Cerebral Asymmetry and Reading Performance: Effect of Language Lateralization and Hand Preference

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Cerebral Asymmetry and ReadingPerformance: Effect of LanguageLateralization and Hand PreferenceSergio Hernaandez a , Juan Camacho-rosales a , Antonieta Nieto a &Josea Barroso aa School of Psychology University of La Laguna , Tenerife, CanaryIslands, SpainPublished online: 24 Oct 2007.

To cite this article: Sergio Hernaandez , Juan Camacho-rosales , Antonieta Nieto & Josea Barroso(1997) Cerebral Asymmetry and Reading Performance: Effect of Language Lateralization and HandPreference, Child Neuropsychology: A Journal on Normal and Abnormal Development in Childhood andAdolescence, 3:3, 206-225, DOI: 10.1080/09297049708400644

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Child Neuropsychology 1997, Vol. 3, No. 3, pp. 206-225

0929-7049l97/0303 -206$12.00 0 Swets & Zeitlinger

Cerebral Asymmetry and Reading Performance: Effect of Language Lateralization and Hand Preference*

Sergio Hernindez, Juan Camacho-Rosales, Antonieta Nieto, and Josh Barroso School of Psychology, University of La Laguna, Tenerife, Canary Islands, Spain

ABSTRACT

We propose an alternative approach aimed at relating cerebral asymmetry to reading ability: the joint consideration of language lateralization and hand preference. Specifically, we studied whether children with dominance for language and control of the preferred hand lateralized to the same hemisphere (convergent cerebral organization) were better readers than were children with these processes lateralized to different hemispheres (nonconvergent organization). Eighty children, selected on the basis of the combination of these factors, were assessed using a set of reading tasks. The main finding was that subjects with convergent cerebral organization were superior in reading speed, reading accuracy, and reading comprehension.

Neuropsychological research into reading disability has related this disorder to anomalous cerebral morphology, for example, to the presence of architectonic dysplasias and neuronal ectopias of a developmental nature (e.g., Gala- burda, 1992; Galaburda, Corsiglia, Rosen, & Sherman, 1987; Galaburda & Kemper, 1979; Galaburda Sherman, Rosen, Aboitiz, & Ge- schwind, 198.5), disorders in the magnocellular visual subsystem (e.g., Eden et al., 1996; Rich- ardson & Gruzelier, 1994), variations in the morphology of the corpus callosum (e.g., Hynd et al., 1995; Njiokiktjien, de Sonneville, & Vaal, 1994), and absence or attenuation of anatomical asymmetries (e.g., Galaburda et al., 1985; Haslam, Dalby, Johns, & Rademaker, 1981; Larsen, Hoien, Lundberg, & Odegaard, 1990; Steinmetz & Galaburda, 1991). Reading disorders have also been associated with electrophysiological (EEG, ERP) and metabolic brain anomalies in several regions involved in language processing (e.g., Brunswick & Rippon, 1994; Duffy, Denckla, Bartels, & Sandini, 1980;

Johannes, Mangun, Kussmaul, & Munte, 199.5; Paulesu et al., 1996). Moreover, there have been reports of an elevated prevalence of left-handedness among people with dislexia (e.g., Annett & Kilshaw, 1984; Geschwind & Behan, 1982, 1984), and some evidence suggesting an anomalous pattern of cerebral functional asymmetry from divided sensory field and dual-task studies (e.g., Hugdahl, Helland, Faerevaag, Lyssand, & Asbjornsen, 199.5; Pirozzolo & Rayner, 1979; Stellern, Collins, & Bayne, 1987). The common goal in most studies has been to examine the relationship between cerebral asymmetry and reading failure. From a neurofunctional approach, this has given rise to two lines of research: (1) studies that associate reading disabilities with hand preference, and (2) those that relate reading disorders to language lateralization.

Hand preference is the most obvious behavioural manifestation of hemispheric specialization in humans. The “right-side’’ population bias in hand preference is a well-established

This research was supported by a grant from the Consejeria de Educaci6n del Gobierno de Canarias, Number U01.06.88. Address correspondence to: Jost Barroso, School of Psychology, Campus de Guajara, Universidad de La Laguna, 38200 La Laguna, Tenerife, Canary Islands, Spain. Accepted for publication: June 2, 1997.

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CERE3RAL ASYMMETRY AND READING 207

phenomenon. Several disorders have been linked with left-hand preference, albeit contro- versially. With respect to reading, Annett and Kilshaw (1984), Eglinton and Annett (1994), Geschwind and Behan (1982, 1984), and Schachter, Ransil, and Geschwind (1987) have reported that left handedness or mixed handedness are more common among disabled readers. However, this relationship has been disputed (e.g., Bishop, 1990; Hugdahl, Synnevag, & Satz, 1990; Jariabkova, Hugdahl, & G16s, 1995).

Differences in language lateralization between good and poor readers have been suggested by electrophysiological and brain metabolism studies (e.g., Duara et al., 1989; Gross- Glen et al., 1990; Miles & Stelmack, 1994; Mor- ris, Obrzut, & Coukthard-Morris, 1989: Naylor, Wood, & Harter, 1995; see, however, Galin, Herron, Johnstone, Fein, & Yingling, 1988), but this topic has been studied mainly using divided sensory field and dual-task paradigms. Several studies with dichotic listening tasks and verbal stimuli have found evidence of these differences. Specifically, there are reports of an attenuation of the right-ear advantage (REA; Kershner & Morton, 1990), of an absence of ear advantages (Thompson, 1976), or a trend towards a left-ear advantage (Thompson, Zurif & Carlson, 1970), in disabled readers. However, Boliek, Obrzut, and Shaw (1988), Hynd. Obrzut, Weed, and Hynd (1979), Obrzut, Hynd, Obrzut, and Pirozzolo ( I98 1 ), Obrzut, Conrad, Bryden, and Boliek (1988), and Springer and Eisenson (1977) found no differences in the pattern of language Iateralization between good and poor readers. In some cases, the differences in lateralization between both groups appear to depend on the age of the subjects (Obrzut, Boliek, Bryden, & Nicholson, 1994). Similarly, some divided visual field studies have shown a reduced right visual field superiority (Kershner, 1977; Marcel & Rajan, 1975) or an absence of visual field effect in poor readers (McKeever & Van Deventer, 1975; Pirozzolo & Rayner, 1979). In other cases, disabled readers did not differ from normal readers on tachistoscopic verbal tasks (McKeever & Van Deventer; Olson, 1973).

Obrzut, Hynd, Obrzut, and Leitgeb (1980), and Stellern, Collins, Cossairt, and Gutierrez (1986), using the concurrent-task method, found verbal asymmetrical interference in both groups of readers (verbal activity interferes with right- hand more than left-hand performance). How- ever, Stellern et al. (1987) pointed out that this asymmetry of interference is frequently reversed in poor readers. It can be argued that the lack of agreement among these laterality studies may be due to the fact that disabled readers are considered as a homogeneous group.

At present, there is considerable evidence that reading disabilities are a heterogeneous entity (e.g., Rourke &Gates, 1981). In this sense, various proposals for classification systems have been made (e.g., Bakker, 1978; Boder, 1973; Petrauskas & Rourke, 1979; Pirozzolo, 1981). In recent research studies with people with dyslexia, various researchers have attempted to find distinctive patterns of cerebral asymmetry among subtypes of people with dyslexia. Em- ploying Boder’s classification scheme, Cohen, Hynd, and Hugdahl(1992) report an attenuation of verbal asymmetry in dysphonetic children and the normal left-hemisphere (LH) superiority in dyseidetics. Employing the Bakker classification system, Massuto, Bravar, and Fabro (1994) also found a reduction of verbal LH superiority in children with L-dyslexia (a group equivalent to dysphonetics) but an absence of asymmetry in P-dyslexics (a group equivalent to dyseidetics). There are reports of other distinctive patterns of asymmetry (Dalby & Gibson, 1981), and of the presence of the same asymmetry in the different subtypes and in normal readers (Aylward, 1984; Obrzut, 1979). Consequently, inclusion of the type of dyslexia variable has not eliminated the contradiction in results.

Review of the literature allows, in our opinion, the establishment of several conclusions. First, that the relationship between cerebral asymmetry and reading performance is supported by abundant evidence. However, the terms in which this relationship is established have not been explained in a satisfactory way by either hand preference studies or by languagelateralization studies.

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208 SERGIO HERNANDEZ ET AL. ~

Second, both these lines of research have had independent development, with little interaction. Thus, hand-preference studies have emphasised the relationship between left handedness and reading disabilities. In these cases, left-handed people have been considered as an homogenous group, without taking into consideration their pattern of language lateralization. On the other hand, language-lateralization studies have re- stricted their experimental samples to right- handed subjects or have used hand preference only as a control variable.

