- Email: [email protected]
Crossed aphasia in multilinguals
BRAIN
AND
LANGUAGE
34, 169-180 (1988)
Crossed Aphasia in Multilinguals PRATHIBHA Department
of Speech
AND G. N. RANGAMANI
KARANTH
Pathology,
All India Gangothri,
Institute Mysore
of Speech
and Hearing,
Manasu
Reports of crossed aphasia in single case studies of bilinguals have led to incidence studies of crossed aphasia among larger groups of stroke patients. Among a few others, studies carried out in India (K. R. Nair & Virmani, 1973 Indian Journal of Medical Research, 61,9; P. Chary, 1986, In Language processing in bilinguals: Psycholinguistic and neuropsychological perspectives) have lent support to the notion of a higher incidence of crossed aphasia among bi- and multilinguals and form major citations in support of the hypothesis that bilingualism could lead to a greater bilateral cerebral representation of languages. This paper reports on the incidence of crossed aphasia in a large unselected population of stroke patients in monolingual and multilingual speakers of South India, which is in agreement with the previous reports of a higher incidence of crossed aphasia in multilinguals. However, along with this high incidence of crossed aphasia a low incidence of sinistrality was also seen. In order to confirm these findings and their significance two further studies were carried out-an incidence study of crossed aphasia in a population of mono- and multilingual aphasics and an incidence study of hand dominance in a normal population. The results and their significance to the issue of crossed aphasia in multilinguals are presented. D 19x8 Academic
Press, Inc.
INTRODUCTION
Language representation in the brain of bilinguals has captured the interest of researchers since a higher incidence of crossed aphasia in bilinguals as against monolinguals has been reported (Gloning & Gloning, 1965; Nair & Virmani, 1973; Albert & Obler, 1978; Galloway, 1980; Chary, 1986). While most of these reports of crossed aphasia have consisted We are grateful to Dr. G. N. N. Reddy, Director, NIMHANS and Dr. M. Gowrie Devi, Professor and Head of the Department of Neurology, NIMHANS for giving us access to the case files of the stroke patients seen at NIMHANS in 1984. We also thank Professors Max Coltheart and Andre Roth Lecours for their comments on the earlier drafts of this paper. The suggestions of the two reviewers are gratefully acknowledged. Address correspondence and reprint requests to Dr. Prathibha Karanth, Mailbag No. 6, Manasa Gangothri P.O., Mysore 570 006, India. 169 0093-934X188 $3 .OO Copyright 0 I988 by Academx Press. Inc All rights of reproduction m any form reserved.
170
KARANTH
AND
RANGAMANI
of single case reports, a few larger studies have also been reported. Nair and Virmani (1973) report a high incidence of aphasia in unilateral rightsided lesions among right-handed bilinguals. Gloning and Gloning (1965) on the other hand report that among their admittedly small sample of polyglot aphasics whose cases they reviewed three of the four left-handers had aphasia with right-sided lesions. These reports along with other reports on differential loss and recovery of the two or more languages of the multilingual aphasic as also experimental evidence for asymmetrical lateralization in bilinguals have led Albert and Obler (1978) to contend that the language organization of the average bilingual may be more ambilateral than that of a monolingual and that “bilinguals are more likely than monolinguals to have their language less markedly left dominant” (Albert & Obler, 1978, p. 239). Seemingly supportive evidence for this contention came from Galloway (1980) who reported a higher incidence of crossed aphasia among polyglots as compared to monolinguals on the basis of a review of literature. However, in contrast April and Han (1980) on the basis of a review of patient charts from two hospitals failed to find a trend toward increased incidence of crossed aphasia in a multiracial population. Further, they report that a similar survey in the Taiwan University Hospital found the incidence of crossed aphasia in bilingual patients from nonalphabetic language backgrounds was not higher than the 4% cited previously in European literature. Chary (1986), while confirming a higher incidence of crossed aphasia in her subject population drawn from a multilingual society, found the incidence of crossed aphasia to be near equal among both multi- and monolinguals. With few exceptions, most of the studies on crossed aphasia in multilinguals have relied on selected case studies with hardly any attempt made at comparison of the incidence in larger monolingual and multilingual populations. The resultant selection biases that complicate interpretations of results and generalization of findings are pointed out by Galloway (1980), Vaid and Genesee (1980), and Paradis (1987). As pointed out by Vaid and Genesee (1980), the relative importance of the cases of polyglot aphasia and their complexities for understanding neuro- and psycholinguistic aspects of bilingualism are dependent upon accurate estimates of their prevalence. This point has been reiterated by Paradis (1987) who states that “since most cases of aphasia subsequent to left hemisphere damage are not reported and since most cases of crossed aphasia-unilingual or bilingual40 get reported because of their exceptional character, one cannot conclude from the few selected cases of aphasia in bilinguals reported (contrasted with the large populations of unselected consecutive cases of unilingual aphasics from whom incidence of crossed aphasia has been derived) that the right hemisphere plays a greater role (let alone a major role) in bilinguals” (p. 7).
CROSSED APHASIA
171
One of the few larger studies carried out in this area, on a series of unselected cases has been that of Nair and Virmani (1973) who studied 78 hemiplegics to evaluate the frequency and nature of speech disturbances associated with right-hemispherical lesions. Of the 78 subjects 50 were dysphasic. Among these 50, 15 were left-hemiplegic with dysphasia and 12 of these were right-handed giving rise to a high incidence of crossed aphasia. This report has been a major citation in support of the hypothesis that bilinguals are less strongly lateralized for language than unilinguals. However, a closer look at this study makes one agree with Solin (1987) that the report “has been radically and repeatedly misinterpreted. No comparison between the incidence of crossed aphasia among bilingual and unilingual subjects can possibly be derived” (p. 11) from this study as no mention is made of the number of bi/multilinguals as against monolinguals in their subject population as a whole or among the aphasics including the crossed aphasics. It is therefore essential to look into the incidence of crossed aphasia in a large unselected population and to compare the incidence of crossed aphasia in multilinguals and monolinguals within this population. This was the aim of the present study. METHOD The case files of all patients treated for stroke in the Department of Neurology, National Institute of Mental Health and Nemo Sciences, Bangalore, India in 1984 were reviewed. Out of a total of 205 seen in that year, 9 patients with thalamic lesions and other associated conditions such as Dementia, Parkinsonism, and Psychiatric illness were omitted. Further, only those whose records gave clear information on the following variables, as noted below, were included in the study. (a) Handedness. Premorbid hand usage was determined for the following activities, viz., eating, writing (hammering/sewing in the case of illiterates), throwing, cutting, and brushing teeth. The patients were classified as right-banders/left-handers depending upon whether they used right/left-hand, respectively, for all five activities listed above. Those that did not use any one hand exclusively for all of the above listed five activities were classified as ambidextrous. (b) Presence or absence of aphasia. Based upon the “presence” or “absence” of aphasia as diagnosed by the neurologist in charge the patients were divided into two groups, viz., aphasics and nonaphasics. Patients with dysarthria but no aphasia were included in the nonaphasic group. (c) Side oflesion. The patients were classified as having right- or left-hemispheric lesions based on the diagnosis by qualified neurologists after a detailed neurological evaluation including angiography and computerized tomography. Careful selection based on availability of clear cut information on handedness, presence or absence of aphasia, and side of lesion resulted in a total of 94 subjects. Of the 94, 49 had right-hemiplegia/paresis 34 of whom were aphasics, 38 had left-hemiplegia/paresis 6 of whom were aphasic, and 7 had no limb involvement, 6 of whom were aphasic. Their distribution with reference to age, sex, and handedness are given in Table 1.
