The Role of The Role of Auditory Processing Auditory Processing

in Reading and in Reading and LiteracyLiteracy

Donna Geffner, Ph.D.Donna Geffner, Ph.D.St. John’s UniversitySt. John’s University

Jamaica, NY Jamaica, NY geffnerd@stjohns.edugeffnerd@stjohns.edu

DefinitionsDefinitionsNeuroanatomyNeuroanatomy Impact of trainingImpact of trainingEarly deprivation Early deprivation

(OME)(OME)

Links

Dyslexia DefinitionDyslexia Definition

It is a learning disability It is a learning disability characterized by problems in characterized by problems in expressive or receptive oral and expressive or receptive oral and written language. These written language. These problems may emerge in problems may emerge in reading, spelling, writing, reading, spelling, writing, speaking or listening. speaking or listening.

Dyslexia is a language based Dyslexia is a language based learning disability. It accounts for learning disability. It accounts for approximately 85% of all people approximately 85% of all people with a learning disability. Dyslexia with a learning disability. Dyslexia refers to a cluster of symptoms refers to a cluster of symptoms resulting in people having difficulties resulting in people having difficulties with specific language skills, with specific language skills, particularly reading. Students with particularly reading. Students with dyslexia may experience difficulties dyslexia may experience difficulties in other language skills such as in other language skills such as spelling, writing and speaking. spelling, writing and speaking.

The International Dyslexia Association, (2002)

Dyslexia, the most Dyslexia, the most commonly known learning commonly known learning disability, is the term used disability, is the term used to describe difficulty with to describe difficulty with language processing and its language processing and its impact on reading, writing impact on reading, writing and spelling” (NCLD, 2002).and spelling” (NCLD, 2002).

Developmental dyslexics, Developmental dyslexics, individuals with an individuals with an unexplained difficulty in unexplained difficulty in reading, have been shown to reading, have been shown to have deficits in have deficits in phonological phonological processingprocessing – the awareness of – the awareness of the sound structure of words the sound structure of words and more fundamental deficits and more fundamental deficits in in rapid auditory processingrapid auditory processing..

Developmental Dyslexia

Phonological ProcessesPhonological Processes

““Phonological processing Phonological processing difficulties include problems difficulties include problems storing, retrieving and using storing, retrieving and using phonological codes in phonological codes in memory as well as deficits in memory as well as deficits in phonological awareness and phonological awareness and speech production. speech production.

Phonological Awareness is the single Phonological Awareness is the single most important predictor of success most important predictor of success with reading (Adams and Bruck, 1995).with reading (Adams and Bruck, 1995).

Children who are aware of the sounds Children who are aware of the sounds of speech appear to acquire sound-of speech appear to acquire sound-letter correspondence knowledge and letter correspondence knowledge and use this knowledge to decode printed use this knowledge to decode printed words. Those who lack an awareness words. Those who lack an awareness of the sounds contained in words will of the sounds contained in words will have difficulty associating sounds with have difficulty associating sounds with letters (Adams and Bruck, 1995).letters (Adams and Bruck, 1995).

Phonological AwarenessPhonological Awareness

The phonological awareness The phonological awareness skills of sound deletion, sound skills of sound deletion, sound categorization, sound blending categorization, sound blending and syllable segmentation were and syllable segmentation were identified as effective in the identified as effective in the selection of children in need of selection of children in need of early intervention (Swank and early intervention (Swank and Catts, 1994).Catts, 1994).

Auditory and Visual Auditory and Visual Processing (Multisensory)Processing (Multisensory)

Children with dyslexia often exhibit Children with dyslexia often exhibit weaknesses in auditory and/or visual weaknesses in auditory and/or visual processing. They may have weak processing. They may have weak phonemic awareness, meaning they phonemic awareness, meaning they are unaware of the role sounds play are unaware of the role sounds play in words. They have difficulty in words. They have difficulty rhyming words, blending sounds to rhyming words, blending sounds to make words, or segmenting words make words, or segmenting words into sounds.into sounds.

Link One: Definition Link One: Definition

Individuals with dyslexia exhibit a Individuals with dyslexia exhibit a central difficulty in the central difficulty in the processing of speech sound. processing of speech sound. These difficulties are manifested These difficulties are manifested on such tasks as rhyming, on such tasks as rhyming, syllable counting and sounding syllable counting and sounding out pseudowords.out pseudowords.

Research also suggests that Research also suggests that phonological processing deficits may phonological processing deficits may result from the result from the auditory deficit in auditory deficit in rapid processingrapid processing..