This situation is illustrated by a recent study by Obrzut, Boliek, and Bryden (1997). These authors used meta-analytic techniques to aggre- gate data regarding the influence of handedness, reading ability, and selective attention on ear advantages in dichotic listening. Hand preference is considered as an independent variable which is combined with reading ability in only one (Obrzut, Conrad, & Boliek, 1989) of the 15 studies chosen. In fact, the authors conclude that more systematic studies will be necessary to understand the nature of the relationships among handedness, reading performance, and functional lateralization.

Because results have been inconsistent from the point of view of an isolated consideration of hand preference or language lateralization, an alternative approach may be to take into account the combination of both factors. If we consider the combination of these factors, we find four possible forms of cerebral organization: on the one hand, two groups made up of subjects with left-hemisphere language lateralization, one group with right-hand preference and the other with left-hand preference; on the other hand, two groups with right-hemisphere language lateralization, in one case associated with right- hand preference, and in the other case associated wih left-hand preference. We exclude the cases of language bilateralization or mixed hand preference, because they pose a different problem, related to the degree of asymmetry, which re- quires specific treatment.

Taking into consideration these four groups, we can follow two lines of argument. First, it could be argued that the predominant cerebral organization, left-cerebral dominance for lan-

guage and right-hand preference. is the most efficient cerebral organization for the correct acquisition andlor execution of reading. Conse- quently, every form of cerebral organization different from this would imply the existence of lesser reading ability. This line of argument leads us to a situation without experimental support: that left-handed people, by the mere fact of being left-handed, should show some kind of reading disorder.

The second line of argument emphasizes that in the predominant form of cerebral organization, the same hemisphere is dominant for language functions and also responsible for control of the preferred hand. Thus, this “convergence” could be the decisive factor. Other patterns of cerebral organization that do not result in this convergence could be less efficient for reading, possibly producing some degree of linguistic impairment that is especially manifested in reading performance. That is, the reading ability of subjects with processing of language and motor control of the preferred hand lateralized to a same hemisphere, language-left-hemisphere dominance plus right-handedness (LLD-RH), and language-right-hemisphere dominance plus left-handedness (LRD-LH), would be superior to the reading ability of subjects with these processes lateralized to different hemispheres, language-left-hemisphere dominance plus left- handedness (LLD-LH), and language-right- hemisphere dominance plus right-handedness

To our knowledge, this issue has not been examined previously. The main goal of this study was to examine the relationship between “convergent” cerebral organization and reading ability. For this purpose, we studied the performance on a set of reading tasks of children grouped on the basis of their hand preference and hemispheric dominance for language. We selected subjects from regular school classes because, if the effect of the proposed pattern of cerebral organization is relevant for reading performance, it should be apparent in children without reading disorders that require special school programs (dyslexics or children with learning disabilities). Given the population distribution of both hand preference and hemispheric domi-

(LRD-RH) .

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209 CEREBRAL ASYMMETRY AND READING -

nance for language, it was necessary to study both factors in a large sample. From this study, we selected two groups of subjects with convergent cerebral organization and two groups with a pattern of nonconvergent cerebral organization. Additionally, w e took into consideration the gender factor in the selection of subjects, a variable that has been related to cerebral asymmetry as well as to reading performance.

METHOD

Selection Procedure The initial sample comprised 154 right-handed subjects (104 males and 50 females) and 77 left- handed subjects (48 males and 29 females), determined by the hand-preference subtest of the Harris Tests of Lateral Dominance (Harris, 1947). Each child was observed performing the following 10 tasks: throwing a ball, winding a watch, hammer- ing a nail, brushing their teeth, combing their hair, turning a door knob, using an eraser, using scis- sors, cutting with a knife, and writing. Children who used their right hand for 8 or more activities were considered to be right-handed. Children who used their left hand for 8 or more activities were considered left-handed. Mean age was 10.28 years ( S D = 0.93; range 9-12) for males and 10.29 years (SD = 0.97; range 9-12) for females. All were fourth-, fifth-, and sixth-grade students. Approxi- mately half were recruited from private schools and the other half from public schools. All of the participants were of normal intelligence (IQ of 90 or higher) as determined by full scale scores on the Wechsler Intelligence Scale for Children (WISC; Wechsler, 1949). All subjects were “blind” to the purpose of the experiment. None had any evidence of emotional, neurological, or uncorrected sensory disorders. All attended school regularly. All were Spanish-speaking monolinguals and their partici- pation was voluntary.

We used the dual-task method to assess hemispheric specialization of language, an experimental paradigm usually employed in this type of study (e.g., Bathurst & Kee, 1994; Dalby & Gibson, 1981; Hiscock & Inch, 1995; McFarland, Ashton, Rich, & Donald, 1989). In the present study we used a motor unimanual task and a verbal task. The motor task consisted in the alternative tapping of two keys on a computer keyboard with the index and middle fingers. The verbal task required vocalization: The children were instructed to repeat a sequence of four animal names (dog, cow, horse,

and rabbit) in 10 s. Vocal responses were taped. There were three single-task conditions: tapping with the right hand (TR), tapping with the left hand (TL) and the verbal task condition (V). The two dual-task conditions were: tapping with the right hand and the concurrent verbal task (TRV) and tapping with the left hand and the concurrent verbal task (TLV). Two 10-s trials were given in all conditions. The resulting 10 test trials (6 single- task and 4 dual-task) were counterbalanced to con- fro1 order of tapping hand (right or left) and single- or dual-task trial.

Approximately half of the children started the task with their left hand and the other half started with their right hand. All subjects were given two practice trials for each task. Children were told to move their fingers as quickly as possible without making mistakes. The computer keyboard was placed in each manual trial in such a way that the tapping keys were ipsilateral to the hand to be used. The computer screen recording the data was not visible to the subjects.

When the verbal task was involved, the children were additionally instructed to repeat the sequence of names as many times as possible. Instructions for the dual-task trials placed equal emphasis on tapping and vocalization. A beep from the micro- computer started and ended each trial. The manual performance was scored by the number of correct responses to the required sequence. A conventional interference index was calculated (e.g., Hiscock & Kinsbourne, 1978; Simon & Sussman, 1987; White CIZ Kinsbourne, 1980): Tapping performance for each hand in the dual-task condition was measured against the baseline rate of tapping for that hand obtained in the single-tapping condition. Right- hand interference (RI) was calculated using the formula RI = [(TR - TRV)/TR] x 100. The left- hand interference index (LI) was obtained similarly. Subjects who experienced facilitation in both hands were excluded (n = 11, 6 males and 5 females).

We calculated the asymmetry of the interference (AI) using the formula A1 = RI-LI in order to allocate children to either the group with left-hemisphere dominance for language, or to the group with right-hemisphere dominance. Subjects with A1 scores greater than or equal to +5 (proportion- ally, verbal task disrupted right-hand performance more than left-hand performance) were assigned to the left-hemisphere group, whereas subjects with A1 scores equal to or lower than -5 were allocated to the right-hemisphere group. Subjects with A1 scores between +5 and -5 were excluded ( n = 46, 31 males and 15 females).

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210 SERGIO HERNANDEZ ET AL.

Finally, the allocation to the two groups was confirmed by the results of a dichotic listening test following the consonant-vowel-consonant (CVC) combination. For each subject an ear laterality index (ELI) was obtained by the formula:

[(Right-ear scores-Left-ear scores)/(Right-ear scores+Left-ear scores)] x 100.

ELI scores equal to or higher than +10 confirmed the allocation to the left-hemisphere group; ELI scores equal to or lower than -10 confirmed the allocation to the right-hemisphere group. Eighteen subjects (12 male and 6 female) who were not confirmed were excluded from the final experimental sample.

Subjects One hundred and fifty-six subjects included from the initial sample were classified into four groups, based on joint consideration of hand preference and cerebral language lateralization, as follows: (1) LLD-RH (n = 84; 60 males and 24 females); (2) LRD-RH (n = 24; 14 males and 10 females); (3) LLD-LH (n = 27; 15 males and 12 females); and (4) LRD-LH (n = 21; 14 males and 7 females). Twenty children were randomly selected from each group; the proportion between genders was main- tained whenever possible. Mean age and IQ for each group and the distribution by gender are shown on Table 1. All groups were equivalent in age [F(7,72) = 0.4715, p = ,85211 and in IQ [F(7,72) = 0.5032, p = 32921.

Table 1. Subject Characteristics of Experimental Groups.

