Monthly Archives: March 2009
Functional abnormalities in the dyslexic brain: A quantitative meta-analysis of neuroimaging studies
This study used foci from 17 original studies on functional abnormalities in the dyslexic brain to identify brain regions with consistent under- or overactivation. Studies were included when reading or reading-related tasks were performed on visually presented stimuli and when results reported coordinates for group differences. Activation likelihood estimation (ALE) was used for quantification. Maxima of underactivation were found in inferior parietal, superior temporal, middle and inferior temporal, and fusiform regions of the left hemisphere. With respect to left frontal abnormalities, we found underactivation in the inferior frontal gyrus to be accompanied by overactivation in the primary motor cortex and the anterior insula. Tentative functional interpretations of the activation abnormalities are provided. Hum Brain Mapp, 2009. © 2009 Wiley-Liss, Inc.
from Human Brain Mapping
Tuning of the visual word processing system: Distinct developmental ERP and fMRI effects
Visual tuning for words vs. symbol strings yields complementary increases of fast occipito-temporal activity (N1 or N170) in the event-related potential (ERP), and posterior-anterior gradients of increasing word-specific activity with functional magnetic resonance imaging (fMRI) in the visual word form system (VWFS). However, correlation of these coarse ERP and fMRI tuning responses seems limited to the most anterior part of the VWFS in adult and adolescent readers (Brem et al. [ [2006]]: Neuroimage 29:822-837). We thus focused on fMRI tuning gradients of young readers with their more pronounced ERP print tuning, and compared developmental aspects of ERP and fMRI response tuning in the VWFS. Children (10.3 y, n = 19), adolescents (16.2 y, n = 13) and adults (25.2 y, n = 18) were tested with the same implicit reading paradigm using counterbalanced ERP and fMRI imaging. The word-specific occipito-temporal N1 specialization, its corresponding source activity, as well as the integrated source activity (0-700 ms) were most prominent in children and showed a marked decrease with age. The posterior-anterior fMRI gradient of word-specific activity instead which was fully established in children did not develop further, but exhibited a dependence on reading skills independent of age. To conclude, prominent developmental dissociation of the ERP and fMRI tuning patterns emerged despite convergent VWFS localization. The ERP response may selectively reflect fast visual aspects of print specialization, which become less important with age, while the fMRI response seems dominated by integrated task- and reading-related activations in the same regions. Hum Brain Mapp, 2009. © 2009 Wiley-Liss, Inc.
from Human Brain Mapping
Altered frontal-parietal functioning during verbal working memory in children and adolescents with heavy prenatal alcohol exposure
This study evaluated the neural basis of verbal working memory (WM) function in a group of 20 children and adolescents with fetal alcohol spectrum disorders (FASDs) and 20 typically developing comparison participants using functional magnetic resonance imaging (fMRI). Both groups showed prominent activation in the frontal-parietal-cerebellar network known to be important for verbal WM. Despite equivalent behavioral performance between groups, alcohol-exposed individuals showed increased activation relative to typically developing individuals in left dorsal frontal and left inferior parietal cortices, and bilateral posterior temporal regions during verbal WM. These effects remained even when group differences on IQ were statistically controlled. This pattern of increased activation coupled with equivalent behavioral performance between groups suggests that individuals with FASD recruit a more extensive network of brain regions during verbal WM relative to typically developing individuals. These findings may suggest that frontal-parietal processing during verbal WM is less efficient in alcohol-exposed individuals. Hum Brain Mapp 2009. © 2009 Wiley-Liss, Inc.
from Human Brain Mapping
Tinnitus cure ‘is a step closer’
Although the studies carried out by the Australian researchers were in guinea pigs – the animal rather than the human variety – they believe their findings will ultimately help people with tinnitus.
from the BBC
Researchers studying hearing loss find auditory regions of the brain convert to the sense of touch
Virginia Commonwealth University School of Medicine researchers have discovered that adult animals with hearing loss actually re-route the sense of touch into the hearing parts of the brain.
from EurekAlert.org
Incidence and predictors of post-stroke aphasia: The Arcadia Stroke Registry
Conclusions: Female gender, diabetes and heart disease were independent prospective predictors of aphasia. The study offers a quantitative estimate of the public health problem of post-stroke aphasia in Greece and suggests that the role of diabetes in post-stroke aphasia may be more important than previously appreciated.
from the European Journal of Neurology
Assistive devices and cerebral palsy: the use of assistive devices at school by children with cerebral palsy
Conclusions The findings not only demonstrate the significance of child–environment interaction but also provide evidence that children’s views may be different from those of adults because they are at a different developmental stage and act out different roles in their environment.
Implications of family environment and language development: comparing typically developing children to those with spina bifida
Conclusions The relationship between language performance and family environment appears statistically and intuitively sound. As in our previous study, the positive link between family focus on intellectually and culturally enhancing activities and language performance among children with myelomeningocele and shunted hydrocephalus remains robust. Knowledge of this relationship should assist parents and professionals in supporting language development through activities within the natural learning environment.
