When light reaches the retina, the process of vision initiates. Approximately six decades ago, scientists uncovered that each visual cell’s receptive field activates when light hits a small central region but is inhibited by surrounding light. If light covers the entire field, the cell’s response is subdued.
Vision commences with light passing through the cornea and lens, forming a clear image on the retina, much like a camera. The retinal image is reversed, with objects above the center projecting to the lower part and vice versa. Electrical signals carrying information from the retina travel via the optic nerve to the brain, where further processing enables sight.
Hence, visual processing starts with comparing light levels in small retinal regions and their surroundings. Visual data from the retina is transmitted through the lateral geniculate nucleus to the primary visual cortex, situated in the occipital lobe at the back of the brain. This cortex, like the retina, contains densely packed cells in multiple layers. The middle layer, receiving messages from the lateral geniculate nucleus, exhibits responses akin to those in the retina and lateral geniculate cells. Cells above and below this layer respond differently, showing preferences for shapes, angles, and orientations.
Although the intricacies of visual processing mechanisms remain incompletely understood, recent studies in monkeys suggest that visual signals are channeled into three distinct processing systems: one for shape, another for color, and a third for movement, location, and spatial arrangement.
Human psychological studies corroborate findings from animal research, indicating that perceptions of movement, depth, perspective, object size, shading, and texture gradations are predominantly influenced by contrasts in light intensity rather than color.
Perception relies on organizing various elements to group related ones together, a function of the brain’s ability to unite and segregate image parts from their backgrounds. The integration of these systems culminates in the perception of vivid images of solid objects, as the brain extracts biologically relevant information at each stage and associates neuronal firing patterns with past experiences.
REFERENCES
https://www.brainfacts.org/thinking-sensing-and-behaving/vision/2012/vision-processing-information