In Search of the Core Features of Dyslexia: Observations Concerning Dyslexia in the Highly Orthographically Regular Finnish Language

A goal of many researchers in recent years has been to explore the core feature(s) of dyslexia. Three methods that could be used for this purpose are as follows. One method is to examine and specify in detail the cognitive/reading deficits still present in adulthood and thus to identify deficit(s) instead of a delay. The second method is to use crosslinguistic comparisons (see Jackson, Hu, & Ju, Vol. I, 1994; Assink & Kattenberg, Vol. I, 1994; Wolf, Pfeil, Lotz, & Biddle, Vol. I, 1994). Any real core feature of dyslexia should be present universally independent of the language and language-specific experience among those who have received adequate training in reading. The third method is to…

Familial dyslexia: neurocognitive and genetic correlation in a large Finnish family.

Neuropsychological findings of individuals with dyslexia (n=24) from a large, three-generation Finnish family are presented. We have previously performed whole genome linkage scanning in this family and found that dyslexia in this kindred segregates with a single locus in the pericentromeric area of chromosome 3. Those included in the analyses were carefully evaluated for general cognitive ability, reading and spelling skills, and reading-related neurocognitive skills. The neurocognitive type of dyslexia segregating in this family consisted of deficits in phonological awareness, verbal short-term memory, and rapid naming. Severe dyslexia also seemed to be connected with a general language d…

Developmental pathways of children with and without familial risk for dyslexia during the first years of life.

Comparisons of the developmental pathways of the first 5 years of life for children with (N = 107) and without (N = 93) familial risk for dyslexia observed in the Jyvaskyla Longitudinal study of Dyslexia are reviewed. The earliest differences between groups were found at the ages of a few days and at 6 months in brain event-related potential responses to speech sounds and in head-turn responses (at 6 months), conditioned to reflect categorical perception of speech stimuli. The development of vocalization and motor behavior, based on parental report of the time of reaching significant milestones, or the growth of vocabulary (using the MacArthur Communicative Development Inventories) failed t…

Spoken-Word Segmentation and Dyslexia

We used magnetoencephalography to elucidate the cortical activation associated with the segmentation of spoken words in nonreading-impaired and dyslexic adults. The subjects listened to binaurally presented sentences where the sentence-ending words were either semantically appropriate or inappropriate to the preceding sentence context. Half of the inappropriate final words shared two or three initial phonemes with the highly expected semantically appropriate words. Two temporally and functionally distinct response patterns were detected in the superior temporal lobe. The first response peaked at approximately 100 msec in the supratemporal plane and showed no sensitivity to the semantic appr…

Assessing Reading Skills with a Computer-aided Set of Tests Based on the Dual-route Theory of Reading

Abnormal Auditory Cortical Activation in Dyslexia 100 msec after Speech Onset

Abstract Reading difficulties are associated with problems in processing and manipulating speech sounds. Dyslexic individuals seem to have, for instance, difficulties in perceiving the length and identity of consonants. Using magnetoencephalography (MEG), we characterized the spatio-temporal pattern of auditory cortical activation in dyslexia evoked by three types of natural bisyllabic pseudowords (/ata/, /atta/, and /a a/), complex nonspeech sound pairs (corresponding to /atta/ and /a a/) and simple 1-kHz tones. The most robust difference between dyslexic and non-reading-impaired adults was seen in the left supratemporal auditory cortex 100 msec after the onset of the vowel /a/. This N100m…