Instruments Reading performance was assessed using seven tasks included in the Test de Analisis de Lectoescritura-TALE (Test for assessment of reading and writing skills; Toro & Cervera, 1984): five tasks involved reading aloud (a) Capital letters (30 items); (b) Small letters (30 items); (c) Syllables (20 items); (d) Words (50 items); and (e) Text; a Silent Reading task and a Reading Comprehension task. In the Letter tasks, all of the letters in the Spanish alphabet were presented in two separate lists for capital and small letters. In the Syllable task, the list presented included syllables with different structures (CV, VC, CVC, CCV). The Words task required reading a list of familiar words. In the Text task, subjects read aloud a text of 142 words, including different syntactic structures. A similar text was used for Silent Reading. The Reading Comprehension task involved answering 10 questions about the text used in Si- lent Reading. An additional task, the Instant Read- ing task, required the immediate reading of 20 words printed on a card.

Design and Procedure A 2 x 2 x 2 factorial design was used with Lan- guage Lateralization (Left-, Right-hemisphere), Hand Preference (Right-, Left-hand) and Gender (Male, Female) as intergrouping factors (independent variables). Dependent variables were Reading Speed, Reading Accuracy, Reading Comprehen- sion, and Reading Efficiency. Both time of reading (Reading Speed) and number of errors (Reading

Convergent Nonconvergent

LLD-RH LRD-LH LLD-LH LRD-RH

M (SD) M ( S D ) M (SD) M (SD)

Males (n = 10) (n = 13) (n = 10) ( n = 10) Age (years) 10.1 (0.9) 10.2 (1.1) 9.7 (0.6) 10.3 (0.8) WISC FSIQ 113.20 (14.84) 109.38 (12.19) 116.20 (15.53) 106.40 (16.50)

Females ( n = 10) (n = 7) (n = 10) (n = 10) Age (years) 10.1 (0.8) 10.4 (1.1) 10.4 (1.5) 10 (0.8) WISC FSIQ 106.50 (18.67) 109.43 (9.02) 111.30 (14.64) 110.10 (12.94)

Total (n = 20) ( n = 20) (n = 20) (n = 20) Age (years) 10.1 (0.9) 10.3 (1.2) 10.1 (1.1) 10.1 (0.8) WISC FSIQ 109.85 (16.76) 109.40 (10.93) 113.75 (14.90) 108.25 (14.56)

Nore. LLD-RH: language left-hemisphere dominance plus right-handedness; LRD-LH: language right-hemisphere dominance plus left-handedness; LLD-LH: language left-hemisphere dominance pIus left-handedness; LRD-RH: language right-hemisphere dominance plus right-handedness: WISC FSIQ: Full Scale Intelligence Quotient.

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CEREBRAL ASYMMETRY AND READING ~

21 1

Accuracy) were recorded for Capital Letters, Small Letters, Syllables, Words, and Text. Reading time was recorded for Silent Reading and the number of correct responses was recorded for Reading Com- prehension. In addition, we calculated a Reading Efficiency index to assess the time-accuracy relationship in those tasks where both measures were available (Capital Letters, Small Letters, Syllables, Words, Text, and Comprehension). This index was calculated by the formu1a:RE = (CR/RT) x 100 (De Vega, Carreriras, Gutierrez-Calvo, & Alonso- Quecuty, 1990), where CR is the number of correct responses and RT is the reading time. The Reading Efficiency index for Comprehension was calculated from the time of reading and correct responses to the text used in the Silent Reading task. In the Instant Reading task, a list of words was presented using a methodology similar to that suggested by Boder and Jarrico (1 982). Children were told to read the words aloud as quickly as possible. An error was recorded if the subject failed to read a word within 2 s or misread the word. Four sequences of presentation of the reading tasks were used. Subjects were randomly assigned to the different sequences. Each subject was assessed individually in a quiet room for approximately 30 min. The children were informed that the tests were timed speed tests. They were instructed to read as quickly and as accurately as possible, except in Instant Reading where the instructions emphasised speed. Reading tests were administred by a researcher blind to group assign- ment.

RESULTS

Scores in Speed, Accuracy, Reading Compre- hension, and Reading Efficiency were analysed separately by multivariate and univariate analyses of variance (MANOVAs, ANOVAs), exam- ining the Language Lateralization, Hand Prefer- ence, and Gender factors. Mean reading scores and standard deviations as a function of factors examined in the analyses of variance are shown in Tables 2 and 3.

Reading Speed In the MANOVA performed with all dependent measures of reading speed, the only significant effect was the Language Lateralization x Hand Preference interaction (A = 0.7921) [F(6,72) = 2.950, p < ,011. Moreover, this interaction was

significant in the univariate analyses (ANOVAs) for Syllables [F(1,72) = 5.336, p < .05]; Words IF(1,72) = 12.74, p < ,0051, Text [F(1,72) = 17.23, p < .001] and Silent Reading [F(1,72) = 8.578, p < .01] (see Fig. 1) No other significant effects were observed.

Reading Accuracy In the MANOVA performed with all measures of reading accuracy, a significant Language Lateralization x Hand Preference interaction was obtained (A = 0.8201) [F(6,72) = 2 , 4 4 8 , ~ < .05]. No other significant interactions or main effects were observed. This interaction was also significant in the ANOVAs for Words [F( 1,72) = 7.271, p < .01]; Instant Reading [F(1,72) = 11.97, p < .OOS] and Text [F( 1,72) = 8.41 8, p < ,011 (see Fig. 2). In addition, the ANOVA performed for Words showed a significant effect for Gender [F(l,72) = 5.49, p < .05]: Males had higher errors scores ( M = 3.60) than females ( M = 2.49). The Hand Preference x Gender interaction was significant in the ANOVA for Capital letters [F( 1,72) = 6.06, p < .05]. Simple Effects Contrast showed a gender difference in the right-handed groups [F(1,72) = 5.73, p < .051 but not in the left-handed groups: Right-handed males had higher error scores ( M = 2.305) than did females ( M = 1.21 0).

Reading Comprehension The ANOVA revealed the Language Laterali- zation x Hand Preference interaction as the only significant effect [F( 1,72) = 7.37, p < .001] (see Fig. 3).

Reading Efficiency In the MANOVA performed with all indexes of reading efficiency, the only significant effect was the Language Lateralization x Hand Prefer- ence interaction (A = 0.7486) [F(6,72) = 3.749, p < ,0051. Likewise, in the univariate analysis this interaction was significant for Syllables [F(1,72) = 5.418, p < ,051, Words [F(1,72) = 11.72, p < .005], Text [F(1,72) = 17.32, p < .001], and Reading Comprehension [F( 1,72) = 11.71, p < .OOS]. No other significant effects were observed.

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Tabl

e 2.

M

ean

Rea

ding

Sco

res a

s a F

unct

ion

of L

angu

age L

ater

aliz

atio

n G

roup

and

Gen

der.

Cer

ebra

l Lan

guag

e D

omin

ance

Left

Hem

isph

ere

Rig

ht H

emis

pher

e

Tota

l (n =

40)

M

ales

(n

= 2

0)

Fem

ales

(n

= 2

0)

Tota

l (n =

40)

M

ales

(n

= 2

3)

Fem

ales

(n =

17)

M

(SD

) M

(S

D)

M

(SD

J M

(S

D)

M

(SD

) M

(S

D)

Rea

ding

Spe

ed (s

) C

apita

l Let

ters

Sm

all L

ette

rs

Sylla

bles

W

ords

Te

xt

Sile

nt R

eadi

ng

Cap

ital L

ette

rs

Smal

l Let

ters

Sy

llabl

es

Wor

ds

Text

In

stan

t Rea

ding

Rea

ding

Com

preh

ensi

on

Cap

ital L

ette

rs

Smal

l Let

ters

Sy

llabl

es

Wor

ds

Text

Rea

ding

Acc

urac

y (e

rror

s)

Com

preh

ensi

on (c

orre

ct re

spon

ses)

Rea

ding

Eff

icie

ncy

Inde

x

Rea

ding

Com

preh

ensi

on

22.5

4 21

.06

13.4

8 47

.63

84.0

8 73

.42

1.68

1.

44

0.37

2.

83

6.42

5.

50

4.86

135.

64

144.

40

153.

01

106.

68

177.

30

7.56

(6.2

1)

(5.1

8)

(3.1

1)

(12.

58)

(30.

47)

(31.

78)

(1.4

2)

(1.4

6)

(0.7

7)

(2.3

3)

(5.2

8)

(3.3

4)

(2.4

0)

(40.

64)

(39.

53)

(35.

07)

(31.

33)

(49.

83)

(4.5

6)

22.1

7 20

.69

13.1

2 47

.21

81.2

0 72

.82

1.74

I .

25

0.45

3.

10

5.50

6.

30

5.25

135.

66

147.

92

154.

78

105.

90

180.

42

8.1 1

(5.2

2)

(5.3

1)

(2.5

2)

(1 1.

50)

(24.

80)

(34.

16)

(1.2

0)

(1.2

3)

(0.9

4)

(2.4

9)

(3.9

9)

(3.7

7)

(2.0

3)

(38.

