doi:10.1093/brain/awh340
Brain (2005), 128, 261–267
More than words: a common neural basis for
reading and naming deficits in developmental
dyslexia?
Eamon J. McCrory,1,2 Andrea Mechelli,3 Uta Frith2 and Cathy J. Price3
1
Department of Psychology, Institute of Psychiatry,
Institute of Cognitive Neuroscience, University College
London and 3Wellcome Department of Imaging
Neuroscience, Institute of Neurology, London, UK
2
Correspondence to: Eamon J. McCrory, Institute of
Psychiatry, Department of Psychology, De Crespigny Park,
London SE5 8AF, UK
E-mail: [email protected]
Summary
Dyslexic individuals show subtle impairments in naming
pictures of objects in addition to their difficulties with
reading. The present study investigated whether word
reading and picture naming deficits in developmental dyslexia can be reduced to a common neurological impairment. Eight dyslexic subjects, impaired on measures of
reading, spelling and naming speed, were matched for
age and general ability with 10 control subjects.
Participants were scanned using PET during two experimental conditions: reading words and naming pictures in
the form of corresponding line drawings. In addition, two
high-level baseline conditions were used to control for
visual and articulatory processes. Relative to the control
group, the dyslexic participants showed reduced activation in a left occipitotemporal area during both word reading and picture naming. This was the case even in the
context of intact behavioural performance during scanning. Abnormal activation in this region, as reported
previously for reading, is therefore not specific to
orthographic decoding but may reflect a more general
impairment in integrating phonology and visual information. Our investigation points to a common neurological
basis for deficits in word reading and picture naming in
developmental dyslexia.
Keywords: dyslexia; reading; naming; functional imaging; left occipitotemporal cortex
Received April 8, 2004. Revised July 1, 2004. Second revision September 14, 2004. Accepted October 4, 2004.
Advance Access publication December 1, 2004
Introduction
It has long been proposed that the cognitive processes
engaged when reading a word overlap considerably with
those engaged when naming a known object (Geschwind,
1965; Wolf, 1991). In both instances we perceive and identify
a visual stimulus and retrieve its associated lexical form,
which is then output during articulation. It is also well established that picture naming provides a means to index literacy
skill. Naming performance in kindergarten, for example,
represents a powerful predictor of later reading ability (Jansky
and de Hirsch, 1972; Wolf and Goodglass, 1986).
It is therefore not surprising that dyslexic children show
early impairments on tasks of picture naming in addition to
their difficulties with reading. For example, dyslexic children
present with impairments on tasks of rapid automatic
naming, in which a series of pictures are named sequentially
(Denckla and Rudel, 1976). The cognitive complexity of this
task has precluded a straightforward explanation of this
Brain Vol. 128 No. 2
#
impairment (Wolf, 1991; Manis et al., 1999). In contrast,
their impairments in confrontation naming, in which individual pictures are named discretely, are generally thought to be
attributable to a phonological impairment (Katz, 1986;
Snowling et al., 1988; Swan and Goswami, 1997).
By adulthood, impairments in confrontation naming have
largely resolved, in contrast to continuing deficits in reading
(Felton et al., 1990; Hanley, 1997). Yet how can this be
accounted for if a common phonological deficit is hypothesized to underlie both impairments? A number of observations
suggest that a deficit in lexical retrieval persists into adulthood
but at a more subtle level. For example when adult dyslexics
must name single pictures in a rapid fashion, impairments do
emerge (e.g. Wolff et al., 1990). Similarly, deficits are commonly reported in adult dyslexics when pictures are named
sequentially on tasks of rapid automatic naming (e.g. Felton
et al., 1990).
Guarantors of Brain 2004; all rights reserved
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E. J. McCrory et al.
During both reading and naming, a stored phonological
code is retrieved. This code is likely to consist of phonological
segments that are activated and assembled into a sequence that
controls production (Levelt, 1989). During reading, orthographic codes are postulated to have direct connections
with phonological codes; despite a large amount of empirical
research, it is still a matter of debate how these connections
are instantiated (Plaut et al., 1996; Zorzi et al., 1998;
Coltheart et al., 2001). In contrast, during picture naming,
phonology is accessed via the semantic system (Warren
and Morton, 1982; Glaser, 1992). Despite these differences,
both words and pictures are thought to access the same lexical
store of word forms but pictures are thought to show privileged access to semantics and words a privileged access to
phonology (Warren and Morton, 1982; Glaser, 1992). So while
word reading is faster than picture naming, word classification
is slower than picture classification (Segui and Fraisse, 1968).
