Mysterious form of referred sensation in man.

Abstract

A phenomenon is described in which scratching a small excrescence on the skin on one part of the body is referred to a distant point as a "prick" or a "tingle." "Referral" points are elicited mainly by absent-minded scratching of the skin when attention is not focused on the local sensation produced by the scratch. Location of "referral" points seems to follow definite patterns: in all instances, "referral" points occurred on the same side of the body as the "stimulus" points; each "referral" point was rostral to its "stimulus" point; and each "stimulus" point was associated with only one "referral" point. "Stimulus' and "referral" points seem to have a fixed relationship. Pathways from a "stimulus" point to a "referral" point are not known at present. Although parallels can be drawn between this phenomenon and Bender's "double simultaneous stimulation" phenomenon, both remain mysteries.For many years I had occasionally observed that scratching the skin on one part of my body-for example, the knee-elicited a very brief unmistakable sensation of a "sting" or "prick" on some distant part-for example, the tip of the shoulder. Somehow it did not occur to me until 5 years ago to keep records of each effective scratch "stimulus" and of each resulting "referral" point.This Fig. 1 shows one of these charts with only three views of the body and gives records of -the phenomenon elicited on different parts of the body on three occasions. Xs mark stimulus points; dots mark "referral" points. Lines join each of the three pairs: I, scratching a spot on the left leg below the knee elicited a "sting" just posterior to the left axilla; II, scratching a spot just above the left knee resulted in a "sting" just anterior to the left axilla; III, a scratch on a spot on the inner surface of the right knee elicited a "sting" on the middle of the lower right back. RESULTSConditions That Favor Appearance of Phenomenon. These were: (i) absent-minded scratching-e.g., during reading, writing, talking; (ii) warm, sweaty skin; (iii) wearing light, loose clothing; (iv) generally relaxed frame of mind.Anatomy of Stimulus Point. In most instances, each stimulus point occurred over a usually just perceptible excrescence on the skin. The excrescences were just barely large enough to offer slight resistance to the nail of the scratching finger.Nature of Referral Point. We have had difficulty in describing the sensation of the referral response to the scratch. It can be described either as a "sting," a "prick," or a "tingle," but in any case it is a clear-cut sensation. It occurs instantaneously with the scratch, rarely lasts more than a second or two, and usually becomes refractory to any further immediate scratching. In some instances, however, immediate repetitions of the scratch four or five times within a few seconds elicited a "sting" with each scratch.Thus far, we have not found that referral points can be detected either by sight or touch. We have not actually been able to locate many referral points with any degree of accuracy bec...

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