Incidence and clinical presentation of dysarthria and dysphagia in the acute setting following paediatric traumatic brain injury
Conclusion Despite the low incidence of dysarthria and dysphagia across the entire TBI cohort, this sub-group may place longer-term burden on SLP services, having prolonged periods of ventilation, extended periods of hospitalization and a complex co-morbid clinical presentation compared with controls. The prevalence of co-morbid communication and swallowing impairments suggests a need for integrated rather than single discipline (i.e. dysphagia stream only) SLP services.
A longitudinal study of autism spectrum disorders in individuals diagnosed with a developmental language disorder as children
Conclusion Our results provide additional support to the notion that DLD is a marker of increased vulnerability to the development of ASD.
The effect of long-term unilateral deafness on the activation pattern in the auditory cortices of French-native speakers: influence of deafness side
Conclusion
The results show that cortical reorganization induced by unilateral deafness mainly occurs in subjects with left-sided deafness. This suggests that anatomical and functional plastic changes are more likely to occur in the right than in the left auditory cortex. The possible perceptual correlates of such neurophysiological changes are discussed.
from BMC Neuroscience
Adaptive training leads to sustained enhancement of poor working memory in children
Working memory plays a crucial role in supporting learning, with poor progress in reading and mathematics characterizing children with low memory skills. This study investigated whether these problems can be overcome by a training program designed to boost working memory. Children with low working memory skills were assessed on measures of working memory, IQ and academic attainment before and after training on either adaptive or non-adaptive versions of the program. Adaptive training that taxed working memory to its limits was associated with substantial and sustained gains in working memory, with age-appropriate levels achieved by the majority of children. Mathematical ability also improved significantly 6 months following adaptive training. These findings indicate that common impairments in working memory and associated learning difficulties may be overcome with this behavioral treatment.
Categorical speech perception deficits distinguish language and reading impairments in children
We examined categorical speech perception in school-age children with developmental dyslexia or Specific Language Impairment (SLI), compared to age-matched and younger controls. Stimuli consisted of synthetic speech tokens in which place of articulation varied from ‘b’ to ‘d’. Children were tested on categorization, categorization in noise, and discrimination. Phonological awareness skills were also assessed to examine whether these correlated with speech perception measures. We observed similarly good baseline categorization rates across all groups; however, when noise was added, the SLI group showed impaired categorization relative to controls, whereas dyslexic children showed an intact profile. The SLI group showed poorer than expected between-category discrimination rates, whereas this pattern was only marginal in the dyslexic group. Impaired phonological awareness profiles were observed in both the SLI and dyslexic groups; however, correlations between phonological awareness and speech perception scores were not significant. The results of the study suggest that in children with language and reading impairments, there is a significant relationship between receptive language and speech perception, there is at best a weak relationship between reading and speech perception, and indeed the relationship between phonological and speech perception deficits is highly complex.
An objective method to measure electrode independence in cochlear implant patients with a dual-masker forward masking technique
This study introduced a dual-masker forward masking technique and evaluated whether this objective method could measure electrode independency in a cochlear implant; more particularly, whether the optimal locations and number of active electrodes could be determined. This method further enabled the investigation of the efficacy of current steering, because the proposed recording method could also be described as applying a sequentially current steered masker.
The paradigm requires 5 frames involving 2 maskers and 1 probe and is referred to as the Apple Core method (MP5-AC). For each recording, both the masker and probe amplitude were varied independently, producing 3-D eCAP plots that showed the eCAP amplitude for independent variations of masker and probe amplitudes. A simple quantitative model was developed to aid interpretation of the results. Theory and model were clinically tested in 14 patients. On the basis of the model, the multi-variate, color coded plots could be subdivided into seven distinct regions, each depicting a unique relationship between the probe and the maskers. The model’s predictions supported interpretation of the results, and indicated independence for the probe electrode contacts only at lower current levels and/or at greater inter-electrode separations. The clinical results revealed a lack of selectivity in the electrode array for stimulus levels larger than 600µA. This suggests that sequential current steering is only capable of producing a single excitation area at higher current levels, or smaller electrode distances, without additional loudness correction being applied.
Thus, the MP5-AC paradigm provided insight concerning the independence of electrodes and the efficacy of current steering in clinical patients. However, its current clinical applicability is limited because measurements were adequate only in anaesthetized patients.
from Hearing Research
Reflections on 40 Years of Amplification
This article is fourth in a series on the work of master clinicians in audiologic/aural rehabilitation, contributed by ASHA Special Interest Division 7, Aural Rehabilitation and its Instrumentation. This interview focuses on H. Gustav Mueller, PhD, professor of audiology at Vanderbilt University, who has a private consulting practice in Bismarck, N.D. He is the senior audiology consultant for Siemens Hearing Instruments and a contributing editor for The Hearing Journal.
from the ASHA Leader
