perusretinotopinen

Perusretinotopinen, a Finnish term meaning basic retinotopic, describes the fundamental organizational principle of the visual cortex in which the spatial layout of the retina is preserved in cortical representations. In essence, neighboring points on the retina map to neighboring neurons and cortical locations, creating a topographic map of the visual field.

In humans and many other mammals, this retinotopic organization is most clearly observed in early visual areas such as V1, V2 and V3. The maps are contralateral: stimuli in the left visual field are represented in the right hemisphere and vice versa. The fovea, the center of the visual field, is disproportionately represented in cortex (foveal magnification), so small regions of the retina near the fovea occupy larger cortical areas than peripheral regions. The retinotopic map proceeds with eccentricity, so central vision is overrepresented relative to peripheral vision.

Retinotopic organization can be described in terms of polar angle (direction in the visual field) and eccentricity (distance from the fovea). Phase-encoded visual stimuli, such as rotating wedges and expanding rings, are commonly used in functional imaging and electrophysiology to delineate the borders and orientation of retinotopic maps. This approach helps identify cortical areas and understand how the brain represents spatial information.

Beyond the primary visual cortex, many higher visual areas retain retinotopy, though their maps can be less uniform and intermingled with specialized selectivities for features like color, motion, or texture. Retinotopic maps remain a central concept for interpreting visual perception, brain organization, and the effects of lesions or developmental changes on spatial vision.

The concept is a foundational aspect of neuroanatomy and vision science, informing both basic research and clinical assessment of visual field deficits.

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