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The patient can't voluntarily report anything, or can report very little. In this case the patient would laugh or smile at jokes and do similar things because they are relatively involuntary acts. However, he could not move his body voluntarily. He took an amount of abuse because doctors and other people thought he was faking. They'd try to shake or threaten him out of it.
In about 1964 I took a course from Dr. Sebastian Peter Grossman in which he described the function of that area of the brain, and I realize what I may have been seeing about seven years before.
It's been years and I no longer have my note nor have been involved in the area. A MRI or even an EEG might detect the problem. However, it would take someone who even knows it exists or suspects it to look for it.