William James, the father of American psychology, wrote gloriously about consciousness a hundred years ago. But following James, his field became dominated by behaviorism which focused exclusively on experimental methods with measurable data. Because conscious awareness can neither be observed nor measured, the very concept became marginalized, and consciousness became quite literally a ?dirty word? in academic psychology for most of the 20th century. Beginning in the late 1980s, consciousness re-emerged as an important scientific topic, but has remained largely hidden in psychology?s closet. One reason, I believe, is that psychology is wedded to a strictly computational view of brain function.
Modern science views the brain as a computer, with firings of individual nerve cells, or neurons, playing the role of ?bit states? in silicon. The notion of discrete brain neurons was established by Spanish neuroanatomist Santiago Ramon-y-Cajal in 1909, eclipsing the previous view put forth by Italian scientist Camille Golgi of the brain as a tangled syncytium of uninterrupted filaments. Networks of discrete Cajal neurons connected by variable-strength synapses can perform computation, process information and explain cognitive brain functions like sensory processing and control of behavior. Neurons are viewed as integrate-and-fire switches, no different from simple technological devices. Networks of simple neurons give rise to complex behavior.
But consciousness remains mysterious. Though they represent great advances in scientific understanding of the brain, non-conscious cognitive functions are nonetheless referred to as ?easy problems?, ?zombie modes? or ?auto-pilot?.
What about consciousness? How do we experience emotional feelings and vivid awareness? That consciousness does not naturally derive from computation among neurons has been famously termed the ?hard problem? by philosopher David Chalmers. But if consciousness does not emerge from computation among neurons, from where does it emerge? We have some clues.
1) A finer scale Maybe neurons aren?t so simple. Single cell organisms like paramecium swim around, avoid obstacles, find food and mates and have sex, using their internal cytoskeleton for information processing and movement. The cytoskeleton is not only each cell?s bone-like support and dynamic motor, but also its on-board computer. Inside neurons, extensive cytoskeletal networks organize synapses, modify neuronal structure, engage in memory and are damaged in Alzheimers disease. Beneficial effects of anti-depressant drugs on conscious mood require weeks to occur because of the need for time-consuming cytoskeletal remodeling inside neurons. Cytoskeletal structures are suggested to be molecular-level information devices, and perhaps even quantum computers. So rather than emerging from computation among simple neurons, mechanisms underlying consciousness are likely to extend downward in size to a finer scale inside neurons.
2) Moves through the brain Consciousness and non-conscious modes are not always separable. We often walk or drive while daydreaming, seemingly on auto-pilot with consciousness somewhere else. But when novelty occurs we consciously perceive the scene and assume conscious control. Consciousness can somehow tune into and take over auto-pilot functions. When things return to normal, our consciousness again wanders and the auto-pilot resumes monitoring and control. So the essential conscious/non-conscious distinction is between neuronal computation which at any given moment is, or is not, accompanied by some added fleeting feature which conveys conscious experience and choice. Consciousness is likely to involve some collective neuronal activity which moves through the brain?s neuronal networks, able to tune into and take over non-conscious auto-pilot function.
3) Sideways circuits The best measurable correlate of consciousness is gamma synchrony EEG, electrical oscillations in the high frequency range from 30 to 90 Hz. Evidence suggests gamma synchrony moves through the brain?s neuronal networks, correlating with conscious experience and choice. For example when our conscious minds are ?in the gutter? (thinking about sex) gamma synchrony is occurring in ventral tegmentum and nucleus accumbens, brain regions concerned with pleasure and reward. But gamma synchrony doesn?t derive from neuronal computation. Gamma synchrony is driven by ?sideways circuits??neighboring neurons fused together by electrical synapses called gap junctions. Neurons woven together in this way are subsets of Golgi syncytia (termed dendritic webs or hyper-neurons). ?Finer scale? conscious processes inside neurons of Golgi syncytia can spread and unify through gap junctions. As gap junctions open and close, Golgi syncytia move through the brain as spatiotemporal envelopes of gamma synchronized neurons, conveying a conscious agent able to experience and control?tune into and take over?otherwise non-conscious functions.
As a metaphor consider a passenger airplane cruising on auto-pilot. The conscious pilot is present, but not directly in control?perhaps he/she is reading a magazine, chatting in the main cabin or even sleeping and dreaming. Suddenly turbulence occurs, or an alarm sounds. The conscious pilot ?tunes in and takes over?, directing his/her attention to the view and instrument readings in the cockpit, and assuming motor control of the plane, correcting course or elevation to avoid the turbulence. When the situation is resolved the auto-pilot resumes monitoring and control of the plane, and the conscious pilot resumes previous activities, perhaps visiting with a flight attendant in the galley.
In the brain, Cajal?s neurons compute non-conscious auto-pilot functions. But Golgi?s syncytia are the conscious pilot, moving through neuronal networks to tune into and take over otherwise non-conscious auto-pilot functions.
To approach an understanding of consciousness, psychology must expand its narrow focus on simple neurons arranged in complex synaptic networks. Psychology must look sideways, to gap junction-mediated synchronized circuits, and inward, inside neurons to finer scales of organization.
Stuart Hameroff M.D.
Professor, Anesthesiology and Psychology
Director, Center for Consciousness Studies
The University of Arizona, Tucson, Arizona
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