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articles
A cultural effect on brain function
© 2000 Nature America Inc. • http://neurosci.nature.com
E. Paulesu1, E. McCrory2, F. Fazio1, L. Menoncello1, N. Brunswick3, S. F. Cappa4,5, M. Cotelli4,
G. Cossu6, F. Corte6, M. Lorusso7, S. Pesenti7, A. Gallagher2, D. Perani1, C. Price3, C. D. Frith3,
and U. Frith2.
1
Scientific Institute H S. Raffaele, INB-CNR, University of Milan-Bicocca, Milan, Italy
2
Institute of Cognitive Neuroscience, University College London, 7 Queen Square, London WC1N 3AR, UK
3
Wellcome Department of Cognitive Neurology, Institute of Neurology, 12 Queen Square, London WC1N 3GB, UK
4
Neurology Department, University of Brescia, Brescia, Italy
5
Psychology Department, University Vita e Salute H San Raffaele, Milan, Italy
6
Istituto di Fisiologia Umana, University of Parma, Parma, Italy
7
Scientific Institute Eugenio Medea-La Nostra Famiglia, Bosisio Parini, Italy
Correspondence should be addressed to U.F. ([email protected])
We present behavioral and anatomical evidence for a multi-component reading system in which
different components are differentially weighted depending on culture-specific demands of orthography. Italian orthography is consistent, enabling reliable conversion of graphemes to phonemes to
yield correct pronunciation of the word. English orthography is inconsistent, complicating mapping
of letters to word sounds. In behavioral studies, Italian students showed faster word and non-word
reading than English students. In two PET studies, Italians showed greater activation in left superior
temporal regions associated with phoneme processing. In contrast, English readers showed greater
activations, particularly for non-words, in left posterior inferior temporal gyrus and anterior inferior
frontal gyrus, areas associated with word retrieval during both reading and naming tasks.
In English there are 1120 ways of representing 40 sounds (phonemes)
by different letters or letter combinations (graphemes)1. The mappings between graphemes, phonemes and whole word sound are
essentially ambiguous, as illustrated by pairs such as pint/mint,
cough/bough, clove/love. By contrast, in Italian, 33 graphemes are
sufficient to represent the 25 phonemes of the language2, and the
mappings from graphemes to phonemes are unequivocal. Young
Italian readers can achieve 92% accuracy on word reading tests after
only 6 months of schooling3, whereas learning to read in English
takes much longer. Compared to German, another consistent
orthography, accuracy levels in English are lower and reading speed
is slower even after three years of schooling4,5. Adult English readers are slower at reading non-words than readers of the consistent
Serbocroat orthography6. We investigated reading in Italian and
English university students. These students read high-frequency regular words in their respective languages, a set of international words
and two sets of non-words derived from both languages. We also
investigated the neurophysiological basis of reading in Italian and
English using positron emission tomography (PET).
RESULTS
Italian students were faster at both word and non-word reading,
even when the non-words were derived from English words. Control tasks showed that this advantage could not be attributed to
faster reaction times, articulation speed, naming speed or verbal
fluency (Table 1 and Fig. 1). Both groups were slower at reading
non-words as compared with words. This difference was significantly greater for English readers. The Italian students read nonwords and international words derived from Italian faster than
those derived from English. The English students were unaffected
by the source of the words.
nature neuroscience • volume 3 no 1 • january 2000
We conducted two PET scan studies, again with university students. The first study addressed explicit reading. Here participants
had to read words and non-words aloud. A second study addressed
implicit reading, where we assessed physiological responses induced
by the mere presence of print in the visual field. Participants were
not asked to read the stimuli, but to perform a visual feature-detection task on words, non-words and false-font stimuli7.
Results from both experiments were combined to show only
those effects that were reliable in both studies (Fig. 2 and Table 2).
We identified a common brain system that was active during reading, explicitly and implicitly, across the two languages. This system included inferior frontal and premotor cortex, superior,
middle and inferior temporal gyri and fusiform gyrus on the left,
and superior temporal gyrus on the right. The majority of the lefthemisphere areas were more active for non-words than for words,
although no single region showed reliably greater activation for
words. Interaction effects showed a language-related difference:
English readers, particularly when reading non-words, showed
greater activations in the left posterior inferior temporal region
and in the anteriormost part of the inferior frontal gyrus. When
reading words or non-words, Italian readers showed greater activations at the junction between left superior temporal gyrus and
inferior parietal cortex, a region known as planum temporale.