172
KARANTH
AND RANGAMANI TABLE
SUBJECT DESCRWTION
Male Female
1
OF THE CURRENT
STROKE POPULATION
Age range
Mean age
Righthanders
Lefthanders
14-80 years 30-72 years
55.19 53.19
77 16
1 0
RESULTS AND DISCUSSION
The results obtained in terms of incidence of aphasia in cases of unilateral brain damage among right- and left-handers in the current study are shown along with that of Nair and Virmani (1973) in Table 2. As against these Segalowitz and Bryden (1983), based on four large scale studies carried out in the West, give the figures of incidence of aphasia in cases of unilateral brain damage, as shown in Table 3. The incidence of crossed aphasia obtained in this study, that of 17.9%, corresponds with the higher figures reported in other Indian studies involving both large groups of stroke patients with or without aphasia (Nair & Virmani, 1973-50%) and large scale studies of polyglot aphasics (Chary, 198613.2%) and is much higher than the 3% reported by Segalowitz and Bryden (1983). A further analysis was carried out to compare the incidence of crossed aphasia among the monolinguals as against the multilinguals of our subject population. Out of the 94 patients, information on language background was available in only 78 patients, These patients were divided into two groups, viz., multilinguals and monolinguals. Multilinguals were those patients who possessed an ability to understand and speak more than one language, while monolinguals were those with an ability to understand and speak only one language. The number of multilinguals among the 78 were 61, a majority of these had Kannada as their mother tongue but some had Tam& Urdu, Telugu, Malayalam, Marathi, Hindi, or Tulu as their mother TABLE
2
INCIDENCE OF APHASIA AFTER UNILATERAL BRAIN DAMAGE OBTAINED STUDY (N = 94) AND THOSE REPORTED BY NAIR AND VIRMANI,
Current study (N = 94) Nair and Virmani, (N = 78)
1973
IN THE CURRENT (N = 78)
Handedness
Left lesion
Right lesion
Right-handers Left-handers Right-handers Left-handers
39154 l/l 32147 314
7139 1Z/24 313
173
CROSSED APHASIA TABLE INCIDENCE
3
OF APHASIA IN CASES OF UNILATERAL BRAIN DAMAGE SEGALOWITZ AND BRYDEN, 1983 (N = 1761)
IN THE WEST-
Handedness
Left lesion
Right lesion
Right-handers Left-handers
5761934 3617 1
321680 19176
tongue. The most common second languages were English, Kannada, Tarnil, Telugu, and Hindi. The other languages spoken by the multilinguals were Malayalam, Marathi, Gujarathi, Nepalese, Tulu, and Coorgi. The number of languages spoken by individual multilinguals ranged from two to six. Among the 17 monolinguals, 16 were speakers of Kannada and 1 spoke Tamil. Incidence of aphasia was calculated for the multilingual and monolingual groups separately and are given in Table 4 with reference to side of lesion and handedness. A comparison of dextral crossed aphasia in multilinguals versus monolinguals shows a higher incidence of crossed aphasia in multilinguals25%, as against 0% in monolinguals. No comparison can be made with the data reported by Nair and Virmani (1973) as they do not specify the number of multi- and monolinguals or the respective incidence of aphasia among them, in their subject population of hemiplegics. Chary (1986) who also found a higher incidence of crossed aphasia in her study, reports a near equal incidence of crossed aphasia in both mono- and multilinguals. Since Chary’s subjects differed from those of this study in several respects, in that all her 88 subjects were aphasics with differing etiology and a wider age range, her findings will be taken up for comparison and discussion with a similar group later in this paper. An interesting and perhaps pertinent feature of our results is the low incidence of sinistrality in our subject population. Table 5 gives the incidence figures for sinistrality as identified by various studies on aphasia. These incidence figures agree with the figures of 5-12% which are reported to be the incidence of sinistrality in the general population TABLE INCIDENCE MONOLINGUAL
Multilinguals (A’ = 61) Monolinguals (N = 17)
4
OF APHASIA WITH UNILATERAL BRAIN DAMAGE IN THE MULTISPEAKERS AMONG THE SUBJECTS OF THE CURRENT STUDY (N
AND = 78)
Handedness
Left lesion
Right lesion
Right-handers Left-handers Right-handers Left-handers
27 136 l/l 7110 -
6124 o/7 -
174
KARANTH
AND RANGAMANI TABLE
INCIDENCE
5
OF SINISTRALITY AS IDENTIFIED VARIOUS STUDIES ON APHASIA
Sinistrality incidence
Studies 1. 2. 3. 4. 5.
