Impact of language proficiency and orthographic transparency on bilingual word reading: An fMRI investigation

by Gayane Meschyan and Arturo E. Hernandez

Bilingual Brain

Bilingual Brain

What differences, if any, exist between the cerebral representation of each languages?

What brain areas are involved in a bilingual's ability to speak two languages like switching (or controlling) between languages?

What potential factors are contributing to the cerebral organization of a second language?

Major Factors Investigated Level of L2 proficiency Age of L2 acquisition

Different effects on the neural systems subserving semantic and syntactic processing

proficiency level - a more pronounced effect on the cortical representation of semantic processing

age of L2 acquisition - a more pronounced effect on the neural organization of grammatical processing

Age of L2 Acquisition

More sensitive syntactic processing even when the L2 was learned as young as 1 to 3 years of age (Weber-Fox and Neville, 1996)

Less sensitive semantic processingHigh level of proficiency attained in L2

can minimize the effects of learning the L2 later in life (Perani et al., 1998; Wartenburger et al., 2003)

Level of Proficiency Less sensitive semantic processing

English–French bilinguals with a high level of proficiency in French (L2): similar rCBF activation patterns for the L1 and L2 during word repetition (Klein et al., 1994) and during lexical–semantic retrieval tasks (Klein et al., 1995)

In a cued word generation task with Chinese– English bilinguals being highly proficient in English (L2): remarkably similar neural activation patterns for participants’ native language Mandarin and their second language English irrespective of the age of L2 acquisition (Chee et al. 1999)

Orthographic Transparency L1 English vs. L1 Italian w/single word reading

task (Paulesu et al. 2000)

Orthographically transparent language (Italian) Relatively stronger activation in the posterior

region of the left superior temporal gyrus (STG), which is for phonological processing

The greater involvement of this region: more phonologically mediated, given the ease with which phonological forms of such words are constructed, relative to English words?

Research Question

How the neural activation patterns for the two languages would differ with Spanish-English bilinguals (L1 Spanish less proficient and L2 English more proficient) during a single word reading task?

Single Word Reading Task

More likely to recruit the semantic system, which is more affected by proficiency

Exclusively focusing on the role of proficiency level on cerebral organization of a second language

Predictions

Spanish (L1, lower level of proficiency, orthographically transparent): greater activity in articulation (e.g., supplementary motor area [SMA], putamen, insula) Proficiency: greater load on articulatory

processes Task requiring articulatory motor processing

English (L2, higher level of proficiency, orthographically opaque): greater activity in the visual cortex and parietal lobe regions More load for graphemic analysis and

recoding

Method: Participants Twelve (7 females, 5

males) early Spanish –English bilingual college students between 20 - 25

No consistent exposure to any other language but Spanish and English

More proficient in English, their second language, than Spanish (L1)

The word-reading behavioral results - a behavioral version of the fMRI task

Materials and Procedure

Silent word reading: a total of 96 words (48 English, 48 Spanish)

Spanish and English words: matched on frequency and imageability.

1 word

1s

1 word

1s

1 word

1s

1s 1s

One Block (24 words)

Four Blocks (96 words)

EnglishRest

24sSpanish

Rest24s

Rest24s

Rest24s

Rest24s

English Spanish

Results: Behavioral

A behavioral version of the fMRI task, containing different stimuli, was administered prior to the fMRI scan with overt word reading

No difference in accuracy of word reading Spanish word reading: significantly longer The longer response times for words read in

the less proficient language (Spanish): more effortful, hence slower, articulatory motor processing?

fMRI: Spanish vs. English

fMRI: Spanish vs. English

Spanish/ English vs. Rest

Spanish vs. Rest Activity in similar brain regions, such as STG

(BA 22) and SMA/cingulate, putamen, and the insula

Activation in the pre-central gyrus (BA 6), the inferior parietal lobe (IPL; BA 40), and the pre-cuneus

English vs. Rest Activity in parietal regions Activity in the pre-cuneus and the pre-

cuneus/ cuneus border

Discussion

Proficiency Effect

Orthography Effect

Proficiency Effect

The less practiced, hence less proficient, native language Additional brain regions (e.g., SMA/cingulate,

putamen, insula), which are involved in articulatory motor processing: for speech-motor preparation and execution components of reading

The lateralization of the SMA, putamen, and insula activation to the right hemisphere: more effortful articulatory motor function placing greater processing load on a system also tend to recruit homologous regions in the right hemisphere

Greater articulatory motor effort, which results in slower reading and production times

Orthography Effect Spanish word reading: great activation in the left STG

more phonologically driven? the region of left STG most active in the present study -

more anterior: spatial smoothing during data analysis? Potentially related to language proficiency as well?

English word reading: greater activity in right inferior parietal lobe (IPL; BA 40) and in the region bordering the left parietal and occipital lobes the more complex orthographic patterns of English

words, which place greater demands on word recoding (i.e., grapheme to phoneme conversion) and require greater visual analysis?

the lateralization of IPL activity to the right hemisphere for English words relative to Spanish ones: the greater demands placed on the grapheme-to-phoneme recoding of orthographically opaque English words versus transparent Spanish ones?

Comments and Questions

Research Design

The authors talk about 'proficiency' and 'age of acquisition' as motivating factors for their research, but in the case of heritage speakers, I think they have to distinguish between 'proficiency' and 'formal study'.  The 'formal study' data in Spanish vs. English (3.42 yrs in Span vs. 15.58 yrs in Engl) could make a difference here in terms of how these predominantly aural/oral learners of Spanish are able to map phonology to orthography in Spanish, regardless of whether Spanish is transparent or opaque in orthography. 

If the left STG is more 'phonologically driven', it may not be because of the orthographical transparency of Spanish, but the fact that these bilinguals learned and use their language aurally/orally and not in written mode. 

Yet another study of similar Span/Eng bilinguals in terms of these proficiency measures who had more formal training in Spanish to see if the lack of formal training in mapping orthography/phonology makes a difference here.

Research Design (cont’d) A better description of all types of bilinguals

referred to in articles cited (all bilinguals are not equal)

Monolingual controls of the same materials in Spanish (from the region most representative of the heritage of these speakers) and English

Materials:  some words in Spanish aren't that 'transparent'!  What exactly did the subjects see?

Why wasn't there a 'check' to see if participants were really reading? 

Another study with spanish/english L1/L2 reversed would be nice.

Spanish vs. English Are there any fundamental differences between the

orthography- phonology mapping rules in English and Spanish, as opposed to language exposure, that might have contributed to the brain activation patterns they found here?

The authors attribute the differences in activation of the parietal and occipital regions to "the more complex orthographic patterns of English words".  Given that English and Spanish have similar alphabets, how are English words more orthographically complex? 

Do languages differ in their articulatory requirements though? is it possible spanish requires more articulation, and that could explain some of the results? 

L1 vs. L2

How do people usually define L2? The language experience of L1 and

L2 provided in the article are actually not too different, which makes it kind of surprising to me that there are indeed differences in the brain response.

Proficiency Effect on Articlatory Region

Why is it that the role of the articulatory motor system is predicted to diminish as proficiency increases?  Do articulatory processes become more automatic and easy, or does articulation become unnecessary as reading skill improves?

Orthography Effect

Isn't it possible that increased activity of/access to phonology would lead to increased articulation? After all, articulation requires that phonology be accessed first, so in an opaque orthography where phonological information is difficult to access, one might expect to see less (or slower) activation of articulatory regions.