DISCUSSION
In spite of the large amount of empirical data on normal and
abnormal reading, it is still a matter of debate as to how word and
non-word reading is achieved, particularly in a deep orthography
such as English8–12. Our behavioral results showed that even with
simple and regularly spelled stimuli, background effects of the
complex English orthography incur a cost in terms of reading
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Fig. 1. Vocal reaction times in single word and non-word reading.
Reading high-frequency words and non-words derived from the words
in each language. Italian students had faster reading latencies than
English students (F1,70 = 140.04, p < 0.001; Table 1). Both groups read
words faster than non-words (F2,140 = 114.90, p < 0.0001), but this effect
was more marked for English (group by task interaction; F2,140 = 15,53;
p < 0.0001). In a post-hoc analysis of non-word reading, English students
were equally slow when reading non-words derived from Italian or from
English words. In contrast, Italian students, although significantly faster
than English students for both kinds of non-words (group main effect;
F1,70 = 13.6; p < 0.0005), were faster still with non-words derived from
Italian words (group × task interaction effect: F1,70 = 42,51; p < 0.0001).
In reading familiar international words, analysis of variance showed no
overall group effect (F1,70 = 0.97; n.s.), but a group by task interaction
(F1,70 = 7.9; p < 0.007). This was because Italian subjects were faster at
reading international words conforming to their own orthography.
English subjects
Reading latency (ms)
Italian subjects
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Words
Non-words Non-words
from Italian from English
International International
words
words
conforming to conforming to
English
Italian
speed. According to a dual-route perspective, two processes are
necessary in reading, letter-to-sound conversion and access to a
lexicon of orthographic patterns to resolve ambiguities in pronunciation8,9,11. According to a single-route connectionist perspective, one process is needed, which involves conversion from
orthography to phonology, and in a deep orthography such as English, an extensive translation from orthography to semantics to
phonology10,12. Our data can be interpreted within either of these
models. The complexity of English orthography derives partly from
the historical influence of other orthographies, including Italian
spelling patterns. Thus, for English readers, Italian non-words had
the same bigram frequency as English non-words and did not slow
them down. In contrast, Italians read the English non-words with
their less-familiar spelling patterns more slowly, as expected from
their lower bigram frequency in Italian.
Our PET scan data provide the first cross-cultural anatomical information about a common reading system for different
alphabetic orthographies. Reading in both complex and transparent orthographies depends on a distributed network of primarily left-sided language areas. Within the common network,
Table 1. Performance in reading tasks and in control tasks in 36 university students from London and 36 from Milan.
Reading tasks
Words
English subjects
(n = 36)
Italian subjects
(n = 36)
Mean difference
Two-tailed t value
p value
(± s.d.)
(ms)
442.6 ± 47.4
Non-words
derived from
Italian words
(NW1) (ms)
526.4 ± 93.9
Non-words
derived from
English words
(NW2) (ms)
528.8 ± 101.5*
International words
conforming to
Italian (IW1)
(ms)
450.9 ± 48.2
International
words conforming
to English (IW2)
(ms)
448.0 ± 57.4**
410.7 ± 33.1
437.3 ± 39.0
485.9 ± 56.8+
424.8 ±36.5
452.8 ± 53.3++
31.9
3.3
< 0.0015
89
5.2
< 0.0001
42.8
2.2
< 0.03
26.1
2.6
< 0.012
–4.8
0.37
0.7
Control tasks
Simple vocal
reaction time
English subjects
(n = 36)
Italian subjects
(n = 36)
Mean difference
Two-tailed t value
p value
(ms)
310.5 ± 37.8
Articulation
speed for pairs of
words (words in
15 min)
40.4 ± 3.5
Semantic verbal
fluency
(animal names in
1 min)
25.4 ± 6.7
Letter verbal
fluency (words
starting with ‘m’
in 1 min)
16.5 ± 6.7
Picturenaming
latency
(ms)
546.7 ± 41.8
313.1 ± 28.8
41.9 ± 6.1
27.5 ± 6.4
16.6 ± 4.7
561.0 ± 47.5
2.6
0.33
0.73
1.5
1.3
0.19
2.1
1.3
0.18
0.1
0.08
0.93
14.4
1.4
0.17
The results of the control tasks show that differences in reading speed were not due to differences in the sample population or to more general factors such
as sensorimotor speed, articulation speed or verbal fluency. Other statistical comparisons: *Comparison of NW1 and NW2 for English subjects; mean difference, –2.4 ms; paired t35 = –0.5; n.s. +Comparison of NW1 and NW2 for Italian subjects; mean difference, –48.6 ms; paired t35 = –9.6; p < 0.0001.