IN
Conrad (1949) Bingley (1958) Penfield and Roberts (1959) Newcombe and Ratcliffe (1973) Nair and Virmani (1973)
5.93% 6.54% 8.55% 11.7% 8.97%
(Bryden, 1982). In comparison the 1.1% incidence of sinistrality found here is rather low. The incidence of sinistrality may have important implications for studies on the incidence of crossed aphasia. In order to further confirm and clarify the results obtained in this study, data was obtained on a different group of patients all of whom were aphasic. The subjects of this second group were all of the 48 aphasic patients examined at the All India Institute of Speech and Hearing, Mysore during 1984-1985. Unlike the earlier group of patients all of whom were stroke patients with or without aphasia all 48 subjects of this group were aphasic. Of these 32 were multilinguals and 16 monolinguals. Their language background was similar to that of the earlier group. Of the 48, all of whom were right-handed 35 had right-hemiplegia/hemiparesis, 4 had left-hemiplegia/paresis and 9 had no limb involvement. Their distribution with reference to age, sex, and handedness is given in Table 6. Of these 48 subjects 4 had crossed aphasia-right-handers with righthemisphere lesion and aphasia. Two of these 4 were multilinguals and the other 2 monolinguals. Table 7 compares the incidence of crossed aphasia among the multi- and monolingual aphasics of this study with that of a similar group reported by Chary (1986). As may be seen, while Chary (1986) found a near equal incidence among monolinguals (12.8%) and multilinguals (13.630/o), the incidence TABLE DESCRWTION
OF THE APHASIC
SUBJECTS
6
OF THE SECOND
GROUP
IN THE CURRENT
STUDY
(N = 48)
Male Female
N
Age range
Mean age
Righthanders
Lefthanders
38 10
14-81 30-75
47.47 57.3
38 10
-
175
CROSSED APHASIA TABLE INCIDENCE
7
OF CROSSED APHASIA AMONG MULTI- AND MONOLINGUAL BY CHARY, 1986, AND AS FOUND IN THE CURRENT
APHASICS AS REPORTED STUDY
of lesion
Side
Language background Chary, 1986 (N = 88)
Monolinguals Multilinguals
Current study (N = 48)
Handedness
Left
Right-handers Left-handers Right-handers Left-handers
34 2 19 2
Right-handers Left-handers Right-handers Left-handers
14 30 -
-
Monolinguals Multilinguals
-
Right Bilateral ____5 13 I 2 3 s 2 0 2 2 -
-
of crossed aphasia in our population is 12.5% and matches with that reported by Chary, among monolinguals, but is 6.25% and much smaller than that reported by Chary, among multilinguals. The incidence of crossed aphasia among polyglots, reported earlier by Gloning and Gloning (1965) and Galloway (1980), are given in Table 8. In contrast to these figures ranging from 6.3 to 15% the incidence of crossed aphasia following unilateral brain lesions in monolingual patients is generally agreed to be less than 5% as may be seen from the incidence figures derived from the incidence of aphasia in an unselected population reported by Segalowitz and Bryden (1983) given in Table 9. The results obtained in our surveys of incidence of crossed aphasia in a stroke population, as also that of incidence of crossed aphasia in a second all aphasic population, confirm a higher incidence of crossed aphasia in our population as reported in the earlier Indian studies of Nair and Virmani (1973) and Chary (1986). However, it is not clear that this higher incidence of right-handers with right-hemisphere lesions becoming aphasic is necessarily related to or caused by multilingualism. While the TABLE INCIDENCE
OF CROSSED APHASIA GLONING,
Gloning and Gloning, 1965 Galloway,
1980
8
AMONG POLYGLOTS AS REPORTED BY CLONING 1965, AND GALLOWAY, 1980
AND
Handedness
Left lesion
Right lesion
Right-handers Left-handers Right-handers Left-handers
72.7% 25.0% 85.0% 33.0%
9.1% 75.0% 15.0% 67.0%
176
KARANTH
AND RANGAMANI TABLE
INCIDENCE
OF CROSSED
9
APHASIA IN UNSELECTED POPULATIONS BY SEGALOWITZ AND BRYDEN, 1983
OF MONOLINGUALS
AS GIVEN
(p. 350)
Handedness
Left lesion
Right lesion
Right-handers Left-handers
95.4% 67.8%
4.6% 32.2%
findings of Nair and Virmani (1973) are uninterpretable in this respect as they have not given separate figures for mono- and multilinguals among their crossed aphasics, Chary (1986) found a near equal incidence of crossed aphasia among both multi- and monolinguals. In the current data, while both groups show a higher incidence of crossed aphasia, in the first group the higher incidence was among multilinguals, while in the second the incidence figures of crossed aphasia were higher for monolinguals. If multilingualism resulted in bilateral representation of language we should have found a far higher proportion of multilinguals among our crossed aphasics. At the same time it must be pointed out that our data differ from the earlier studies in two important ways both of which may be related to the question of the findings on the representation of language in the brain of the multilinguals. In the first study we had a 100% incidence of aphasia in left-handers with left lesions. In the second study there were no lefthanders. It appears then that given these populations, (i) the incidence of left-handedness is low; (ii) if one were to find a left-hander then he/she would invariably left-dominant for language; and (iii) there are no left-handers with right-dominance for language.
be
These factors we feel are important and crucially linked to the findings of higher incidence of crossed aphasia in our population. Despite the fact that there is “only a weak relation between handedness and speech lateralization” (Bryden, 1982, p. 171) it is generally used as an indicator of expectations in terms of speech lateralization. This is true of the studies on crossed aphasia where the aphasics did not confirm the expectations of cerebral lateralization made on the basis of their handedness and were therefore termed as “crossed aphasics.” Bryden (1982) reports that incidence of left-handedness is generally considered to be between 5 and 12% “although the specific figures vary considerably as a function of the source of the sample and the procedure for measuring handedness” (p. 157). Apart from the fact that criteria for determining left-handedness is very broad, incidence of left-handedness
CROSSED
APHASIA
177
is also subject to change due to social pressures and cultural changes. The source of the sample would then bring about a considerable change in the figures on incidence of left-handedness. To quote Bryden (1982) “data would suggest that the frequency of left handedness has risen from about 5% to 11% during the 20th century at least in U.K. and North America. The social pressure to make the child write with the right hand and to conform to the norm may have been far greater in the first half of the century than it is now” (p. 158). Consequently those that would have earlier been classified as right-handers would now be seen as lefthanders. Given that that incidence of crossed aphasia is determined primarily on the basis of handedness, the incidence of which is itself subject to social pressures, the high incidence of crossed aphasia could well be due to the factor of an increased incidence of forced or apparent right-handedness. This does seem to be the case with our data where all three factors are operant. The social taboo on left-handedness is still very strongly present in India. It is only in the recent past and that too among the literate urban population that left-handedness is accepted. The social taboo on the use of left hand would result in a large number of potential left-handers being forced at an early age to become right-handers and would result in a low incidence of left-handedness with a concomitant increase in the incidence of apparent or reported right-handedness. This would be more so with respect to the older age groups in which the