ABSTRACT
Acquired language impairments following a brain lesion—aphasia—are usually the consequence of a left-hemisphere lesion (Lecours & Lhermitte, 1979). This fact has been known since the nineteenth century. First, came the unpublished, early, but intelligent, observations of a young surgeon, Marc Dax (1836/1865), who treated young soldiers with and without acquired language impairments after saber blows on the left or right side. However, the first published position paper concerning the relationship between language and the left hemisphere is attributed to Paul Broca (1865). Broca clearly stated that the same hemisphere was responsible for the dominant hand and for language, thus linking language abilities and the left hemisphere in right-handers. This statement proved to be largely, but not entirely, true. First, it rapidly became obvious that Broca's statement only applied to right-handers. The neurobiological bases of language in left-handers and ambidextrals follow other rules that are still unclear, such that a majority of left-handers will become aphasic following a left-hemisphere lesion (Joanette, 1989). Second, there is a small, but measurable, proportion of right-handers in whom language representation appears to depend heavily upon the right hemisphere, as exemplified by the occurrence of crossed aphasia (Bramwell, 1899; Joanette, 1989). Professor Luigi Vignolo contributed significantly to this literature on crossed aphasia. He published the first MRI-ascertained case of crossed aphasia (Faglia & Vignolo, 1990) and contributed to a thorough and critical review of published cases (Faglia, Rottoli, & Vignolo, 1990; Mariën, Engelborghs, Vignolo, & De Deyn, 2001). More than anyone else, Vignolo and his colleagues have made it clear that crossed aphasics' brain organization does not mirror that usually seen in right-handers, since a right-hemisphere lesion frequently affects both language and visuo-spatial abilities (Paghera, Mariën, & Vignolo, 2003). His interest in crossed aphasia has extended until recently, as he has contributed to an impressive and critical review of all cases of crossed aphasia, including some important methodological recommendations for future studies (Mariën, Paghera, De Deyn, & Vignolo, 2004). However, even if one limits oneself to right-handers—and to non-exceptional right-handers at that—Paul Broca's statement is still only partially true. The goal of this chapter is to describe the theoretical aspects and clinical implications of the right hemisphere's contribution to language abilities, and the impact on communicative abilities of a lesion in that hemisphere.
