Maria Antonietta De Luca

Reading Words and Pseudowords: An Eye Movement Study of Developmental Dyslexia ☆

The pattern of eye movements during reading was studied in 12 developmental dyslexics and in 10 age-matched controls. According to standard reading batteries, dyslexics showed marked reading slowness and prevalently used the sublexical procedure in reading. Eye movements were recorded while they read lists of short and long words or pseudowords. In normal readers, saccade amplitude increased with word length without a concomitant change in the number of saccades; in contrast, the number of saccades increased for long pseudowords. In dyslexics, the eye movement pattern was different. The number of saccades depended on stimulus length for both words and pseudowords while saccade amplitude remained small and constant. The sequential scanning shown by dyslexics for both words and pseudowords appears consistent with the cognitive description of the reading disorder which indicates the preferential use of the sublexical print-to-sound correspondence rules.

Eye movement patterns in linguistic and non-linguistic tasks in developmental surface dyslexia

Ten subjects who could be reliably assessed as surface dyslexics were selected on the basis of a large test battery. Eye movements in non-linguistic and linguistic tasks were studied in these subjects. Stability of fixation on a stationary stimulus was examined. Performance of dyslexics was no different from that of an age-matched control group. Similarly, no difference was observed between the two groups when they were requested to saccade to a rightward or leftward target. On the other hand, while reading short passages, dyslexics showed an altered pattern of eye movements with more frequent and smaller rightward saccades as well as longer fixation times. The reading pattern was analysed by eye tracking. Numerous fixations were used to read a single word in a fragmented way. Longer words showed a higher number of fixations. Overall, it was concluded that surface dyslexia is not associated with oculo-motor dysfunction and the study of eye movements in reading reveals the processing through orthography-to-phonology conversion characteristic of surface dyslexia. The importance is stressed of examining selected groups of subjects in the psychophysiological study of dyslexia.

Length Effect in Word Naming in Reading: Role of Reading Experience and Reading Deficit in Italian Readers

Vocal reaction times (RTs) in naming 3- to 8-letter words were measured in proficient and dyslexic readers (Study 1). In proficient readers, RTs were independent of word length up to 5-letter words, indicating parallel processing. In the 5- to 8-letter range, RTs increased linearly, indicating sequential processing. Reading experience was associated with both faster discrimination of individual elements and parallel processing of increasingly large word parts. In dyslexics, RTs increased linearly with increasing length indicating reliance on sequential decoding. Individual analysis indicated 2 profiles of RTs (Types A and B). In Study 2, the distinction between A and B dyslexics was not associated with the use of different reading procedures. However, a more marked speed deficit characterized Type B dyslexics.

Rapid naming, not cancellation speed or articulation rate, predicts reading in an orthographically regular language (Italian)

This study examined the influence of rapid automatization naming (RAN) measures on various parameters of reading performance in children who were native speakers of a language with a shallow orthography (Italian). Participants included 281 children enrolled in first-to-sixth grade. They were given a Naming test, in which they had to name rapidly matrices of colors, objects, or digits, a Cancellation test, using the same stimulus materials, and an oral Articulation test. Performance on all tests improved steadily across ages tested. Performance on the Naming test, but not on the Cancellation and Articulation tests, predicted speed and accuracy in reading; none of these measures reliably predicted the reading comprehension measure. Data on a Blending test were also available for a subsample of first- and third-graders. Both RAN and phonological ability contributed independently to the prediction of reading ability (accuracy and speed) in these participants. The results extend observations on RAN to an orthographically shallow language (Italian) and suggest an element of continuity between languages with opaque and transparent orthographies.

Morpheme-based reading aloud: Evidence from dyslexic and skilled Italian readers

The role of morphology in reading aloud was examined measuring naming latencies to pseudowords and words composed of morphemes (roots and derivational suffixes) and corresponding simple pseudowords and words. Three groups of Italian children of different ages and reading abilities, including dyslexic children, as well as one group of adult readers participated in the study. All four groups read faster and more accurately pseudowords composed of root and suffix than simple pseudowords (Experiment 1). Unlike skilled young and adult readers, both dyslexics and younger children benefited from morphological structure also in reading aloud words (Experiment 2). It is proposed that the morpheme is a unit of intermediate grain size that proves useful in processing all linguistic stimuli, including words, in individuals with limited reading ability (dyslexics and younger readers) who did not fully develop mastering of whole-word processing. For skilled readers, morphemic parsing is useful for reading those stimuli (i.e., pseudowords made up of morphemes), for which a whole-word lexical unit does not exist; where such whole-word lexical units do exist, skilled readers do not need to rely on morphological parsing because they can rely on a lexical (whole-word) reading unit that is larger than the morpheme.

Developmental surface dyslexia is not associated with deficits in the transient visual system

DEFICITS of the transient visual system have been reported in unselected groups of dyslexics. The aim of this study was to examine whether this finding holds when subjects with a specific type of developmental reading disorder (surface dyslexia) are considered. Ten Italian children were examined. They all presented the characteristic markers of surface dyslexia: slow and laborious reading with errors in tasks which cannot be solved with a grapheme-phoneme conversion (i.e. homophones). Contrast sensitivity thresholds to phase-reversal gratings were within normal limits for most subjects both for stimuli presented centrally and in the right parafovea. This indicates that developmental surface dyslexia is not associated with a deficit in the transient system. In contrast, sensitivity to high spatial frequency stationary stimuli was reduced.

