Trends in Cognitive Sciences
OpinionA temporal sampling framework for developmental dyslexia
Section snippets
Dyslexia and auditory neuroscience
Developmental dyslexia affects ∼7% of children and is defined as a specific learning difficulty affecting reading and spelling that is not due to low intelligence, poor educational opportunities or overt sensory or neurological damage [1]. Across languages, children with dyslexia have poor phonological processing skills, leading to the dominant phonological core deficit [2] model of this heterogeneous disorder. Here, I propose a novel causal framework for developmental dyslexia, the temporal
The temporal sampling framework
Although current phonological models of dyslexia are based on deficits in subsyllabic phonology (e.g. awareness of onset-rimes and phonemes, see Glossary), developmental dyslexia also involves impaired syllabic and prosodic perception [17] (Table 1). A general difficulty in distinguishing different modulation frequency ranges, which particularly affects the slower temporal rate in speech processing and tracking of the AE, would affect the efficiency of syllabic segmentation. Rise times are
A developmental perspective
As both dyslexia and SLI are developmental disorders of learning, the phonological deficits in these disorders, according to the TSF, must arise because basic auditory processing is atypical from birth. Indeed, human infants show syllabic sensitivity as neonates [29], using rhythmic cues to segment syllables and words from the acoustic signal to build a lexicon of spoken word forms. Deficiencies in processing low-frequency modulations in infancy would reduce rhythmic sensitivity and impair
Predictions from the TSF
The TSF makes several novel predictions about sensory, cognitive and behavioural deficits in dyslexia, some of which have been previously been explored and some of which can be evaluated using data from other research perspectives [22]. In particular, the postulated rise-time deficits can explain a host of seemingly disparate perceptual and linguistic deficits. For example, rise time is a crucial cue to the perception of syllable stress and also to rhythmic timing [42]; therefore, both should
The temporal sampling framework and other sensory theories
As noted earlier, there are many sensory deficits in dyslexia (see Table 1 for examples). Theories of attention difficulties in dyslexia [37] fit the TSF, as attention is enhanced when stimuli arrive in phase with neural oscillations [26]. Impaired phase locking in dyslexia could explain the atypical visual and auditory cueing effects that underpin sluggish attention-shifting theory [37]. Theories based on magnocellular dysfunction [35] have suffered from inconsistent data [56]. Researchers now
Concluding remarks
The TSF proposes a specific deficit in dyslexia with low-frequency phase locking mechanisms in auditory cortex, which is argued to have an impact on phonological development. The proposed auditory phase locking deficit might also have implications for the efficient functioning of other sensory systems. Being able to define the core neural deficit(s) underlying dyslexia will improve the efficacy of educational interventions. The TSF suggests a novel focus on the syllable in educational
Acknowledgements
I thank David Poeppel, Steven Greenberg and Ian Winter for many helpful discussions during the development of this framework, and Vicky Leong, Denes Szücs and Martina Huss for their comments. U.G. is supported by a Major Research Fellowship from the Leverhulme Trust and funding from the Medical Research Council (G0400574).
Glossary
- Allophone
- acoustically different forms of the same phoneme; for example, the sound corresponding to the letter P in the spoken syllables ‘spin’ and ‘pin’ is acoustically different, the sound in ‘spin’ being more like /b/, but both sounds are treated in English as the phoneme /p/.
- Amplitude
- volume of sound (intensity).
- Amplitude envelope (AE)
- the summation over time of the intensity fluctuations (amplitude modulations) in the different frequency channels in the speech signal.
- Formant
- a concentration of
References (73)
Neuronal oscillations and visual amplification of speech
Trends Cogn. Sci.
(2008)- et al.
Phase patterns of neuronal responses reliably discriminate speech in human auditory cortex
Neuron
(2007) Detection of sound rise time by adults with dyslexia
Brain Lang.
(2005)- et al.
Rhythmic processing in children with developmental dyslexia: auditory and motor rhythms link to reading and spelling
J. Physiol.
(2008) Endogenous cortical rhythms determine cerebral specialization for speech perception and production
Neuron
(2007)A precursor of language acquisition in young infants
Cognition
(1988)- et al.
Speech perception: motoric contributions versus the motor theory
Curr. Biol.
(2009) - et al.
To see but not to read: the magnocellular theory of dyslexia
Trends Neurosci.
(1997) - et al.
Dyslexia: a deficit in visuo-spatial attention, not in phonological processing
Trends Cogn. Sci.
(2010) Sensitivity to dynamic auditory and visual stimuli predicts nonword reading ability in both dyslexic and normal readers
Curr. Biol.
(1998)
Developmental dyslexia: the cerebellar deficit hypothesis
Trends Neurosci.
Discrimination of speech sounds by children with dyslexia
J. Exp. Child Psychol.
Reduced neural integration of letters and speech sounds links phonological and reading deficits in adult dyslexia
Curr. Biol.
Context-dependent encoding in the human auditory brainstem relates to hearing speech in noise: implications for developmental dyslexia
Neuron
The magnocellular deficit theory of dyslexia: the evidence from contrast sensitivity
Vision Res.
Normal and anomalous development of visual motion processing: motion coherence and ‘dorsal stream vulnerability’
Neuropsychologia
Are poor mathematics skills associated with visual deficits in temporal processing?
Neurosci. Lett.
On the automaticity/cerebellar deficit hypothesis of dyslexia: balancing and continuous rapid naming in dyslexic and ADHD children
Neuropsychologia
Rhythmic motor entrainment in children with speech and language impairment: tapping to the beat
Cortex
Dyslexia and the anchoring-deficit hypothesis
Trends Cogn. Sci.
Better to lose the anchor than the whole ship
Trends Cogn. Sci.
Cortical speech processing unplugged: a timely subcortico-cortical framework
Trends Cogn. Sci.
Infant music perception: domain-general or domain-specific mechanisms?
Cognition
Foresight Mental Capital and Wellbeing Project. Learning Difficulties: Future Challenges
Explaining the differences between the dyslexic and the garden-variety poor reader: the phonological-core variable-difference model
J. Learn. Disabil.
Neuronal oscillations in cortical networks
Science
Speech perception at the interface of neurobiology and linguistics
Philos. Trans. R. Soc. Lond. B Biol. Sci.
On the possible role of brain rhythms in speech perception: Intelligibility of time-compressed speech with periodic and aperiodic insertions of silence
Phonetica
Neural processing of amplitude-modulated sounds
Physiol. Rev.
The significance of temporal modulation frequencies for speech intelligibility
Amplitude envelope onsets and developmental dyslexia: a new hypothesis
Proc. Natl. Acad. Sci. U. S. A.
Deficits in beat perception and dyslexia: evidence from French
Neuroreport
Sensitivity to rhythmic parameters in dyslexic children: a comparison of Hungarian and English
Read. Writ.
Language-universal deficits in developmental dyslexia: English, Spanish and Chinese
J. Cogn. Neurosci.
Auditory temporal processing and dyslexia in an orthographically consistent language
Cortex
Effect of temporal envelope smearing on speech perception
J. Acoust. Soc. Am.
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