61)

(39.

60)

(32.

54)

(29.

88)

(45.

46)

(3.9

3)

22.9

0 (7

.18)

21

.43

(5.1

5)

13.8

5 (3

.64)

48

.05

(13.

87)

86.9

5 (3

5.68

) 74

.01

(30.

09)

1.62

(1

.63)

1.

62

(1.6

7)

0.30

(0

.57)

2.

55

(2.1

9)

7.35

(6

.28)

4.

70

(2.7

0)

4.47

(2

.73)

135.

61

(43.

59)

140.

89

(40.

17)

151.

24

(38.

20)

107.

47

(33.

48)

174.

19

(54.

86)

7.02

(5

.17)

24.3

9 21

.26

14.1

5 48

.83

92.5

3 68

.1 1

I .85

1.

85

0.88

3.

35

6.88

5.

10

4.3

1

124.

06

138.

89

142.

28

102.

47

160.

76

7.20

(6.7

3)

(4.6

1)

(3.4

9)

(13.

23)

(32.

29)

(25.

78)

(I .5

3)

(1.5

1)

(1.6

4)

(2.4

6)

(4.8

4)

(3.1

4)

(2.3

5)

(34.

51)

(33.

58)

(33.

04)

(27.

23)

(46.

34)

(4.9

9)

24.5

0 (6

.84)

20

.77

(4.6

7)

14.2

9 (4

.38)

49

.81

(14.

98)

94.7

0 (3

6.05

) 69

.54

(29.

92)

2.04

(1

.71)

1.

94

(1.7

5)

1.17

(1

.87)

4.

04

(2.5

8)

7.91

(5

.04)

5.

22

(3.1

3)

4.59

(2

.20)

123.

75

(38.

21)

142.

40

(37.

37)

142.

28

(39.

90)

100.

53

(29.

71)

157.

53

(46.

26)

7.77

(5

.23)

24.2

4 2 1

.94

13.9

7 47

.52

89.6

0 66

. I8

1.60

1.

73

0.47

2.

41

5.47

4.

94

3.94

124.

48

134.

14

142.

28

105.

10

165.

13

6.42

(6.7

8)

(4.6

0)

(1 32

) (1

0.72

) (2

7.18

) (1

9.55

)

(1.2

5)

(1.1

6)

(1.1

8)

(1.9

7)

(4.3

0)

(3.2

3)

(2.5

6)

(29.

92)

(28.

06)

(21.

74)

(24.

09)

(47.

52)

(4.6

9)

Not

e. C

apita

l Let

ters

= 3

0 ite

ms:

Sm

all L

ette

rs =

30

item

s: S

ylla

bles

= 2

0 ite

ms;

Wor

ds =

50

item

s; In

stan

t Rea

ding

= 2

0 ite

ms

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Tabl

e 3.

M

ean

Rea

ding

Sco

res

as a

Fun

ctio

n of

Pre

ferr

ed H

and

Gro

up a

nd G

ende

r.

Han

d Pr

efer

ence

Rig

ht H

and

Left

Han

d

Tota

l (n =

40)

M

ales

(n =

20)

Fe

mal

es (

n =

20)

T

otal

(n

= 4

0)

Mal

es (

n =

23)

Fe

mal

es (

n =

17)

M

isD

i M

(SD)

M

(SD)

M (SD)

M

(SO

) M

(SD)

Rea

ding

Spe

ed (s

) C

apita

l Let

ters

Sm

all L

ette

rs

Sylla

bles

W

ords

Te

xt

Sile

nt R

eadi

ng

Cap

ital L

ette

rs

Smal

l Let

ters

Sy

llabl

es

Wor

ds

Text

In

stan

t Rea

ding

Rea

ding

Com

preh

ensi

on

Cap

ital L

ette

rs

Smal

l Let

ters

Sy

llabl

es

Wor

ds

Text

R

eadi

ng C

ompr

ehen

sion

Rea

ding

Acc

urac

y (e

rror

s)

Com

preh

ensi

on (

corr

ect r

espo

nses

)

Rea

ding

Eff

icie

ncy

Inde

x

22.3

6 20

.48

13.5

0 47

.50

86.4

8 68

.29

1.76

1.

62

0.53

3.

08

6.43

4.

90

4.36

136.

68

148.

06

153.

74

107.

62

176.

63

7.03

(6.3

3)

(5.3

8)

(3.7

9)

(13.

89)

(34.

38)

(24.

16)

(1.5

9)

(1.5

8)

(1.2

0)

(2.7

2)

(5.2

0)

(3.3

3)

(2.5

6)

(41 .

I 8)

(40.

87)

(37.

52)

(32.

72)

(55.

37)

(4.7

7)

22.7

3 20

.74

13.9

2 48

.86

89.6

7 71

.19

2.30

1.

93

0.80

4.

10

7.45

5.

70

4.65

132.

08

146.

50

150.

61

104.

50

172.

55

7.43

(6.0

5)

(6.0

1)

(4.7

7)

(1 6.

28)

(40.

13)

(29.

48)

(1.8

4)

(1.9

5)

(1.5

1)

(3.1

6)

(5.5

5)

(3.5

4)

(2.4

1)

(42.

82)

(44.

93)

(41.

84)

(35.

12)

(56.

38)

(4.5

1)

21.9

9 20

.23

13.0

9 46

.14

83.2

9 65

.40

1.21

1.

32

0.25

2.

05

5.40

4.

10

4.07

141.

28

149.

63

156.

88

110.

74

180.

7 1

6.64

(6.7

3)

(4.8

2)

(2.5

2)

(11.

28)

(28.

18)

(I 7

.65)

(1.0

8)

(1.0

7)

(0.7

2)

(1.7

3)

(4.7

5)

(2.9

7)

(2.7

4)

(40.

02)

(37.

47)

(33.

43)

(30.

71)

(55.

49)

(5.1

1)

24.5

6 21

.84

14.1

3 48

.97

90.1

3 73

.24

1.78

1.

66

0.73

3.

10

6.88

5.

70

4.81

123.

01

135.

23

141.

55

101.

54

161.

44

7.73

(6.5

6)

(4.2

7)

(2.7

5)

(11.

84)

(28.

62)

(33.

05)

(1.3

5)

(1.4

1)

(1.4

0)

(2.0

5)

(4.9

2)

(3.1

1)

(2.1

9)

(33.

47)

(30.

85)

(29.

55)

(25.

35)

(39.

83)

(4.7

8)

-

Not

e. C

apita

l Let

ters

= 3

0 ite

ms;

Sm

all L

ette

rs =

30

item

s; S

ylla

bles

= 2

0 ite

ms;

Wor

ds =

50

item

s; I

nsta

nt R

eadi

ng =

20

item

s

24.0

2 (6

.37)

20

.72

(3.8

6)

13.5

9 (2

.37)

48

.38

(10.

63)

87.3

3 (2

2.94

) 70

.97

(34.

02)

1.54

(1

.01)

1.

35

(1.0

7)

0.87

(1

.60)

3.

17

(1.8

5)

6.22

(3

.83)

5.

74

(3.4

4)

5.11

(1

.88)

126.

87

(34.

92)

143.

63

(31.

91)

145.

91

(32.

55)

101.

75

(29.

47)

164.

38

(37.

43)

8.36

(4

.77)

25.2

9 23

.35

14.8

6 49

.76

93.9

2 76

.3 1

2.09

2.

09

0.53

3.

00

7.76

5.

65

4.41

1 17.

80

123.

86

135.

65

101.

25

157.

46

6.88

(6.9

4)

(4.4

3)

(3.1

1)

(13.

60)

(35.

30)

(32.

47)

(I .7

0)

(1.7

0)

(1.0

7)

(2.3

5)

(6.1

1)

(2.6

9)

(2.5

6)

(31.

68)

(26.

09)

(25.

80)

(27.

26)

(43.

73)

(4.7

9)

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2

g 10- = 2 'Riybt Hnndem

, *Lett Hsnders

SYLLABLES WORDS

+Ri*hl Handers

*Left Harderr

1 6o 1

, * I d 1 Handers

TEXT

IZ0 1 LOO

Y z 80

g 20

SILENT READlNG

* Rl~hl-HaOders

~ +lrfl-Hsnders

Left Hemisphere Rigbl Hemisphere LANGUAGE LATERAUZATION

Fig. 1 . Mean reading time for significant interactions between Language Lateralization and Hand Preference.

