Piero Scaruffi

These are excerpts and elaborations from my book "The Nature of Consciousness"

Dreams as a Chemical System Hobson thinks that, whether asleep or awake, the brain always does pretty much the same thing. The dreaming brain employs the same systems and processes as the brain when awake, except that those processes are not activated by stimuli from the outside world; that the outcome of those processes does not result in (significant) body movements; and that self-awareness and memory are dormant. The input, the output, the processor and the working space of the brain while awake are replaced by something else; but the “software” is the same. What makes a difference is the neurotransmitters that travel through the brain. What differs between awake and asleep states is very small, but enough to alter dramatically the outcome: during sleep the brain is bombarded by erratic pulses from the brain stem and flooded with nervous system chemicals of a different sort. Neurotransmitters make brain circuits more or less sensitive.  Aminergic neurotransmitters originate in the brain stem and terminate in the amygdala. Cholinergic neurotransmitters originate in the basal forebrain and terminate in the cortex. During waking states, the brain is controlled by the aminergic neurotransmitters, made of molecules called "amines". During sleep, the brain is controlled by the cholinergic neurotransmitters, made of a molecule called "acetylcholine". Cholinergic chemicals free the system used for cognition and behavior. They paralyze the body by sending pulses to the spinal chord, even though motor neurons are always in motion. Hobson’s idea is that wake and sleep are two different chemical systems hosted in the same "processor". These two chemical systems are in dynamic equilibrium: if one retracts, the other advances. This means that our consciousness can fluctuate between two extremes, in which either of the chemical systems totally prevails (neither is ever completely absent). This also means that the brain states of wake and sleep are only two extremes, between which there exists a continuum of aminergic-cholinergic interactions, and therefore a continuum of brain states.  This system can be said to control the brain.  It resides in the brain stem and from there it can easily control both the lower brain (senses and movement) and the upper brain (feelings and thought). When it doesn't work properly, when the balance of chemicals is altered, mental diseases like delirium occur. It is not surprising that diseases such as delirium are so similar to dreams: they are driven by exactly the same phenomenon.  Hobson claims that the brain is in awake, dream or (non-REM) sleep mode depending on whether amines are prevailing, cholines are prevailing or amines and cholines are "deadlocked".  Three factors account for the brain behavior at any time: activation energy (amount of electrical activity), information source (internal or external) and chemical system (amines or cholines). When activation energy is high, the information source is external and the mode is aminergic: the brain is awake.  As activation energy decreases, the external information source fades away and amines and cholines balance each other: the brain falls asleep.  When activation energy is high, the information source is internal and the mode is cholinergic: the brain is dreaming.  During an hallucination: activation energy is high, the information source is internal and the mode is aminergic.  In a coma: activation energy is low, the information source is internal and the mode is cholinergic.  The extremes are rare and usually traumatic. Normally, both external and internal sources contribute to cognitive life, and both amines and cholines contribute to the brain state. The interplay of external and internal sources means that our perceptions are always mediated by our memory.  Hobson thinks that our brains do not merely react to stimuli: they also “anticipate”.  The internal source tells us what to expect next, and thus helps us cope with the external source.  Emotions are, in a sense, a measure of how well the internal source matches the external source: anxiety is caused by a major mismatch, whereas contentedness is a sign of matching sources.  When we dream, the spinal cord is paralyzed and the senses are disconnected.  This is because of the cholinergic neurotransmitters that come from the brain stem. Hobson believes that sleep has the function to reinforce and reorganize memory: ultimately, to advance them from short-term memory to long-term memory.  Amines are necessary for recording an experience, while cholines consolidate memory. Again, it looks like during REM sleep memory is consolidated.  The aminergic system is responsible for attention, focus, awareness. The cholinergic system is responsible for the opposite process: focus on nothing, but scan everything.  As for the content of dreams, Hobson thinks that they reflect a biological need to keep track of place, person (friend, foe or mate) and time. He draws this conclusion from considerations about what is typical (and bizarre) of dreams: disruptions in orientation. The bottom line is that dreams are meaningful: the mind makes a synthetic effort to provide meaning to the signals that are generated internally (during a dream, memory is even "hypermnesic", i.e. is intensified).  Wishes are not the cause of the dreaming process, although, once dreaming has been started by the brain stem, wishes may be incorporated in the dream. Therefore, Hobson thinks that dreams need not be interpreted: their meaning is transparent.  Or, equivalently, dreams must be interpreted in the realm of neurophysiology, not psychology. The interplay between the aminergic and the cholinergic systems may be responsible for all conscious phenomena (for Hobson, dreams are as conscious as thinking) and ultimately for consciousness itself. After all, conscious states fluctuate continuously between waking and dreaming. Dreams, far from being subjective, are "impersonal necessities forced on brain by nature".   Back to the beginning of the chapter "Dreams" | Back to the index of all chapters