August 1, 2013 Departments

From the Journals: August 2013

Catch up on the latest findings by researchers in communication sciences and disorders in this roundup of study results.

Classroom Phonological Awareness Instruction Improves Literacy Outcomes

A short, intensive period of classroom phonological awareness instruction in the first year of school can raise the literacy profiles of children with and without spoken language difficulties, according to a study in the April 2013 issue of Language, Speech, and Hearing Services in Schools.

Despite strong investment in raising literacy achievement for all children, significant inequalities in literacy persist in some of the world's most advanced economies.

Researchers used a quasi-experimental design to measure the phonological awareness, reading and spelling development of 129 5-year-olds. Thirty-four children received 10 weeks of phonological awareness instruction from their classroom teachers. Ninety-five children continued with their usual reading program, which included phonics instruction but did not target phonological awareness.

Children who received phonological awareness instruction demonstrated superior literacy outcomes compared to children who followed the usual literacy curriculum. Children with spoken language impairment showed significant improvements in phonological awareness, reading and spelling, but had a different response pattern to instruction compared to children with typical language. Significantly, 6 percent of children who received phonological awareness instruction experienced word decoding difficulties at the end of the program, compared with 26 percent of the children who followed the usual literacy curriculum.

Children With Specific Language Impairment Vulnerable to Speech-Sound Competition

A study in the April 2013 issue of the Journal of Speech, Language, and Hearing Research replicates previous findings that children with specific language impairment name pictures more slowly than do chronological age-matched peers. But the results also suggest that children with specific language impairment are more vulnerable to increased competition from words with frequent phonotactic patterns, which also come from dense phonological neighborhoods.

Rapid naming depends on two factors known to be problematic for children with SLI—lexical retrieval and nonlinguistic speed of processing. Although all studies implicate a speed-of-processing deficit as a contributing factor, researchers do not agree on the influence of language factors. The study aimed to explore word frequency and phonotactic pattern frequency as potential lexical factors contributing to the naming deficits experienced by children with SLI.

Researchers asked three groups of children—20 children with SLI (median age 9 years, 8 months), 20 younger controls, and 20 chronological age-matched peers—to name pictures whose labels varied by word and phonotactic pattern frequency. Reaction time results revealed significant main effects of group and word frequency. Effects due to word frequency were comparable for all groups, but a significant interaction between group and phonotactic pattern frequency revealed that phonotactic pattern frequency effects (that is, greater vulnerability to increased competition from high-frequency and high-density words) were greater for children with SLI than for vocabulary-matched children or chronological age-matched peers.

Parent and Teacher Ratings Reveal Poor Executive Function in Children With SLI

Parent and teacher perceptions of executive functioning in children with specific language impairment align with prior findings of executive function deficits documented on neuropsychological assessments and experimental tasks, according to a study in the May 2013 issue of the American Journal of Speech-Language Pathology. The results provide additional evidence of the relationship between language abilities and executive functioning in early child development.

Researchers assessed 19 preschoolers with specific language impairment and 19 age- and gender-matched typically developing peers, using the Behavior Rating Inventory of Executive Function-Preschool Version, a rating scale designed to investigate executive behaviors in everyday activities. The participants' parents and teachers also completed the BRIEF–P.

Parents and teachers rated the executive functioning of children with specific language impairment significantly worse than that of controls. Adults' perceptions of the children's executive functioning significantly correlated with the children's language abilities.

Wide Dynamic Range Compression Improves Speech Recognition

In a systematic review, researchers found moderate evidence suggesting that audibility is improved, and speech recognition either maintained or improved, when a wide range of sounds is compressed into a narrower range, as compared with simply making the sounds louder. The study, published in the December 2012 issue of the American Journal of Audiology, found significant differences between compression limiting and peak clipping on outcomes—that is, speech recognition and self- or parent report—reported across the review.

Researchers developed two clinical questions. One addressed the comparison of linear amplification with compression limiting (reducing peaks in sound by compressing the signal) to linear amplification with peak clipping (reducing peaks by limiting the maximum sound level). The second compared wide dynamic range compression with linear amplification for outcomes of audibility, speech recognition, speech and language, and self- or parent report in children with hearing loss.

Researchers systematically searched 26 databases for studies addressing a clinical question and meeting all inclusion criteria. They evaluated studies for methodological quality, and effect sizes were reported or calculated when possible. The search yielded eight studies. All eight studies included comparisons of wide dynamic range compression to linear amplification, and two of the eight provided comparisons of compression limiting versus peak clipping. Researchers warn that further research is needed before conclusions can be drawn confidently.

