PubMed Health⌕ Search

Biomedical subjects

Heinz Wimmer

Publications and source records attributed to Heinz Wimmer.

15 recordsLinked to original sources
PubMed2006

Evidence for a dysfunction of left posterior reading areas in German dyslexic readers.

The brain activity during a sentence reading task and a visual control task was examined with fMRI in 13 German dyslexic readers and 15 age-matched fluent readers (age: 14-16 years). These participants came from a longitudinal study and the dyslexic readers exhibited a persistent reading fluency deficit from early on. For the first time with German dyslexic readers, and in correspondence with the majority of functional imaging studies, we found reduced dyslexic activation in the left occipitotemporal cortex and in a small region of the left supramarginal gyrus. Enhanced activation was found in left inferior frontal and subcortical regions.

Adolescent↗
PubMed2005

Impaired visual processing of letter and digit strings in adult dyslexic readers.

The slow word reading of developmental dyslexics may stem from a string processing impairment which in turn reflects visual attentional deficits. We indeed found substantially enhanced recognition time thresholds in the dyslexic adult readers. However, their position profiles were hard to reconcile with any of the discussed visual attentional deficit hypotheses and with the prediction that dyslexic readers suffer from an absent string processing system as they exhibited similar M-shaped position profiles for digit and letter strings as the normal reading controls.

Adolescent↗
PubMed2005

Perhaps correlational but not causal: no effect of dyslexic readers' magnocellular system on their eye movements during reading.

During reading, dyslexic readers exhibit more and longer fixations and a higher percentage of regressions than normal readers. It is still a matter of debate, whether these divergent eye movement patterns of dyslexic readers reflect an underlying problem in word processing or whether they are - as the proponents of the magnocellular deficit hypothesis claim - associated with deficient visual perception that is causal for dyslexia. To overcome problems in the empirical linkage of the magnocellular theory with reading, a string processing task is presented that poses similar demands on visual perception (in terms of letter identification) and oculomotor control as reading does. Two experiments revealed no differences in the eye movement patterns of dyslexic and control readers performing this task. Furthermore, no relationship between the functionality of the participants' magnocellular system assessed by the coherent motion task and string processing were found. The perceptual and oculomotor demands required during string processing were functionally equivalent to those during reading and the presented consonant strings had similar visual characteristics as reading material. Thus, a strong inference can be drawn: Dyslexic readers do not seem to have difficulties with the accurate perception of letters and the control of their eye movements during reading - their reading difficulties therefore cannot be explained in terms of oculomotor and visuo-perceptual problems.

Adolescent↗
PubMed2005

Impaired visual processing of multi-element arrays is associated with increased number of eye movements in dyslexic reading.

For assessing simultaneous visual processing in dyslexic and normal readers a multi-element processing task was used which required the report of a single digit of briefly presented multi-digit arrays. Dyslexic readers exhibited higher recognition thresholds on 4- and 6-digit, but not on 2-digit arrays. Individual recognition thresholds on the multi-digit arrays were associated with number of eye movements during reading. The dyslexic multi-element processing deficit was not accompanied by deficient coherent motion detection or deficient visual precedence detection and was independent from deficits in phonological awareness and rapid naming. However, only about half of the dyslexic readers exhibited a multi-element processing deficit.

Adolescent↗
PubMed2005

Developmental dyslexia in a regular orthography: a single case study.

This study of an adult case examined in detail with eye movement measures the reading speed problem which is characteristic for developmental dyslexia in regular orthographies. A dramatic length effect was found for low frequency words and for pseudowords, but not for high frequency words. However, even for high frequency words it was found that reading times were substantially prolonged although number of fixations did not differ. A neurocognitive assessment revealed no visual deficits (parallel processing, precedence detection, coherent motion detection) but speed impairments for certain verbal and phonological processes. We propose that the reading difficulties are phonological in nature, but these difficulties become manifest as inefficiency and not as inability.

Adult↗
PubMed2004

Training reading fluency in dysfluent readers with high reading accuracy: word specific effects but low transfer to untrained words.

