How are external stimuli expressed in the mind? Thoughts, feelings and words are all used to express ideas and feelings for internal thinking. How then does internal thinking differ from thinking that is the result of sensory inputs? Is a visual input broken down into categories and each of those categories expressed differently in the mind?
So if someone sees a white dog they can categorize it at least two ways - 'an object the color white' and 'a dog'. Each of those properties of the dog might trigger a category in the mind.
How is that different than when you just think of a white dog to yourself, however? Are the same mental nodes triggered or does it have a different mental reaction?
The difference between real world stimulation and internal thinking could be compared to hearing someone speak versus thinking or reading the same material. How the persons mind responds differently might be explained by how their brain processes external vs internal stimuli.