The neural basis of speech sound discrimination from infancy to adulthood
Year: 2013
Type: dissertation
Abstract: Rapid processing of speech is facilitated by neural representations of native language phonemes. However, some disorders and developmental conditions, such as developmental dyslexia, can hamper the development of these neural memory traces, leading to language delays and poor academic achievement. While the early identification of such deficits is paramount so that interventions can be started as early as possible, there is currently no systematically used ecologically valid paradigm for the assessment of the neural basis of speech sound processing. Thus, this thesis investigates the feasibility of a mismatch negativity (MMN) paradigm presenting speech sounds embedded in pseudo words to probe the neural discrimination accuracy of sounds in more natural context. Furthermore, the applicability of this paradigm for infant research was determined in a study investigating the effects of additional prenatal speech stimulation on newborn sound processing. The results show, on group level, that while healthy adults neurally detect all speech sound changes used in the experiments, the 4-12 -year-old children s and infants neural processing of speech sounds varies with age. In particular, the preschool children seem to be more proficient in neurally detecting small pitch changes in word context than school-aged children. Furthermore, children s MMNs were found to be associated with improved verbal IQ 14-17 months later, while the positively-displaced MMN, the p-MMR, correlated with poorer performance IQ. The results on the effects of additional prenatal exposure to pitch-modulated speech sounds showed that the MMNs to pitch changes in pseudo words were enhanced after birth, indicating specific learning effects due to additional prenatal stimulation. Furthermore, these learning effects generalized to other types of speech sounds not included in the learning material. Taken together, these findings suggest that the paradigm presenting speech sound changes in word context is viable for probing the neural memory traces for speech sounds from infancy to adulthood. The possibility to assess neural speech sound discrimination broadly in a single EEG recording could be used, for example, to classify between different subtypes of dyslexia. Finally, the neural effects induced by fetal learning suggest that prenatal exposure to sounds, for example, to the voice of the mother, may predispose the infant to be neurally sensitive to such sounds by birth.
Source: Työväentutkimus Vuosikirja
Author: Eino Partanen
Language: English
Subfield: Cognitive Neuroscience
Field: Neuroscience
Domain: Life Sciences
Open Access status: green
OpenAlex ID: W1585999996