Studies of dyslexic individuals are remarkable in showing a
selective deficit in the phonological but not semantic processing of pictures (e.g. Murphy et al., 1988). Such findings
support the view that dyslexia is characterized not by a general
language or semantic deficit, but one which pertains primarily
to phonological representation and retrieval.
Studies of the normal population have investigated the
neural basis for the cognitive processes engaged in phonological retrieval. Tasks of letter, colour and picture naming have
been shown to implicate a common neural system incorporating the left posterior inferior temporal lobe and the left frontal
operculum (Price and Friston, 1997; Moore and Price, 1999).
The functional role of these regions remains to be fully specified. Typically, however, frontal regions are associated with
later stages of retrieval, including articulation (Murphy et al.,
1997) while posterior areas are activated during earlier stages
of phonological retrieval (e.g. Salmelin et al., 1996).
Over the past decade, functional imaging studies have made
significant advances in identifying the neural basis of word
reading in developmental dyslexia (for reviews see Habib,
2000; McCrory, 2003). In general, dyslexic participants
have been reported to show a pattern of differential activation
relative to normal readers that have clustered in three key left
hemisphere regions: (i) a set of left frontal regions largely
centred on the inferior frontal gyrus; (ii) the left temporoparietal region, including the supramarginal gyrus and the posterior aspect of the superior temporal gyrus (Wernicke’s area);
and (iii) the left posterior inferior temporal lobe (BA 37), now
more commonly referred to as the occipitotemporal region.
A consensus is emerging that the most robust differences in
activation arise in the left occipitotemporal area in dyslexic
participants (Salmelin et al., 1996; Rumsey et al., 1997;
Brunswick et al., 1999; Paulesu et al., 2001; Shaywitz
et al., 2002) even when behavioural performance has
been matched (Brunswick et al., 1999) and across different
orthographies (Paulesu et al., 2001). These differences
have been consistently interpreted in the context of impaired
phonological processing in dyslexia (Rumsey et al., 1997;
Brunswick et al., 1999; Paulesu et al., 2001; Shaywitz
et al., 2002). Yet while these studies have employed a variety
of paradigms they share one common feature: the use of
orthographic stimuli. Therefore, we cannot exclude the possibility that reduced activation in this area reflects orthographic rather than phonological processing.
Studies of skilled reading have not provided a consistent
account of the role of the left occipitotemporal area. Recently,
the emphasis has been on the association of this area with
visual word form processing (Cohen et al., 2000; McCandliss
et al., 2003). However, although this left occipitotemporal
area is activated during reading, it is also activated by a
range of tasks that do not engage visual word-form processing, such as naming colours and pictures (Moore and Price,
1999; Chao et al., 2002), reading Braille (Buchel et al., 1998)
and making manual responses to pictures of meaningless
objects (Phillips et al., 2002). This response profile suggests
the left occipitotemporal area has a more general function
(Price and Devlin, 2003). Nevertheless, we still need to consider whether the area is more involved in reading than nonorthographic processes. Our functional imaging experiments
have suggested that activation is higher during picture naming
than reading in normal participants (Price and Devlin, 2003).
However, Hasson and colleagues found greater activation for
written words than pictures of tools during a one back task (i.e.
is present stimulus identical to previous stimulus?) (Hasson
et al., 2002). Thus, the degree to which left occipitotemporal
activation is engaged during the processing of orthographic
and non-orthographic stimuli may depend on the nature of the
task and the differential demands on a shared processing
function. If the left occipitotemporal activation reflects phonological retrieval, then abnormal activation is more likely to
be detected by dyslexics who are engaged in phonological
tasks such as reading. A recent MEG study (Tarkiainen et al.,
2003) showed that face stimuli elicited normal left occipitotemporal activation in dyslexic participants, which contrasts
with the reduced left occipitotemporal activation that has been
observed in dyslexic participants during reading. However,
the face stimuli and task used by Tarkiainen and colleagues
did not require any phonological processing. Thus, abnormal
left occipitotemporal activation might be abnormal if faces or
objects had to be named.
Previous imaging studies that have used tasks which explicitly entail phonological processing have had to contend with
impaired behavioural performance by dyslexic participants
(e.g. Rumsey et al., 1997; Shaywitz et al., 1998). The difficulty here is how one interprets differences at the neural level,
if at the behavioural level the performance of the two groups
differs. Poor behavioural performance alone may be sufficient
to explain some, if not all, of the observed activation differences. Picture naming, for several reasons, may represent an
ideal paradigm to overcome these concerns. While picture
naming is markedly impaired in dyslexic children (e.g.