The outcome of a training study attempting to increase German speaking poor readers' reading fluency is reported. The aim of the training was to help children establish orthographic representations for a limited set of training words as well as for high-frequency onset clusters. A sample of 20 dysfluent readers (8-11 years) received a computerized training of repeated reading of a limited set of 32 training words over a period of up to 25 days. Each day training words were presented up to six times with a special emphasis on the onset segment. Post-tests were carried out one and five weeks after the last training day. A considerable decrease in reading times could be achieved for the trained words that remained stable for both post-tests, however, even for the limited set of training words a remarkable amount of repetitions did not lead to age adequate word recognition speed. Generalization to untrained words starting with a trained onset cluster (transfer words) was statistically reliable but small.

Child↗
PubMed2004

When does the brain register deviances from standard word spellings?--An ERP study.

Event-related potentials (ERPs) in response to the standard form of words (e.g., taxi) were compared with ERPs in response to letter-altered (e.g., taksi) or case-altered forms (e.g., taXi). The altered forms always resulted in the same reading as the standard forms. First divergences between ERPs were found at around 160 ms. At occipital sites, the peak amplitude of the N160 was higher for standard than letter-altered strings. At frontal and central sites, the standard strings diverged from the altered strings persistently by higher positivity from about 160 ms onwards. These early ERP differences between standard and altered visual word forms speak for early contact between the letter input and stored visual-orthographic representations of words.

Adult↗
PubMed2004

Do current connectionist learning models account for reading development in different languages?

Learning to read a relatively irregular orthography, such as English, is harder and takes longer than learning to read a relatively regular orthography, such as German. At the end of grade 1, the difference in reading performance on a simple set of words and nonwords is quite dramatic. Whereas children using regular orthographies are already close to ceiling, English children read only about 40% of the words and nonwords correctly. It takes almost 4 years for English children to come close to the reading level of their German peers. In the present study, we investigated to what extent recent connectionist learning models are capable of simulating this cross-language learning rate effect as measured by nonword decoding accuracy. We implemented German and English versions of two major connectionist reading models, Plaut et al.'s (Plaut, D. C., McClelland, J. L., Seidenberg, M. S., & Patterson, K. (1996). Understanding normal and impaired word reading: computational principles in quasi-regular domains. Psychological Review, 103, 56-115) parallel distributed model and Zorzi et al.'s (Zorzi, M., Houghton, G., & Butterworth, B. (1998a). Two routes or one in reading aloud? A connectionist dual-process model. Journal of Experimental Psychology: Human Perception and Performance, 24, 1131-1161); two-layer associative network. While both models predicted an overall advantage for the more regular orthography (i.e. German over English), they failed to predict that the difference between children learning to read regular versus irregular orthographies is larger earlier on. Further investigations showed that the two-layer network could be brought to simulate the cross-language learning rate effect when cross-language differences in teaching methods (phonics versus whole-word approach) were taken into account. The present work thus shows that in order to adequately capture the pattern of reading acquisition displayed by children, current connectionist models must not only be sensitive to the statistical structure of spelling-to-sound relations but also to the way reading is taught in different countries.

Child↗
PubMed2004

The visual word form area and the frequency with which words are encountered: evidence from a parametric fMRI study.

Cohen and Dehaene et al. proposed that the Visual Word Form Area (VWFA) in the left midfusiform gyrus, contrary to its name, is limited to the extraction of an abstract letter string and not involved in proper visual word recognition. We examined this prelexical function of the VWFA by a parametric block design with five levels of written word frequency. The lowest level was represented by pseudowords and the highest level by words of very high frequency. Contrary to the assumed prelexical function of the VWFA, increasing frequency was associated with decreasing brain activation in a large posterior cluster of the left hemisphere including middle and posterior fusiform regions. The same negative relation between frequency and activation was found in several left frontal clusters. The relation of increasing frequency and decreasing activation in occipitotemporal regions corresponds to a similar relation in the same brain regions found by studies which experimentally manipulated object or face familiarity. This convergence suggests that fusiform regions are specialized for extracting and storing abstract patterns when processing visual objects and these patterns serve as recognition units in subsequent encounters with the same objects.

Adolescent↗
PubMed2004

Eye movements of dyslexic children when reading in a regular orthography.

