Different types of consciousness and thought processes are associated with major brain areas. The brain-evolution theories (Papez, MacLean) describe man as possessing three brains: the reptilian (top of brain stem); the old- or palaeo-mammalian (limbic system or limbic cortex); and the new, neo-mammalian or neo-cortex. Anatomically, the stem is encircled by the limbic system, and this in turn is enveloped by the neo-cortex, thus constituting a pattern of brain-within-brain. This system can be described as the brain's vertical structure. The horizontal structure is the division of the cerebrum into two hemispheres: the left brain and the right brain which, unlike the vertical, is now well-integrated, joined by the great cerebral commissure, or corpus callosum, although several thousand years ago the hemispheres may have acted independently or bicamerally (J Jaynes). Colin Wilson sees the right and left hemispheres as responding to each other in the same way as two comedians such as Laurel and Hardy react to each other's cues. Correspondingly, problems arise when cooperation breaks down. Wilson considers that the quality of consciousness can be enhanced by understanding the functions of each hemisphere and consciously trying to bring about control or cooperation between them.
Another feature of the brain affecting consciousness is its processing of images and other inputs to compare them with stored memories or anticipations. This creates an interference pattern between the two components and sets up a holographic redundancy, or distribution of "learning-experience" to be stored in many areas by the brain (K Pribram).
Consciousness in its different forms can be affiliated to the anatomy of the brain: the triple brain and the left and right brain being, currently, the most prominent examples. Consciousness can also be related or correlated to brain and blood chemistry (taking hormones and other substances into account); and to electrical brain waves (alpha, beta, epsilon, theta, etc). Consciousness as a function of the brain is also influenced by genetic traits. Consciousness, however, may not be totally reducible to brain functioning as certain phenomena, viz creative genius and extra-sensory perception, are not fully understood.
