Mind and Body Possessed: Schizophrenia and Rapid Eye Movement Behavioral Disorder
Auditory and visual hallucinations are primary symptoms observed in the 1.1 percent of the American population who suffer from Schizophrenia (1). Strikingly, the hallucinatory nature and the individual’s interaction with these episodes bare strong resemblances to aspects of Rapid Eye Movement Behavioral Disorder (REM Behavioral Disorder), a sleeping disorder that is recognized by an individual’s physical interaction, or “acting out,” of a particular dream experienced (2). Many people who suffer from Schizophrenia demonstrate violent behavior, as do people with REM behavioral disorder during the REM phase of sleep in which dreaming occurs (3, 4). The presence of hallucinations leading to violent behavior in two separate and distinct disorders, one in which the individual is awake and alert and one in which the individual is asleep and in a low state of consciousness, raises the question: What accounts for the similar characteristics observed in both disorders?
A common misconception of schizophrenic patients among people is that they are “split personalities,” and this can be attributed to lack of knowledge of the disease (5). Today, through extensive research and greater understanding of the nervous system, brain and its expression through behavior, biological explanations are proposed to hypothesize the mode for hallucinations experienced by Schizophrenic individuals. Studies have found that a lack of corollary discharge signals is the cause of schizophrenic hallucinations. One study consisted of measuring the corollary discharge signal level in a group of individuals, a fraction of whom were healthy and a fraction of whom were Schizophrenic. The healthy subjects had a normal level of corollary discharge signals whereas the test subjects who suffered from Schizophrenia lacked an adequate amount of these interneurons. This correlation led researchers to believe that there was a direct link between corollary discharge signals and Schizophrenia in individuals (6). By this, schizophrenia, a disease recognized by its symptomatic hallucinations, could be explained in terms of a malfunctioning nervous system. It is hypothesized that the nervous system, in all individuals, attempts to generate voices independently when there is no auditory stimulus present. The role of corollary discharge signals in this case is to notify the rest of the nervous system to ignore that self-fabricated stimulus, and as a result there is no physical display of interaction with these voices in healthy individuals. Under circumstances where there is a lack of corollary discharge signals, there is an interaction between fabricated input neurons and regular output neurons, and as a result the individual experiences hallucinations with which they interact explicitly under the impression that the auditory pseudo-stimuli are true voices (7).
Rapid Eye Movement Behavioral Disorder is a psychiatric disorder discovered in 1986 that occurs during the Rapid Eye Movement (REM) phase of sleep (2). Under normal conditions, during the REM phase of sleep, one undergoes atonia, or muscle paralysis, preventing the body from performing physical activity during sleep (2). Individuals who suffer from REM Behavioral Disorder exhibit symptoms such as acting out their dreams with physical activity during sleep that range from simple twitching of muscles to very violent behavior (2) that could ultimately cause serious injuries to the affected individual and those surrounding them.
Another phase demonstrates similar properties to REM. Hypnagogia is a mental state that occurs immediately before an individual falls asleep, or rather the stage of “border-line” between the state of being awake and asleep (9, 8). The phase consists heavily of hallucinations including the experience of sensations involving visual, auditory and physical stimuli, all of which are reminiscent of dream sensations that could occur during the REM stage of sleep (9).
The hallucinations that occur during Hypnagogia and the REM phase of sleep suggest a relation of mechanisms between Schizophrenia as well as the sleep disorder REM Behavioral Disorder. Furthermore, the similarity between the hypnagogia stage right before sleep and the REM stage during sleep suggests that the former is the onset of a lack of corollary discharge signals that result in hallucinations with which one interacts during the REM stage.
From the muscular point of view, it could be speculated that the lack of corollary discharge signals impedes the ability to cease muscular movement and sustain paralysis throughout sleep. Under normal conditions, muscle paralysis would occur, however during REM in individuals with REM Behavioral Disorder, muscle paralysis fails to take course and the individual is able to physically enact their dream (2). From a consciousness point of view, a lack of corollary discharge signals renders the ability for the individual to ignore any interaction with visual and auditory illusions during dreaming, this being analogous to the lack of corollary discharge signals preventing the disregard of fabricated auditory stimuli in Schizophrenics.
So then, where is the divide between Schizophrenic hallucinations and REM dreams that not only exhibit similar characteristics, but also can be accounted for by the same source: lack of corollary discharge signals? To account for this, the I-function could be considered as the factor of difference between these two disorders, since it is the fundamental instrument of consciousness.
The I-function is an abstract element of the nervous system whose function is to recognize one’s state of being. At the neuronal level, the I-function is able to recognize or become aware of a particular state if neurons are able to communicate properly in order to form the nerves that extend down the central nervous system and branch throughout various regions of the body. Thus communication is made possible via corollary discharge signals, or interneurons, whose lack of adequate presence can alter the state of consciousness. Since Schizophrenia and REM Behavioral Disorder both lack sufficient levels of corollary discharge signals, we can infer that they are each individually altered states of consciousness.
The underlying similarities between Schizophrenia and REM Behavioral Disorder can be explained with the corollary discharge signal model. The critical value of corollary discharge signals is proven in both neurological disorders, given their purpose to serve as the links within the nervous system that complete the nervous system circuit and enable it to function properly. Lower levels of corollary discharge signals however can ultimately have the affect of altering the state of consciousness of an individual. But perhaps the most striking feature of these signals is the divide it creates between hallucinations in Schizophrenia and dreaming in those who suffer from REM Behavioral Disorder. There is a fine line between the two states of consciousness during hallucinatory episodes in Schizophrenics and the violent outbursts during dreaming in REM Behavioral Disorder patients, and the presence, or rather absence of corollary discharge signals is a governing factor in both disturbances.
7) Paul Grobstein notes, Neurobiology and Behavior, March 2008