Principles of bilingual aphasia assessment and interpretation of findings / Michel Paradis

Principles of bilingual aphasia assessment and interpretation of findings / Michel Paradis. In "Perspectives neuropsycholinguistiques sur l'aphasie - NeuroPsychoLinguistic Perspectives on Aphasia", colloque international organisé par l'Unité de Recherche Interdisciplinaire Octogone de l'Université Toulouse II-Le Mirail (France). Toulouse, 21-23 juin 2012.

Assessment:Because patients may recover each of their languages to vastlydifferent extents (parallel, differential, successive, selective,blending, (alternating) antagonistic recoveries and selectiveaphasia) (Paradis, 2008), all languages previously spoken by thepatient should be assessed. Not testing one of a patient’slanguages may have detrimental social and/or clinical consequences.It is therefore no longer ethically acceptable to assess aphasicpatients on the basis of the examination of only one of theirlanguages. However, the evaluation instrument should not be a meretranslation of a battery designed for, and standardized in, anotherlanguage, for a number of reasons: For instance, syntacticconstructions, such as the passive in English, are rarely if everused, or are much simpler, in some languages. Hence, mosttranslations will not yield interpretable results. Correspondingitems in another language must be selected so as to tap the sameinformation as the original, in accordance with the rationale thatmotivated the construction of the items in the first place. The testsmust be functionally equivalent and directly comparable, task bytask, with respect to both degree of difficulty and nature of thematerial being tested, well beyond its cultural compatibility. Thisis why the Bilingual Aphasia Test was designed. Its various versionsare culturally and linguistically equivalent and criteria ofcross-language equivalence vary with each task (Paradis, 2011). 
Interpretationof test results: It is important to realize that manifestations ofaphasia symptoms differ across various languages in accordance withtheir specific structures. The reason why a certain type of error ismore prevalent in one of a patient's languages may be due to one ormore of several factors: The incidence of obligatory contexts, thefrequency of use of a structure in a given language, the structuralcomplexity of the item; the presence or absence of redundancy;whether nouns and verbs exist as bare roots or must necessarily beinflected; whether, when inflections are omitted the remaining formis pronounceable or not, and whether the form is memorized orderivable by rule – namely, regular or irregular (Paradis, 2001).The type of error depends on the type of aphasia, but potentialerrors in each case are constrained by the structural characteristicsof each language. 
Inaddition, for a meaningful analysis that leads to effectiverehabilitation, the age of appropriation, the degree of practice ofL2, as well as the age at time of assessment in case of a latelearned L2, must be taken into consideration. Depending on the ageand manner of acquisition and the degree of use of a second language,its cerebral representation will depend on different cerebralmechanisms. Early acquired languages rely to a great extent onautomatized implicit linguistic competence that is subserved byprocedural memory whereas later learned languages rely to a greaterextent on consciously controlled explicit metalinguistic knowledgethat is subserved by declarative memory (Paradis, 2008). As a result,double dissociations are observed in the better preservation of thefirst language (in amnesia and Alzheimer's disease) or of the secondlanguage (in aphasia, Parkinson's disease, and psychoses) These agefactors may also affect the transfer of therapeutic benefits from atreated to a non-treated language.