The cerebrum is the vehicle through which we negotiate reality. I have two meanings here: one physical, the other conceptual. In a context defined by others, the cerebrum enables us to coordinate our bodies to accomplish specific acts. When we have the power to define the context, the cerebrum synthesizes knowledge and imaginings in a way that enables us to manifest reality. Naturally, these characterizations are didactic extremes: in most circumstances, we participate simultaneously in both types of negotiation.

The cerebrum is organized in cortexes and lobes. It is covered in folds, the deepest of which are called sulci.The nerve bodies are most dense in the gray tissue of the folds, and the lobes and cortexes are connected to each other and the rest of the nervous system by axons bundled in tracts. The most prominent of these is the corpus callosum, which connects the left and right sides of the brain, but there are also intra-lobular tracts that run from front to back. The right side of the brain is generally recognized as tying more deeply into our emotional and intuitive response to events, while the left side is involved in abstract interpretation of experience. Typically, men tend to think more "left", while women are generally "right". (Er - are you all OK with that?)

Running from ear to ear over the top of our head are the homonculous lobes, responsible for interpreting our tactile senses and controlling our voluntary movements. Under our temples are the lobes responsible for speech and interpretation of sound. At the back of the brain is the visual cortex, and lobes responsible for visual association. Abstract thought seems to occur primarily in the forebrain, just behind the forehead.

It is fun to experiment with the balance of energy in these systems. It is fairly easy to isolate the visual system, and the auditory system. Sensory deprivation tanks are designed to defeat our tactile responses. As one center shuts down (reduces its demands on the energy supply available to the brain), other centers become more active. My experience is that exposure to these states, and some practice, eventually leads to a conscious facility in manipulating our cerebral activity.