aphasic population are found. This low incidence of left-handedness in aphasic populations in India is supported by the findings of two previous unpublished studies. In a comparative evaluation of dominant and nondominant cerebral hemisphere lesions consequent to occlusive cerebrovascular disease Nagaraj (1979) found 1 among his 40 patients to be lefthanded. These 40 patients were from the same source as that of our first subject population. The incidence of left-handedness in this stroke population was 2.5%. Pauranik (1985), in a study of 50 aphasics carried out at Indore in North India, found 2 of his 50 adult patients to be lefthanded, giving a 4% incidence of sinistrality in his subject population (personal communication). The incidence of left-handedness as reported by Nair and Virmani (1973) and Chary (1986) however is closer to that reported in Western studies which might be due to the fact that while the former data were drawn from the cosmopolitan city of Delhi, the latter included subjects from a much wider and younger age range (7 to 70 years) than is usual in aphasiological studies. In order to confirm the possible link between a low incidence of lefthandedness and crossed aphasia two further measures were carried outan incidence study of left-handedness in a normal population from the same social and cultural background and an extrapolation of the incidence figures of cerebral specialization for language obtained on our clinical
178
KARANTH
AND RANGAMANI TABLE
HANDEDNESS
Male Female
IN A NORMAL
10
POPULATION-CURRENT
STUDY
(N
=
120)
Age range
Mean age
Righthanders
Lefthanders
21-82 23-78
46.52 46.95
58 59
2 1
data on that given by Rasmussen and Mimer (1977) on the basis of the sodium amytal tests. A survey of incidence of sinistrality was carried out on 120 normal subjects in Mysore, selected randomly from the same socioeconomic and cultural background as the subjects of this study. The group of 120 subjects consisted of an equal number of males and females and an equal number of multi- and monolinguals. Further there were 20 subjects each in the age range of 21 to 30, 31 to 40, 41 to 50, 51 to 60, and 61 to 82 years. These subjects were classified as right- or left-handers using the same criteria as stated earlier. The distribution of subjects with reference to age, sex, and handedness is given in Table 10. The incidence of sinistrality in this population is a low 2.5%. Further all three sinistrals were found in the age range of 21-30 years. Three of the remaining subjects (two females and one male in the age range of 41 to 60 years) gave history of forced shift. They are classified here as right handed as they would now be identified as right handers in terms of handedness usage. Segalowitz & Bryden (1983) based on an average of incidence of aphasia for each hand-hemisphere combination across four studies estimate aphasia following unilateral damage to the left hemisphere of 62.1% in right handers and 52.8% in left handers with comparable figures of 3% for right handers and 25.1% for left handers in right hemisphere lesions. On the basis of these incidence figures on clinical data Segalowitz & Bryden extrapolate through statistical means an estimated distribution of language lateralization as given in Table Il. These figures they point out agree with similar estimates using very TABLE ESTIMATED
DISTRIBUTION
OF CEREBRAL SEGALOWITZ
11
LATERALIZATION AND BRYDEN,
OF LANGUAGE
IN NORMALS-
1983
Handedness
Left hemisphere
Bilateral
Right hemisphere
Right-handers Left-handers
95.5% 61.4%
19.8%
4.5% 18.8%
179
CROSSED APHASIA TABLE ESTIMATED
DISTRIBUTION
OF LANGUAGE
12
LATERALIZATION
ON THE BASIS OF THE CURRENT
DATA Handedness
Left hemisphere
Right hemisphere
Right-handers Left-handers
80.13% 100.00%
19.87% -
different approaches such as sodium amytal testing (Rasmussen & Milner, 1977) and dysphasia following unilateral electroconvulsive therapy (Warrington & Pratt, 1973). A similar extrapolation on our data results in figures as given in Table 12. These figures obtained on the basis of handedness clearly are not in agreement with what is known of cerebral specialization for speech in the general population and are supportive of our contention that in cultures where social pressure acts against left-handedness, the expectation of cerebral dominance cannot be based on handedness alone and when so based can lead to erroneous conclusions. Such errors could perhaps be minimized by calculating crossed aphasia incidence figures for the population as a whole rather than for right- and left-handers separately as has been done in most of the studies on crossed aphasia. The overall incidence figures on data such as ours would clearly show a concomitant decrease in the incidence of left-handers and left-handed aphasics with an increase in incidence of crossed aphasia. CONCLUSION In conclusion, while it could well be that cerebral representation of language in bi- and multilinguals is different than that in monolinguals, interpretations of higher incidences of crossed aphasia in polyglots as being due to multilingualism per se should be done with caution particularly when based on variables such as handedness which are known to vary subject to other factors such as cultural and social pressures. REFERENCES Albert, M., & Obler, L. 1978. The bilingual bruin. New York: Academic Press. April, R. S., & Han, M. 1980. Crossed aphasia in a right handed bilingual Chinese manA second case. Archives of Neurology, 31, 342-346. Bryden, M. P. 1982. Laterality-Functional asymmetry in the intact bruin. New York: Academic Press. Chary, P. 1986. Aphasia in a multilingual society: A preliminary study. In J. Vaid (Ed.), Language processing in bilinguals: Psycholinguistic and neuropsychological perspectives. Hillsdale, NJ: Erlbaum. Galloway, L. 1980. Towards a neuropsychological model of bilingualism and second language performance: A theoretical article with a critical review of current research and some
KARANTH
180
AND RANGAMANI
new hypotheses. In M. Long, S. Peck, & K. Bailey (Eds.), Research in second language acquisition. Rowley, MA: Newbury House. Gloning, I., & Gloning, K. 1965. Aphasia in polyglots-Contribution to the dynamics of language disintegration as well as to the question of the localization of these impairments. In M. Paradis (Ed.), Readings on aphasia in bilinguals and polyglots. Canada: Marcel Didier Inc., 1983. Nagaraj, D. 1979. Comparative evaluation of dominanr and non-dominant cerebral hemisphere lesions. Unpublished thesis, Department of Neurology, NIMHANS, Bangalore University. Nair, K. R., & Virmani, V. 1973. Speech and language disturbance in hemiplegics. Indian Journal
of Medical
Research,
61, 9.
Pauranik, A. 1985. Aphasia testing in Hindi speaking patients. Unpublished thesis, Department of Neurology, AIIMS, New Delhi. Paradis, M. 1987. The assessmenf of bilingual aphasia. Hillsdale, NJ: Erlbaum. Rasmussen, T., & Milner, B. 1977. The role of early left brain injury in determining lateralization of cerebral speech functions. In S. J. Segalowitz (Ed.), Language functions and brain organization. New York: Academic Press. Segalowitz, S. J., & Bryden, M. P. 1983. Individual differences in hemispheric representation of language. In S. J. Segalowitz (Ed.), Language function and brain organization. New York: Academic Press. Solin. 1987. In M. Paradis (Ed.), The assessment of bilingual aphasia. Hillsdale, NJ: Erlbaum. Vaid, J., & Genesee, 1980. Neuropsychological approaches to bilingualism: A critical review. Canadian Journal of Psychology, 34(4), 417-445. Warrington, E. K., & Pratt, R. T. C. 1973. Language laterality in left handers assessed by unilateral ECT. In S. J. Segalowitz (Ed.), Language functions and brain organization. New York: Academic Press.