**Comparison of IW1 and IW2 for English subjects; mean difference, 2.9 ms; paired t35 = 0.4; n.s. ++Comparison of IW1 and IW2 for Italian subjects; mean
difference, –28.0 ms; paired t35 = –4.8; p < 0.0001.
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articles
Fig. 2. Functional commonalities and differences between English and
Italian reading systems. Brain areas are rendered on a standard brain conforming to stereotactic space. Stereotactic coordinates of the statistically
significant areas are given in Table 2. The first row shows the common
reading system as revealed by conjunction of the main effects of reading
minus baseline for the implicit and explicit reading experiments in both
English and Italian subjects. The second row shows the main effect of nonword reading minus word reading for all groups. No significant difference
was found between word reading minus non-word reading. The third row
shows those regions of greater activation in English subjects during nonword reading. These include the left inferior posterior temporal areas and
the anterior portion of the inferior frontal gyrus. English subjects had
greater activations than Italian subjects when reading non-words. The
fourth row shows the left planum temporale region, which was more
active in Italian than English subjects, regardless of word type.
however, some brain areas were more highly activated by one
orthography than the other.
These differences provide a physiological basis for the differences observed in our behavioral studies. The inferior basal temporal area and the anterior part of the interior frontal gyrus were
more strongly activated in English readers, especially for nonword reading. These brain regions have been associated with
object and word naming, and semantic processes in several prenature neuroscience • volume 3 no 1 • january 2000
vious studies13–16. A situation in which Italian readers need to
access word names/orthography is the assignment of stress for
words of more than two syllables with consonant/vowel structure (for example, tavolo)17,18. In an unpublished PET study (E.P.
et al.), Italian students had to indicate which syllable in a word
was stressed. Strong activation of the posterior basal temporal
area was observed during this task (Table 2). The enhanced activation shown by English readers in this region may reflect the
fact that the pronunciation of a stimulus in English always
involves such access and hence requires time and resources. One
possibility is that ambiguity is resolved via the activation of multiple neighboring alternatives in the orthographic lexicon, which
allow the selection of a correct pronunciation. This may explain
the activation of areas related to naming and semantic processing
during a non-word reading task.
The behavioral data showed that reading in a complex and
inconsistent orthography comes at a considerable cost. Reading
in Italian can proceed more efficiently because of the consistent
mapping between individual letter sounds and whole-word
sound. Italian readers showed comparatively stronger activation
of the left planum temporale (at the temporoparietal junction),
a brain region that has been linked to phonological processing19–22. Phonological procedures of reading in Italian may involve
a greater proportion of the overall processing effort. Conversely, in the case of English, semantic/orthographic procedures may
predominate. These may be automatically evoked, given the
degree of orthographic complexity. Physiologically, the assumption in both cases is that the enhanced involvement of a particular component of the reading system is reflected in greater
metabolic demands in the area associated with the component.
As reading seems to involve multiple components, a richer interaction among these components must be postulated than proposed by either single- or dual-route theories of reading.
Our evidence adds to the knowledge provided by studies of
neurological patients. The investigation of acquired dyslexia and
dysgraphia has indicated a role for perisylvian lesions in producing
impairments in phonological processing (phonological dyslexia
and dysgraphia)23,24, whereas lexical disorders of written language,
such as surface dyslexia and lexical agraphia, have been associated with lesions sparing the perisylvian cortex25 or with conditions,
such as semantic dementia, associated with temporal-lobe atrophy26. Our findings, although broadly consistent with these functional anatomical assignations, also show that, in normal reading,
these different components have different prominence depending
on the transparency of the orthography. The culture-specific physiological differences for normal reading suggest that differences
between Italian and English alexic and agraphic patients may be
due to differences in orthography27. The present findings indicate
that cultural factors, as reflected in orthographic systems, can powerfully shape neurophysiological systems.
METHODS
Students from London (n = 36; mean age ± s.d., 20.6 ± 3.3) and Milan
(n = 36; 20.8 ± 3.0), matched on course of study (arts, science and engineering) read bisyllabic words and non-words in their respective languages.
Words were nouns that had stress on the first syllable, and were among
the 7500 most frequent in Italian and in English. Non-words were derived
from these words by changing one or two phonemes but leaving the syllabic
structure intact. All participants read all non-words according to their own
orthography. There were 40 words and 40 non-words, divided into blocks
of 20 and presented on a computer screen in a counterbalanced order.
English words were as regular as possible, for example, cabin, market, cottage and apron were matched with cagin, marnet, connage and afton as
corresponding non-words. Italian examples were marmo, ponte, moto
and carta with margo, ponda, moco and corla as corresponding non-words.
