Dream Catcher

The neuroscience of our night life

Dual Process Theories of Mind and Dreams

Dual process theories of Mind shed new light on the meaning of dreams.

Dual process theories of Mind are theories of Mind that are supported by literally thousands of experimental studies. In dual-process theories of the Mind two major information processing systems. “System 1” and “System 2”, are theorized to support most forms of cognitive processing. System 1 processes information in a fast automatic, pre-conscious or unconscious mode. Representations constructed by System 1 lack episodic content and are not tagged for time or place. Decisions are oriented toward loss aversion rather than risk taking. Outputs of System1 processes are experienced as involuntary or not generated by the voluntary Self. Brain structures activated during System 1 processing are centered on the amygdala, the ventral striatum, dorsal cingulate cortex, ventromedial prefrontal cortex and lateral temporal cortex.

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Conversely, System 2 processes information in a slow, effortful, conscious and deliberative manner. Outputs of System 2 are experienced as generated voluntarily by the Self. Representations require working memory capacity to construct and are tagged for time and place. Brain structures activated during System 2 processing are centered on the hippocampus, the rostral cingulate cortex, the lateral parietal and prefrontal lobes and the medial temporal lobe.

Are dreams a product of System 1 or System 2 processes? On the face of it most of the dreams we recall in the morning are experienced as involuntary events within which things happen to the Self. There is very little conscious, deliberative thought in these dreams and virtually no self-reflective thought (except in the special case of lucid dreams). These dreams that we recall in the morning are typically the vivid dreams that occur during REM sleep.

Interestingly enough the neuroanatomy of REM sleep is strikingly similar to the neuroanatomy of System 1. REM sleep is associated with high activation levels in the amygdala (a system 1 structure) and low activation levels in the dorsal prefrontal cortex (a system 2 structure). Therefore, REM sleep dreams appear to involve an activation of System 1 processes and a de-activation, or low level of activation in System 2 processes. System 2 processes can be engaged in REM dreams as there occasionally are dreams that appear to involve some amount of rational problem solving and deliberative thinking on the dreamer’s part. In lucid dreams dorsal prefrontal cortical activation occurs during REM and we get partial System 2 engagement.

If we assume that this equation of REM dreams with System 1 processes to be largely correct where does that leave non-REM dreams or specifically those dreams associated with N2 or Stage 2 sleep and sleep spindling phenomena?

Non-REM dreams are less bizarre, less emotional and less aggressive than REM dreams. In addition, rational deliberative thought and Self-reflection are much more common in non-REM dreams than in REM dreams. Thus, it may be the case that Non-REM dreams preferentially and partially engage System 2 over System 1 processes, while REM dreams do the opposite.

But System 2 is associated with conscious self-reflection. Is the dreamer in non-REM sleep conscious? The engagement of System 2 processes in non-REM dreams suggests that conscious thought would be possible in non-REM dreams. But if conscious, deliberative thought does occur in non-REM dreams it is not exactly like the consciousness experienced during waking life.

Focused, concentrated, protracted problem solving does not appear to occur often in either non-REM or REM dreams. When problem solving does occur in dreams it is often the end process of a deliberative chain of thought that occurred during waking life. The working memory-sensitive, inference driven, number crunching, deliberative thought of problem solving in waking life is hard to do in dreams, REM or non-REM. On the other hand the AHA! experience of insight can and often does occur in dreams. If waking consciousness allows for some hard thinking it can also interfere with insight. Dream sleep however discards the distractions associated with waking life and allows for apprehension of the right solution to the problems that regularly defeat waking consciousness.

Another area that needs to be addressed when referring to System 1 and System 2 processes in relation to dreams is the issue of sleep-related memory processing. But that will need to await a subsequent post unless my readers wish to address the issue?

 

Patrick McNamara, Ph.D., is Associate Professor of Neurology at Boston University School of Medicine and the author of numerous books and articles on the science of dreams.

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