The results of the preceding analyses revealed that there were no differences in reading performance when subjects are categorized by left- or right-lateralization of language. This same pattern was observed for right- or left-hand preference. On the contrary, a Language Lateralization x Hand Preference interaction was obtained in the analyses conducted for most of the dependent measures (see Figs. 1-3). To directly examine our hypothesis, namely, that children with convergent cerebral organization are more efficient readers than children with nonconvergent

cerebral organization, we used a new experimental design to contrast the efficiency of the convergent group with that of the nonconvergent group. First, we analysed reading performance of the two groups that made up the convergent group (LLD-RH and LRD-LH). The multivariate and univariate analyses performed showed no differences in any dependent mea- sure. Similarly, there were no differences in reading performance between the two groups that made up the nonconvergent group (LLD-LH and LRD-RH). Given these results, we exam-

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215 CEREBRAL ASYMMETRY AND READING

WORDS

- 8 s\" 'OI

0 P

E 4 6l *Right Handers

*Left Handers

Left Hemisphere Right Hemisphere

LANGUAGE LATERALIZATION

40 1 :*.] m

w

INSTANT READING

4\

*RIght Handers

TEXT

*Right Handers , *Left Handers

Left Hemisphere Right Hemisphere

LANGUAGE LATERALIZATION

Fig. 2. Mean errors for the significant interactions between Language Lateralization and Hand Preference.

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L

O l 0 -

a z

READING COMPREHENSION

*Right Handers

, *Left Headers

Fig. 3. Mean correct responses for the significant interaction between Language Lateralization and Hand Pref- erence in Reading Comprehension.

ined directly our predictions regarding the convergence effect by two-way multivariate and univariate analyses of variance using Group (convergent, nonconvergent) and Gender (male, female) as independent variables. Mean reading scores and standard deviations as a function of these factors are shown in Table 4.

Reading Speed In the MANOVA Group (convergent, nonconvergent) x Gender (male, female) performed with all measures of reading time, there was a significant main effect for Group (A = 0.8 11 I ) [F(4,76) = 4.25, p < .005]. ANOVAs revealed that the reading time of the convergent group was lower than that of the nonconvergent group in the following: Syllables [F( 1,76) = 5.691 , p < .05], Words [F(1,76) = 13.22, p < .OOl], Text [F( 1,76) = 17.47, p < .001], and Silent Reading [F(1,76) = 8.94, p < .005] (see Fig. 4). No other effects were significant.

Reading Accuracy The MANOVA conducted with all reading accuracy measures again revealed a significant Group effect (A = 0.8350) [F(3,76) = 4.873, p < .005]. In the subsequent ANOVAs the only significant effect was Group: nonconvergent subjects were less accurate (more reading errors) than convergent subjects in Words [F(1,76) =

7.47,p< .Ol],InstantReading [F(1,76)= 13.26, p < .0011, and Text [F(1,76) = 7.916, p < .01] (see Fig. 5).

Reading Comprehension The convergent group was better than the nonconvergent group [F(1,76) = 7.520, p < .01] in the comprehension task (see Fig. 6). No significant gender differences were found.

Reading Efficiency In the MANOVA performed with all reading efficiency indexes, there was a significant main effect for Group (A = 0.7729) [F(4,76) = 5.359, p < .005]. In the ANOVAs a superiority of convergent group was again obtained for Syllables [F(1,76) = 5.812, p < .05], Words [F(1,76) = 12.34, p < .005], Text [F(1,76) = 17.15, p < .001], and Reading Comprehension [F(1,76) = 12.37, p < .005]. No other effects reached sig- nificance.

DISCUSSION

The aim of this research was to demostrate that the convergence of language dominance and motor control of the preferred hand in the same hemisphere represents a more efficient cerebral organization for reading performance than does

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Tabl

e 4.

Mea

n R

eadi

ng S

core

s as

a F

unct

ion

of C

onve

rgen

t-Non

conv

erge

nt G

roup

.

Con

verg

ent

Non

conv

erge

nt

Tota

l (n

= 40

) M

ales

(n

= 2

3)

Fem

ales

(n =

17)

To

tal (

n =

40)

M

ales

(n

= 2

0)

Fem

ales

(n =

20)

M

(sn)

M

(S

O)

M

(SO

) M

(SD)

M

M

fsD

)

Rea

ding

Spe

ed (s

) Sy

llabl

es

Wor

ds

Text

Si

lent

Rea

ding

Wor

ds

Text

In

stan

t Rea

ding

Rea

ding

Com

preh

ensi

on

Sylla

bles

W

ords

Te

xt

Rea

ding

Com

preh

ensi

on

Rea

ding

Acc

urac

y (e

rror

s)

Com

preh

ensi

on (c

orre

ct re

spon

ses)

Rea

ding

Eff

icie

ncy

Inde

x

12.9

6 43

.34

74.8

3 61

.58

2.43

5.

10

4.10

5.32

156.

43

115.

24

189.

56

9.19

(2.4

9)

(9.1

6)

(14.

23)

( 19.

02)

(1.7

2)

(3.3

0)

(2.6

8)

(2.2

1)

(35.

42)

(27.

50)

(37.

26)

(4.6

3)

13.0

9 43

.92

76.2

5 63

.58

2.74

4.

91

4.35

5.72

152.

97

112.

52

183.

32

9.66

(2.3

6)

(8.6

8)

(I 5

.30)

(2

3.62

)

(1.8

1)

(2.7

3)

(2.8

7)

(1.9

6)

(35.

43)

(26.

72)

(35.

64)

(4.4

6)

12.7

8 42

.55

72.9

0 58

.88

2.00

5.

35

3.76

4.79

161.

12

118.

93

193.

94

8.54

(2.7

2)

(10.

00)

(I 2.

85)

(10.

09)

(1.5

4)

(4.0

3)

(2.4

4)

(2.4

6)

(35.

95)

(28.

92)

(40.

03)

(4.9

2)

14.6

8 53

.13

101.

78

79.9

5

3.75

8.

20

6.50

3.85

138.

86

93.9

1 14

8.51

5.

58

(3.7

9)

(14.

18)

(37.

85)

(33.

97)

(2.7

8)

(5.9

6)

(3.3

1)

(2.3

4)

(31.

11)

(27.

25)

(50.

18)

(4.2

0)

14.4

9 53

.99

102.

41

79.6

8

4.60

8.

95

7.30

3.95

142.

49

99.1

1 14

7.31

5.

93

(4.6

6)

(15.

86)

(39.

58)

(37.

65)

(2.9

5)

(5.5

5)

(3.4

4)

(1.9

4)

(38.

41)

(29.

49)

(50.

1 I)

(4.0

3)

14.8

6 52

.27

101.

15

80.2

2

2.90

7.

45

5.70

3.75

135.

23

95.7

1 14

9.70

5.

22

(2.7

7)

(12.

63)

(37.

06)

(30.

84)

(2.3

8)

(6.0

9)

(3.2

3)

(2.7

3)

(21.

99)

(25.

45)

(51.

52)

(4.4

4)

Nof

e. Sy

llabl

es =

20

item

s; W

ords

= 5

0 ite

ms;

Inst

ant R

eadi

ng =

20

item

s.

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21 8 SERGIO HERNANDEZ ET AL.

120

lo0 n a

F Y 8 0

P 5" U

3 " B

20

0

. . . . . . . . . . . . .

. . . . . . . . . . . . .

. . . . . . . . . . . . .

. . . . . . . . . . . . . *

WcawvERaEwr *** m O " 0 N E N T . . . . . . . . . . . . . . . . . . . . . . . .

. . .

. . .

. . .

. . .

z

'*** . . " "

WORDS TMT

READING TASKS

. . . . . . . . .

** . . . . . . . . . . . . .

Fig. 4. Mean reading time for Convergent and Nonconvergent groups. *p < .05; **p < ,005; ***p < ,001.

. . . . . . . . . . . . . . .

. . . . . . . . . . . . . . .

. . . . . . . . . . . . . . .

. . . . . . . . . . . . . . .

. . . . . . . . . . . . . . . *

. . . . . . . . . .

. . . . . . . . . . . . . .

. . . . . . . . .

. . . . . . . . .

. . . . . . . . .

. . . . . . . . .

a- . . . . . . . . . . . . . . . . . . . . . .

. . . . . . . . . . . .

. . . . . . . . . . . . .

. . . . . . . . . . . . . . . . . . . . . . . . . .

. . . . . . . . . . . . . . . . . . . . . . . . . .

** . . . . . . . . .

INSTANTREAMNQ

READING TASKS

Fig. 5. Mean of errors for Convergent and Nonconvergent groups. * p < .01; **p < ,001.

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CEREBRAL ASYMMETRY AND READING 219

8

. .

Fig. 6. Mean of correct responses for Convergent and Nonconvergent groups in Reading Comprehension. *p< .Ol .

the lateralization of these processes to different hemispheres. Thus, neither lateralization of language by itself nor hand preference are determi- nant factors for good reading performance.

The results obtained suggest that. indeed, the Language-Lateralization and Hand-Preference factors, when considered independently, do not affect reading performance. This absence of effect is highly consistent, for i t occurs for all pa- rameters assessed and all tasks used. This sup- ports our predictions and, therefore, the proposal for a joint consideration of both factors.

