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After an arm is amputated, the brain region that used to receive input from the hand is taken over by input from its neighbor on the somatosensory map, which is the face. Touching the patient's cheek therefore produces sensations felt in the missing hand, with a point-for-point map of the fingers on the face. This shows that adult brain maps are not fixed wiring but can reorganize within weeks.
Patients whose phantom arm felt frozen in a painful clench placed their intact hand in a box with a vertical mirror, so its reflection appeared where the missing limb should be. Seeing the phantom seem to move restored a sense of motion, and for some patients the clenching pain eased or the phantom shrank away. A cheap visual illusion overrode a pain that drugs and surgery had failed to treat.
The felt body is a model the brain assembles from vision, touch, proprioception and motor commands, not a direct readout of the flesh. When these signals conflict, the brain resolves the conflict in favor of whatever story is most coherent. That is why a phantom can feel frozen: sending motor commands to it without ever receiving confirming feedback can teach the brain that it is paralyzed.
The left hemisphere builds a consistent belief system and explains away evidence that does not fit, working like a spin doctor. The right hemisphere acts as a devil's advocate that detects serious discrepancies and forces the model to be revised. When the right parietal lobe is damaged, patients with a paralyzed left arm deny the paralysis and invent excuses, because nothing is left to trigger that revision.
In Capgras delusion, the pathway from face recognition in the temporal cortex to the amygdala is disconnected. The patient recognizes a parent's face but feels no emotional warmth, so the brain concludes the person must be an impostor. Skin-conductance tests confirm that the normal emotional response to familiar faces is missing, and the delusion is absent over the phone, where voice recognition uses an intact route.
Some patients with temporal lobe epilepsy have intense mystical experiences and become preoccupied with religion. Their skin-conductance response is heightened specifically for religious words and images. This suggests limbic circuits tag stimuli with emotional significance, and that when these circuits are over-driven, the sense of cosmic meaning and divine presence can arise directly from neural activity.