Cilia Research Opens New Avenues for Treating Hearing Loss

Experiments at Johns Hopkins University have unearthed clues about which protein signaling molecules are allowed into hollow, hair-like "antennae"—cilia—that alert cells to critical changes in their environments.
Researchers found that the size limit for entry is much greater than previously
thought, allowing most of a cell's proteins into cilia, according to a study published online in the journal Nature Chemical Biology on May 12, 2013.

Primary cilia protrude from most cells in a wide variety of organisms, and defects in cilia have been implicated in everything from polycystic kidney disease to vision and hearing loss. The researchers believe that the specific collection of proteins in each cilium, customized to the needs of each cell type, is determined by whether and how cilia keep proteins inside once they enter—not which ones they allow in initially. Previous research suggested a fixed pore at the base of a cilium allows only relatively small molecules inside. By developing more sensitive experimental methods, scientists demonstrated that molecules almost 10 times larger than those known before could enter.

The researchers first engineered an anchor-like molecule that selectively embedded itself in the membranes of cilia. On the inside end of the anchor was half of a "molecular snapper." Inside the watery interior of the cell, the team placed fluorescent molecules of known size, fitted with the other half of the molecular snapper. If these fluorescent molecules entered cilia, they would carry their fluorescence with them and be trapped inside when the snappers clicked together, allowing the researchers to easily take images of them.

By repeating this experiment many times with molecules of increasing size, the team was able to show that every molecular size they tested was able to enter the cilia. The only difference between the molecules of different sizes was their rate of entry: Smaller molecules entered more quickly than larger ones.

Environmental Enrichment as Autism Treatment

In the first successful experiment with humans using a treatment known as sensory-motor or environmental enrichment, researchers documented marked improvement in young boys with autism when compared to traditional behavioral therapies, according to research published online in the American Psychological Association journal Behavioral Neuroscience, May 20, 2013.

Researchers divided 28 boys with autism, ages 3 to 12, into two groups based on age and autism severity. For six months, both groups participated in standard behavioral therapy—but boys in one of the groups also underwent daily environmental enrichment exercises.

Parents of children in the enrichment group—with the help of kits containing scents, textured and household items, and manipulatives—conducted two daily sessions of four to seven exercises involving different combinations of sensory stimuli for touch, temperature, sight and movement. Each session took 15 to 30 minutes to complete. The children also listened to classical music once a day.

Following six months of treatment, 42 percent of the children in the enrichment group significantly improved in behaviors such as relating to people and responding to sights and sounds, compared to 7 percent of the standard care group. The children in the enrichment group also improved on scores for cognitive function, which covers aspects of perception and reasoning, whereas the average scores for the children in the standard care group decreased. In addition, 69 percent of parents in the enrichment group reported improvement in their child's overall autism symptoms, compared to 31
percent of parents in the standard care group.

The researchers are conducting a larger randomized clinical trial that includes girls. Another important next step will be to test environmental enrichment therapy when a child is not also receiving other standard treatments, the authors noted.

Shift of Language Function Impedes Post-Stroke Aphasia Recovery

In a study designed to differentiate why some stroke patients recover from aphasia and others do not, investigators have found that an active right hemisphere bodes poorly for language recovery. Patients who recovered from aphasia returned to normal left-hemispheric language activation patterns—a discovery that may open up new rehabilitation strategies—according to results published in the July 2013 issue of Restorative Neurology and Neuroscience.

Researchers recruited 27 right-handed adults who experienced a left-middle cerebral artery infarction at least one year prior to study enrollment. After language testing, nine participants were considered to have normal language ability and 18 considered to have aphasia. Participants completed a battery of language tests and a semantic decision/tone decision cognitive task during functional magnetic resonance imaging to map language function and determine stroke volume.

The authors found that those who had stronger left-hemispheric fMRI signals performed better on linguistic tasks than those who had stronger signal shifts to the right hemisphere. As expected, they also found a negative association between the size of the functional lesion and performance on some linguistic tests. Right cerebellar activation was also linked to better post-stroke language ability.

The authors say that although a shift to the non-dominant right hemisphere may be associated with restored language function in children who have experienced left-hemispheric injury or stroke, for adults such a shift has been hypothesized to impede recovery. For adults, the left hemisphere may be necessary for language function preservation and recovery. The fact that left perisylvian lesion size is predictive of right-hemisphere activation may also help to explain the study's findings.


  

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