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Extensive psychophysical tests were conducted on a patient with a well circumscribed tumor located just inferior and posterior to the retroinsular cortex of the right hemisphere. Statistically significant laterality differences were observed, with the left hand exhibiting: (1) a higher mechanical pain threshold, (2) a higher heat pain threshold, (3) a greater cold pain tolerance, and (4) a poorer ability to discriminate roughness. The patient was re-examined 2.5 months after operative removal of the tumor and was found to have regained normal sensitivity in his left hand. Pre- and postoperative MRIs showed resolution of the tumor's mass effect on the retroinsular and neighboring parietal operculum, which likely included the second somatosensory cortex. This dramatic change in sensory capacity signifies an essential role for the posterior insula and parietal operculum in normal pain and tactile perception.
Greenspan et al. (Wed,) studied this question.