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Table 2. Functional commonalities and differences between English and Italian reading systems and meta-analysis of
previous neuroimaging findings during naming/semantic tasks and phonological tasks.
Brain region
x
Left hemisphere
y
z
z score
x
Right hemisphere
y
z
z score
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(a) Main effect of reading
Inferior frontal gyrus (BA 44)
–44
4
20
4.6
–
–
–
–
Inferior frontal gyrus / insula
–38
22
12
4.4
–
–
–
–
Precentral gyrus (BA 6/4)
–48
–8
32
4
–
–
–
–
Insula
–22
–2
16
4.4
32
–26
6
3.4
Temporo/parietal junction (BA 22/40)
–38
–36
22
3.6
70
–40
24
3.5
Superior temporal gyrus (BA 22)
–64
–44
12
5.3
54
–24
6
5.2
Middle temporal gyrus (BA 21)
–60
–50
8
5
–
–
–
–
Inferior temporal gyrus (BA 20)
–50
–58
–22
5.6
–
–
–
–
Fusiform gyrus (BA 37)
–40
–52
–24
7.4
–
–
–
–
Caudate nucleus
–18
–10
22
3.5
26
–6
20
3.4
Thalamus
–8
–30
0
5.2
24
–12
14
4
Cerebellum
–
–
–
–
22
–68
–26
5
(b) Non-words minus words
Precentral gyrus (BA6)
–42
0
44
3.7
–
–
–
–
Anterior inferior frontal gyrus (BA 45)
–42
24
14
3.4
–
–
–
–
Superior temporal gyrus (BA 22)
–70
–30
0
2.8
–
–
–
–
Middle temporal gyrus (BA 21)
–48
–58
–6
3.4
–
–
–
–
Inferior temporal gyrus (BA 20/37)
–52
–60
–14
3.2
–
–
–
–
Middle occipital gyrus (BA 19)
–48
–68
–6
2.8
–
–
–
–
Inferior temporal gyrus (BA 20)
–54
–52
–20
2.7
–
–
–
–
Inferior temp/fusiform gyri (BA 20/37)
–46
–68
–16
2.3
–
–
–
–
Fusiform gyrus (BA 37)
–48
–44
–14
2.3
–
–
–
–
(c) Greater activations for non-words in English readers as compared with Italian readers
Anterior inferior frontal gyrus (BA 45)
–46
18
20
2.7
–
–
–
–
Inferior temporal gyrus (BA 21/37)
–58
–58
–14
2.9
–
–
–
–
–
–
–
–
(d) Greater activations for words and non-words in Italian readers as compared with English readers
Superior temporal gyrus (BA 22/42)
–48
–34
16
2.6
(e) Other tasks activating left basal temporal region for whole-word processing
Naming33
–37
–46
–20
Semantics; words and pictures13
–46
–46
–20
Conjunction word and object naming34
–44
–62
–16
Stress assignment+
–48
–58
–20
(f) Other tasks activating left anterior inferior frontal gyrus for whole-word processing
Semantic verbal fluency16
–36
24
16
Meta-analysis of semantic tasks15*
–37
27
14
(g) Other tasks activating left perisylvian temporal region: orthographic translation and sub-lexical phonological processing
Words–pictures35
–42
–40
20
Words–pictures36
–58
–46
28
Nonword–word32
–50
–36
32
Phonological short-term memory22
–44
–32
24
Localization is based on stereotactic coordinates. These coordinates refer to the location of maximal activation indicated by the highest z score in a particular
anatomical structure. Distances are relative to the intercommissural (AC–PC) line in the horizontal (x), antero-posterior (y) and vertical (z) directions. Z
scores indicate the magnitude of the statistical significance. *Average stereotactic coordinates derived by a published meta-analysis (‘semantic decision’)15.
+Stereotactic coordinate of activation associated with stress-assignment task for visually presented trisyllabic Italian words (E.P. et al., unpublished results).
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The bigram frequency of the stimuli was analyzed in terms of the number
of occurrences of a given bigram in a corpus of the 7500 most frequent
words in each language (DeMauro Vocabulario di Base28; CELEX English
database, http://www.kun.nl/celex). The absolute bigram frequency of the
stimuli across languages was different, as expected by their different orthographic and phonological structure (English words versus non-words,
266.2 versus 246.4; Italian words versus non-words, 455.2 versus 403.8).
Within each set of stimuli, there was a nonsignificant trend for a lower
bigram frequency of the non-words, and there was no significant interaction with language. In a separate task, subjects read 12 familiar international words with the same meaning in both languages: tennis, boiler,
basket, corner, partner, bitter, coma, taxi, panda, bravo, villa and pasta.
