How do we “see” with our eyes closed when we are dreaming?
—Robert J. Evans, via e-mail
Robert O. Duncan, a behavioral scientist at York College, the City University of New York, explains:
as you suggested by the phrasing of your question, people don’t actually see in their dreams. Sight depends on light entering the eye and stimulating the retina—something that doesn’t happen when we are lying in the dark with our eyes shut. Nevertheless, studies that compare the vivid imagery of dreams with daytime vision reveal similar patterns of activity in the visual cortex, the largest brain area devoted to vision.
That is why some researchers believe dream visions come from visual centers in the brain. In the mid-1970s dream researcher J. Allan Hobson and his colleagues at Harvard Medical School proposed that the brain spontaneously generates electrical pulses while dreaming. These signals, known as PGO waves, originate in the visual cortex and in two other visual regions of the brain: the pons and the lateral geniculate nucleus.
PGO waves are most prominent during rapid eye movement (REM) sleep, the part of sleep when most dreaming occurs. The spontaneous activity from PGO waves may start in the visual areas of the brain but ultimately creates a cascade of activity that taps into the brain regions that house memories.
But not all investigators agree that dream imagery originates in visual areas. Several dream researchers have proposed the opposite path, suggesting that dreams originate in the regions that store memories and then connect to visual brain areas. This theory would explain why dream images are only as detailed as our memories.
For instance, let’s say you are thinking of your grandmother. Your memory of her might not include the mole she has on the right side of her face, something you would clearly see if you were sitting next to her. The lack of detail that is characteristic of memory occurs also in dream visions.
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10 Comments
Add CommentYou could be off a little on your theory on where dream images come form. Have you ever asked a person who was born blind what kind of dreams they have? Do 'at birth' blind people see images or sound in their dreams? If a 'at birth' blind person dreams, can they even explain to you what they see since they do not know color or images, but only what they feel in their environment.
Reply | Report Abuse | Link to thisIn managing computer databases, new data is often stored very quickly in order to keep pace with arrival rates and data acquisition requirements. It's common practice to reorganize and optimize the storage of the recently acquired data at a later time, when demands are less stringent.
Reply | Report Abuse | Link to thisIn fact, database management software often requires that database access be shut down during this process, which can further encode data to reduce total storage requirements and to build relationships and indexes to the data to optimize retrieval performance and enhance functionality.
These methods employed to manage 'short term' and 'long term' memories may likely also be employed by the brain. The most appropriate time to perform these 'offline' tasks would be during sleep.
Or he could be spot on with this theory of the origin of dreams in the brain. If someone was born blind, they would never have an memories of colors or images, so it could still be going off the data stored in his memories.
Reply | Report Abuse | Link to thisIndeed, and it might explain why people with sleep deprivation have so many cognitive problems.
Reply | Report Abuse | Link to thisI wonder, it a lack of dreaming, rather than a lack of sleeping has similar effects on the mind.
Good question. A quick check indicates there have been some studies with deprivation of rapid eye movement sleep only, but I don't find any study of its effect on memory functions.
Reply | Report Abuse | Link to thisBy the way, my comment was meant to infer that the manipulation of memories during sleep likely accounts for the visual effects during dreaming and its correspondence with rapid eye movement, indicating that it is the process of memory recollection and alteration that stimulates the visual system.
In managing computer databases, new data is often stored very quickly in order to keep pace with arrival rates and data acquisition requirements. It's common practice to reorganize and optimize the storage of the recently acquired data at a later time, when demands are less stringent.
Reply | Report Abuse | Link to thisIn fact, database management software often requires that database access be shut down during this process, which can further encode data to reduce total storage requirements and to build relationships and indexes to the data to optimize retrieval performance and enhance functionality.
These methods employed to manage 'short term' and 'long term' memories may likely also be employed by the brain. The most appropriate time to perform these 'offline' tasks would be during sleep.
The manipulation of memories during certain periods of sleep likely accounts for the visual effects during dreaming and its normal correspondence with rapid eye movement, indicating that it is the process of memory recollection and alteration that stimulates the visual system.
It is likely the reencoding of memories (which may include constructing pointers to shared common features to reduce neuronal allocation requirements) and their indexing or association with other memories that likely contribute to the perception of surrealistic experiences while dreaming. The rapid eye movement may indicate that these processes occur at relatively high speeds, unencumbered by other physical events.
How about visual experience in dreams being produced from synesthetic motivation.
Reply | Report Abuse | Link to thisThat is the - that the visual cortex is being investigated by alternate sense modalities which although active during the original storing of memories - were overridden by the need for visual perception during the original conscious representation of the visual scene. So whilst conscious perception fulfils the needs of the important visual modality, other sense modalities 'scan' the original scene from the their own perspective for salience.
This might be why we move during our sleep. the body is scanning individual modlities from the perspective of alternate modality perspectives.
Perhaps the question we should first ask is how does the brain construct an image outside of us? The eyes only input information, it is the brain that creates the illusion of what lies beyond us.
Reply | Report Abuse | Link to thisI have had dreams in both color and black and white. I don't (consciously) see in black and white, so why would I dream in black and white?
Reply | Report Abuse | Link to thisA person born blind still has the visual processing parts of the brain. Those parts just don't get visual input from the eye. I'm not sure what those parts of the brain do without input but other than gradual decrease in mass from lack of use, the brain matter is still there.
Reply | Report Abuse | Link to thisI dream in color and sometimes black and white. My guess is that the black and white dreams are where colors are not as important as other recorded inputs.