In this sense, the next important result to be emphasized is that the interaction between Lan- guage Lateralization and Hand Preference is significant in most analyses. Specifically, it reaches significant values in Reading Speed, for Syllables, Words, Text and, Silent Reading; in Reading Accuracy, for Words, Text, and Instant

Reading; in Reading Comprehension; and in the pertinent Efficiency Indexes. Therefore, the only factor that shows a consistent relationship with reading performance is the interaction between the type of hemispheric specialization for language of the subject and his lher hand preference.

A second basic premise of our hypothesis is the identical reading performance between the two types of cerebral organization where convergence occurs (LLD-RH and LRD-LH), as well as between the two types where such a convergence does not exist (LLD-LH and LRD- RH). Indeed, the second analysis block shows that there are no differences among the subgroups that are representative of each type of cerebral organization. On the contrary, when we compare the reading skill of subjects with convergent cerebral organization with the reading

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performance of subjects with nonconvergent organization, results show that the convergent group is superior in all aspects assessed: The convergent group has faster reading speed, makes fewer mistakes in reading, and shows greater reading comprehension.

Another aspect to consider is the type of reading task affected by the pattern of cerebral organization. Our results show that reading of Let- ters (capital and small) is not influenced by Lan- guage Lateralieation, Hand Preference, or the interaction of both. This result was to be expected, as this is a low-level task. Therefore, convergent versus nonconvergent organization seems to be relevant for the reading process at reading levels of some complexity, from the reading of syllables or isolated words to text comprehension.

The results for Syllables deserve an additional comment. Syllables are elements with no lexical representation; therefore, the effect of convergence seems to occur already at pre-lexical levels. This is not a surprising result, because we have consistent evidence suggesting that, in Spanish, a phonetically regular language, syllables are a sub-lexical functional unit involved in reading processes (Carreiras, Alvarez, & De Vega, 1993; De Vega et al., 1990). It would be necessary to check whether this result can be extended to other languages with non- transparent orthography and where syllables are not so well defined.

The superiority achieved by the convergence group in Reading Comprehension is particularly relevant. This superiority is manifest not only in the accuracy of the Comprehension task but also in the corresponding Reading Efficiency index. In this sense, the information provided by the RE is particularly important, as it shows that the superiority of the convergent group in reading comprehension is not achieved at the expense of reading speed. The reading process is not limited to a conversion of visual stimuli into phonemes, syllables, or words, but also involves the inte- gration of the meaning of words and sentences to access the overall meaning of the text. Thus, comprehension of a text could be considered as the culmination of the reading process (De Vega et a].). Therefore, our results show the impor-

tance of the pattern of cerebral organization proposed in achieving good performance at the highest level of the reading process.

The result regarding gender differences must be emphasized. The Gender factor was included in all analyses but affected only reading accuracy for words and, in interaction with hand preference, for Capital Letters. As can be seen, these are isolated and not very consistent data. Therefore, we consider our results as indicative of an absence of actual influence of the Gender factor. In research regarding cerebral asymmetry, many studies have addressed the issue of gender differences. It has been hypothesized that women present a trend towards language bilateralization (e.g., McGlone, 1980; Nieto, HernBndez, GonzBlez-Feria, & Barroso, 1990), and a lower incidence of left-hand preference. This issue has also been addressed in studies on reading disorders, where a larger proportion of males among the dyslexic population has been postulated (Chritchley & Chritchley, 1978).

Our results indicate that males and females show the same reading performance when they have the same asymmetrical organization for language and hand preference. This fact has ma- jor implications for studies directed at establishing differences in the presence of each gender among the population with reading disorders. These differences might not be determined by the gender factor itself, but may rather be re- flecting the distribution of different types of brain organization in the samples used. In this regard, the issue would not be merely to observe whether there is a greater prevalence of either gender, but rather to study the distribution of each type of cerebral organization, convergent or nonconvergent, in each gender.

The results of this study cannot be compared directly to those obtained in previous studies. As far as we know, the effect on reading performance of the convergence of language dominance and control of the preferred hand in the same hemisphere has not been previously examined. Furthermore, most of the previous studies aimed at linking cerebral asymmetry with reading skill have used subjects with dislexia, or subjects grouped under the generic classification of learning disabilities.

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CEREBRAL ASYMMETRY AND READING 22 1

Our proposal is that convergent cerebral organization facilitates reading performance. We do not consider this to be the only relationship between brain function and reading. There are other factors, such as cerebral maturation, the processes of interhemispheric interaction (facilitation -inhibition), genetic factors, and so forth, which may also modulate the acquisition and execution of this process, possibly in an interac- tive fashion. Therefore, the source of reading disorders is possibly multifactorial.

In this sense, the usual procedure (that is, comparing language lateralization or hand preference between dyslexics and normal readers) is not appropriate to confirm our proposed relationship between a given cerebral organization and reading performance. Apart from the fact that in some cases the selection criteria of subjects with reading disabilities can be question- able - diagnosis through self-reports, inclusion of other disorders, and so forth -the results obtained through these procedures are bound to be confusing. Even assuming that it has been prop- erly selected, a sample of people with dyslexia will be made up not only of subjects who show a pattern of nonconvergence but will probably also include subjects whose disorder originates from other factors. Accordingly, we have used a different approach in our study, comparing the reading performance of children without reading disorders that require special schooling programs (children with dyslexia or learning disabilities) but who are differentiated by the type of asymmetrical cerebral organization.

Despite the previous considerations, we wish to mention two recent studies. First, a study by Hughdal e t al. (1995) compared language lateralization of dyslexic subjects and normal readers and included a group of left-handed subjects in both cases. Even though the aim of these authors was not to study the effect of convergence upon reading performance, the methodology used makes it possible for us to establish some comparisons between their results and those which could be expected from our hypothesis. Based on data from a dichotic listening task, they reported that the group of right- handed dyslexic subjects, contrary to the right- handed normal readers, did not show the

expected REA (right-ear advantage). The distribution of right-handed subjects in the dyslexic group was 57% with REA; 36% with LEA, and 7% with no ear advantage (NEA). This distribution was significantly different from that observed in the case of the control subjects: 83% with REA, 10% with LEA, and 7% with NEA. In the case of left-handed subjects, neither the dyslexic group nor the control group showed REA. The distribution of the dyslexic group was: 36% with REA, and 64% with LEA; and in the control group, 27% with REA, 55% with LEA, and 18% with NEA. No differences were found between the distribution of subjects in both groups.

Regarding right-handed dyslexic subjects, the generalization of our hypothesis would imply the existence of a higher percentage of subjects with LEA, that is, with right lateralization of language. However, the differences between distributions of dyslexic and control subjects provides partial support for our hypothesis. In the dyslexic group there was an important de- crease in the number of subjects with REA as compared to control subjects; that is, there was a smaller number of dyslexic subjects with convergent organization (83% among controls, 57% among dyslexics); also, the number of subjects with LEA increased; that is, the number of subjects with nonconvergent cerebral organization increased (10% among controls, 36% among dyslexics).

As to the group of left-handed subjects, the resulting distribution is surprising. The distribution of the control group subjects deviated con- siderably from the result expected from the data on cerebral dominance of language for this population. The estimates made for different types of clinical studies - incidence of aphasia after a unilateral lesion, Wada amytal test, and electro- convulsive therapy (ECT) - indicate that approximately 60% to 70% of left-handed subjects presented a left lateralization of language (e.g., Loring et al., 1990; Rasmusen & Milner, 1977). Similar results have been obtained using the dichotic listening technique (Strauss, 1986).

In our own study, we observed that 54.8% of the 77 left-handed subjects evaluated showed left-language lateralization, according to the

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results of the concurrent task. These data dis- agree with the percentage obtained by Hugdahl et al.: 27% of left-handed subjects with REA. Possibly, the sample used by these authors (n = 11) was too small for its distribution to be significant for the left-handed population. In this sense, j t does not seem appropriate to attempt a generalization of our hypothesis for a sample of such characteristics.

A second study to consider is that of Obrzut et al. (1997). These authors, using meta-analytic techniques, studied the differences in patterns of ear advantage among children of different reading levels, hand dominance, and ages. They reported a consistent right-ear advantage (REA) in right-handed good readers across different attention conditions (free recall, directed left, directed right). Although based on these data it is not possible to know the distribution of these subjects in terms of their lateralization, the group results coincide with the predictions de- rived from our hypothesis: There will be a pre- dominance of convergent cerebral organization in subjects with a good reading level. In this case, given that the subjects were right-handed, they must have left lateralization for language. The left-handed good readers consistently demonstrated absence of ear advantages (NEA). Ac- cording to our hypothesis, a group of left- handed good readers will be made up largely of subjects with right-language lateralization. This would result in the group as a whole evidencing LEA or, at least, in the disapearance of REA found in right-handers.