Katz, 1986; Swan and Goswami, 1997), confrontation naming
is normal in dyslexic adults (e.g. Felton et al., 1990). When
naming proceeds in rapid succession, either in a sequence (e.g.
Felton et al., 1990) or singly (Wolff et al., 1990), dyslexic
Reading and naming in developmental dyslexia
263
Table 1 Neuropsychological data and behavioural performance during scanning
Variable
Age (years)
IQ tests (WAIS-III)
Full-scale
Verbal
Performance
Standardized literacy tests
Reading WRAT-R (standardized scores)
Spelling WRAT-R (standardized scores)
Verbal memory tasks (maximum = 19)
WAIS digit span
WAIS letter–number sequencing
Naming tasks
Rapid naming (pictures)
Rapid naming (digits)
Performance during PET scanning
Word reading accuracy (% correct)
Picture naming accuracy (% correct)
Word reading latency (ms)
Picture naming latency (ms)
Dyslexics (n = 8)
Controls (n = 10)
P
20.0 (0.9)
20.3 (2.9)
n.s.
123.9 (10.9)
119.5 (6.0)
124.6 (6.7)
125.1 (9.7)
124.4 (6.8)
120.8 (13.4)
n.s.
n.s.
n.s.
88.1 (14.4)
85.9 (14.6)
112.7 (4.7)
107.8 (6.5)
**
**
7.4 (1.2)
8.1 (1.6)
12.5 (2.4)
12.2 (3.5)
**
**
36.6 (6.5)
19.9 (4.0)
28.9 (3.8)
16.3 (3.2)
*
*
99.4
95.8
715.6
808.0
(1.7)
(8.0)
(110.5)
(99.0)
100 (0)
98.8 (5.2)
708.1 (87.5)
871.5 (104.9)
n.s.
n.s.
n.s.
n.s.
Standard deviations are shown in parentheses. WAIS-III = Wechsler Adult Inventory Scale—III; WRAT = Wide Range Achievement
Test-Revised; n.s. = not significant. *P < 0.05; **P < 0.01.
adults manifest a performance deficit. This pattern suggests
that although dyslexic adults manifest a developmental
improvement in picture naming, a cognitive impairment in
phonological retrieval persists—and this impairment is behaviourally manifest under speeded conditions. In this way picture naming may allow us to engage the cognitive component
of interest (phonological retrieval) while not giving rise to
detectable behavioural impairments.
The present study aimed to investigate the neural correlates
of picture naming and word reading in developmental
dyslexia, using PET. Dyslexic individuals are thought to
have a common deficit in phonological retrieval that extends
beyond literacy to encompass picture naming (e.g. Katz,
1986; Swan and Goswami, 1997). It is hypothesized that
this deficit persists into adulthood and is detectable at the
neural level. We propose that the atypical left occipitotemporal activation in developmental dyslexia reflects an impairment in phonological retrieval beyond that implicated by
orthographic decoding. Specifically, the dysfunction in this
region should be manifest during both word reading and picture naming since both tasks require phonological retrieval.
The alternative possibility is that atypical activation in the
occipitotemporal region is specific to orthographic stimuli.
This would be inconsistent with the idea that impaired performance during reading and naming can be reduced to a
common phonological deficit.
Methods
Participants
Eight dyslexic participants and 10 control participants with no
history of language difficulty were recruited. All participants
were right-handed, physically healthy males and none reported a
history of neurological or psychiatric disorder. The dyslexic
readers all had a documented history of reading difficulty identified
in childhood or adolescence; all participants had gained entrance
into university. Both groups were well matched for educational
level, age and full-scale, verbal and performance IQ, as shown in
Table 1.
Neuropsychological measures
General ability
General intellectual ability was assessed with the administration
of a full Wechsler Adult Inventory Scale—III (Wechsler, 1997).
Full-scale, verbal and performance IQs were calculated across
groups.
Reading and spelling
Literacy skills were assessed using the Wide Range Achievement
Test—Revised (Jastak and Wilkinson, 1984).
