The word imagination came from the Latin word ‘imagio’ or ‘imagin’, which simply means ‘image’. This word soon evolved and became ‘imaginari’, which means ‘to imagine oneself’. We have changed and edited this word and its meaning to such an extent that it now means ‘the faculty or action of forming new ideas, images or concepts of external objects not present to the senses’. Only recently has imagination been studied from a neuroscientific perspective, so very little is known about it. The neurological process that allows us to imagine things is not clear, with much debate surrounding the many theories within the field of cognitive neuroscience. Going back to the definition of imagination, it is arguable that the definition is partially incorrect, and in fact, some of the theories for the neuroscience of imagination go against that definition.
Imagination and The Senses
Most people have seen a dog, and most people have seen a dinosaur (a picture of one), but not many have seen a dog riding a dinosaur. Can you imagine it though? If you try, you’ll find that it’s certainly possible, but how exactly does the brain combine these two images to create something it has never seen before? The exact details of how we imagine things is not well-known, but we know that it has a lot to do with both the five senses and memory.
When you look at a dog, for example, a group of neurons related to dogs, called a neuronal ensemble, in the posterior cortex activates and then goes on to activate the visual cortex, which resides primarily in the occipital lobe . When you imagine a dog, we see that many of the same areas of the brain “light up” or are activated. The key difference between seeing and imagining is that the medial temporal lobe and hippocampus, areas involved in memory, are activated instead of the visual cortex . But this only works if we are using our memory to remember a dog we have already seen. How do we imagine something completely new, like a dog riding a dinosaur? The “Mental Synthesis Theory” proposes an answer for this.
The “Mental Synthesis Theory”
The “Mental Synthesis Theory” states that if the neuronal ensemble for a dog and that for a dinosaur are activated at the same time, then it is likely that the two will overlap, appearing as a single object, and you will see a dog riding a dinosaur. It is thought that the prefrontal cortex coordinates the neuronal ensembles that are activated at the same time in the posterior cortex. The distance between each ensemble and the prefrontal cortex is not always the same, so how does the message reach both at the same time? It is thought that differences in the amount of myelination within each pathway may explain this phenomena. Myelin can speed up the transmission of action potentials by 10, 100, or even 1000 times, so if a proximal destination has a lightly-myelinated pathway from the prefrontal cortex and a distal destination has a heavily-myelinated pathway from the prefrontal cortex, the message can still reach both destinations at the same time.
Once two things, such as a dog and dinosaur, are imagined together for the very first time, the amount of myelination on these pathways may change in order for the action potential to reach both neuronal ensembles at the same time . This occurs because the prefrontal cortex expects one to imagine these two objects together multiple times and tries to synchronize the firing. The “Mental Synthesis Theory” has helped us understand how we recall objects from our memory and incorporate them into our imagination.
Imagination and Creativity
It is thought that approximately half of our neurons sense the environment (sensory neurons) and the other half react to stimuli from it (motor neurons) with multiple possible paths from a single sensory neuron to a single motor neuron. Most extra paths are unnecessary links leftover from pruning during the development of the nervous system and are not very active or useful to us. Or so we think. In reality, these excess pathways are thought to be where random creative ideas stem from . Much is still unknown about this theory, but it seems that creative thoughts are the product of interaction of many parts of the brain and mainly the cooperation of the Default Mode Network and the Central Executive System . The Default Network is a group of brain regions that show lower levels of activity when engaged in a particular task, such as paying attention, and higher levels of activity when we are awake and not involved in any specific mental exercise, but rather daydreaming, recalling memories, imagining the future, or just “thinking" without any explicit goal. The Central Executive System is responsible for the control and regulation of cognitive processes. It coordinates working memory and long term memory. The Default Mode Network and the Central Executive System work hand in hand to create our random thoughts, which may develop into creative and innovative ideas.
Imagination and Hallucinations
Hallucinations have been defined as ‘perceptions in the absence of an external stimulus and are accompanied by a compelling sense of their reality.’ Hallucinations and imagination can be easily mistaken for each other, but there are some main differences to help distinguish them. While hallucinations are sensations that appear real to the person experiencing them, most of us know that what we perceive through our imaginations are not real. Though we can differentiate between these two experiences, the processes behind them are not fully clear to neuroscientists. Imagination is caused by a specific, external stimulus at some stage, while hallucinations are often signs of an illness, and their origin or why they occur is not very well understood. Additionally, people do not have control over their hallucinations but do have at least some control over their imaginations .
Going back to the definition of imagination (‘the faculty or action of forming new ideas, or images or concepts of external objects not present to the senses’), we see that it may be incorrect from a neuroscientific perspective, since usually one is not forming original ideas, but rather one is piecing together objects like pieces of a puzzle to form a ‘new’ idea. Imagination seems to always involve familiar pieces and never completely foreign objects; however, in saying that, we have only seen the tip of the iceberg of imagination. Although we do not currently know much about imagination, through research and further experiments we can uncover the true and complete process of imagination and the reason behind this fascinating process.
Hello! My name is Kimaya and I am a student at UNSW who aspires to work in the neuroscience field in the future. I am interested mainly in the auditory system as well as glial cells. Apart from neuroscience I am interested in reading novels, photography, and learning new languages- I can currently speak 5 languages.