NEUROPSYCHOLOGY OF DREAMING

  By Fonya Lord Helm, Ph.D., ABPP

It has been known for about fifty years that what we usually think of as dreaming occurs four or five times each night at intervals of about every 90 minutes, and that dreams last for periods of 10 to 40 minutes with the last period of dreaming being the longest. During these periods, the brain is very active, as active as when we are awake, but in a different way. There is a redistribution of regional blood flow in the brain and some of the areas that are active in waking are active during dreaming.

According to Hobson (1999), REM-sleep brain activation differs from that of waking in that there is selective activation of occipital, parietal and limbic zones with a selective inactivation of frontal regions. The human positron emission tomography (PET) data indicate that, during REM sleep, the pontomesencephalic brainstem and the limbic and paralimbic cortical structures are activated. Both brain imaging and brain lesions studies reveal an unexpectedly prominent role of the limbic system–the area most involved in emotion–in the selection and elaboration of dream plots. Large parts of the visual cortex are operating, but the frontal lobes that do our most sophisticated thinking are inhibited and for the most part shut down.

Subjectively, the dream is a visuomotor phenomenon, full of vision and a sense of motion as we are constantly moving through dream space. In the REM sleep of lower animals–rats and cats–the neurotransmitter acetylcholine increases greatly and serotonin and norepinephrine (noradrenaline) drop from their steady high levels during waking to almost zero. Hobson also thinks that this same neuromodulatory differentiation will be found in humans, too, and notes that recently Wilson et al. (1997) have demonstrated a REM-related decline in serotonin in humans.

Freud was prescient when he developed two models of dreaming: one in “The Interpretation of Dreams” (1900) that addressed ordinary dreams and the other in “Beyond the “Pleasure Principle” (1920) that addressed nightmares resulting from traumatic experiences.

In “The Interpretation of Dreams” (1900) Freud developed his first model of dreaming, worked with his own dreams, and put forward a wish-fulfillment theory of dreams. Freud’s second model of dreaming turns up twenty years later in “Beyond the Pleasure Principle” (1920) and presents the idea of the repetition compulsion as superceding the idea of wish-fulfillment in the traumatic dream. It is interesting that positron emission tomography (PET) scans show that larger areas of the brain are activated during nightmares and dreams related to specific trauma and that smaller areas are activated in during regular dreams that occur during rapid eye movement (REM) sleep. We know much less about nightmares and traumatic dreams, however, some of which may appear in REM sleep. Hobson (1999) also has found that night terrors, classic nightmares, and other manifestations of the motoric, emotional, and autonomic stormscan arise in NREM sleep, and automatic processes of a primitive and presumably subcortical origin can be released in NREM sleep. In fact, the experience of arousal from NREM sleep may be one of unmitigated terror.

 

References:

Freud, S. (1900). Interpretation of dreams. Standard Edition, 4&5: 1-627.

—–(1920). Beyond the pleasure principle. Standard Edition, 18: 1-64.

Hobson (1999). The new neuropsychology of sleep: Implications for psychoanalysis. Neuro-Psychoanalysis, 1: 157-183.

Wilson, C.L., James, M.L., Behnke, E.J., Fried, I., Bregin, A., Simmons, G., Mahan, C., Engel, J., & Maidment, N.T. (1997). Direct measures of extracellular serotonin change in the human forebrain during waking. Soc. Neurosci. Abstr., 23: 2130. (cited by Hobson, 1999)