Participants were German dyslexic readers (13-year-olds) who-compared to English dyslexic readers-suffer mainly from slow laborious reading and less from reading errors. The eye movements of eleven dyslexic boys and age-matched controls were recorded during reading of text passages and pseudoword lists. For both text and pseudoword reading, the dyslexic readers exhibited more and much longer fixations, but relatively few regressions. Increased length of words and pseudowords led to a greater increase in number of fixations for dyslexic than normal readers. Comparisons across studies suggest that the present German dyslexic eye movement findings differ from English-based findings by a lower frequency of regressions (presumably due to the higher regularity of German) and from Italian findings by longer fixation duration (presumably due to the greater syllabic complexity of German).

Child↗
PubMed2003

On the automaticity/cerebellar deficit hypothesis of dyslexia: balancing and continuous rapid naming in dyslexic and ADHD children.

The present study examined the relationship of reading disability (RD) and attention deficit hyperactivity disorder (ADHD) to balancing problems. In the cerebellar deficit hypothesis of dyslexia of Nicolson et al. [Trends Neurosci. 24 (2001) 508], balancing problems are taken as sign of a cerebellar deficit and were found to be associated with dyslexia. Four groups of 10 children each, representing all combinations of RD (absent versus present) and ADHD (absent versus present), were included. However, poor balancing (assessed both singly and together with a secondary task) was not found to be associated with RD, but with ADHD. In contrast, poor performance on continuous rapid naming tasks (digit and color naming) was found to be associated with RD and not with ADHD.

Attention Deficit Disorder with Hyperactivity↗
PubMed2002

Children with dyslexia and right parietal lobe dysfunction: event-related potentials in response to words and pseudowords.

Hari and Renvall (Trends Cogn. Sci., 5 (2001) 525) proposed that dyslexic children suffer from sluggish attention deployment due to a right parietal lobe dysfunction. To examine this hypothesis, good and poor readers (12, 11-year-old boys in each group) had to read familiar words (low attentional demand) and pseudowords (high attentional demand). The amplitude of the event-related potential at around 100 ms post-stimulus (N1) in response to words and pseudowords was used as measure of attention deployment. Consistent with the attention deficit/right parietal lobe dysfunction hypothesis, poor readers showed lower N1 amplitudes in response to pseudowords, but not in response to words at central sites of the right hemisphere. However, poor readers also showed lower N1 amplitudes to both words and pseudowords at left frontal sites suggestive of an early deficit in activating phonological codes.

Attention↗
PubMed2002

Dyslexia: verbal impairments in the absence of magnocellular impairments.

Sensitivity to dynamic visual and auditory stimuli was assessed in dyslexic children (Grade 7) who at school entrance had suffered from the well-established double-deficit of impaired phonological sensitivity and deficient rapid naming performance. A visual magnocellular deficit was assessed by the coherent motion detection task of the Oxford group. An auditory magnocellular deficit was assessed by the illusory sound movement perception task of Hari and Kiesilä. On both tasks our dyslexic subjects' performance was similar or even better than the performance of normally reading controls. Differences in the inclusion of ADHD cases in dyslexic samples is discussed as a potential explanation of differences in results.

Acoustic Stimulation↗
PubMed2002

No deficits at the point of hemispheric indecision.

This study attempted to replicate a recent finding by Crow et al. [Neuropsychologia 36 (1998) 1275] showing that about equal skill of right and left hand (i.e. hemispheric indecision) is associated with deficits in cognitive and scholastic achievement. The present study assessed hemispheric indecision by using Annett's [Left, Right, Hand and Brain: The Right Shift Theory, Lawrence Erlbaum, London, 1985] peg moving test and by assessing the consistency of hand preference at school entrance. Non-verbal intelligence, reading and spelling accuracy were assessed about three years later. The sample consisted of 530 boys. Contrary to Crow et al., children with about equal hand skill did not show deficits in non-verbal intelligence, reading and spelling. Also, there were no deficits when inconsistent hand preference was taken as indication of hemispheric indecision. The findings cast doubt on the hemispheric indecision hypothesis and speak specifically against Orton's [Reading, Writing and Speech Problems in Children, Norton, New York, 1937] position, revived by Crow et al., that delayed or absent hemispheric dominance may lead to difficulties with the acquisition of reading and spelling.

Child↗