Thus, the results obtained by Obrzut et al. (1 997) lend partial support to our predictions (i.e., no ear advantages). As far as the poor readers are concerned, right-handed as well as left- handed the absence of a consistent pattern of ear advantages does not alIow us to extract conclusions. In summary, the results of Obrzut et al. (1997) demonstrated relationships between handedness, reading ability, and cerebral dominance although, as the authors point out, the results regarding handedness and reader group must be considered with caution as the number of left-handed subjects was small. In general, the data from this research can be considered to support our hypothesis and the results of our study.

In summary, our results have shown that subjects for whom the same hemisphere is dominant for language and control of the preferred hand have better reading performance than do those subjects where such a convergence does not occur. The convergence effect is clearly seen in tasks that involve pre-lexical functional units (syllables), isolated words, texts, and reading comprehension. Males and females do not ex- hibit differences in reading performance when they have the same asymmetrical organization.

In our opinion, this study represents a contribution to the neuropsychology of reading, specifically as regards the relationship between cerebral asymmetry and reading performance. This contribution has an integrating character, because it establishes a specific relationship among factors that most previous studies have related only independently with the reading process. Future research should establish the weight of this factor on reading performance differences and on reading disorders. In this regard, we are currently studying the incidence of the proposed cerebral organization in poor readers and dyslexics. At the same time, we are also interested in establishing the effect of convergence on reading performance in adult readers. Finally, even though we have specified in this research the influence of this asymmetrical organization on reading skills, we believe that its effects could well reach other spheres of language, and that the study of such effects could also offer a very promising line for research.

REFERENCES

Annett, M., & Kilshaw, D. (1984). Lateral preference and skill in dyslexics: Implications of the right shift theory. Journal of Child Psychology and Psy- chiatry, 25, 357-377.

Aylward, E. H. (1984). Lateral asymmetry in subgroups of dyslexic children. Brain and Language, 22, 221-231.

Bakker, D.J. (1978). Hemispheric differences and reading strategies: Two dyslexias? Bulletin of the Orton Society, 29, 84-100.

Bathurst, K., & Kee, D.W. ( I 994). Finger-tapping interference as produced by concurrent verbal and nonverbal tasks: An analysis of individual differ-

Dow

nloa

ded

by [

Uni

vers

ity o

f B

ath]

at 0

8:03

23

Nov

embe

r 20

14


ences in left-handers. Brain and Cognition, 24, 123-136.

Bishop, D.V.M. [ 1990). Handedness, clumsiness and developmental language disorders. Neuropsychol- ogia, 28, 68 1-690.

Boder, E. (1973). Developmental dyslexia: A diagnos- tic approach based on three atypical reading patterns. Developmental Medicine and Child Neurol-

Boder, E., & Jarrico, S. (1982). The Boder Test of Reading-Spelling Patterns. New York: Grune & Stratton.

Boliek, C.A., Obrzut, J.E., & Shaw, D. (1988). The effects of hemispatial and asymmetrically focused attention on dichotic listening with normal and learning-disabled children. Neuropsychologia, 26, 4 17-433.

Brunswick, N., & Rippon, G. (1994). Auditory event- related potentials, dichotic listenig performance and handedness as indices of lateralisation in dyslexic and normal readers. International Journal of Psychophysiology, 18, 265-275.

Carreriras, M., Alvarez, C.J., & De Vega, M. (1993). Syllable frequency and visual word recognition in Spanish. Journal of Memory and Language, 32,

Cohen, M., Hynd, G., & Hugdahl, K. (1992). Dichotic listening performance in subtypes of developmental dyslexia and a left temporal lobe brain tumor contrast group. Brain and Language, 42, 187-202.

Critchley, M., & Critchley, E.A. (1978). Dyslexia defined. London: Heinemann Medical Books.

Dalby, J.T., & Gibson, D. (1981). Functional cerebral lateralization in subtypes of disabled readers. Brain and Language, 14, 34-48.

De Vega, M., Carreriras, M., Gutierrez-Calvo, M., & Alonso-Quecuty, M.L. (1990) . Lecrura y comprensidn: Una perspectiva cogniriva (Reading and comprehension: A cognitive perspective]. Ma- drid, Spain: Alianza.

Duara, R., Gross-Glenn, K., Baker, W., Loewenstein, D., Chang I. Y., Apicella, A., Yoshii, F., Pascal, S., & Lubs, H. (1989). PET studies during reading in dyslexics and controls. Journal of Cerebral Blood Flow Metabolism, 9, 342.

Duffy, F.H., Denckla, M.B., Bartels, P. H., & Sandini, G. (1980). Dyslexia: Regional differences in brain electrical activity to topographic mapping. Annals of Neurology, 7, 41 2-420.

Eden, G.F., Vanmeter, J.W., Rumsey, J.M., Maisog, J.M., Woods, R.P., & Zeffiro, T.A. (1996). Abnor- mal procesing of visual motion in dyslexia revealed by functional brain imaging. Nature, 382,

Eglinton, E., & Annett, M. (1994). Handedness and dyslexia: A meta-analysis. Perceptual Motor Skills, 79, 1611-1616.

ogy, 15, 663-687.

766-780.

66-69.

Galaburda, A.M. ( 1992). Neurology of developmental dyslexia. Current Opinion in Neurology and Neu- rosurgery, 5, 7 1-16.

Galaburda, A.M., Corsiglia, J., Rosen, G.D., & Sherman, G.F. (1987). Planum temporale asymmetry, reappraisal since Geschwind and Levitsky. Neuropsychologia, 25, 85 3- 868.

Galaburda, A.M.. & Kemper, T.L. (1979). Cytoarchi- tectonic abnormalities in developmental dyslexia: A case study. Annals of Neurology, 6, 94-100.

Galaburda, A.M., Sherman, G.F., Rosen, G.D., Aboi- tiz, F., & Geschwind, N. (1985). Developmental dyslexia: Four consecutive patients with cortical anomalies. Annals of Neurology, IS, 222-233.

Galin, D., Herron, J., Johnstone, J., Fein, G., & Yingling, C. (1988). EEG alpha asymmetry in dyslexics during speaking and block design tasks. Brain and Language, 35, 241 -253.

Geschwind, N., & Behan, P. (1982). Left-handedness: Association with inmmune disease, migraine, and developmental learning disorders. Proceedings of the National Academy of Sciences, 29, 5097-5 100.

Geschwind, N., & Behan, P. (1984). Laterality, hor- mones and immunity. In N. Geschwind & A.M. Galaburda (Eds.), Cerebral dominance (pp. 21 1- 224). London: Harvard University Press.

Gross-Glenn, K., Duara, R., Yoshii, F., Baker, W., Chang J. Y., Apicella, A,, Boothe, T., & Lubs, H. A. (1990). PET scan studies: Familial dyslexics. In G.Th. Pavlidis (Ed.), Perspectives on dyslexia vol. I : Neurology, neuropsychology and genetics (pp. 109-1 18). New York: John Wiley & Sons.

Harris, A.J. (1947). Harris Test of Lateral Domi- nance. New York: Psychological Corporation.

Haslam, R.H., Dalby, J.T., Johns, R.D., & Rade- maker, A.W. ( I 98 I) . Cerebral asymmetry in developmental dyslexia. Archives of Neurology, 38,

Hiscock M., & Inch, R. (1995). Asymmetry of verbal- manual interference: Dissociation between rate and variability in left-handers. Brain and Cognition, 29, 307-325.

Hiscock, M., & Kinsbourne, M. (1978). Ontogeny of cerebral dominance: Evidence from time-sharing asymmetry in children. Developmental Psychol-

Hugdahl, K., Synnevag, B., & Satz, P. (1990). Immune and autoimmune diseases in dyslexic children. Neuropsychologia. 28, 7, 673-679.

Hugdahl, K., Helland, T., Faerevaag, M.K., Lyssand, E.T., & Asbjornsen, A. (1995). Absence of ear advantage on the consonant-vowell dichotic listening test in adolescent and adult dyslexics: Specific auditory-phonetic dysfunction. Journal of Clinical and Experimental Neuropsychology, 17, 833-840.

Hynd, G.W., Obrzut, J.E., Weed, W., & Hynd, C.R. (1979). Development of cerebral dominance: Dich-

679-682.

ogy, 14, 321-329.

Dow

nloa

ded

by [

Uni

vers

ity o

f B

ath]

at 0

8:03

23

Nov

embe

r 20

14

224 SERGIO HERNANDEZ ET AL

otic listening asymmetry in normal and learning- disabled children. Journal of Experimental Child

Hynd, G.W., Hall, J., Novey E.S., Eliopulos, D., Black, K., Gonzalez, J.J., Edmonds, J.E., Riccio, C., & Cohen, M. (1995). Dyslexia and corpus callosum morphology. Archive of Neurology, 52, 32- 38.