Only the last six conform to Italian orthography.
We used several control tasks. Simple vocal-reaction time was measured by asking subjects to say ‘go’ as quickly as possible every time a
small dot appeared on a computer screen at random intervals. Articulation speed was measured by asking subjects to repeat aloud as quickly as
possible, for 15 seconds, pairs of words common to both vocabularies
(gorilla/banana; tennis/polo). Two tasks measured ease of word retrieval.
In the verbal-fluency tasks, subjects generated in one minute as many
words as possible starting with the letter ‘m’ (letter fluency) or belonging to the category ‘animals’ (semantic fluency). In a picture-naming
task, subjects were instructed to name as quickly as possible pictures
whose names were words common to both vocabularies and were
rehearsed in advance: banana, bus, computer, gorilla, hamburger, pizza,
piano, spaghetti.
There were two PET scan experiments. In the explicit reading experiment, subjects read aloud words and non-words from their respective
orthographies. The stimuli included those used in the behavioral reading
experiment. The baseline was the resting state. The rate of presentation on
the computer screen was 2 s on and 1 s off. In the implicit-reading experiment7, participants performed a feature-detection task. This involved
detecting the presence or absence of ascenders (graphic features that go
above the midline of the word, as in b, l, or t but not in a, c or o) within
visually presented words, non-words and false-font strings. The false
fonts were created by substituting letters in the real words with non-letters matched for size and presence or absence of ascenders (for example,
‘cannon’ became
and ‘meter’ became
). The
requirements of the task remained constant across stimuli: a subject
pressed one key of a response box with the right index finger if one or
more ascender was present, and another key with the right middle finger if ascenders were absent. The stimuli included words and non-words
used in the other experiments and were presented at the same rate.
Subjects for PET studies. These studies were approved by the Ethics Committees of the Institute of Neurology (London) and Institute H San Raffaele (Milan). Six English and six Italian university students, matched
for age and IQ, participated in each study. In the explicit reading experiment, Italian subjects’ mean age and mean IQ ± s.d. were 27.8 ± 6.6 and
120.2 ± 6.7. English subjects’ mean age and mean IQ were 23.2 ± 2.9 and
113.2 ± 5.8. In the implicit reading experiment, Italian subjects’ mean
age and mean IQ were 24.7 ± 4.4 and 123 ± 10.3. English subjects’ mean
age and mean IQ were 24.5 ± 2.9 and 122.2 ± 13.9.
Data analysis. A full description of the H215O PET activation scanning
technique and data analysis can be found elsewhere29. Regional cerebral
blood flow (rCBF) was measured by recording the distribution of radioactivity following the intravenous injection of 15O-labeled water (H215O)
with a CTI Siemens Ecat HR+ PET scanner (CTI, Knoxville, Tennessee)
in London and the GE-Advance scanner (General Electric Medical System, Milwaukee, Wisconsin) in Milan. Twelve consecutive scans were
obtained for each subject in each experiment. The three stimulus conditions were presented in a counterbalanced order. Task-related differences in regional cerebral blood flow were examined using statistical
parametric mapping (SPM ‘96) software (Wellcome Department of Cognitive Neurology, London, UK) on stereotactically normalized and
smoothed PET images29. For each experiment, data were analyzed according to a random-effect model. Replications of each task were collapsed
into average images, yielding one average scan per reading task per subject, and the residual variance of subsequent statistical analyses incorporated the appropriate inter- and intra-subject variance components,
nature neuroscience • volume 3 no 1 • january 2000
permitting a mixed-effects analysis appropriate for population inference30. The analysis was based on a 2 (English, Italian subjects) × 2
(implicit, explicit reading) × 3 (words, non-words, baseline) factorial
design. We first calculated the main effect of the activation patterns associated with reading as the conjunction of the four main effects of reading
(reading minus baseline) in each of the four groups (statistical threshold, p < 0.001 corrected for spatial extent)31. We then calculated the main
effect of non-word minus word reading and vice versa, and the differences between groups as group × task interaction effects. All interaction
effects were computed on the voxels identified by the linear contrast of the
relevant main effects. For these latter, more subtle comparisons, a threshold of p < 0.01 was adopted32.
ACKNOWLEDGEMENTS
The studies were funded by the EEC-BIOMED II grant (contract BMH4-CT960274) and by the Gatsby Charitable Foundation. We are grateful to Andrew Holmes
for statistical advice and Caroline Moore for help with preparing the bibliography.
RECEIVED 18 AUGUST; ACCEPTED 16 NOVEMBER 1999
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