When the brain surgeon, Dr. Wilder Penfield stimulated certain brain cells with electrodes, long forgotten conversations, songs, jokes and childhood memories were evoked from his patients.
If your brain registers everything that pours into your senses, then you should learn how to elicit that information from your brain's storehouse.
Certain concentration skills can be learned to help initiate this process.
As a practice exercise, obtain and arrange the following materials.
Cut a 15" X 15" square of black construction paper and paste a white 6" X 6" square in the center of it.
Attach this paper arrangement to a light colored wall at about eye level (when seated in a chair).
Seat yourself about 3 feet away and get in a comfortable, relaxed position.
Close your eyes and for a couple of minutes, visualize a giant blackboard in your mind.
Let distracting images pass on by, but keep your blackboard clear.
Now open your eyes and gaze at the center of the square for 2 or 3 minutes.
Move your eyes to a spot on the wall alongside the paper pattern and observe the after-image.
When it starts to fade, imagine it is still there.
Now close your eyes and recreate the whole pattern in your mind's eye.
Keep it as steady as possible on your mental blackboard.
Repeat the procedure 2 more times.
As a variation of the above exercise, cut a 15" X 15" square of black construction paper and paste a white 10" wide 5-pointed star in the center of it.
Repeat the same gazing and visualizing procedure as before.
Now visualize zooming in on the star to within a close proximity of it.
Now zoom out to a point where it is very small.
Repeat this process 2 more times; then see it back to normal size again.
Now view it upside down in your mind's eye; then slowly rotate your perspective in a circular motion around it.
Then reverse your rotational perspective and circle around it the other way.
Practice with other forms, pictures and objects and increase your eidetic imaging skills.
As a further exercise, cut a 15" X 15" square of white construction paper and paste a 6" diameter circle of sky blue paper in the middle.
Attach it to the wall at about eye level, and seat yourself in a relaxed position about 3 feet away.
With closed eyes, visualize your mental blackboard.
Now open your eyes and look at the blue circle.
Mentally zoom in towards the circle and then back out again.
Repeat several times.
Next, while looking at the center of the circle, mentally rotate your conscious awareness around the circle -- slowly at first, then faster and faster, then back to a slower revolution, then stop.
Practice for no more than 10 minutes per day on each exercise, and soon any page in your study book can be reflected onto your mental blackboard for review.
Eliminate verbalizing (internally or externally) during these exercises, because the formation of eidetic images can be adversely affected.
Mere after-images are only the initial stages in eidetic imagery, and eventually evolve to more complete visual detail later.