This may impair the individual’s This may impair the individual’s ability to ability to discriminate auditory cues discriminate auditory cues necessarynecessary to distinguish phonemes – to distinguish phonemes – the smallest meaningful unit of the smallest meaningful unit of sound in a particular language. sound in a particular language.

It is not surprising then that It is not surprising then that children with CAPD are at risk for children with CAPD are at risk for reading disabilities. reading disabilities.

Knowledge of letter-sound Knowledge of letter-sound associations, which include letter associations, which include letter –sound recognition, letter sound –sound recognition, letter sound recall, and the ability to print a recall, and the ability to print a given letter sound, has been given letter sound, has been identified by Duncan and identified by Duncan and Seymour (2000) as the best Seymour (2000) as the best indicator, in the early school indicator, in the early school years, of later literacy.years, of later literacy.

The issue is whether difficulties The issue is whether difficulties in processing both non-speech in processing both non-speech and speech tasks are the result and speech tasks are the result of a general auditory deficit, or of a general auditory deficit, or a speech perception deficit. a speech perception deficit.

Controversy: Auditory Deficit Controversy: Auditory Deficit or Speech Perception Deficitor Speech Perception Deficit

Is It Spoken Language Is It Spoken Language Skill?Skill?

According to Isabelle Liberman, dyslexia According to Isabelle Liberman, dyslexia is in the is in the spoken spoken language skill of language skill of phoneme awareness, and that dyslexics phoneme awareness, and that dyslexics often have problems with other aspects often have problems with other aspects of phonological processing such as name of phonological processing such as name retrieval and verbal short-term memory.retrieval and verbal short-term memory.

This indicates that comorbidity between This indicates that comorbidity between dyslexia and certain speech and dyslexia and certain speech and language disorders is inevitable, language disorders is inevitable, although not every individual with although not every individual with dyslexia reaches the clinical threshold dyslexia reaches the clinical threshold for a diagnosable speech or language for a diagnosable speech or language disorder. disorder.

Is it Temporal Is it Temporal Processing?Processing?

The temporal deficit hypothesis suggests The temporal deficit hypothesis suggests that persons with developmental dyslexia that persons with developmental dyslexia have sensory impairments, which involve have sensory impairments, which involve the processing of rapidly changing the processing of rapidly changing acoustic information such as that acoustic information such as that encountered in formant transitions. encountered in formant transitions.

This deficit is thought to affect the This deficit is thought to affect the development of reading by disrupting the development of reading by disrupting the normal acquisition of phonological normal acquisition of phonological representations critical for sound-representations critical for sound-grapheme associationsgrapheme associations

(Reed 1989, Tallal, Miller & Fitch (Reed 1989, Tallal, Miller & Fitch 1993)1993)

Principal Auditory Principal Auditory Components of Temporal Components of Temporal

ProcessingProcessing Temporal integration – duration and intensity of the Temporal integration – duration and intensity of the

stimulistimuli The perception of temporal order (TOJ) – rapidly The perception of temporal order (TOJ) – rapidly

presented linguistic and nonlingustic stimulipresented linguistic and nonlingustic stimuli Short-term memory - necessary to recall elements Short-term memory - necessary to recall elements

in sequence (Jutras & Gagne et al., 2003)in sequence (Jutras & Gagne et al., 2003) Temporal resolution – interval between two Temporal resolution – interval between two

consecutive stimuli, may include gap detection, consecutive stimuli, may include gap detection, masking level difference, detection of amplitude masking level difference, detection of amplitude modulation, detection of temporal asynchronization modulation, detection of temporal asynchronization (Moncrieff, 04)(Moncrieff, 04)

The auditory hypothesis states that there is a deficit in the processing of acoustic signals entering the nervous system in rapid succession.

Rapid Auditory ProcessingRapid Auditory Processing

Children with language impairments have difficulty in discriminating and sequencing rapidly presented auditory information.

When the stimuli are short tones, short vowels, or short transition consonants in combination with brief interstimulus intervals, SLI children have trouble discriminating and sequencing them. Because such differences occur in speech and non-speech stimuli, the underlying notion of a deficit in audition was proposed.

Listeners show deficits on tests tapping the discrimination of basic acoustic dimensions, including frequency discrimination, detection of frequency modulated tones, and binaural release from masking.

Abnormal mismatch negativity was seen in the dyslexia group in response to changes in tone frequency.

Griffiths et al. Griffiths et al. (2003)(2003)

Other studies linking auditory skills to reading include the work of Moncrieff and Musiek (2002) in which a Dichotic Digits Task, a measure of temporal integration, was utilized to differentiate dyslexic readers from normals.

Results of the Dichotic Digits Test indicated control subjects to be within normal limits for both ears, while the dyslexic group demonstrated more interaural asymmetry, particularly due to the right ear performing better than the left.