Training of developmental surface dyslexia improves reading performance and shortens eye fixation duration in reading

Eighteen surface dyslexics were studied. Their reading deficit was evaluated on the basis of two standard test batteries. Nine subjects were submitted to reading training that consisted of reading briefly presented words. Nine dyslexics acted as a control group (receiving delayed treatment). Accuracy and speed of reading improved after therapy; also the performance in a lexical decision task improved. No effect was observed for a task using homophone contrasts. Furthermore, reading comprehension did not change as a function of training. All dyslexics were submitted to two experimental procedures: measurement of vocal reaction times (RTs) to reading single words and analysis of eye movements in reading short passages. Vocal RTs were faster for the treated group after therapy. As for eye movements, mean fixation duration was shorter after training. Other parameters (number and size of rightward saccades and number of regressions) showed small improvement with time, independent of training. When the control group was submitted to therapy in the next school year, similar improvements in reading were obtained. Overall, training affected reading parameters that appear to reflect the speed of extraction of visual information.

Differential adaptive properties of accumbens shell dopamine responses to ethanol as a drug and as a motivational stimulus

Non‐adaptive activation of dopamine transmission in the nucleus accumbens shell by drugs of abuse has been attributed a fundamental role in the mechanism of drug addiction. In order to test this hypothesis, we compared in the same subject the effect of an addictive drug (ethanol) and of taste stimuli, including ethanols own taste, on dialysate dopamine in the nucleus accumbens shell as an estimate of dopamine transmission and on taste reactivity as an expression of motivational valence. Ethanol was also monitored in the dialysates. In naive rats, intraoral infusion of a 20% sucrose + chocolate solution elicited a monophasic increase of dialysate dopamine immediately after the intraoral infusion. In contrast, intraoral infusion of 10% ethanol, 10% ethanol + 20% sucrose or 10% ethanol + 20% sucrose + chocolate solutions elicited a biphasic increase of nucleus accumbens dopamine with an early taste‐related rise and a late rise related to dialysate ethanol. Pre‐exposure to the ethanol solutions 24 h before resulted in the absence of the early dopamine rise and permanence of the late dopamine rise. This late dopamine rise was actually increased as compared with that of the nonpre‐exposed group when sucrose‐containing ethanol solutions were tested. The results indicate that single trial pre‐exposure to the ethanol solutions differentially affects the responsiveness of nucleus accumbens shell dopamine to the direct intracerebral action of ethanol and to the effect of its taste with potentiation, or no change of the first and abolition of the second. These observations point to the existence of major differences in the adaptive regulation of nucleus accumbens dopamine transmission in the shell after drug as compared with taste reward. These differences, in turn, are consistent with a role of nucleus accumbens shell dopamine in the mechanism of the behavioural effects of addictive drugs.

Lexicality and Stimulus Length Effects in Italian Dyslexics: Role of the Overadditivity Effect

The effect of lexicality and stimulus length was studied in 32 third- and fourth-grade Italian dyslexics and in 86 age-matched controls. A visual lexical decision task was used. As proposed by Faust et al. (1999), the results were analyzed in terms of raw reaction time (RT) data and using the z-score transformation to control for the presence of overadditivity effects. In terms of RTs, dyslexics showed a larger difference between words and nonwords (lexicality effect) and between short and long stimuli (length effect) than proficient readers. When data were transformed into z scores, only the group by length interaction remained significant while that with lexicality vanished. This pattern indicates that stimulus length has a specific role in Italian dyslexics’ reading deficit; in contrast, slowness in responding to nonwords was not specific but was interpreted as one aspect of dyslexics’ general inability to deal with alphabetical material (overadditivity effect).

Isolating global and specific factors in developmental dyslexia: a study based on the rate and amount model (RAM)

Using the reading-age match approach, research on developmental dyslexia focuses on specific (e.g., phonological) deficits and disregards the possible role of global influences in determining the disturbance. In the present study, we set out to investigate the role of both global and specific factors in Italian developmental dyslexics using the rate-amount model (RAM; Faust et al. in Psychol Bull 125:777–799, 1999). Vocal reaction times (RT) in naming pictures, words and non-words of varying length were measured in a group of 26 sixth- to eighth-grade dyslexics and 81 age-matched control readers. Dyslexics’ raw RTs showed greater lexicality (longer RTs to non-words than words) and length (longer RTs to long stimuli than short ones) effects than controls’. We found that one global factor predicted most individual variation in naming words and non-words, but not pictures. When data transformations, effective in controlling for the global factor, were applied to the data, the greater lexicality effect in dyslexics vanished, due to the influence of the global factor and not a specific failure in the non-lexical reading procedure. Conversely, the greater length effect in dyslexics persisted. Overall, dyslexics’ reading performance was best explained as due to the influence of both a global factor for processing orthographic material prelexically and to the specific influence of stimulus length. This conceptualisation appears more promising for bridging the gap between behavioural and functional imaging studies than traditional approaches, which focus on the detection of specific reading deficits. It is concluded that RAM is a useful tool for disentangling the components that are impaired in reading and for defining the characteristics of the global factor, because the paradigm is more powerful for studying developmental dyslexia than the reading-age match method.