Do differences in brain activation challenge universal theories of dyslexia?

It has been commonly agreed that developmental dyslexia in different languages has a common biological origin: a dysfunction of left posterior temporal brain regions dealing with phonological processes. Siok, Perfetti, Jin, and Tan (2004, Nature, 431, 71-76) challenge this biological unity theory of dyslexia: Chinese dyslexics show no deficits in posterior temporal brain regions but a functional disruption of the left middle frontal gyrus. Here, I will argue that these data do not challenge universal cognitive theories of dyslexia according to which weaknesses in the ability to process the phonological features of language are at the origin of dyslexia.     

Phoneme monitoring in silent naming and perception in adults who stutter

The present study investigated phonological encoding skills in persons who stutter (PWS). Participants were 10 PWS (M = 31.8 years, S.D. = 5.9) matched for age, gender, and handedness with 12 persons who do not stutter (PNS) (M = 24.3 years, S.D. = 4.3). The groups were compared in a phoneme monitoring task performed during silent picture naming. The phonological complexity of the target items in the task was varied such that participants monitored either compound words or noun phrases. Performance in this task was compared to phoneme monitoring performed on aurally presented target words to investigate whether any differences observed in silent naming were also evident in perception. Analysis of the response time data, in milliseconds, indicated that PWS were significantly slower as compared to PNS in phoneme monitoring during silent naming; group differences were not obtained in the perception task. The groups were also comparable in the response time to phoneme monitoring within compound words and noun phrases in both silent naming and perception. The findings suggested that PWS were slower in the encoding of segmental, phonological units during silent naming. Furthermore, absence of such differences in perception ruled out a general monitoring deficit in PWS. Findings are interpreted within the context of the psycholinguistic theories of stuttering that postulate phonological encoding and/or monitoring as a causal variable in stuttering.

Educational objectives: As a result of this activity, the participant should: (1) describe relevant literature on phonological encoding skills in children and adults who stutter, (2) identify paradigms that can be used to investigate phonological processing in PWS, and (3) discuss the role of phonological encoding in speech production.     

Quality of phonological representations, verbal learning, and phoneme awareness in dyslexic and normal readers

This study of dyslexia was concerned with the quality of phonological representations of lexical items. It extended the studies of verbal learning in dyslexia from learning new vocabulary items (pseudo-names) to the learning of more well-specified variants of known words. The participants were 19 dyslexic adolescents in grades 4 to 6 and 19 younger normal readers in grade 2 matched on single word decoding. The dyslexics were significantly outperformed by the reading-age controls in non-word reading and in phoneme awareness. The dyslexics also took longer time to learn to associate a set of pseudo-names with pictures of persons although the dyslexics learned to associate familiar names with pictures as quickly as the controls did. The acquisition of new phonological representations of words was studied in an imitation task with maximally distinct pronunciations of long, familiar words. The dyslexics gained less than the controls in this task. They also gained less on one measure taken from a phoneme substitution task with the same words as in the distinctness task. The results are interpreted in the light of the hypothesis that poorly specified phonological representations may be an underlying problem in dyslexia.     

Modulation of brain activity during phonological familiarization

We measured brain activity in 12 adults for the repetition of auditorily presented words and nonwords, before and after repeated exposure to their phonological form. The nonword phoneme combinations were either of high (HF) or low (LF) phonotactic frequency. After familiarization, we observed, for both word and nonword conditions, decreased activation in the left posterior superior temporal gyrus, in the bilateral temporal pole and middle temporal gyri. At the same time, interaction analysis showed that the magnitude of decrease of activity in bilateral posterior temporal lobe was significantly smaller for LF nonwords, relative to words and HF nonwords. Decrease of activity in this area also correlated with the size of behavioral familiarization effects for LF nonwords. The results show that the posterior superior temporal gyrus plays a fundamental role during phonological learning. Its relationship to sublexical and lexical phonological processing as well as to phonological short-term memory is discussed.     

Symbol-string sensitivity and adult performance in lexical decision

In this study of adult readers, we used a symbol-string task to assess participants' sensitivity to the position of briefly presented, non-alphabetic but letter-like symbols. We found that sensitivity in this task explained a significant proportion of sample variance in visual lexical decision. Based on a number of controls, we show that this relationship cannot be explained by other factors including: chronological age, intelligence, speed of processing and/or concentration, short term memory consolidation, or fixation stability. This approach represents a new way to elucidate how, and to what extent, individual variation in pre-orthographic visual and cognitive processes impinge on reading skills, and the results suggest that limitations set by visuo-spatial processes constrain visual word recognition.     