Dichotic Listening/ Interaural Dichotic Listening/ Interaural AsymmetryAsymmetry

Frequency Pattern Test (FPT) & Duration Pattern Test (DPT) have been used to measure APD for cortical deficits and learning difficulties.

On a measure of durational patterning and frequency patterning, Walker et al., (2002) found that on tasks of temporal processing, individuals with reading disorders generally display deficits in discriminating between rapidly presented acoustic stimuli.

Duration and FrequencyDuration and Frequency

Studies have suggested that Studies have suggested that adults with reading disorders adults with reading disorders also demonstrate difficulty with also demonstrate difficulty with phonemic discrimination tasks, phonemic discrimination tasks, decoding skills and phonological decoding skills and phonological processing.processing.

Temporal Order Temporal Order DiscriminationDiscrimination

When 2 groups of adult listeners completed two tasks examining the rapid auditory processing of sequential stimuli, adults with dyslexia showed poor levels of literacy and phonological processing when compared to a group of age- and IQ-matched students without dyslexia.

Griffiths et al., Griffiths et al., 20032003

Auditory processing deficits may be present in dyslexic children, but temporal processing deficits are not necessary to cause language and reading disorders.

Not all children with reading disorders will demonstrate similar deficits on any one auditory processing task.

LINK TWO – LINK TWO – Neuroanatomical/ Neuroanatomical/

NeuroimagingNeuroimaging Some of these controversies are

being resolved with the current use of electromagnetic resonance studies.

Functional fMRI- neuroimaging- and Positon Emission Tomography (PET) have been used to study dyslexic adults and children to see functional organization of the brain.

From a review of neuro-imaging studies, dyslexics show a disruption in white matter connectivity between posterior and frontal regions. These results give support for a neurobiological etiology of developmental dyslexia.

It has been shown that developmental dyslexics have brain disruption responses to phonological and rapid auditory processing demands, as well as white matter abnormalities (Elise Temple, Department of Human Development, Cornell University May, 2002).

In spite of the neurobiological and genetic influences on dyslexia, there is a biological basis for the disorder. Neuroimaging data indicate that brain processes related to sound structure of language are disrupted in dyslexia.

Disruptions in both phonological and auditory processing in dyslexia are linked to abnormalities in neural processing.

Neuroimaging studies of phonological processing in adult dyslexics who were performing rhyme detection tasks show a reduction or absence of activity in the left hemisphere temporoparietal cortex.

(Temple et al., 2001, Temple et al., 2002, Shaywitz et al., 1998)

Neural disruption in phonological processing is observed among a variety of age groups, explicit or implicit tasks, ability levels, analysis techniques, languages. All studies show decreased activity in left hemisphere posterior language regions-temporoparietal cortex in dyslexic subjects, as compared to normal reading subjects.

Neural DisruptionsNeural Disruptions

Shaywitz et al., (1998) using fMRI found decreased activity in temporoparietal regions-superior temporal gyrus and angular gyrus, during phonological processing of both letter and pseudo rhyme.

NeurologyNeurology

An fMRI study by Bernal & Altman An fMRI study by Bernal & Altman (2003) included 17 abnormally delayed (2003) included 17 abnormally delayed speech children and 35 age-matched speech children and 35 age-matched children without delayed speech.children without delayed speech.

The preliminary results indicated that The preliminary results indicated that children with unusually delayed speech children with unusually delayed speech tended to have higher levels of right tended to have higher levels of right brain lobe activity than children brain lobe activity than children without delayed speech, who tended without delayed speech, who tended to use the left side of their brains when to use the left side of their brains when they listen.they listen.

Event related potentials suggest that neural processing of rapid auditory stimuli is disrupted in dyslexics. During fMRI, rapid and slow temporal changes characteristic of speech nonlinguistic syllables, were presented.

Dyslexic adults showed a disruption in the neural response to rapid auditory stimuli.

Temple et al., 2001

Neuroimaging of Rapid Neuroimaging of Rapid Auditory StimuliAuditory Stimuli

Normal readers showed activation in the left prefrontal cortex, middle and superior frontal gyri during rapid stimuli.

Dyslexic readers showed no left prefrontal response to the rapid stimuli.

Temple et al., Temple et al., 20012001

Left prefrontal response to rapid Left prefrontal response to rapid stimuli was correlated with rapid stimuli was correlated with rapid auditory processing ability. The auditory processing ability. The better the individual’s rapid better the individual’s rapid auditory processing ability, the auditory processing ability, the greater the response of the left greater the response of the left prefrontal cortex to rapid stimuli as prefrontal cortex to rapid stimuli as opposed to slow stimuli (Temple et opposed to slow stimuli (Temple et al., 2001).al., 2001).