Naming
Naming ability was evaluated using two tasks of rapid automatic
naming. In a picture naming task, five pictures were repeated 10
times along five rows, each 10 items in length (after Denckla and
Rudel, 1976). Participants were asked to name each picture, working
as fast as possible across each row until the end. The mean time was
calculated across two trials. The same procedure was used for the
digit version. Participants were asked to read aloud, as fast as possible, strings of 50 single-syllable digits (the number 7 was excluded
as the only digit with a two-syllable name). Digits were chunked into
blocks of five (e.g. 68248 83542 99634), although participants were
told to read each digit as a single number, i.e. the string 51368 had to
be read as ‘five, one, three, six, eight’. The task was presented twice
with different strings of 50 digits. Again, a mean score, in seconds,
was calculated.
264
E. J. McCrory et al.
Candle
i
ii
iii
iv
Fig. 1 Examples of visual stimuli presented during scanning: (i)
word; (ii) false font string; (iii) picture; (iv) nonsense shape.
PET stimuli and tasks
Stimuli
In total, 120 names were selected from the Snodgrass and Vanderwart set of pictures (Snodgrass and Vanderwart, 1980), and were
presented as either words or line drawings [Fig. 1(i) and 1(iii)]. Word
length ranged in length from one to four syllables (mean = 1.72;
SD = 0.8) and from two to nine phonemes (mean = 4.73; SD = 1.77).
Mean word frequency was calculated as 399 occurrences per 17.9
million for combined written and verbal frequency (Celex database).
A set of published norms (Morrison et al., 1997) for the Snodgrass
and Vanderwart (1980) set of pictures indicated a high mean name
agreement score (0.92) and a relatively early mean age of acquisition,
of 51 months (SD = 16.72). The stimuli were divided into two sets, A
and B. Half the participants saw set A as pictures and set B as words;
the remaining participants saw set A as words and set B as pictures. In
this way no participant read and named the same items. Pictures were
all scaled to measure 5–8 cm in width and 5–8 cm in height. Words
were presented in lower case Courier font, size 72 points.
In addition, meaningless control stimuli were carefully designed
for both reading and naming tasks [Fig. 1(ii) and 1(iv)]. For words, two
sets of false fonts were created, one short and one long, to match for
word length. For pictures, a set of nonsense line drawings was also
created to control for the visual features of each object. The rated
visual complexity of these non-objects was matched with published
ratings (Morrison et al., 1997) of visual complexity of the real objects.
Experimental paradigm
The experimental paradigm comprised four conditions: word
reading, picture naming, false fonts and nonsense shapes. In the
reading and naming conditions, subjects were asked to read or
name aloud each item when it appeared on the screen. The false
fonts were either short strings or long strings. For the short strings,
participants were instructed to respond ‘yes’, and to the long false
font condition they responded ‘okay yes’. Similarly, there were
two types of nonsense shape trial. In one, participants responded
‘yes’ and in the other they responded ‘okay yes’. The false font
and nonsense shape tasks were designed to control for visual processing, articulation processes and auditory feedback. These baselines
are similar to those employed in previous studies to control for
the visual processing of the words and pictures (e.g. Bookheimer
et al., 1995; Moore and Price, 1999). Fifteen stimuli were
presented per scan, each for 500 ms, with a fixed interstimulus
interval of 2000 ms.
PET scanning
Regional cerebral blood flow was measured using a CTI Siemens
Ecat HR + PET scanner. Each activation scan involved the intravenous administration of 5 mSv of 15O-labelled water at the constant
rate of 10 ml/min. From the start of each scan, background radiation
was measured for 30 s, after which the infusion was given. The
activation task was started approximately 30 s later, 10 s prior to
the onset of the 90-s acquisition period. This protocol conforms to
guidelines established by ARSAC UK and was approved by the
Medical Ethics Committee of the Institute of Neurology. A total
of 12 scans were acquired: four for the word reading task, four
for the picture naming task, two for the false font task (one long,
one short) and two for the nonsense shape task.
Data analysis
Behavioural measures were quantified and compared between groups
using factorial analyses of variance. The PET data were analysed
using SPM99 (Friston et al., 1995a) implemented in MATLAB
Version 4.2 (MathsWorks, MA, USA) on a SPARC1 workstation
(Sun Microsystems, UK). Head movements that occurred during the
course of the PET scan were corrected by realigning the time series
with the first scan. The reconstructed transaxial PET images were
spatially normalized for brain size and shape with 2 3
2 3 2 mm voxels (Friston et al., 1995b) These images were subsequently smoothed in three directions with a Gaussian filter (full
width, half maximum) of 16 3 16 3 16 mm. This smoothing
had the effect of increasing signal-to-noise ratio and allowing for
normal between-subject variation in gyral anatomy. Statistical
analyses were performed at the single subject level, to examine
the effects of reading > false fonts and picture naming > nonsense
shapes in each subject independently. These contrasts were then used
in second-level analyses in which unpaired t-tests modelled betweensubject variance and compared the effects in the control and dyslexic
groups (Holmes and Friston, 1998). Statistical significance was
inferred at P < 0.05 corrected for multiple comparisons across the
whole brain.
