The Nature and Function of Digital Information Compression Mechanisms in the Brain and in Digital Television Technology

摘要

Why compare human vision with digital television? Both of these systems perform similar functions. In both, light rays carrying information are reflected off objects and are picked up by a camera-like device and transmitted to a complex mechanism that performs computations on them. In television these computations construct a representation of the objects in the form of the pictures on the TV screen. This representation needs to be optimized for the viewer (i.e., the viewer should be pleased with the resolution and frame rate and ideally should perceive the same as when viewing natural objects). In vision the computations construct the phenomenal objects that experienced in a person's visual field in consciousness—as Crick ( 1994 , p. 159) described it “We have for example a vivid internal picture of the external world.” The brain actually has multiple “TV screens,” i.e., multiple visual maps, which “look” at each other. So, here again, there is sort of TV screen, which should be optimized for the viewer. At the end reciprocal communications give rise to consciousness. Recently a key information compression mechanism has been discovered in the brain that operates in a manner very similar to the same mechanism used in digital television (Nortmann et al., 2013 ): for details of this see below. So a comparative study of both systems may have three useful consequences. It may reveal to what extent skillful TV engineers and Darwinian evolution come up with similar solutions to the basic problem of making the visual representational mechanisms more efficient. Discoveries of how the natural system works may give clues to digital TV designers for new mechanisms to try in their system. Likewise neuroscientists might look for any evidence that further mechanisms used by TV engineers also occur in the brain. Brain mechanisms We will first review what is known about the mechanisms whereby the brain processes visual information starting at the macroanatomical level. The visual system in the cortex is organized into two streams—the dorsal and the ventral (Ettlinger, 1990 ; Haxby et al., 1991 ; Gooddale and Milner, 1996 ). The dorsal goes from V1 to the parietal lobe and deals with visually guided behavior (“where” and “how”). The ventral goes from V1 to the temporal lobe and deals with object recognition and identity (“what”). These authors called these the “perception” and “action” pathways. The subtle relations between the concept of “where” and how mechanisms on the one hand and the “perception” and “action” pathways on the other have been addressed by Lebedev and Wise ( 2002 ). Then there is the color pathway that goes from V1 to V4 in the temporal lobe, and the motion pathway that goes from V1 to V5 in the middle temporal lobe. It has long been established that the brain's visual system processes information from the retina by three anatomically and functionally separate parallel distributed pathways that mediate color, form (Gooddale and Milner's ventral stream) and motion. Gooddale and Milner's dorsal path deals with organizing visually guided behavior and not perception. This tripartite system is supported by the evidence on how vision returns after injuries to the visual cortex. Schilder ( 1942 ) reports that the first faculty to return is pure motion, usually rotary, without any color or form. Then “space” or “film” colors appear floating in space. This is followed by objects, often only in parts such as the handle of a teacup. Lastly complete objects are seen into which the colors enter. In order to avoid unnecessary complications that tend to result from trying to translate directly between the technical terminology used in neuroscience and that used in digital television, we propose to use a neutral terminology as follows. The tripartite systems used in both the consciousness-related system in the brain and in digital TV may be identified as composed of the color system (V4), the motion system (V5), and a system that deals the construction of visual phenomenal objects (Object Construction System or OCS). These three systems may function independently, as in the cases reported by Schilder ( 1942 ). They can also be selectively deleted leaving only the other two to function. For example, in neuroscience, the color system is deleted in achromatopsia where the subject sees everything in black and white (Sacks, 1997 ). Thus, the OCS system can be identified as a black and white processing system. Cases in which motion is selectively deleted, or illusionarily added, have been reported in experiments using hallucinogens such as mescaline (Smythies, 1953 ). In one such case the subject reported, “The perception of a moving burning cigarette was a great surprise to me. Not a continuous line or circle was seen, as under normal conditions in the dark room, but a number of small glowing balls. At the end of the movement I could see the entire movement as it were fixed by a number of glowing balls standing in the air. T