AND
LANGUAGE
34, 169-180 (1988)
Crossed Aphasia in Multilinguals PRATHIBHA Department
of Speech
AND G. N. RANGAMANI
KARANTH
Pathology,
All India Gangothri,
Institute Mysore
of Speech
and Hearing,
Manasu
Reports of crossed aphasia in single case studies of bilinguals have led to incidence studies of crossed aphasia among larger groups of stroke patients. Among a few others, studies carried out in India (K. R. Nair & Virmani, 1973 Indian Journal of Medical Research, 61,9; P. Chary, 1986, In Language processing in bilinguals: Psycholinguistic and neuropsychological perspectives) have lent support to the notion of a higher incidence of crossed aphasia among bi- and multilinguals and form major citations in support of the hypothesis that bilingualism could lead to a greater bilateral cerebral representation of languages. This paper reports on the incidence of crossed aphasia in a large unselected population of stroke patients in monolingual and multilingual speakers of South India, which is in agreement with the previous reports of a higher incidence of crossed aphasia in multilinguals. However, along with this high incidence of crossed aphasia a low incidence of sinistrality was also seen. In order to confirm these findings and their significance two further studies were carried out-an incidence study of crossed aphasia in a population of mono- and multilingual aphasics and an incidence study of hand dominance in a normal population. The results and their significance to the issue of crossed aphasia in multilinguals are presented. D 19x8 Academic
Press, Inc.
INTRODUCTION
Language representation in the brain of bilinguals has captured the interest of researchers since a higher incidence of crossed aphasia in bilinguals as against monolinguals has been reported (Gloning & Gloning, 1965; Nair & Virmani, 1973; Albert & Obler, 1978; Galloway, 1980; Chary, 1986). While most of these reports of crossed aphasia have consisted We are grateful to Dr. G. N. N. Reddy, Director, NIMHANS and Dr. M. Gowrie Devi, Professor and Head of the Department of Neurology, NIMHANS for giving us access to the case files of the stroke patients seen at NIMHANS in 1984. We also thank Professors Max Coltheart and Andre Roth Lecours for their comments on the earlier drafts of this paper. The suggestions of the two reviewers are gratefully acknowledged. Address correspondence and reprint requests to Dr. Prathibha Karanth, Mailbag No. 6, Manasa Gangothri P.O., Mysore 570 006, India. 169 0093-934X188 $3 .OO Copyright 0 I988 by Academx Press. Inc All rights of reproduction m any form reserved.
170
KARANTH
AND
RANGAMANI
of single case reports, a few larger studies have also been reported. Nair and Virmani (1973) report a high incidence of aphasia in unilateral rightsided lesions among right-handed bilinguals. Gloning and Gloning (1965) on the other hand report that among their admittedly small sample of polyglot aphasics whose cases they reviewed three of the four left-handers had aphasia with right-sided lesions. These reports along with other reports on differential loss and recovery of the two or more languages of the multilingual aphasic as also experimental evidence for asymmetrical lateralization in bilinguals have led Albert and Obler (1978) to contend that the language organization of the average bilingual may be more ambilateral than that of a monolingual and that “bilinguals are more likely than monolinguals to have their language less markedly left dominant” (Albert & Obler, 1978, p. 239). Seemingly supportive evidence for this contention came from Galloway (1980) who reported a higher incidence of crossed aphasia among polyglots as compared to monolinguals on the basis of a review of literature. However, in contrast April and Han (1980) on the basis of a review of patient charts from two hospitals failed to find a trend toward increased incidence of crossed aphasia in a multiracial population. Further, they report that a similar survey in the Taiwan University Hospital found the incidence of crossed aphasia in bilingual patients from nonalphabetic language backgrounds was not higher than the 4% cited previously in European literature. Chary (1986), while confirming a higher incidence of crossed aphasia in her subject population drawn from a multilingual society, found the incidence of crossed aphasia to be near equal among both multi- and monolinguals. With few exceptions, most of the studies on crossed aphasia in multilinguals have relied on selected case studies with hardly any attempt made at comparison of the incidence in larger monolingual and multilingual populations. The resultant selection biases that complicate interpretations of results and generalization of findings are pointed out by Galloway (1980), Vaid and Genesee (1980), and Paradis (1987). As pointed out by Vaid and Genesee (1980), the relative importance of the cases of polyglot aphasia and their complexities for understanding neuro- and psycholinguistic aspects of bilingualism are dependent upon accurate estimates of their prevalence. This point has been reiterated by Paradis (1987) who states that “since most cases of aphasia subsequent to left hemisphere damage are not reported and since most cases of crossed aphasia-unilingual or bilingual40 get reported because of their exceptional character, one cannot conclude from the few selected cases of aphasia in bilinguals reported (contrasted with the large populations of unselected consecutive cases of unilingual aphasics from whom incidence of crossed aphasia has been derived) that the right hemisphere plays a greater role (let alone a major role) in bilinguals” (p. 7).
CROSSED APHASIA
171
One of the few larger studies carried out in this area, on a series of unselected cases has been that of Nair and Virmani (1973) who studied 78 hemiplegics to evaluate the frequency and nature of speech disturbances associated with right-hemispherical lesions. Of the 78 subjects 50 were dysphasic. Among these 50, 15 were left-hemiplegic with dysphasia and 12 of these were right-handed giving rise to a high incidence of crossed aphasia. This report has been a major citation in support of the hypothesis that bilinguals are less strongly lateralized for language than unilinguals. However, a closer look at this study makes one agree with Solin (1987) that the report “has been radically and repeatedly misinterpreted. No comparison between the incidence of crossed aphasia among bilingual and unilingual subjects can possibly be derived” (p. 11) from this study as no mention is made of the number of bi/multilinguals as against monolinguals in their subject population as a whole or among the aphasics including the crossed aphasics. It is therefore essential to look into the incidence of crossed aphasia in a large unselected population and to compare the incidence of crossed aphasia in multilinguals and monolinguals within this population. This was the aim of the present study. METHOD The case files of all patients treated for stroke in the Department of Neurology, National Institute of Mental Health and Nemo Sciences, Bangalore, India in 1984 were reviewed. Out of a total of 205 seen in that year, 9 patients with thalamic lesions and other associated conditions such as Dementia, Parkinsonism, and Psychiatric illness were omitted. Further, only those whose records gave clear information on the following variables, as noted below, were included in the study. (a) Handedness. Premorbid hand usage was determined for the following activities, viz., eating, writing (hammering/sewing in the case of illiterates), throwing, cutting, and brushing teeth. The patients were classified as right-banders/left-handers depending upon whether they used right/left-hand, respectively, for all five activities listed above. Those that did not use any one hand exclusively for all of the above listed five activities were classified as ambidextrous. (b) Presence or absence of aphasia. Based upon the “presence” or “absence” of aphasia as diagnosed by the neurologist in charge the patients were divided into two groups, viz., aphasics and nonaphasics. Patients with dysarthria but no aphasia were included in the nonaphasic group. (c) Side oflesion. The patients were classified as having right- or left-hemispheric lesions based on the diagnosis by qualified neurologists after a detailed neurological evaluation including angiography and computerized tomography. Careful selection based on availability of clear cut information on handedness, presence or absence of aphasia, and side of lesion resulted in a total of 94 subjects. Of the 94, 49 had right-hemiplegia/paresis 34 of whom were aphasics, 38 had left-hemiplegia/paresis 6 of whom were aphasic, and 7 had no limb involvement, 6 of whom were aphasic. Their distribution with reference to age, sex, and handedness are given in Table 1.