Results
Behavioural data
Accuracy and latency of response for both reading and
naming tasks were recorded during PET scanning and compared between groups using factorial analyses of variance (see
lower part of Table 1). The two groups performed with comparable levels of accuracy. Likewise, reading and naming
latencies did not differ significantly between the control
and dyslexic groups. Significant phonological deficits, however, characterized these dyslexic participants when performing more sensitive standardized literacy and verbal memory
tasks outside the scanner (see upper part of Table 1).
PET data
For picture naming relative to nonsense shapes, the control
group activated the left occipitotemporal region (x = 46,
y = 52, z = 16; Z-score = 5.2; P < 0.01 corrected for
multiple comparisons across the whole brain) but the dyslexic
group showed a much smaller effect in this region (x = 46,
y = 52, z = 16; Z-score = 2.8). For reading relative to false
fonts, the control group activated the left occipitotemporal
area (x = 48, y = 54, z = 16; Z-score = 3.7), but no
activation was detected in this region for the dyslexic
group even when lowering the statistical threshold to P < 0.1
Reading and naming in developmental dyslexia
Word
Reading
-16
-54
-48
-16
-54
-48
Picture
Naming
Fig. 2 Reduced activation in the dyslexic group relative to the
controls in the left occipitotemporal region for word reading and
picture naming.
(uncorrected). No frontal activation was detected for either
reading or naming; this is likely to reflect the fact that articulation was also required in the baseline task.
Direct comparison of the two groups identified reduced left
occipitotemporal activation in the dyslexic group relative to
the control group for both word reading relative to false fonts
(x = 46, y = 52, z = 16; Z-score = 5.4; P < 0.05 corrected
for multiple comparisons across the entire brain) and picture
naming relative to nonsense shapes (x = 48, y = 54, z = 16;
Z-score = 4.8; P < 0.05 corrected for multiple comparisons
across the entire brain) (Fig. 2). Critically, there was no significant interaction between task and group, even when lowering the statistical threshold to P < 0.1 (uncorrected). No
other areas expressed differential activation for the control
and the dyslexic group.
Discussion
The primary aim of this study was to investigate whether
two tasks of lexical retrieval—reading and naming—were
characterized by a common pattern of neural activation in
dyslexic adults. Our findings confirmed this prediction: both
tasks elicited significantly reduced activation in the left
occipitotemporal region in dyslexic participants, even in
the context of matched behavioural performance.
At the neural level, abnormal activation during word processing in dyslexia in the left occipitotemporal was expected
on the basis of previous studies (Salmelin et al., 1996;
Rumsey et al., 1997; Brunswick et al., 1999; Paulesu et al.,
2001; Shaywitz et al., 2002). However, the observation that a
similar pattern also emerges during picture naming sheds light
on the interpretation of these results. Specifically, we have
shown reduced occipitotemporal activation in the absence of
any orthographic decoding. This suggests that abnormal
neural activation in dyslexic individuals reflects a more general impairment in retrieving phonology from visual input. In
other words, reduced activation in the same occipitotemporal
region may underlie the reading and naming deficits observed
in developmental dyslexia.
It appears that, by adulthood, naming impairments
become behaviourally manifest when items are named rapidly
265
either in a serial format, as in the rapid automatic naming
tasks reported in the present study (Table 1), or when
named rapidly in a discrete trial format (Wolff et al.,
1990). It may be the case that such rapid naming stresses
phonological retrieval in a way that results in slowed behavioural performance. There may, for example, be a refractory
period which limits performance. The finding of a common
neurological impairment during both picture naming and
word reading strongly supports this view, that a common
deficit in phonological processing underpins the behavioural
impairments observed developmentally in word reading and
picture naming (Swan and Goswami, 1997). That is, the
dyslexic’s difficulties in lexical retrieval are most parsimoniously accounted for by a single underlying cognitive deficit,
without the need to postulate additional deficits (cf. Wolf and
Bowers, 1999).
