Synesthesia comes from the Greek "syn" (meaning union) and "aisthesis" (sensation), literally interpreted as a joining of the senses. Synesthesia is an involuntary joining in which the real information from one sense is joined or accompanies a perception in another. Dr. Cytowic reports extensive research into the physical, psychological, neural, and familial background of a group of synesthets. His findings form the first complete picture of the brain mechanisms that underlie this remarkable perceptual experience. His research demonstrates that this rare condition is brain-based and perceptual and not mind-based, as is the case with memory or imagery. "Synesthesia" offers a unique and detailed study of a condition which has confounded scientists for more than 200 years.

The Committee of Neurotraumatology of the World Federation of Neurosurgical Societies decided to elaborate a Glossary of Neuro- traumatology, and for this purpose appointed a subgroup of members of this Committee, headed by Dr. E. S. Gurdjian, whose report follows this preface. The main reason for the Committee's decision was the hope that the diffusion of the Glossary through "Acta Neurochirurgica" may bring about a better understanding of neurotraumatological terminology on a worldwide scale. The Glossary should facilitate the classification and the comparison of traumatic lesions of the Nervous System. It will consequently be easier to compile statistics and correctly interpret the informations thus obtained. The very commendable initiative of the Congress of Neurological Surgeons in revising the terminology of head injuries and in publishing this work in Vol. 12 (1966) of "Clinical Neurosurgery" constitutes an important contribution. In 1977 the Glossary now presented endeav- ours to complete and bring up to date the definitions of anatomical or physiological modifications in the neurotraumatological field. We wish to express our thanks to Dr. Gurdjian and to the other members of the Neurotraumatological Committee who were responsible for the elaboration of this Glossary and whose efforts to standardise, as much as possible, the language used by scientists of different nationalities, have resulted in a better understanding between neurosurgeons.