The Dream State

Biology 202
2000 First Web Report
On Serendip

The Dream State

Jessica Miller

Sigmund Freud noted as the Father of modern Psychology, believed that the function of dreaming was to allow the release of repressed instinctual impulses in a way that would preserve the ability to sleep, and that the instigating force causing dreams to occur was always a repressed thought or wish. Though Freud was an avid student of neurobiology, at the time when his suppositions were created scientists were unaware of certain aspects of the nervous system that today make Freudís theory unlikely (2). The stages of sleep, the biology of the brain, and the retention of dream memories all suggest an idea similar but contrary to Freudís theory. These factors lead one to believe that dreams are in fact not always subconscious or repressed thoughts, but often just the mindless ramblings of the brain and nervous system.

To understand dreaming, one must first be aware of the stages of sleep and what each entails. Dreaming is divided into four main categories differentiated by levels of brain activity and the depth of sleep. Stage one dreaming is a very light stage of sleep, lasting only a few minutes, during which the dreamer can be easily awoken by occurrences in the outside world. Next follows stage two sleep, in which the dreaming process begins in the form of vague thoughts, and unclear images drifting about the dreamers mind. Stage two is a much deeper state of sleep than stage one, however, any outside disturbance will quickly succeed in awakening the person. The sleeper continues into stage three sleep, during which muscles relax and heart rate, blood pressure, and breathing slow and become steady and even. Waking a person at this stage of sleep is very difficult. In stage four sleep actual dreaming occurs, blood pressure and heart rate fluctuate, and the brain heats up(5). This is the stage when REM (rapid eye movement) occurs, therefore this stage is often called REM sleep(4). The sleeper will experience REM for approximately a ten-minute period, and will continue to cycle through REM and non-REM sleep until woken up (5). Another important aspect in the explanation of dreaming is an understanding of the portions of the brain, which work together to create and terminate dreams and the dreaming state (i.e. REM sleep). A variety of nuclei and brain regions are involved in the initial production of the REM state, including the amygdala, hippocampus, right temporal lobe, and especially the brainstem nuclei located in the lateral and medial pons(1). REM sleep begins with signals from the base of the brain called the pons. The pons are associated with ritcular activity, and send signals to the region of the brain called the thalamus, which intern passes them along to the cerebral cortex for interpretation. While the pons are sending signal to the thalamus, they are also sending signals to the spinal chord, which shut off motor neurons making it impossible for the body to move during sleep and dreaming(3) . Similarly, cerebral blood flow increases in the right temporal and parietal regions during REM. These stages are followed by abnormal and enhanced activity in the right temporal and temporal-occippital area, which causes an increase in dreaming and REM sleep for an uncharacteristically long period of time. The brainstem is the most important actor in dream production, for it controls the steady and specific oscillations between REM and nonREM sleep, the same system that controls body and mind activation in waking periods(4). Overall, dreaming and REM sleep are associated with high levels of activity in the brainstem, occipital lobe, and other nuclei(1).

Though these parts of the brain are all active during REM sleep, it is important to know that the two hemispheres of the brain work unilaterally in dreaming. The right hemisphere of the brain actually creates and displays the dream, shown by an increase in blood flow and electrophysiological stimulation in that hemisphere during REM. The right hemisphere uses a form of visual-spatial and emotional language, which creates the themes and images of the dream through remembered emotions. These sorts of memories, such as those used as the material for dreaming, and those that later will become the remembered dream are called lateralized memories, for they are only remembered by one hemisphere of the brain, the right(1).

Therefore, due to the lateralized remembrance of dreams, the left hemisphere of the brain must access the memories of the right brain when a person is asked to describe a dream or even to remember it. To access the memory banks of the right hemisphere, the left hemisphere must use the corpus callosum or anterior commissure. The left hemisphere of the brain is involved primarily in the encoding and recall of verbal, temporal sequential, and language related memories. As a result, dream interpretation becomes very difficult due to the fact that the left hemisphere is forced to interpret what the right brain has created using a language the left brain does not understand. This accounts for the often sporadic and non-sequential order of dreams, for the right brain, which created the dream, cannot establish sequences. Therefore, the left hemisphere must try to put a dream in order when it is interpreting it. On rare occasions, a person may experience a dream during non-REM sleep, a dream created entirely by the left hemisphere of the brain. These dreams are typically devoid of imagery, being more like a running monologue and interestingly, it is during this type of dreaming that one may talk in his/her sleep(1).

Dreaming has been seen in many forms since the beginning of time, but this seemingly unexplainable event is simply explained by the connections of neuron cells, which we call the nervous system. By exploring such aspects as sleep stages and REM sleep, we can locate where and when our dreams occur. Likewise, the anatomy of the brain, and its firing during dream periods gives the scientist new insight into the purposes which dreaming serves. These purposes have often evaded humanity in the past due to the simple fact that one could never remember their dreams, due to a now understood phenomenon of unilateral communication between the two distinct hemispheres of the brain. Perhaps Freud was correct in assuming that dreams were the key to understanding suppressed or subconscious thought, but perhaps dreams are just a jumble of left over thoughts and images of our days, and the real subconscious thought comes in the form of how we interpret them.

WWW Sources

1) The Neurobiology of Dreaming and Dream Sleep

2) Dreaming, Function, and Meaning

3) Dreaming and REM Sleep

4) Dream Theory 1997: Toward a Computational Neurocognitive Model, by John Antrobus

5) The Dreaming Process

 

 

Comments made prior to 2007

I just read a page about dreams and the subconciuos mind. Its prety good, but there are so many big words, if you know what I mean. Its hard to follow, having to stop and remember the meaning of each word. But its slowly making sense ... Heather, 10 October 2006