Piero Scaruffi(Copyright © 2013 Piero Scaruffi | Legal restrictions )
These are excerpts and elaborations from my book "The Nature of Consciousness"
The nervous system is made of two main subdivisions: the central nervous system (the brain and the spinal cord) and the peripheral nervous system (in particular the autonomic nervous system that controls the heartbeat, breathing and other bodily functions).
This complex apparatus relies on a number of internal clocks: heartbeat (approximately one per second), breathing (approximately once every 4 seconds), REM sleep (4 or 5 times per night, at approximately 90 minute intervals), sleep/wake or “circadian” (every 24 hours), menstruation (every 28 days), hibernation (every 365 days), the thalamus’ rhythm (40 times a second), the amygdala's rhythm, etc.
All these "biorhythms" are registered in the brain, although they cannot be consciously perceived. The synchronization of such a complex system of biorhythms is accomplished by the brain.
In 1972 the US neurologists Robert Moore and Irving Zucker discovered that the suprachiasmatic nucleus (at the base of the hypothalamus), a cluster of about 10,000 neurons, keeps the central clock of the brain, the “circadian” clock, that dictates the day-night cycle of activity. The cells of the suprachiasmatic nucleus perform chemical reactions that take about 24 hours to complete. Those cells are connected to other regions of the brain and the products of their chemical reactions directly affect the activity of those regions.
Triggered by the suprachiasmatic nucleus, melatonin secretion starts after sunset, induces sleep and lowers the temperature of the body. Blood pressure starts to rise with sunrise. Then melatonin secretion stops and we wake up. We become more and more alert, as both blood pressure and body temperature increase. At sunset the cycle resumes.
Circadian rhythms are so common among species (even plants) that they may be one of the oldest attributes of life.
The importance of these clocks cannot be overlooked. The behavior of living organisms changes as the day progresses, because their clocks tell them so. It is not consciousness that tells us what to do: it is our inner clock that dictates much of our behavior. The brain is slave to its clock.
A circadian clock is actually present in every cell of the body: an isolated cell in the laboratory still follows a 24-hour cycle. What the suprachiasmatic nucleus does is to synchronize the 24-hour cycles of all the cells in the body.
We are controlled by several different clocks rather than by just one clock, a fact that appears to be a senseless complication. Part of the complexity of the brain may be due precisely to the need to "transduce" each of these rhythms into the other ones, otherwise different organs could not cooperate.
The operations performed by the various organs of the body occur in continuous quantities, not discrete quantities. For example, we can drink any amount of water (not only some set amounts) and exhale any amount of air. However, the “functioning” of those organs is discrete, not continuous: a clock sets their rhythm.
Somehow the body needs to “pace” each of its many internal functions. The clocks may exist precisely because they enable synchronization among wildly different organs that happen to depend on each other.
A number of biological clocks (many more than we have discovered so far) may be presiding over all the vital activities of the body. In other words, “life” might just be a store of biological clocks. Their rhythms “are” our lives”. These clocks activate programs that keep repeating the same functions at fixed intervals. As they operate and interact with many other such repetitive programs, we live, we act, we behave. Our behavior may simply be the outcome of those numerous programs repeating their mechanical actions. Besides the obvious ones for breathing, heartbeat, seeing, and so forth, there might be repetitive programs for detecting this or that feature of the world, for scanning memory, for learning new knowledge, and so forth, all of them running periodically in the brain over the available information.
Then there are the "brain waves" measured by electro-encephalograms. The frequency of 13-30 Hz ("beta waves") prevails in mental states of concentration, studying, stress (your brain is producing beta waves as you are reading this). Alpha waves (8-13 Hz are typical of states of relaxation and meditation. Theta waves (4-8 Hz) emerge in deep states of meditation, cases of religious ecstasy, and REM sleep. Young children are in theta most of the time. Delta waves (up to 4 Hz) characterize deep sleep. Babies are in delta most of the time. There are also gamma waves (25 to 100 Hz, but mostly 40 Hz) and mu waves (8-13 Hz, same band as the alpha waves, but the mu waves are specialized for the motor cortex).
A sine wave (or sinusoidal oscillation) is determined by three features: amplitude (the energy of each cycle, the difference between crest and rest), frequency (the number of cycles per second, which, given the velocity of propagation, also determines the wavelength, i.e. the distance from crest to crest) and phase. Signals are synchronous when they have the same phase (each cycle of the wave begins and ends at the same time). Coherence measures the phase consistency between two signals. Coherence is one, for example, when the two signals are perfectly synchronous. A signal is generally a combination of several frequencies, each with its own amplitude and phase. The fast Fourier transform is the mathematical technique that separates the various frequency components of a signal. A signal can be synchronous/coherent with another signal at some frequency but not at others. Traditionally, the electroencephalogram measures large-scale electrical activity in the brain. Depending on the mental and bodily state, the "signal" picked up by an electroencephalogram contains different frequencies. When the local electrical activity is measured, instead, local differences become evident.
The idea that the frequency components of the electroencephalogram have a specific function, and the application of mathematical analysis to the electric activity of the cerebral cortex, dates back to the Russian psychologist Mikhail Livanov, who organized a symposium in 1964 on "Mathematical Analysis of the Electrical Activity of the Brain". He speculated that the spatial distribution of these different frequencies through the cerebral cortex played an important role in our cognitive life. While studying rabbits, he observed that the electrical patterns in the motor and visual regions of the brain were synchronous when the rabbit was reacting to a visual stimulus, and concluded that functional correlation between two brain regions manifests itself in the synchrony between the corresponding brain waves.
Livanov, Mikhail: Spatial Organization of Cerebral Processes (1972)
Back to the beginning of the chapter "Inside The Brain" | Back to the index of all chapters