Considering that we observe the world through two small flat retinas behind our eyes, what each of us perceives seems to be a seamless three-dimensional visual world.
The retina responds to light at various wavelengths from the world around us. But this is only the first part of the whole process. Our brains have to do a lot of work with all the raw data they input — stitch them together, choose what to focus on and what to ignore. It is the brain that constructs our visual world.
Neuroscientists and cognitive scientists have recently made great progress in studying how this process works. My own research focuses on how humans maintain the visual world for a short time by choosing visual information to pay attention to and using visual memory. In addition to simple sensory input, there are many other things that can be used to build our perception of the visual world in which we live.
The retina is a sheet of cells at the back of each of our eyes. Some of these cells, called photoreceptors, are photosensitive. There are two main types: rods are sensitive to light and shade differences, and cones are sensitive to color.
These photoreceptors are most concentrated in a small area of the retina called the fovea. It corresponds to our visual center, where the resolution is the highest. As we get farther from the center of our field of vision, the details gradually diminish – that is, around (hence the term “peripheral vision”).
Given the constant movement of the eyes, how does the picture of the world in our minds remain so visibly stable? After investigating this apparent difference, neuroscientists found that the input signals of the eyes were suppressed during scanning, so we would not record the rapid movements and blurred images that would otherwise occur. In addition, our brain uses information about eye muscles that control eye movements to correct eye movements. Because the brain ignores the information input during eye movement, our visual world is mainly perceived during the short period of eye rest (about 200-300 milliseconds). For example, when reading, our eyes only move 10-20% of the time.
Studies of these phenomena and their related mechanisms have shown that human beings have created a more indicative version of the environment through eye gaze than previously thought. This sketch version of the environment is often referred to as a scenario point. It contains conceptual information about the basic categories of scenes – is it natural, man-made, urban landscape? – and overall layout, which may be limited to some objects and/or functions. The schematic version of the environment is far from the “avatar” scene. But it is these schematic information that leads us from one focus to the next, in which more detailed information can be sampled.
If the brain can’t continue to compute like a visual processor, the visual information we receive through our eyes will still be a mess and confusion. The corrective nervous mechanism explains the movement of our eyes. Visual memory and attention work together to allow the flow of information from one source to the next. Together, these processes allow our brains to create a coherent and stable visual world.