Anne J. Sperling

Deficits in perceptual noise exclusion in developmental dyslexia

We evaluated signal-noise discrimination in children with and without dyslexia, using magnocellular and parvocellular visual stimuli presented either with or without high noise. Dyslexic children had elevated contrast thresholds when stimuli of either type were presented in high noise, but performed as well as non-dyslexic children when either type was displayed without noise. Our findings suggest that deficits in noise exclusion, not magnocellular processing, contribute to the etiology of dyslexia.

Selective magnocellular deficits in dyslexia: a "phantom contour" study

A technique by Rogers-Ramachandran and Ramachandran [Vis. Res. 38 (1998) 71-77] was adapted to evaluate magnocellular (M) and parvocellular (P) visual processing efficiency, with identical task structure, in normal and dyslexic children. A battery of phonological, orthographic and cognitive tasks was administered to assess reading ability and component reading skills in both groups. For the visual processing experiment, children identified shapes created by patterns of dots flickering in counter-phase. The dots were black and white in the M condition, versus isoluminant red and green in the P condition. A staircase procedure determined the childrens threshold flicker rate for shape identification. Dyslexics displayed selectively slower visual processing in the M condition but not in the P condition. Across all subjects, performance in the M condition was correlated with measures of orthographic skill, consistent with previous findings linking M processing and orthographic skill. Within the dyslexic group, processing in the M condition was negatively correlated with level of phonological awareness. The results are not consistent with the argument that dyslexics with phonological impairments suffer from deficits across all sensory modalities, as those children with the poorest phonological awareness displayed magnocellular processing well within the normal range.

Repetition priming in oral text reading: A therapeutic strategy for phonologic text alexia

Background: Phonologic text alexia (PhTA) is a reading disorder in which reading of pseudowords is impaired, but reading of real words is impaired only when reading text. Oral reading accuracy remains well preserved when words are presented individually, but when presented in text the part‐of‐speech effect that is often seen in phonologic alexia (PhA) emerges. Aims: To determine whether repetition priming could strengthen and/or maintain the activation of words during text reading. Methods & Procedures: We trained NYR, a patient with PhTA, to use a strategy, sentence building, designed to improve accuracy of reading words in text. The strategy required NYR to first read the initial word, and then build up the sentence by adding on sequential words, in a step‐wise manner, utilising the benefits of repetition priming to enhance accuracy. Outcomes & Results: When using the strategy, NYR displayed improved accuracy not only for sentences she practised using the strategy, but unpractised sentences as well. Additionally, NYR performed better on a test of comprehension when using the strategy, as compared to without the strategy. Conclusions: In light of research linking repetition priming to increased neural processing efficiency, our results suggest that use of this compensatory strategy improves reading accuracy and comprehension by temporarily boosting phonologic activation levels.

Functional reorganization supporting learning and maintenance in a case of phonologic alexia

There were no statistically significant di!erences in accuracy between the sets of to-be-trained (13% correct) or untrained (10%) words at T1/ pre-treatment. McNemar tests between trained/overlearned words and untrained words were statistically significant (p < .001) at T2/post-treatment (54% vs. 19%); T3/post-overlearning (89% vs. 9%); and T4/maintenance (83% vs. 14%). There were no statistically significant di!erences in BOLD signal between to-be-trained and untrained words pre-treatment. Post-treatment, in contrasting trained vs. untrained words, three clusters of activation were centered in left and right inferior frontal cortex and in the left lingual gyrus (cluster FWE-corrected p < .05), with the greatest spatial extent and degree of activation in the cluster centered in right homologous Broca’s area (BA45). Post-overlearning, greater activation was observed in left hemisphere structures, including perilesional activation in left (L) superior and inferior parietal cortex and precuneus, and L middle and anterior

Using repetition priming to improve oral reading in phonological text alexia

In Phonological Text Alexia (PhTA), pseudoword reading is poor, as is functor and affix reading in text. Reading of real words in isolation remains well preserved (Friedman, 1996). The syndrome may result from the phonological representations of functors being activated incompletely or at reduced speed. An alternate explanation is that while functors/affixes are activated normally, their activation levels decay at a pathologically rapid rate. If activation is either incomplete/slowed or if it decays rapidly, single functor reading should be unaffected, while functor reading in text would be impeded by interference from surrounding words. PhTA patients would therefore benefit from therapies that strengthen or prolong functor activation. One such technique that provides an immediate and transitory boost to word activation levels is repetition priming (Dean and Young, 1996). We hypothesized that repetition priming could be utilized to strengthen and/or maintain activation of functors during text reading. We created a treatment program to train a strategy, ‘Sentence Building’, in which the patient learns to read sentences by building them in steps. The repetition of the words as the sentences are built is predicted to help speed and maintain activation of the words on subsequent steps. We predict improved accuracy when the patient applies the mastered strategy to novel sentences.

Speeded functor reading: A new treatment program for phonological text alexia

In phonological text alexia (PhTA), a variant of phonological alexia, single word oral reading, including function word (functor) reading is intact, while oral text reading, particularly functors in text, is impaired (Friedman, 1996; Friedman & Lott, 1995). Patients with PhTA have decreased digit and word spans, impaired pseudoword repetition, and poor performance on tasks using rapid serial visual presentation. These findings suggest a decreased ability to hold multiple phonological codes in short-term memory (STM), resulting in increased retroactive inhibition or some form of phonological interference. Increased inhibition might have a stronger impact on functors than on content words, as content words’ semantic activation strengthens their overall activation levels, while functors cannot rely on such strong semantic activation. Moreover, the phonological representations of functors may not be activated completely or at normal speed, a hypothesis for which there is some evidence (Beeson & Insalaco, 1998). If functor activation is slowed but not impaired, accuracy of single functor reading would be unaffected, while functor reading in text would be impeded by interference from surrounding words. We designed a treatment to strengthen and speed the activation of the phonological representations of functors in a patient with PhTA that uses repeated exposure to functors and practice with rapid reading of these words.