Amber Badgerow
November 7, 2011
PSY 213
John Olmsted
The Phenomenal Production of Dreams
Question:
Dreaming is an amazing phenomenon. It involves vivid visual, kinesthetic, and audio mental imagery that occurs while one is asleep and has only a partial connection to environmental stimuli. The function of dreaming is in much debate and a popular topic of research, but not as much research has been devoted to the neural mechanisms of dreaming. How are dreams, that incorporate mental sensory imagery, emotional experiences, and cognitive processes, generated?
Prediction:
Dreams may involve similar networks associated with daydreaming/mind wandering and the mind’s eye. The production of dreams may be a more or less whole brain process that incorporates the Parieto-Occipito-Temporal junction (PTO), which is responsible for perceptual processing, the frontal lobes of the brain, and the limbic system. This would connect sensory, memory, thought process, and emotions to dreaming.
Article 1: “Cognitive and emotional processes during dreaming: A neuroimaging view”
This article was written by Martin Desseilles, Thien Thanh Dang-Vu, Virginie Sterpenich, and Sophie Schwartz to collectively review neuroimaging studies on rapid eye movement (REM) sleep that provide insight into the neurobiology of dreams. REM sleep is associated with more vivid dreams and more occurrences of dreams compared to non-rapid eye movement (NREM) sleep. Neuroimaging of the brain has showed that the basal forebrain, the pontine tegmentum, the limbic/paralimbic region, and the thalamus have increased brain activity during REM sleep. Studies have also found that the basal ganglia, cerebellum, and the primary motor and premotor cortices (all motor regions) are activated during REM sleep, which could relate to the movement element in dreams. It has also been found that, while the primary visual cortex is inactivated during REM sleep, the visual association regions show significant activation. This could indicate that mental visual information is processed in a network separate from that of external stimuli processing, which would explain how those with blindness caused by brain damage can still have visual dreams. Activity was seen in the precuneus, suggesting a correlation between dreaming and the default mode network (DMN), which has been proposed to form a central imagery network through high-level cognitive processes that promote mental imagery. Furthermore, activation of the temporal and occipital cortex during REM sleep might be the underlying mechanism of auditory and visual content in dreams. During REM sleep, decreased activity in the parietal cortex and the lateral and inferior prefrontal cortex could explain why people easily accept bizarre elements of dreams and exercise little control over dreams' proceedings. Activation of the medial prefrontal cortex may contribute to a dreamer's ability to associate emotions, intentions, and thoughts to people in dreams. These studies give an idea of the neural mechanisms that produce the sensory, emotional, and cognitive elements of dreams.
Article 2: “The neural substrate for dreaming: Is it a subsystem of the default network?”
G. William Domhoff wrote this article to present studies that support the idea that the neural mechanism of dreaming is related to the default network. Neuroimaging has shown that the default network is active during simulation, mind wandering, and daydreaming. Studies have also shown activity of this network during the onset of sleep and some activity during REM sleep. Lesion studies, that associated the anterior cingulate cortex, medial prefrontal cortex, basal forebrain, and the limbic region with dreaming, were supported by neuroimaging studies that found that those same regions were more active during REM sleep than NREM.
The auditory and visual association cortices, the pontine tegmentum, and the occipital-temporal lobe have also been found to be active during REM sleep. More recent studies show that the dorsolateral prefrontal cortex is more active in REM than NREM, which differed from earlier studies that found the region to be less active during both stages of sleep. The neural mechanisms of dreams have a connection to the default network because they both promote unregulated thought that is independent of stimulus. Research by Smallwood and Schooler provide similarities between mind wandering and dreaming. Simulation can be involved in mind wandering as in dreaming, but also involves self-reflective unsystematic thinking. Functional MRI studies of mind wandering further support the connection since many of the brain regions activated during sleep/dreaming were also active during mind wandering. A study by Christoff et al. (2009) identified the two fundamental governing brain areas of the default network- the dorsolateral prefrontal cortex and the dorsal anterior cingulate cortex. Subsystems of this network were suggested by further studies. However, there is evidence that the posterior regions of the default network are not very active in REM sleep, which has caused scientists to doubt the possibility of the dreaming network as a subsystem of the default network. Yet, still others reason that the dream subsystem has no need for external monitoring or episodic memories and therefore may be able to function without those areas. The similarities cannot be ignored and only further research can help determine whether the workings of dreaming are a subsystem of the default network.
Source Validity:
Although both sources were from credible authors, they were collective reviews of numerous studies, which has both positive and negative aspects toward validity. Collective reviews provide
numerous sources of specific information that can be seen as a whole. Also, they present repeated studies to ensure accurate results. However, it is difficult to examine the methods, subjects, and particular goals of each study referenced. Therefore, the validity/reliability of each source in a collective review is somewhat unknown. The author of a collective review is also able to extract only certain information from studies for his or her purposes. Since there was a single author, the second article is more questionable as bias could be a greater issue. Despite these issues both articles presented useful information to understanding the neurobiology of dreams.
Reflection on Hypothesis:
The research supported my hypothesis that the neural mechanisms of dreaming involve the PTO, frontal lobes, and limbic system and may be related to the default network. It also revealed that the visual and auditory cortices were active during REM sleep, which is associated with dreaming.
Works Cited:
Desseilles Martin, Dang-Vu Thien Thanh, Sterpenich Virginie, and Schwartz Sophie. “Cognitive
and emotional processes during dreaming: A neuroimaging view.” Consciousness and
Cognition 20.4 (2011): 998–1008. Elsevier Inc. ScienceDirect. Web. November 7, 2011.
http://0-www.sciencedirect.com.library.pcc.edu/science/article/pii/S1053810010001935
Domhoff G. William. “The neural substrate for dreaming: Is it a subsystem of the default
network?” Consciousness and Cognition 20.4 (2011): 1163–1174. Elsevier Inc.
ScienceDirect. Web. November 7, 2011.
http://0-www.sciencedirect.com.library.pcc.edu/science/article/pii/S1053810011000468
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