Phonological recoding and rapid orthographic learning in third-graders' silent reading: a critical test of the self-teaching hypothesis

This study examined rapid orthographic learning following silent reading in third-grade children as a function of number of target nonword repetitions and test delay. In each of two test sessions at least 6 days apart, children read a series of short stories, with each story containing a different nonword repeated either four or eight times. In the second session, after the stories had been read, children were asked to read short lists of target nonwords or homophonic alternatives. Children read target nonwords faster than homophones, indicating that they had formed functional orthographic representations of the target nonwords through phonologically recoding them during silent story reading. They also preferred target nonwords to homophones in an orthographic choice task in which the alternatives included the target, the homophone, and a visually similar foil, although here orthographic learning was stronger for items encountered eight times within stories and stronger for items tested immediately. These findings provide critical evidence in support of Share's self-teaching through phonological recoding hypothesis.     

Phonological alexia with vowel-consonant dissociation in non-word reading

We present a patient with alexia secondary to cerebral lesion whose errors in the reading of non-words affect vowels more than consonants. The interest of the case resides in: (1) the documentation of a vowel-consonant dissociation selectively affecting the reading of non-words; and (2) the localization of the alteration in a specific stage of the perilexical reading pathway, that is, the blending of phonetic chains. The case contributes to the discussion on the nature of representations and the processing of vowels and consonants.     

汉语儿童的语音意识特点及阅读能力高低读者的差异

选取小学３,４,５年级儿童各２０名作为被试,系统探讨了儿童汉语普通话的音节意识、首音韵脚意识和音位意识的特点及发展,根据老师的评价把被试分为好的读者和差的读者。研究结果表明,语音意识测验成绩随年级的增长而提高;音节意识与首音一韵脚意识先于音位意识而发展;好、差读者在语音意识测验成绩上差异显著,而且,年级差异与好、差读者差异的程度和趋势是一致的,好、差读者在语音意识发展的速度上是不同的。     

Do dyslexia and stuttering share a processing deficit?

This study assessed the prevalence of childhood stuttering in adults with dyslexia (AWD) and the prevalence of dyslexia in adults who stutter (AWS). In addition, the linguistic profiles of 50 AWD, 30 AWS and 84 neurotypical adults were measured. We found that 17 out of 50 AWD (34 %) reported stuttering during childhood compared to 1 % of the neurotypical population. This was moderated by the severity of dyslexia: People with mild dyslexia showed a lower prevalence rate (15 %) of childhood stuttering than those with severe dyslexia (47 %). In addition, we observed that 50 % of the AWS (n = 30) fulfilled the diagnostic criteria of dyslexia, even though they had never been diagnosed as dyslexic. Compared to neurotypical adults, phonological working memory, awareness, and retrieval were similarly reduced in AWS and AWD. The findings supports the view that stuttering and dyslexia may share a phonological deficit.     

Subliminal repetition primes help detection of phonemes in a picture: Evidence for a phonological level of the priming effects

In this research, we combine a cross-form word–picture visual masked priming procedure with an internal phoneme monitoring task to examine repetition priming effects. In this paradigm, participants have to respond to pictures whose names begin with a prespecified target phoneme. This task unambiguously requires retrieving the word-form of the target picture's name and implicitly orients participants' attention towards a phonological level of representation. The experiments were conducted within Spanish, whose highly transparent orthography presumably promotes fast and automatic phonological recoding of subliminal, masked visual word primes. Experiments 1 and 2 show that repetition primes speed up internal phoneme monitoring in the target, compared to primes beginning with a different phoneme from the target, or sharing only their first phoneme with the target. This suggests that repetition primes preactivate the phonological code of the entire target picture's name, hereby speeding up internal monitoring, which is necessarily based on such a code. To further qualify the nature of the phonological code underlying internal phoneme monitoring, a concurrent articulation task was used in Experiment 3. This task did not affect the repetition priming effect. We propose that internal phoneme monitoring is based on an abstract phonological code, prior to its translation into articulation.