1 - Retinotopy Flashcards
What is retinotopy?
Retinotopy is the mapping of visual input from the retina to neurons in the visual stream.
What is eccentricity?
Eccentricity is the distance away from the fixation point or fovea.
Why does V2 have bigger receptive fields compared to V1?
This is because a single V2 cell is connected to multiple V1 cells. This causes the V1 cell receptive fields to merge together and form a big V2 receptive field. This is called convergence.
Cortical magnification starts at the retina. Explain how.
In the fovea, there are many one-to-one connections, causing every receptor to have its own cell in the brain. This causes huge cortical magnification and very tiny receptive fields.
In the periphery, multiple receptors have to share a braincell (convergence). This causes smaller cortical magnification and big receptive fields.
Which meridian forms the border between V1 and V2
The vertical meridian.
V1 is usually found hidden inside a specific sulcus, what is the name of this sulcus?
The calcarine sulcus
The contralateral lower visual quadrant is represented in…
The upper bank of V1 and the upper gyrus of V2
Why is Peter de Weerd not a fan of figure 1 in Gattas?
In this figure all meridians come together in one point, the fovea, which makes 0 sense when we consider cortical magnification. The fovea usually takes up a lot of space instead of this tiny point. That is why Peter prefers the own masterpiece he made.
When we follow the brain gyri and sulci in the ventral to dorsal direction we come across V2, V1 and V2 again. When you look at where the receptive fields are for these areas, there is a clear pattern that emerges for each visual area. What is it?
The receptive fields in V2, when following in the ventral to dorsal direction, go counterclockwise and the receptive fields of V1 go clockwise.
What is retinotopic mapping
Point-by-point representation of the retinal surface in another structure in the visual system
What is the method of Gattas
Recordings form small groups of neurons in anesthetised and paralyzed macaques. Seated in front of hemispherical screen and by showing a white opaque stimuli, RF boundaries were marked on the screen for each recorded neuron.
He also did histology - small electrolytic lesions were made at the recording site in order to find the area back and the sections were Nissl stained for cell bodies
What is the method of Sereno
fMRI
Mapping of polar angle by showing a slowly rotating semicircular checkerboard stimulus
Eccentricity by showing a thick ring that contracts or dilates
