I This Week’s Citation Classic______CC/NUMBER 23 Meizack K & WaU P D. Pam mechanism®: a new theory. Science 150:971-9, 1965. [Dept. Psycho!., McGill Univ., Montreal, Canada and Dept. Biol., Massachusetts Inst. Technol., Cambridge, MA] I I The theory proposes that the dorsal horn of Descartes’ idea, proposed in 1664, that the spinal cord acts like a gate which modu- is like a bell-ringing alarm system lates the flow of nerve impulses from the whose sole purpose is to signal injury to the peripheral fibers to the central nervous body. system. The gate is influenced by peripheral “In the 1960s, a wave of new facts3 and fiber activity and by descending influences ideas that had evolved graduallyl- was from the brain. (The Science Citation Index~ beginning to crest, and the gate-control (SCI®) and the Social Sciences Citation Index® theory rode in on the wave of the times. No (SSCI®) indicate that this paper has been cited one was more astounded at its success than over 975 times since 1965.] we were. Naturally, acceptance was not im- mediate or total, but in spite of continuing controversy about details, the concept that injury-signals can be radically modified and even blocked at the earliest stages of Ronald Melzack transmission in the nervous system is now Department of Psychology virtually universally accepted. A fortunate McGill University aspect of our publication in 1965 is the use Montreal, H3A 1 Bi of the phrase ‘gate control.’ It evokes an im- Canada age that is readily understood even by those and who do not grasp the complex physiological Patrick D. Wall mechanisms on which the theory is based. Department of Anatomy The fact that the theory had relevance to a University College London wide variety of fields in medicine, psychol- London WC1E 6BT ogy, and biology also led to its frequent cita- England tion. “The theory’s emphasis on multiple deter- February 15, 1982 minants of pain has also provided a concep- tual framework for the recent recognition of the complexity of clinical pain. Until the “When we proposed the gate-control middle of this century, pain was considered theory in 1965, we hardly expected the primarily to be a symptom of disease or in- astonishing increase in research studies and jury. We now know that chronic, severe pain new therapeutic approaches that was stimu- is a problem in its own right that is often lated by it. Fortunately, the theory came at a more debilitating and intolerable than the time when the field was ripe for change. A disease process which initiated it. The prob- small number of original thinkers had lem of pain has therefore been transformed fought hard to replace the old concept of a from a mere symptom to be dealt with by specific pain pathway by a more dynamic the various medical specialties to a special- conception in which pain is determined by ty in its own right which is now one of the many factors in addition to injury—by past most exciting, rapidly advancing fields of experiences, culture, attention, and other science and medicine. Happily, the main activities in the nervous system at the time beneficiary has been the suffering person. of injury. This small band of courageous The new concept provided the foundation people hammered away at the established, and framework for a host of novel, exciting traditional theory. But despite occasional approaches to the treatment of pain. For a lip service to their ingenuity, the field con- recent survey4 the reader can refer to J.J. tinued unchanged, holding tenaciously on to Bonica et a!.”

1. MelucS R, StoderWA & Livingston W K. Effects of discrete brainstens lesions in cats on perception of noxious stimula*ion.J. N.urophysiology 21:353-67. 1958. 2. Mebads R & WaS P 0. in the nature of cutaneous sensory mechanisms. Brain 15:331-56, 1962. 3. Wall P 0. Presynaptic control of impulses at the first central synapse inthe cutaneous pathway. Progr. Brain Re:. 12:92-118, 1964. 4. Beaten Ii, Liebesiclad I C & Albe-Feasaid 0. Advances inpain research and therapy. NewYork: Raven Press, 19’79. Vol.3.956 p.

22 LS CURRENTCONTENTS® ~ 1982 by ISI® LI