BRAIN-BEHAVIOR RELATIONSHIPS - SOME MODELS AND RELATED STATISTICAL PROCEDURES FOR THE STUDY OF BRAIN-DAMAGED PATIENTS

The study of brain-damaged patients provides the opportunity to examin e the anatomy of brain functions, and has been renewed by the developm ent of structural neuroimaging, Despite the development of neuroimagin g and neuropsychological assessment, major uncertainties persist on th e exact delimitation of the brain areas involved in specific processes , and these contribute to the enduring controversies over the effectiv e lesions associated with neuropsychological disorders, These uncertai nties are mainly due to the methods used in the study of brain-behavio ur relationships, which frequently rely on a group comparison design. The aim of this study was to provide models for the study of brain-beh aviour relationships and to assess the reliability of related statisti cal procedures, In the present work, four theoretical modes of brain-b ehaviour relationship consistent with neuropsychological data are put forward: unicity, equivalence, association and summation. The first ex perimental study was based on a simulated population of patients, Lesi ons associated with the occurrence of a deficit were predetermined acc ording to modes of brain-behaviour relationship and were compared with lesions selected by statistical analysis, The study showed that (i) t he group comparison design did not allow determination of the effectiv e lesion, (ii) stepwise regression analysis was sensitive to the relat ive frequency of lesions, especially when the occurrence of a deficit depended on two lesions, but did not allow determination of the mode o f brain-behaviour relationship, and (iii) the classification tree test described the data very satisfactorily and permitted the determinatio n of the mode of brain-behaviour relationships, In order to assess the validity of statistical analyses, a second study was performed in whi ch lesion locations associated with motor weakness in stroke patients were examined, Selected lesions were compared with the anatomy of the human motor system. The study mainly showed that (i) the stepwise regr ession analysis of selected lesions was not related to the presence of a motor deficit, and (ii) the classification tree test provided perfe ct agreement with motor weakness predicted by lesion locations and sug gested an equivalence mode of brain-behaviour relationship consistent with current neurological knowledge. These studies provide models of b rain-behaviour relationships and related statistical procedures that m ay allow more precise documentation of the anatomy of brain functions and its pathology, and further investigation of the modalities of brai n-behaviour relationships.