how is the brain able to give us images when we are imagining something?
In: Biology
The visual system of the brain is a very layered system. The early layers detect things like brightness and edges. This gradually gets built up into things like basic shapes, and depth, and contours, and then into recognizable items. These recognizable items become recognizable simply due to the repetitive nature of your exposure to them; i.e. if I show you a random shape enough times, it is no longer ‘random’ but rather becomes ‘that one shape’ in your mind.
Now, let’s take a recognizable item, say a rose. This rose has many things associated with it. Think of the rose itself as the center hub in a bicycle wheel… each spoke might extend to something that you associate with the rose; the smell, the color, your first girlfriend, thorns, gardening, the tango.
Of course, this wheel was also not ‘built in’, but rather ‘built’. What I mean by that, is that these associations also form over time, over experiences. This happens when neurons ‘fire together’. This is called Hebbian learning. So, when I visually see the rose, and I also smell it, these two things get bound together: associated. The more this happens, the stronger this bond becomes, and the more likely that one will ‘appear’ in consciousness when the other is imagined or represented in some way.
Anyway, back to this rose.
Now, you have probably been imagining this rose. Which is a funny way to get to the point of your question. It makes sense that reading about a rose, and seeing the word ‘rose’, would also be part of this bicycle wheel. So, it also makes sense that your brain would have stored some ‘template’ for what I am writing about. This makes sense, so that YOU can make sense of the world.
What is important to think about and remember here, is that your mental imagery of the rose is exactly that… it is YOUR mental imagery. You and I might have very different ‘roses’. If I lived in a place that normally had white roses, like the ones my mother grows, well then I might be imagining a white rose, while you are imagining a red rose.
In any case, the imagination is probably driven from the ‘top’ (i.e. high level process) down to the low level (i.e. lower visual areas). I imagine (haha) that the concept is first activated, i.e. let me think of a rose, and then this activates a chain of neural activity which kind of ‘backward’ activates all of the visual connections which make up your ‘template’ rose.
Remember, ‘neurons that fire together wire together’. This means, every time you see a rose, it will have general characteristics. Maybe it has a long stem, and then a big round top. So, the neurons which encode for long stems and round tops are firing every time you see a rose. Then, it branches into times where you saw white ones, and red ones, and yellow ones. You can imagine each of them, I am sure. It is like walking down a path, and you can deviate left into the neural activation for the white rose, or straight ahead for red, or maybe to the right for the yellow one.
Are you simply changing the color? Or does the form change too? There are really interesting questions to think about this topic, and it is a fascinating topic indeed. In any case, if you asked me (which, in some way, you did), I would attribute the imaginative process to these ‘association wheels’ combined with a Hebbian learning process which creates networks for repeated experiences. Imagination is then the calling up of these pre-established networks.
I hope that could give a little insight! I am sure a researcher focusing on imagination could give an even better answer, and perhaps refute or confirm some of the things I am saying, but these are my thoughts on the topic.
Source: am Neuroscientist.
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