Dreaming as a purely physiological response

Activation-Synthesis Model

       In 1977, two boundary-breaking researchers proposed a revolutionary theory of dreaming.  In essence, they claimed that dreams do not bear deeper meanings, as many of us think they do, and that they are simply responses to the body’s active physiology that occurs while we sleep. Summing it up in a two-part process, the researchers proposed the activation-synthesis model of dreaming. The first part, the activation aspect, suggests that parts of our brain become very energized during REM sleep and create random information.  The activation that generates this information blends with our own memories, which are already in storage. The blending of the activation and the stored memories, in turn, synthesize a dream. Contrary to the more commonly held view that dreams initiate REM sleep, this view proposes that REM sleep, or the brain’s physiological activation, causes dreaming.(Keep in mind that this theory was proposed much earlier than the theory of the neurology of dreaming discussed on the previous page.)   The researchers further assert that we shouldn’t look to our dreams as bearing deeper meanings or as the manifestation of our unconscious minds, but rather as meaningless and random images created by our bodies’ physiological processes.

The activation portion of the model

       In detail, the theory suggested that while we sleep a location in the brain stem occasionally is activated and creates electrical impulses. This same location controls physical movement and sensory input, which is information coming into the brain from the environment, when we are awake. And while we are asleep, bodily movement is prevented from occurring and the incoming information is prevented from entering our brains.   This happens in order to prevent us from acting out our dreams and also to ensure a good night’s sleep.  The motor output is controlled by mechanisms in the brain stem and so, even if the brain is sending the body messages to move, they cannot be fulfilled. The researchers propose that this may be why we experience the odd sensations of movement during our dreams, such as the inability to run or the eerie feel of slow and controlled movement. The second point to the theory states that the only muscles that are allowed to express themselves are those that control the eyes.  This is why REM sleep is accompanied by rapid eye movement.

       The theory also discusses why dreams are not manifestations of the unconscious mind, such as wishes and repressed images.  It is asserted that because the sleep stage of REM is predictable, the secret truths that present themselves in dreams would appear at any time during sleeping states and not during timed intervals. (However, we now know that dreaming does occur outside of REM sleep). Furthermore, the authors of the theory discussed the differences in the duration of REM sleep across animals.  The bigger the animal, the longer it will experience REM. This provided additional evidence that dreaming, as a function of REM, was completely physiological.

       The pontine brain stem, which is located at the very base of the brain on the posterior end, was thought to be the structure that controlled and created dreaming.  In research performed on cats, this structure of the brain involved neural activity – the firing of neurons – with its peaks that correlated with stages of REM sleep. Further research showed that when the neural firing was diminished, REM sleep ceased and stimulation of the brain stem caused REM sleep to occur more frequently and last for longer periods of time. The attempts to recreate this phenomenon by means of conscious behavior were never successful and therefore the researchers believed that conscious processes couldn’t be controlled by psychology, but rather by physiology. 

The synthesis portion of the model

       It is during the synthesis process of the model that dreams are created. Although the authors didn’t suggest that there wasn't a psychological basis to dreaming, they did assert that psychology or traditional psychoanalytic views could no longer explain dreaming completely. As their research showed that the occurrence and duration of dreaming is predictable and operates on a consistent schedule, they interpreted dreams to be the creations of a clock controlled by the brain’s physiology.

       Moreover, the activation of dreaming is occurring internally, from the electrical energy produced by a relatively simple structure of the brain.  It was thought that when the activation reached the more sophisticated areas of the brain, these structures tried to make sense of them by producing fluid and connected images and appropriate, coherent storylines. The synthesis portion of the model proposes that the irrational narratives of dreams is due to the mixing of the electrical energy of the brain stem with stored images in memory and the brain’s efforts to invest them with meaning. More exactly, the bizarre nature of dreams is a result of the sheer random occurrences of the electrical impulses of the brain.

       In explanation of the extreme amount of memory loss of dreaming upon waking up, the founders of the activation-synthesis model suggested a theory that challenged the popular Freudian theory.  Freud claimed that our attempts to repress our dreams, in the event that they were highly disturbing, explained why we rarely have vivid recollections of our dreams. Contrary to this, researchers have argued that the chemicals that aid in consolidating short-term memories to long-term memories are inhibited during REM sleep. Also, the chemistry of our brain quickly alters when transitioning from a sleeping to wakeful state. The lack of proper consolidation of the memory of our dreams and the altering brain chemistry cause us to forget our dreams. This, it is claimed, occurs unless we experience a very impacting dream or wake up during or immediately after it.


  • Back to Dreaming Main Page
  • Rem and its traditional association to dreaming
  • Characteristics of dreaming and further connections to REM sleep
  • New discoveries of REM and dreaming as associable mental states
  • Conclusion and other implications of dreaming