A contribution to the study of environmental dependency phenomena: the social hypothesis.

Environmental dependency phenomena refer to the symptoms initially described by Lhermitte (1983, 1984) under the terms of "utilization behavior" and "imitation behavior". These clinical signs are linked to essential notions such as free-will and human autonomy, and seem to be specific of the frontal pathology. Surprisingly, few studies have addressed these symptoms and inconsistent definitions are available. To investigate the theoretical and clinical definitions of environmental dependency phenomena, three groups of neurological patients (n=60) with frontal, subcortical, and posterior brain lesions were compared. Clinically, our findings help to rehabilitate the definitions of Lhermitte (1983, 1984) and challenge the classical interpretation in terms of an executive control deficit. The frontal specificity of the disorders and the lack of relation between executive/behavioral deficits were supported. The right orbitofrontal cortex seems particularly involved in environmental dependency. These results offer some evidences for differentiate two historical concepts of neuropsychology, namely the "frontal" and "dysexecutive" syndromes. A new interpretation of environmental dependency phenomena is provided which could be helpful to orient the neuropsychology of frontal syndrome.