MEG Breier et al., (2003) compared 12

children with dyslexia and 11 children without dyslexia during a simple speech task. Magnetoencephalography (MEG) highlighted precise activity in participants’ left and right temporoparietal (TP) language areas while the children discriminated between spoken pairs of syllables.

While distinguishing between sounds, the nonimpaired readers showed more relative activity in the speech part of the left TP area.

During the same task, after a slight delay, impaired readers showed a sharp peak of relative activation in corresponding (but functionally indeterminate) areas on the right side. The poorer the child’s performance in phonological processing, the more their right brains “lit up” during that task.

Pugh et al., (2000) at Yale University Medical School, showed dysfunction at the posterior brain regions centered in and around the angular gyrus in the left hemisphere.

Functional connectivity between the angular gyrus and related occipital and temporal lobe sites was seen across a series of print tasks that varied in demands on phonological assembly. Results indicate that for dyslexic readers, a disruption in functional connectivity in the language-dominant left hemisphere is confined to those tasks that make explicit demands on assembly.

Diffusion Tensor Imaging in Diffusion Tensor Imaging in White Matter ImagingWhite Matter Imaging

Using a new imaging technique, Using a new imaging technique, Diffusion Tensor Imaging (DTI) Diffusion Tensor Imaging (DTI) provides information regarding provides information regarding white matter microstructure. white matter microstructure. Dyslexic adults showed a Dyslexic adults showed a disruption in temporoparietal disruption in temporoparietal white matter, a region of white white matter, a region of white matter connecting left hemisphere matter connecting left hemisphere language areas to more frontal language areas to more frontal and posterior brain areas. and posterior brain areas.

Summary Summary

Developmental Dyslexia has a neurobiological etiology (Temple, et al., 2001).

Neuroimaging studies show us that the dyslexic brain has functional disruptions which are visible during phonological and rapid auditory processing. This supports a neural basis for both of these behaviors.

Similarly in dyslexics, ectopias reside in the left temporal lobe around the medial-superior temporal gyrus. There are large ectopic areas in the left brain with abnormal symmetry of the planum temporale.

Asymmetry and abnormalities on the left side of the brain occur in APD.

The International Dyslexia Association The International Dyslexia Association (2000)(2000)

EctopiasEctopias

Brain imaging scans of the children who participated in the training showed that critical areas of the brain used for reading were activated for the first time and began to function more normally. Additional regions of the brain were activated in what researchers believe the dyslexics use as a compensatory strategy as they learn to read more fluently.

Using fMRI, and scans of brains of 20 dyslexic children 8-12 years of age while they performed a simple rhyming task, enabled researchers to identify active regions of the brain. Changes in blood oxygenation, a process that occurs in parts of the brain where neurons are active, provided information.

Neuroimages of Evidence Neuroimages of Evidence Based PracticesBased Practices

Temple, et al., 2003

During the rhyming task, children with normal reading showed activity in both the language-critical frontal and temporal regions of the brain.

Dyslexics struggled with the task and failed to activate the temporal region, and showed only some activity in the frontal area.

Temple, et al., 2003

Following treatment, children with Following treatment, children with dyslexia showed increased activity in dyslexia showed increased activity in multiple brain areas, along with multiple brain areas, along with increases in left temporal-parietal increases in left temporal-parietal cortex and left inferior frontal gyrus, cortex and left inferior frontal gyrus, bringing brain activation in these bringing brain activation in these regions closer to that seen in normal regions closer to that seen in normal children. These children showed a children. These children showed a correlation between magnitude of correlation between magnitude of increased activation in the left increased activation in the left temporo-parietal cortex and temporo-parietal cortex and improvement in oral language ability. improvement in oral language ability.

Temple, et al., 2003

LINK FOUR – Effects of LINK FOUR – Effects of Auditory Deprivation on Auditory Deprivation on

ReadingReading Evidence exists that mild to

moderate hearing loss can interfere with literacy development, creating delays in reading comprehension and other language academic skills. (Blair, Peterson, and Viehweg, 1985).

Activation of the left temporo-parietal cortex/ superior temporal gyrus is seen during reading tasks, but absent or present in the right cortex in children with dyslexia.

Developmental language disorders have been associated with disorders of temporal processing, an auditory processing task.

Summary

There are neuro-anatomical linkages that indicate shared properties and ectopias in similar areas of the brain responsible for phonemic decoding and rapid auditory processing.

There is also evidence linking training in auditory processing tasks to improved temporal processing, phoneme segmentation, speech perception and reading and language.