From Towards a Science of Consciousness 3 CogNet Proceedings Module
As we walk along a sidewalk, various forms of sensory information from our visual input, sound, swinging arms and contact between our feet and pavement somehow synthesize into a sequence of coherent experiences. Although we take this for granted, exactly how the brain accomplishes this synchronization is not well understood. For example neural conduction time from the sensory neurons of our feet, legs and spinal cord would seem to deliver information about our feet contacting the pavement significantly after visual and auditory experience of the same events. Bergenheim et al. (ref) studied this problem and concluded that the brain somehow compensates by jiggling sensory input to provide a proper frame for timed events. A related problem is how we account for our rapid responses that seem to occur before we are actually conscious of them. In fast-paced activities such as Ping-Pong, and rapid-fire conversation we seem to act almost reflexively, with conscious appreciation lagging slightly behind our seemingly conscious actions (Gray, Penrose). How is this possible?
The whole issue of time in conscious experience is strange, for physics tells us there is no necessary forward flow of time; time just is (e.g., as space just is). If time were really flowing, then in what medium would it be flowing (e.g., minutes per what?). Nevertheless in conscious experience time does seem to flow, although occasionally at different rates. In certain states subjective (internal) time seems to slow down while the external world speeds up, and vice versa. How does the brain manifest the flow of time?
In 1979 Benjamin Libet described a series of experiments performed on patients undergoing neurosurgical procedures under local anesthesia. Thus the subjects' brains were exposed and accessible while they were conscious and communicative. Libet, a neurophysiologist, took advantage of this situation to perform studies that remain widely discussed and enigmatic to this day. Basically Libet and his neurosurgical colleagues stimulated the patients peripherally (e.g., on their finger), and on corresponding regions of sensory cortex and thalamus. They recorded EEG, and most importantly, asked the patients to report precisely when they became consciously aware of the stimuli. As described in the first chapter in this section by Stan Klein, the patients responses were somewhat surprising. For example when stimulated at the finger, the onset of conscious experience was almost immediate, whereas stimulating the corresponding sensory cortex mapping of the same finger resulted in conscious experience only after a significant delay. To account for these and other results Libet concluded that somehow the brain appreciated sensory input after a significant delay but corrected the timing by referring the conscious signal backward in time! Libet's data and conclusions have been widely debated, with quite different interpretations. Some physicists take the backward time referral seriously, as supportive evidence for a quantum mechanism in consciousness. Others believe classical, nonquantum explanations suffice. The debate continues in the first two chapters in this section.
In "Do Apparent Temporal Anomalies Require Nonclassical Explanation?" Stan Klein reviews Libet's findings as well as the arguments and controversy surrounding them. He comes down on the side of classical explanations. In "A Quantum Physics Model of the Timing of Conscious Experience" Fred Alan Wolf takes the opposing view, explaining how quantum mechanisms can account for backward time referral.
In the final chapter in this section "Conscious and Anomalous Nonconscious Emotional Processes: A Reversal of the Arrow of Rime?" Dick J. Bierman and Dean Radin describe a series of experiments that purportedly demonstrate backward referral of emotional experience. Their results have engendered a great deal of controversy because, if true, backward time referral and quantum mechanisms are implicated in day to day, and moment to moment consciousness.
Bergenheim, M., H. Johansson, B. Granlund, and J. Pedersen. 1996. Experimental evidence for a synchronization of sensory information to conscious experience. In Toward a Science of Consciousness: The First Tucson Discussions and Debates (S. R. Hameroff, A. W. Kaszniak and A. C. Scott, Eds.), Cambridge, Mass.: MIT Press, pp. 303 -- 310.
Gray, J. A. 1998. Creeping Up on the Hard Question of Consciousness. In Toward a Science of Consciousness II: The Second Tucson Discussions and Debates (S. R. Hameroff, A. W. Kaszniak and A. C. Scott, Eds.), Cambridge, Mass.: MIT Press.
Penrose, R. 1994. Shadows of the Mind. New York: Oxford University Press.