Jariabkovi, K., Hugdahl, K., & GI&, J. (1995). Im- mune disorders and handedness in dyslexic boys and their relatives. Scandinavian Journal of Psy-

Johannes, S., Mangun, G.R., Kussmaul, C.L., & Miinte, T.F. (1995). Brain potentials in developmental dyslexia: Differential effects of word frequency in human subjects. Neurosciences Letter;

Kershner, J.R. ( I 977). Cerebral dominance in disabled readers, good readers, and gifted children: Search for a valid model. Child Development, 48, 61 -67.

Lershner, J.R., & Morton, L.L. (1990). Directed attention dichotic listening in reading disabled children: A test of four models of maladaptive lateralization. Neuropsychologia, 28, 181-198.

,arsen, J.P., Hoien, T., Lundberg, I., & Odegaard, H. (1990). MRI evaluation of the size and simmetry of the planum temporales in adolescents with developmental dyslexia. Brain and Language, 39. 289- 301.

Loring, D.W., Meador, K.J., Lee, G.P., Murro, A.M., Smith, J.R., Flanigin, H.F., Gallagher, B.B., & King, D.W. (1990). Cerebral language lateralization: Evidence from intracarotid amobarbital testing. Neuropsychologia, 28, 831-838.

Marcel, T., & Rajan, P. (1975). Lateral specialization for recognition of words and faces in good and poor readers. Neuropsychologia, 13, 489-497.

Masutto, C., Bravar, L., & Fabro, F. (1994). Neuro- linguistic differentiation of children with subtypes of dyslexia. Journal of Learning Disabilities, 27,

McFarland, K., Ashton, R., Rich, A., & Donald, A.M. (1989). Lateralised dual-task performance: The effect of muscular-repositioning. Cortex, 25, 433- 447.

McGlone, J. (I 980). Sex differences in functional brain asymmetry: A critical survey. Behavioral and Brain Sciences, 3, 215-227.

McKeever, W., & Van Deventer, A.D. (1975). Dyslexic adolescents: Evidence of impaired visual and auditory processing with normal lateralization and visual responsivity. Cortex, 11, 361-378.

Miles, J., & Stelmack, R.M. (1994). Learning disability subtypes and the effects of auditory and visual priming on visual event-related potentials to words. Journal of Clinical and Experimental Neu- ropsychology, 16, 43-64.

P~ychology, 28, 445-454.

chology, 36, 355-362.

195, 1 83- 186.

520-526.

Morris, G.L., Obrzut, J.E., & Coulthard-Morris, L. (1989). Electroencephalographic and brain stem evoked responses from learning-disabled and control children. Developmental Neuropsychology, 5,

Naylor, C.E., Wood, F.B., & Harter, M.R. (1995). Event related potentials in adults diagnosed as reading disabled in childhood. international Jour- nal of Neurosciences, 80, 339-352.

Nieto, A., Hernindez, S., Gonzilez-Feria, L., & Barroso, J. (1990). Semantic capabilities of the left and right cerebral hemispheres in categorization tasks: Effects of verbal-pictorial presentation. Neuropsychologia, 28, 1175-1 186.

Njiokiktjien, C., De Sonneville, L., & Vaal, J. (1994). Callosal size in children with learning disab Behavioral Brain Research, 64, 2 13-21 8.

Obrzut, J.E. (1979). Dichotic listening and bisensory memory skills in qualitatively diverse dyslexic readers. Journal of Learning Disabilities, 12, 304- 314.

Obrzut, J.E., Boliek, C.A., & Bryden, M.P., (1997). Dichotic listening, handedness, and reading ability: A meta-analysis. Developmental Neuropsychology,

Obrzut, J.E., Boliek, C.A., Bryden, M.P., & Nichol- son, J.A. (1994). Age- and sex-related differences in left- and right-hemisphere processing by learning disabled children. Neuropsychology, 8, 75-82.

Obrzut, J.E., Conrad, P.F., & Boliek, C.A. (1989). Verbal and nonverbal auditory processing among left- and right-handed good readers and reading- disabled children. Neuropsychologia, 27, 1357- 1371.

Obrzut, J.E., Conrad, P.F., Bryden, M.P., & Boliek, C.A. (1988). Cued dichotic listening with right- handed, left-handed, bilingual and learning-disabled children. Neuropsychologia, 26, 1 19- I3 1 .

Obrzut, J.E., Hynd, G.W., Obrzut, A., & Leitgeb, J. L. (1980). Time sharing and dichotic listening asymmetry in normal and learning-disabled children. Brain and Language, 11, 18 1 - 194.

Obrzut, J.E., Hynd, G.W., Obrzut. A., & Pirozzolo, F.J. (1981). Effect of directed attention on cerebral asymmetries in normal and learning-disabled children. Developmental Psychology, 17, l 18- 125.

Olson, M.E. ( 1 973). Laterality differences in tachistoscopic word recognition in normal and delayed readers in elementary school. Neuropsychologia,

Paulesu, E., Frith, U., Snowling, M., Gallagher, A., Morton, J., Frackowiak, R.S., & Frith, C.D. (1996). Is developmental dyslexia a disconnection syn- drome? Evidence from PET scanning. Brain, I 1 9,

Petrauskas, R., & Rourke, B. (1979). Identification of subgroups of retarded readers: A neuropsychological multivariate approach. Journal of Clinical Neu- ropsychology, 1, 17-37.

187-206.

13, 97-1 10.

11, 343-350.

143-157.

Dow

nloa

ded

by [

Uni

vers

ity o

f B

ath]

at 0

8:03

23

Nov

embe

r 20

14


Pirozzolo, F. ( 198 1 ). Language and brain: Neuropsy- chological aspects of developmental reading disability. School Psychology Review, 10, 350-355.

Pirozzolo, F.. & Rayner, K. (1979). Cerebral organization and reading disability. Neuropsychologia,

Rasmussen, T., & Milner, B. (1977). The role of early left brain injury in determining lateralization of cerebral speech functions. Annals of the New York Academy of Science, 299, 355-369.

Richardson, A.J., & Gruzelier, J. (1994). Visual processing, la teral izat ion and syndromes of schizotypy. lnternational Journal of Psychophysi-

Rourke, B., & Gates, R. (1981). Neuropsychological research and school psychology. In G. Hynd & J. Obrzut (Eds.), Neuropsychological assessment and the school-age child (pp. 3-25) New York: Grune & Stratton.

Schachter, S.C., Ransil, B.J., & Geschwind, N. (1987). Association of handedness with hair color and learning disabilities. Neuropsychologia, 25,

Simon. T.F., & Sussman, H.M. (1987). The dual task paradigm: Speech dominance or manual dominance? Neuropsychologia, 25, 559-569.

Springer, S . P., & Eisenson, J. (1977). Hemispheric specialization for speech in language-disordered children. Neuropsychologia, 15, 287-293.

Steinmetz, H., & Galaburda, A.M. (1991). Planum temporale asymmetry: “In-vivo” morphometry

17,485-49 1.

ology, 18, 227-239.

269-277.

affords a new perspective for neuro-behavioral research. Reading and Writing, 3, 331-343.

Stellern, J., Collins, J. , & Bayne, M. (1987). A dual- task investigation of language-spatial lateralization. Journal of Learning Disabilities, 20, 55 1- 556.

Stellern, J., Collins, J., Cossairt, A., & Gutierrez, R. (1986). Interference asymmetry involving concurrent task performed by Native American Indian students. Developmental Neuropsychology, 2, 241 - 255.

Strauss, E. (1986). Hand, foot, eye and ear preferences and performance on a dichotic listening test. Cortex, 22,475-482.

Thompson, M.E. (1976). A comparison of laterality effeccts in dyslexics and controls using verbal dichotic listening tasks. Neuropsychologia, 14,

Toro, J., & Cervera, M. (1984). ZA.L.E. Test de Andisis de Lectoescritura [Test for assessment of reading and writing skills]. Madrid, Spain: Visor.

Wechsler, D. (1949). Wechsler Intelligence Scale for Children. New York: The Psychological Corpora- tion.

White, N., & Kinsbourne, M. (1980). Does speech output control lateralize over time? Evidence from verbal-manual time-sharing tasks. Brain and Lan- guage, 10, 215-223.

Zurif, E.B., & Carlson, G. (1970). Dyslexia in relation to cerebral dominance and temporal analysis. Neuropsychologia, 8, 35 1-36 1.

243-246.

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by [

Uni

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ath]

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Documents

Cerebral Asymmetry and Reading Performance: Effect of Language Lateralization and Hand Preference