The picture naming paradigm employed in the present
study demonstrates the possibility of developing tasks
which tap neural differences in dyslexia, without eliciting
behavioural confounds that can interfere with the interpretation of results. Here, the measurement of neuronal activation
indexes subtle differences in cognitive processing not captured by traditional behavioural measures.
The reduced left occipitotemporal activation found in the
dyslexic participants for word reading (x = –46, y = 52,
z = 16) and for picture naming (x = –48, y = 54, z = 16)
corresponds almost precisely to the peak of the ‘word form
area’ proposed by Cohen and colleagues (x = –43, y = 54,
z = 12; McCandliss et al., 2003). These findings are not
consistent with the hypothesis that dysfunction in this region
is specific to the processing of letter strings (Tarkiainen et al.,
2003). Rather, the pattern of reduced activation in certain
tasks (picture naming and reading) and not others (face processing; Tarkiainen et al., 2003) indicates that (i) this region is
engaged by non-orthographic stimuli, and (ii) the neurological
deficit in this region is an emergent property of the interaction
of multimodal (in this case visual and phonological) information (Buchel et al., 1998). We suggest that it is the strategic
location of this region, between the visual cortex and the more
anterior temporal cortex, in addition to its connections with
frontal regions that endows it with a role in the integration of
visual, phonological and semantic information (Price and
Friston, 2004).
The precise nature of this role remains to be fully delineated. From an evolutionary perspective, the shared effect
of reading and object naming in the left occipitotemporal area
reported here is not surprising, given that reading is a relatively recent (and still by no means universal) human activity.
The difficulties shown by dyslexic individuals during picture
naming are too subtle to impact on their performance within a
non-literate context. However, the interaction of visual and
phonological information needed to read a non-symbolic
alphabetic script leads to evident deficits at the behavioural
level. We need to characterize more precisely the nature of the
deficit in dyslexia in order to explain why a common neural
deficit differentially taxes reading in this way.
266
E. J. McCrory et al.
Future imaging studies are needed to characterize the nature
of the dysfunction in the left occipitotemporal area at the neural
level. For example, do dyslexic participants show reduced
activation in this region when naming environmental
sounds—a process requiring lexical retrieval in the absence
of visual input? Or are differences confined to those tasks in
which the processing of verbo-visual associations are required?
It will also be important to delineate the function of the left
occipitotemporal area in relation to the left frontal operculum,
which can show overactivity in dyslexic readers. It has been
suggested that these two regions may represent aspects of the
same phonological retrieval system in non-impaired readers
(Price and Friston, 1997). In addition, future studies will
need to continue to employ new paradigms to evaluate neural
function in other brain areas. These may elucidate the role of
activation differences in the right hemisphere and the left
frontal region in dyslexia (e.g. Shaywitz et al., 2002).
Typically, regional differences in brain activation are
implicitly assumed to reflect causal factors in dyslexia
(McCrory, 2003). However, current neuroimaging techniques
do not allow causal direction to be established. One proposal
is that a lack of reading experience could account for observed
differences in the left posterior inferior temporal lobe, given
that reading acquisition and ability influence activity in this
region (Petersson et al., 2000). Matching adult dyslexics with
younger controls for reading age, and the use of longitudinal
designs are two ways in which this hypothesis might be tested.
The present study indicates differences in the left posterior
inferior temporal lobe on a non-reading task; this suggests that
differences here may be independent of reading experience.
The use of illiterate or unschooled participants is another way
to explore the impact of experience on the language system
(e.g. Castro-Caldas et al., 1999; Reis et al., 2001). One strong
prediction could be made on the basis of the present findings:
on a task of picture naming adult illiterates, like adult readers,
should show enhanced activation in the left inferior temporal
lobe compared with adult dyslexics. Such a finding would
support the view that dyslexics are characterized by a specific
neural abnormality.
On the basis of our study, novel predictions can be made
that are relevant to the diagnosis and treatment of developmental dyslexia. Children can put a name to a picture even
before they learn to read. This elementary process in the use of
language provides an early measure of a child’s semantic and
phonological knowledge. We provide support for the hypothesis that word reading and picture naming deficits share a
common neurological basis and speculate that the diagnosis
and treatment of picture naming skills in preschool children
may impact upon later reading performance.
Acknowledgements
This work was funded by the Wellcome Trust and the Medical
Research Council. A. M. is supported by MH64445 from the
National Institutes of Health (USA).
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