A vast majority of school-aged children may be able to focus on the voice of a teacher in the middle of the disharmony of a typical classroom all thanks to the brain. This is mainly because the brain seems to automatically focus on relevant, predictable and repeating auditory information. Atleast this is what study authors from Northwestern University claim.
However, for children suffering from developmental dyslexia, the teacher’s voice could perhaps get lost in the background noise. Apparently, the surrounding noise includes banging lockers, whispering children, playground screams and scraping chairs.
New scientific studies suggest that children with developmental dyslexia seem to have difficulties separating pertinent auditory information from competing noise. Developmental dyslexia is known to be a neurological disorder which affects reading and spelling skills in 5 to 10 percent of school aged children.
The study from Northwestern University’s Auditory Neuroscience Laboratory not only confirms those findings but puts forward biological proof that children who report problems hearing speech in noise may also experience from a measurable neural impairment. This neural impairment seems to adversely affect their ability in making use of regularities in the sound environment.
“The ability to sharpen or fine-tune repeating elements is crucial to hearing speech in noise because it allows for superior ‘tagging’ of voice pitch, an important cue in picking out a particular voice within background noise,” says Nina Kraus, Hugh Knowles Professor of Communication Sciences and Neurobiology and director of the Auditory Neuroscience Laboratory.
Kraus along with her co-authors demonstrates that the significant ability of the brain to tune into relevant aspects in the soundscape could perhaps be performed by an adaptive auditory system. Moreover, this system is known to continuously change its activity based on the demands of context.
During the study, good and poor readers were believed to have been asked to watch a video while the speech sound ‘da’ was presented to them via a earphone in two different sessions. Subsequently, the authors seemed to have continuously measured the brain’s response to these sounds.
In the first session, ‘da’ was believed to have been repeated over and over again in what the authors call a repetitive context. In the second, ‘da’ appears to have been presented randomly among other speech sounds which they call a variable context. In an added session, the study authors were noted to have performed behavioral tests in which the children were asked to repeat sentences that were given to them amid increasing degrees of noise.
Lead author of the study, Bharath Chandrasekaran said that, “Even though the children’s attention was focused on a movie, the auditory system of the good readers ‘tuned in’ to the repeatedly presented speech sound context and sharpened the sound’s encoding. In contrast, poor readers did not show an improvement in encoding with repetition. We also found that children who had an adaptive auditory system performed better on the behavioral tests that required them to perceive speech in noisy backgrounds.”
Further, the study suggests that besides conventional reading and spelling based interventions, poor readers who have difficulties processing information in noisy backgrounds could perhaps gain from the employment of comparatively simple strategies. These strategies were known to include placing the child in front of the teacher or utilizing wireless technologies to improve the sound of a teacher’s voice for an individual student.
“The study brings us closer to understanding sensory processing in children who experience difficulty excluding irrelevant noise. It provides an objective index that can help in the assessment of children with reading problems,” explains Kraus.
Interestingly, the study authors found that dyslexic children appear to have shown enhanced brain activity in the variable condition. This may enable dyslexic children to indicate their sensory environment in a broader and arguably more creative manner. Although at the cost of the ability to eliminate irrelevant signals e.g. noise.
For almost two decades, Kraus seems to have been trying to find out why some children with good hearing have difficulties learning to read and spell while others do not. Early in her work, due to the shortfalls she was exploring the complex processes of reading and writing, Kraus was believed to have studied how the cortex encoded sounds. Cortex is known to be the part of the brain responsible for thinking. The study authors at present recognize that problems associated with the encoding of sound also could perhaps take place in lower perceptual structures.
The findings of the study ‘Context-dependent encoding in the human auditory brainstem relates to hearing speech-in-noise: Implications for developmental dyslexia’ have been published in the journal, Neuron.