172
KARANTH
AND RANGAMANI TABLE
SUBJECT DESCRWTION
Male Female
1
OF THE CURRENT
STROKE POPULATION
Age range
Mean age
Righthanders
Lefthanders
14-80 years 30-72 years
55.19 53.19
77 16
1 0
RESULTS AND DISCUSSION
The results obtained in terms of incidence of aphasia in cases of unilateral brain damage among right- and left-handers in the current study are shown along with that of Nair and Virmani (1973) in Table 2. As against these Segalowitz and Bryden (1983), based on four large scale studies carried out in the West, give the figures of incidence of aphasia in cases of unilateral brain damage, as shown in Table 3. The incidence of crossed aphasia obtained in this study, that of 17.9%, corresponds with the higher figures reported in other Indian studies involving both large groups of stroke patients with or without aphasia (Nair & Virmani, 1973-50%) and large scale studies of polyglot aphasics (Chary, 198613.2%) and is much higher than the 3% reported by Segalowitz and Bryden (1983). A further analysis was carried out to compare the incidence of crossed aphasia among the monolinguals as against the multilinguals of our subject population. Out of the 94 patients, information on language background was available in only 78 patients, These patients were divided into two groups, viz., multilinguals and monolinguals. Multilinguals were those patients who possessed an ability to understand and speak more than one language, while monolinguals were those with an ability to understand and speak only one language. The number of multilinguals among the 78 were 61, a majority of these had Kannada as their mother tongue but some had Tam& Urdu, Telugu, Malayalam, Marathi, Hindi, or Tulu as their mother TABLE
2
INCIDENCE OF APHASIA AFTER UNILATERAL BRAIN DAMAGE OBTAINED STUDY (N = 94) AND THOSE REPORTED BY NAIR AND VIRMANI,
Current study (N = 94) Nair and Virmani, (N = 78)
1973
IN THE CURRENT (N = 78)
Handedness
Left lesion
Right lesion
Right-handers Left-handers Right-handers Left-handers
39154 l/l 32147 314
7139 1Z/24 313
173
CROSSED APHASIA TABLE INCIDENCE
3
OF APHASIA IN CASES OF UNILATERAL BRAIN DAMAGE SEGALOWITZ AND BRYDEN, 1983 (N = 1761)
IN THE WEST-
Handedness
Left lesion
Right lesion
Right-handers Left-handers
5761934 3617 1
321680 19176
tongue. The most common second languages were English, Kannada, Tarnil, Telugu, and Hindi. The other languages spoken by the multilinguals were Malayalam, Marathi, Gujarathi, Nepalese, Tulu, and Coorgi. The number of languages spoken by individual multilinguals ranged from two to six. Among the 17 monolinguals, 16 were speakers of Kannada and 1 spoke Tamil. Incidence of aphasia was calculated for the multilingual and monolingual groups separately and are given in Table 4 with reference to side of lesion and handedness. A comparison of dextral crossed aphasia in multilinguals versus monolinguals shows a higher incidence of crossed aphasia in multilinguals25%, as against 0% in monolinguals. No comparison can be made with the data reported by Nair and Virmani (1973) as they do not specify the number of multi- and monolinguals or the respective incidence of aphasia among them, in their subject population of hemiplegics. Chary (1986) who also found a higher incidence of crossed aphasia in her study, reports a near equal incidence of crossed aphasia in both mono- and multilinguals. Since Chary’s subjects differed from those of this study in several respects, in that all her 88 subjects were aphasics with differing etiology and a wider age range, her findings will be taken up for comparison and discussion with a similar group later in this paper. An interesting and perhaps pertinent feature of our results is the low incidence of sinistrality in our subject population. Table 5 gives the incidence figures for sinistrality as identified by various studies on aphasia. These incidence figures agree with the figures of 5-12% which are reported to be the incidence of sinistrality in the general population TABLE INCIDENCE MONOLINGUAL
Multilinguals (A’ = 61) Monolinguals (N = 17)
4
OF APHASIA WITH UNILATERAL BRAIN DAMAGE IN THE MULTISPEAKERS AMONG THE SUBJECTS OF THE CURRENT STUDY (N
AND = 78)
Handedness
Left lesion
Right lesion
Right-handers Left-handers Right-handers Left-handers
27 136 l/l 7110 -
6124 o/7 -
174
KARANTH
AND RANGAMANI TABLE
INCIDENCE
5
OF SINISTRALITY AS IDENTIFIED VARIOUS STUDIES ON APHASIA
Sinistrality incidence
Studies 1. 2. 3. 4. 5.
