosopagnosia?
injury to the fusiform face area
inability to recognize faces
What is the inferotemporal cortex associated with?
extra striate cortex- involved in emotional saliency, object recognition
What do lesions in V5 (MT) result in?
disruptions in motion sensitivity (dorsal stream)
What visual disturbances result from lesions in the parietal lobe?
visuospatial neglect-ignore one side (part of the dorsal stream- where pathway)
What are the cytochrome rich layers of the striate cortex known as?
blobs
What type of information do the cytochrome rich “blobs” receive?
color information
What type of information do the “inter blobs” receive?
form information
What layer are the blob and interblobs located in that receive projections from the parvocellular cells of layer 4C?
layer 2/3
What layer do the magnocellular cells in 4C with motion information project to?
layer 4C-> 4B
