Katsuhiro Mizuno: "Seeing" and "Feeling"

2022/09/02

Biologically speaking, vision can be defined as "optical information captured by receptors in the retina through the eyeball, transmitted to the visual cortex of the cerebrum, and perceived." If there are no problems in the pathway from the eyeball to the optic nerve and further to the primary visual cortex in the occipital lobe, one can "see" things normally. However, the processing of visual information does not end at the primary visual cortex. It is said that among the visual information reaching the primary visual cortex, information such as shape, color, and size is processed in the lower part of the brain (ventral stream), while information such as position and movement is processed in the upper part of the brain (dorsal stream).

When the cerebrum is damaged due to a stroke or other causes, various visual cognitive impairments occur depending on the site of the damage. Damage to the ventral visual processing pathway results in visual agnosia, where the shape and color of objects cannot be recognized. Furthermore, if the primary visual cortex is damaged, one cannot see objects, a condition known as cortical blindness. Patients with visual agnosia or cortical blindness complain that they "cannot see," but in some cases, they can avoid obstacles while walking or catch a ball. This phenomenon is called blindsight (blind sight). Blindsight patients "cannot see" but can move by "feeling" that something is there. Conversely, if the dorsal side of the brain is damaged, a symptom called optic ataxia occurs, where one can "see" an object but cannot reach out and grab it.

Looking back at the retina, photoreceptor cells are concentrated in a central area called the macula, and when focusing on an object, light is further concentrated in the fovea centralis at its center. Seeing things with the fovea is called central vision, and everything else is called peripheral vision. Information from central vision is processed in the ventral part of the cerebrum, while information from peripheral vision is processed in the dorsal part. Since some of the peripheral-dorsal information is sent directly to the motor cortex, one can "feel" and move before "seeing." It is thought that professional baseball players are able to hit a 150 km/h breaking ball by utilizing peripheral vision information. Perhaps at the master level, one can even "see" peripheral vision information as a visual image. "The ball looks like it's standing still" might be what that is like. When I was playing youth baseball, my father, who was the coach, used to tell me to "keep your eyes on the ball and hit it," but since I was naturally uncoordinated, the ball would already be in the catcher's mitt while I was trying to see it with my central vision.

Thinking about such things while watching Shohei Ohtani's performance with a beer in hand has become my favorite way to relax lately.