IN
Conrad (1949) Bingley (1958) Penfield and Roberts (1959) Newcombe and Ratcliffe (1973) Nair and Virmani (1973)
5.93% 6.54% 8.55% 11.7% 8.97%
(Bryden, 1982). In comparison the 1.1% incidence of sinistrality found here is rather low. The incidence of sinistrality may have important implications for studies on the incidence of crossed aphasia. In order to further confirm and clarify the results obtained in this study, data was obtained on a different group of patients all of whom were aphasic. The subjects of this second group were all of the 48 aphasic patients examined at the All India Institute of Speech and Hearing, Mysore during 1984-1985. Unlike the earlier group of patients all of whom were stroke patients with or without aphasia all 48 subjects of this group were aphasic. Of these 32 were multilinguals and 16 monolinguals. Their language background was similar to that of the earlier group. Of the 48, all of whom were right-handed 35 had right-hemiplegia/hemiparesis, 4 had left-hemiplegia/paresis and 9 had no limb involvement. Their distribution with reference to age, sex, and handedness is given in Table 6. Of these 48 subjects 4 had crossed aphasia-right-handers with righthemisphere lesion and aphasia. Two of these 4 were multilinguals and the other 2 monolinguals. Table 7 compares the incidence of crossed aphasia among the multi- and monolingual aphasics of this study with that of a similar group reported by Chary (1986). As may be seen, while Chary (1986) found a near equal incidence among monolinguals (12.8%) and multilinguals (13.630/o), the incidence TABLE DESCRWTION
OF THE APHASIC
SUBJECTS
6
OF THE SECOND
GROUP
IN THE CURRENT
STUDY
(N = 48)
Male Female
N
Age range
Mean age
Righthanders
Lefthanders
38 10
14-81 30-75
47.47 57.3
38 10
-
175
CROSSED APHASIA TABLE INCIDENCE
7
OF CROSSED APHASIA AMONG MULTI- AND MONOLINGUAL BY CHARY, 1986, AND AS FOUND IN THE CURRENT
APHASICS AS REPORTED STUDY
of lesion
Side
Language background Chary, 1986 (N = 88)
Monolinguals Multilinguals
Current study (N = 48)
Handedness
Left
Right-handers Left-handers Right-handers Left-handers
34 2 19 2
Right-handers Left-handers Right-handers Left-handers
14 30 -
-
Monolinguals Multilinguals
-
Right Bilateral ____5 13 I 2 3 s 2 0 2 2 -
-
of crossed aphasia in our population is 12.5% and matches with that reported by Chary, among monolinguals, but is 6.25% and much smaller than that reported by Chary, among multilinguals. The incidence of crossed aphasia among polyglots, reported earlier by Gloning and Gloning (1965) and Galloway (1980), are given in Table 8. In contrast to these figures ranging from 6.3 to 15% the incidence of crossed aphasia following unilateral brain lesions in monolingual patients is generally agreed to be less than 5% as may be seen from the incidence figures derived from the incidence of aphasia in an unselected population reported by Segalowitz and Bryden (1983) given in Table 9. The results obtained in our surveys of incidence of crossed aphasia in a stroke population, as also that of incidence of crossed aphasia in a second all aphasic population, confirm a higher incidence of crossed aphasia in our population as reported in the earlier Indian studies of Nair and Virmani (1973) and Chary (1986). However, it is not clear that this higher incidence of right-handers with right-hemisphere lesions becoming aphasic is necessarily related to or caused by multilingualism. While the TABLE INCIDENCE
OF CROSSED APHASIA GLONING,
Gloning and Gloning, 1965 Galloway,
1980
8
AMONG POLYGLOTS AS REPORTED BY CLONING 1965, AND GALLOWAY, 1980
AND
Handedness
Left lesion
Right lesion
Right-handers Left-handers Right-handers Left-handers
72.7% 25.0% 85.0% 33.0%
9.1% 75.0% 15.0% 67.0%
176
KARANTH
AND RANGAMANI TABLE
INCIDENCE
OF CROSSED
9
APHASIA IN UNSELECTED POPULATIONS BY SEGALOWITZ AND BRYDEN, 1983
OF MONOLINGUALS
AS GIVEN
(p. 350)
Handedness
Left lesion
Right lesion
Right-handers Left-handers
95.4% 67.8%
4.6% 32.2%
findings of Nair and Virmani (1973) are uninterpretable in this respect as they have not given separate figures for mono- and multilinguals among their crossed aphasics, Chary (1986) found a near equal incidence of crossed aphasia among both multi- and monolinguals. In the current data, while both groups show a higher incidence of crossed aphasia, in the first group the higher incidence was among multilinguals, while in the second the incidence figures of crossed aphasia were higher for monolinguals. If multilingualism resulted in bilateral representation of language we should have found a far higher proportion of multilinguals among our crossed aphasics. At the same time it must be pointed out that our data differ from the earlier studies in two important ways both of which may be related to the question of the findings on the representation of language in the brain of the multilinguals. In the first study we had a 100% incidence of aphasia in left-handers with left lesions. In the second study there were no lefthanders. It appears then that given these populations, (i) the incidence of left-handedness is low; (ii) if one were to find a left-hander then he/she would invariably left-dominant for language; and (iii) there are no left-handers with right-dominance for language.
be
These factors we feel are important and crucially linked to the findings of higher incidence of crossed aphasia in our population. Despite the fact that there is “only a weak relation between handedness and speech lateralization” (Bryden, 1982, p. 171) it is generally used as an indicator of expectations in terms of speech lateralization. This is true of the studies on crossed aphasia where the aphasics did not confirm the expectations of cerebral lateralization made on the basis of their handedness and were therefore termed as “crossed aphasics.” Bryden (1982) reports that incidence of left-handedness is generally considered to be between 5 and 12% “although the specific figures vary considerably as a function of the source of the sample and the procedure for measuring handedness” (p. 157). Apart from the fact that criteria for determining left-handedness is very broad, incidence of left-handedness
CROSSED
APHASIA
177
is also subject to change due to social pressures and cultural changes. The source of the sample would then bring about a considerable change in the figures on incidence of left-handedness. To quote Bryden (1982) “data would suggest that the frequency of left handedness has risen from about 5% to 11% during the 20th century at least in U.K. and North America. The social pressure to make the child write with the right hand and to conform to the norm may have been far greater in the first half of the century than it is now” (p. 158). Consequently those that would have earlier been classified as right-handers would now be seen as lefthanders. Given that that incidence of crossed aphasia is determined primarily on the basis of handedness, the incidence of which is itself subject to social pressures, the high incidence of crossed aphasia could well be due to the factor of an increased incidence of forced or apparent right-handedness. This does seem to be the case with our data where all three factors are operant. The social taboo on left-handedness is still very strongly present in India. It is only in the recent past and that too among the literate urban population that left-handedness is accepted. The social taboo on the use of left hand would result in a large number of potential left-handers being forced at an early age to become right-handers and would result in a low incidence of left-handedness with a concomitant increase in the incidence of apparent or reported right-handedness. This would be more so with respect to the older age groups in which the