The Central Nervous System: Correlates of Dreams and Waking Hallucinations

In a previous entry, I explored the connection between the visual system and visual hallucinations reported by individuals with schizophrenia. Since dreams can be understood as the nervous system’s processing of endogenous information, I was interested to understand and explore the correlation between dreams and hallucinations as they are processed by the nervous system.

            Research revealed a fruitful article by Mahowald, Woods, and Schenck titled, “Sleeping Dreams, Waking Hallucinations, and the Central Nervous System.” The authors note that the study concerns the critical evaluation of “the similarities and differences between dreams and hallucinations, with particular reference to the role of the central nervous system in each and with consideration of their patho-physiologic implications.” More of a review of the literature  than an empirical study, the article had 6 major headings: 1) dream mechanisms, 2) hallucination mechanisms, 3) dreaming and hallucinations: state disassociation models, 4) hallucinations (spontaneous and induced) in the non-psychiatric population, 5) dreams and hallucinations as a manifestation of consciousness, 6) hallucinations in neurological disorders.  For the astute reader, a copious and valuable four pages of references follows the article.

            The first section was standard enough. Their presentation of hallucinatory mechanisms stressed a view of endogenous brain activity being released when the individual is dissociated from stimuli: for instance, West’s theory argues that we are always in a dream state; we just are not attending to it because we are constantly stimulated—we can’t see the stars during the day, though they are still there.

            Section 4, while interesting, wasn’t my main interest in the article, as it presented topics such: fasting and sleep deprivation induced hallucinations (especially in religious/mystics), and drug induced hallucinations. Skipping ahead, the final section (6) provided more substance to several related areas, including: hallucinations in Parkinson’s and Alzheimer’s disease, phantom limb syndrome, and Charles Bonnet Syndrome.

            Finally, the fifth section (dreams and hallucinations as a manifestation of consciousness) had interesting correlates to schizophrenic hallucinations. We know that the brain is active during both REM and non REM sleep. Further, we can define consciousness as the brains awareness of all available data presented to it. While awake, this information is our environment, external stimuli. While asleep, however, this stimulus is internally generated. Further, we know from neuroimaging that during REM sleep there is a decrease in PVC (primary visual cortex) and Frontal Association activity. From this information, the researchers hypothesize that “the extrastriate cortices and paralimbic areas may be operating as a closed system, functionally disconnected from the primary visual and the frontal regions responsible for the integration of visual information.”

            Further evidence for this hypothesis that consciousness is maintained by the brain’s spatial and temporal mapping that integrates multiple brain areas can be seen in the fact that both during REM and the wake state there is a 40 Hz oscillatory rhythm throughout the cortex. Such a rhythmic oscillation may provide a continuous “neuronal humming” whereby internal or external irregularities would be conspicuous. What is most interesting is that this rhythm is reset during the wake state by sensory stimuli…but it is not reset during REM sleep.

            The theory, then, is that some deviation of either the spatial or temporal regularity of this rhythm may be at the root of some hallucinations—specifically those experienced by individuals with schizophrenia. Much of the literature uncovered, however, focused squarely on the differences between dreams and hallucinations. The convergence of these themes proved fertile, and we can most certainly anticipate further research involving this intersection. More so as our neurobiological techniques and understanding increases. For instance, it was only 40 years ago that the REM phasic event intrusion hypothesis was offered as an explanation for waking hallucinations in schizophrenia, but this theory was never verified because the prevailing assumption at the time was that dreaming was confined to REM sleep only!

References

Mahowald, M. W., Woods, S. R., & Schenck, C. H. (1998). Sleeping dreams, waking

hallucinations, and the central nervous system. Dreaming, 8(2), 89-102.

doi:10.1023/B:DREM.0000005899.59224.17

by +Phillip J. Kuna

for John G. Kuna, Psy.D. and Associates

drjohngkuna.com