عنوان مقاله [English]
One of the most important and latest issues in neuro-linguistic studies relates to the nature of and the difference between aphasias resulting from damage to the cortical and sub-cortical brain structures in bi/multilingual aphasics. In this paper, language disorders and recovery patterns in two bilingual Azerbaijani Turkish-Persian aphasics with sub-cortical brain lesions were studied. The study was a field research which utilized descriptive statistics. Research population consisted of bilingual aphasics in Zanjan Province who had sub-cortical lesions. For this study, two aphasics were selected from the population. The Turkish and Persian versions of Bilingual Aphasia Test were employed to explore the linguistic behavior of the subjects and to collect the required data. The findings showed that the first patient suffered Broca’s aphasia in both languages. The second patient was diagnosed with Broca’s aphasia in Azerbaijani Turkish and sub-cortical aphasia in Persian. Thus, based on the type of aphasias and the location of brain lesions in the subjects of this study, it appears that the presence of lesions in the sub-cortical area does not necessarily lead to similar language disorders in the first and second languages of the bilingual aphasics. The language recovery patterns of the first and the second subjects were judged to be parallel and differential, respectively. The results revealed that the neuro-linguistic theory of bilingualism and the declarative/procedural memory model could be used to explain the differences in syntactic performance between bilingual aphasics with sub-cortical damage. Research and instructional implications of the study were discussed.
One of the most important and latest issues in neurolinguistic studies is the nature and differences of aphasias resulting from damage to the cortical and sub-cortical brain structures in bi/multilingual aphasics. In 1982, the sub-cortical aphasia was officially considered to be a type of aphasia along with other kinds which had been identified previously. The sub-cortical aphasia happens following lesions to the thalamus and basal ganglia.
Aphasia has been defined from different perspectives. From a neurological perspective, aphasia is an acquired language impairment resulting from a focal brain lesion. This language impairment can be present in all language components (phonology, morphology, syntax, semantics, pragmatics), across all modalities (speaking, reading, writing, signing), and in the output (expression) and input (comprehension) modes.
Traditionally, aphasia seemed to be the result of damages to the brain cortex. However, in the recent decades, using the recent neuroimaging techniques, it became obvious that the subcortical areas in the brain play vital roles in language processing and representation, too. Concerning its complexity and different symptoms, aphasia is divided into different syndromes including Wernicke, Broca, conduction, transcortical sensory, transcortical motor, anomia, global, mixed transcortical and subcortical types.
The issue worth exploring in neurolinguistic studies is the bi/multilinguals with aphasia. Since, they are considered to be unique subjects due to their specific linguistic characteristics which make them different from the monolingual aphasics. One of their unique features is their language recovery patterns. Multilingual individuals differ among themselves according to a number of parameters that may each play a role in shaping any given aphasic patient’s recovery pattern. Different bilingual aphasia recovery patterns are as follows:
1. Parallel recovery; it is called parallel when recovery of each language is proportional to its premorbid proficiency.
2. Differential recovery; it is called differential when it does not reflect premorbid proficiency: one language is recovered better than the other in unexpected ways; the difference between the two may be much greater than before or sometimes the previously least proficient is recovered best.
3. Successive recovery; it describes a pattern where one language remains unavailable until it is spontaneously recovered weeks or months after the other has reached a plateau.
4. Selective recovery; it is selective when one language is never recovered. Sometimes comprehension is retained but the language is unavailable for production.
5. Antagonistic recovery; when one language is recovered first, but it regresses as a second language becomes available and progresses. Sometimes this phenomenon recurs over a period of days, weeks, or months during which language availability alternates. This pattern is called alternating antagonism.
6. Mixed or blending recovery; some patients are unable to speak one language without continually switching back and forth. The aphasics blend two languages in the same way that some monolingual aphasic patients blend words or syntactic constructions. It’s worth mentioning that these recovery patterns are not generalizable and all the patients may not demonstrate the abovementioned patterns.
In this paper, two bilingual Azerbaijani Turkish (L1)-Persian (L2) aphasics with subcortical brain lesions from Zanjan province were studied to determine their aphasia type, linguistic profile and language recovery pattern. Doing this research may have the following consequences: 1) it can be useful in developing and introducing the scientific foundations of neurolinguistics. 2) it helps us to recognize different kinds of aphasias and language recovery patterns.3) it may help the speech-language pathologists to design and develop some rehabilitation programs. 4) the present research provides an opportunity to evaluate the linguistic theories. Furthermore, we used the following theory and model to explain the linguistic behaviors of the subjects:
1. The neurolinguistics theory of bilingualism (Paradis, 2004). It integrates a number of hypotheses–namely the three-store hypothesis, the direct access hypothesis, the activation threshold hypothesis, and the subsystems hypothesis–within the framework of a neurocognitive megasystem that comprises a number of independent neurofunctional systems that collaborate in the representation and processing of verbal communication. These independent systems include a common conceptual system; motivation/aﬀect; and, for each language, implicit linguistic competence, explicit metalinguistic knowledge, and linguistic pragmatics.
2. The declarative and procedural model (Paradis, 2009). The procedural/declarative dimension is a critical element in the appropriation, use and loss of languages. Competence is subserved by procedural memory, as opposed to knowledge, which is subserved by declarative memory. A number of multilingual language disorders can be understood by taking into account the differential roles of declarative and procedural memory in the acquisition and use of each of a patient’s languages.
The bilingual aphasia tests (BAT), both its Persian and Azerbaijani Turkish versions, were employed to collect the required data and evaluate the aphasics’ linguistic performances. It includes 32 subtests.
The findings showed that one patient had Broca’s aphasia in his L1 & L2, and the other patient was diagnosed with Broca’s aphasia in his L1 & subcortical aphasia in his L2. Thus, it seems, based on the type of the aphasia and the location of the damaged area of the subjects, that the presence of the lesion in the subcortical area does not necessarily lead to the similar aphasia in the first and second languages of the patients. According to Paradis (2008), the language recovery pattern of B. SH. was assessed to be parallel, whereas the recovery pattern of A. H. was a differential one. The data also revealed that the neurolinguistic theory of bilingualism (Paradis, 2004) and the declarative and procedural model (Paradis, 2009) can account for the differences in the syntactic performance of the bilingual aphasics with subcortical damage. Finally, some suggestions for further investigation and teaching purposes are made.