aphasic population are found. This low incidence of left-handedness in aphasic populations in India is supported by the findings of two previous unpublished studies. In a comparative evaluation of dominant and nondominant cerebral hemisphere lesions consequent to occlusive cerebrovascular disease Nagaraj (1979) found 1 among his 40 patients to be lefthanded. These 40 patients were from the same source as that of our first subject population. The incidence of left-handedness in this stroke population was 2.5%. Pauranik (1985), in a study of 50 aphasics carried out at Indore in North India, found 2 of his 50 adult patients to be lefthanded, giving a 4% incidence of sinistrality in his subject population (personal communication). The incidence of left-handedness as reported by Nair and Virmani (1973) and Chary (1986) however is closer to that reported in Western studies which might be due to the fact that while the former data were drawn from the cosmopolitan city of Delhi, the latter included subjects from a much wider and younger age range (7 to 70 years) than is usual in aphasiological studies. In order to confirm the possible link between a low incidence of lefthandedness and crossed aphasia two further measures were carried outan incidence study of left-handedness in a normal population from the same social and cultural background and an extrapolation of the incidence figures of cerebral specialization for language obtained on our clinical
178
KARANTH
AND RANGAMANI TABLE
HANDEDNESS
Male Female
IN A NORMAL
10
POPULATION-CURRENT
STUDY
(N
=
120)
Age range
Mean age
Righthanders
Lefthanders
21-82 23-78
46.52 46.95
58 59
2 1
data on that given by Rasmussen and Mimer (1977) on the basis of the sodium amytal tests. A survey of incidence of sinistrality was carried out on 120 normal subjects in Mysore, selected randomly from the same socioeconomic and cultural background as the subjects of this study. The group of 120 subjects consisted of an equal number of males and females and an equal number of multi- and monolinguals. Further there were 20 subjects each in the age range of 21 to 30, 31 to 40, 41 to 50, 51 to 60, and 61 to 82 years. These subjects were classified as right- or left-handers using the same criteria as stated earlier. The distribution of subjects with reference to age, sex, and handedness is given in Table 10. The incidence of sinistrality in this population is a low 2.5%. Further all three sinistrals were found in the age range of 21-30 years. Three of the remaining subjects (two females and one male in the age range of 41 to 60 years) gave history of forced shift. They are classified here as right handed as they would now be identified as right handers in terms of handedness usage. Segalowitz & Bryden (1983) based on an average of incidence of aphasia for each hand-hemisphere combination across four studies estimate aphasia following unilateral damage to the left hemisphere of 62.1% in right handers and 52.8% in left handers with comparable figures of 3% for right handers and 25.1% for left handers in right hemisphere lesions. On the basis of these incidence figures on clinical data Segalowitz & Bryden extrapolate through statistical means an estimated distribution of language lateralization as given in Table Il. These figures they point out agree with similar estimates using very TABLE ESTIMATED
DISTRIBUTION
OF CEREBRAL SEGALOWITZ
11
LATERALIZATION AND BRYDEN,
OF LANGUAGE
IN NORMALS-
1983
Handedness
Left hemisphere
Bilateral
Right hemisphere
Right-handers Left-handers
95.5% 61.4%
19.8%
4.5% 18.8%
179
CROSSED APHASIA TABLE ESTIMATED
DISTRIBUTION
OF LANGUAGE
12
LATERALIZATION
ON THE BASIS OF THE CURRENT
DATA Handedness
Left hemisphere
Right hemisphere
Right-handers Left-handers
80.13% 100.00%
19.87% -
different approaches such as sodium amytal testing (Rasmussen & Milner, 1977) and dysphasia following unilateral electroconvulsive therapy (Warrington & Pratt, 1973). A similar extrapolation on our data results in figures as given in Table 12. These figures obtained on the basis of handedness clearly are not in agreement with what is known of cerebral specialization for speech in the general population and are supportive of our contention that in cultures where social pressure acts against left-handedness, the expectation of cerebral dominance cannot be based on handedness alone and when so based can lead to erroneous conclusions. Such errors could perhaps be minimized by calculating crossed aphasia incidence figures for the population as a whole rather than for right- and left-handers separately as has been done in most of the studies on crossed aphasia. The overall incidence figures on data such as ours would clearly show a concomitant decrease in the incidence of left-handers and left-handed aphasics with an increase in incidence of crossed aphasia. CONCLUSION In conclusion, while it could well be that cerebral representation of language in bi- and multilinguals is different than that in monolinguals, interpretations of higher incidences of crossed aphasia in polyglots as being due to multilingualism per se should be done with caution particularly when based on variables such as handedness which are known to vary subject to other factors such as cultural and social pressures. REFERENCES Albert, M., & Obler, L. 1978. The bilingual bruin. New York: Academic Press. April, R. S., & Han, M. 1980. Crossed aphasia in a right handed bilingual Chinese manA second case. Archives of Neurology, 31, 342-346. Bryden, M. P. 1982. Laterality-Functional asymmetry in the intact bruin. New York: Academic Press. Chary, P. 1986. Aphasia in a multilingual society: A preliminary study. In J. Vaid (Ed.), Language processing in bilinguals: Psycholinguistic and neuropsychological perspectives. Hillsdale, NJ: Erlbaum. Galloway, L. 1980. Towards a neuropsychological model of bilingualism and second language performance: A theoretical article with a critical review of current research and some
KARANTH
180
AND RANGAMANI
new hypotheses. In M. Long, S. Peck, & K. Bailey (Eds.), Research in second language acquisition. Rowley, MA: Newbury House. Gloning, I., & Gloning, K. 1965. Aphasia in polyglots-Contribution to the dynamics of language disintegration as well as to the question of the localization of these impairments. In M. Paradis (Ed.), Readings on aphasia in bilinguals and polyglots. Canada: Marcel Didier Inc., 1983. Nagaraj, D. 1979. Comparative evaluation of dominanr and non-dominant cerebral hemisphere lesions. Unpublished thesis, Department of Neurology, NIMHANS, Bangalore University. Nair, K. R., & Virmani, V. 1973. Speech and language disturbance in hemiplegics. Indian Journal
of Medical
Research,
61, 9.
Pauranik, A. 1985. Aphasia testing in Hindi speaking patients. Unpublished thesis, Department of Neurology, AIIMS, New Delhi. Paradis, M. 1987. The assessmenf of bilingual aphasia. Hillsdale, NJ: Erlbaum. Rasmussen, T., & Milner, B. 1977. The role of early left brain injury in determining lateralization of cerebral speech functions. In S. J. Segalowitz (Ed.), Language functions and brain organization. New York: Academic Press. Segalowitz, S. J., & Bryden, M. P. 1983. Individual differences in hemispheric representation of language. In S. J. Segalowitz (Ed.), Language function and brain organization. New York: Academic Press. Solin. 1987. In M. Paradis (Ed.), The assessment of bilingual aphasia. Hillsdale, NJ: Erlbaum. Vaid, J., & Genesee, 1980. Neuropsychological approaches to bilingualism: A critical review. Canadian Journal of Psychology, 34(4), 417-445. Warrington, E. K., & Pratt, R. T. C. 1973. Language laterality in left handers assessed by unilateral ECT. In S. J. Segalowitz (Ed.), Language functions and brain organization. New York: Academic Press.