Eggermont,Jos
eggermon@ucalgary.ca

Effect of Noise Trauma in Early Age On Cortical Coding of Speech

Abstract
Network Researchers will undertake a study to investigate whether high-frequency hearing loss induced by pure tone trauma at a very young age will cause extensive cortical reorganization. Findings from this study may help to understand the consequences of noise trauma acquired at early age in humans. Children in the industrialized world are more and more exposed to recreational noise and as a result may suffer mild to moderate high frequency hearing losses. The researchers’ finding of topographic map changes in cats cortex after mild-to-moderate juvenile noise trauma, suggests that such cortical map changes may also occur in these children.

Connolly,John F
john.connolly@dal.ca

Using Neuroimaging Methods to Elucidate Mechanisms of Speech Processing and Reading in Healthy, Dyslexic and Down Syndrome Populations.

Abstract
This project has several objectives: 1) to study brain mechanisms that enable the development and subsequent maintenance of reading and speech processing skills; 2) to determine how these brain mechanisms fail leading to problems in these skills such as dyslexia; and, 3) to monitor the manner in which a demonstrably successful remediation program exerts its beneficial effects on behaviour through the alteration of failed brain mechanisms. This research will use three major brain-imaging technologies: event-related brain potential (ERP) recordings including high-resolution event-related potentials (hrERP), magnetoencephalography (MEG), and functional magnetic resonance imaging (fMRI). These studies will be done with children as they develop across the years and will also follow them as they progress through reading remediation.Neuroimaging methods offer unique insights into reading and speech comprehension problems in individuals and provide unprecedented levels of functional monitoring during interventions. It is anticipated that problem readers will show distinct brain activity distinguishing them from efficient readers. Preliminary results already indicate as much. Researchers hypothesize further that successful interventions will exert their effects not by merely changing behaviour to fit subsequent evaluation methods but rather by “normalizing” the manner in which the brain processes text and speech signals. Their approach to these studies will concentrate on phonological and auditory processing functions as our previous work in this area indicates that these functions form the basis of reading.Questions addressed by this research include: 1. What is the developmental course of reading/speech processing (R/SP) brain responses in normal and dyslexic children and how are they related to behavioural measures; 2. Are neural abnormalities seen in adult developmental dyslexics also seen in dyslexic children; 3. Do neural patterns in dyslexia separate into subtypes or individualized patterns; and, 4. Do therapeutic interventions change behavioural and neural abnormalities simultaneously or do neural changes precede behavioural?

Harrison,Robert
rvh@sickkids.on.ca

The development of the neural projections responsible for sound frequency representation in the central auditory system.

Abstract
The understanding of language, and the abilities to read and write are skills which develop in children based on the proper function of the senses of hearing and vision, as well as a range of higher-level brain processing mechanisms. Brain cell (neuron) activity, or rather the collected activity of arrays of neurons, forms the fundamental building blocks of the very complex brain functions required for language and reading skills. This proposal concerns the development and function of these arrays of neurons, particularly those concerned with hearing. The research focuses on a very fundamental aspect of the structure of the auditory system, namely the way in which complex sounds such as speech are coded and represented in the auditory brain. Speech sounds are received by the cochlea of the inner ear and the frequency components in the sounds are immediately analyzed and represented as a pattern of electrical signals in the array of neurons that make up the cochlear nerve (VIIIth cranial nerve). This pattern of neural activity, which represents the speech signal, is transmitted through the lower parts of the brain (brain stem, midbrain, and thalamus) to the auditory centres of the cerebral cortex. Thus the speech signal is now represented at the levels of the brain where it can be identified, compared with stored memory patterns, correlated with visual images etc. It is at this level of the brain where the representations of speech signals can be strung together, with certain rules which define language, and where these patterns can be correlated with visual images of the written word. This structure of the auditory pathways which allow the speech sounds to be coded in the brain is called the “tonotopic” organization. Without a good tonotopic organization to transmit speech information from the ears to the cortex, there will be poor speech understanding, and abnormal development of language and literacy skills. It is the development of these tonotopic representations in the auditory brain that the researchers wish to study. They will look at how the normal tonotopic pathways develop, as well as what can go wrong in early development to produce an inadequate system, i.e. one which would result in an impairment of language and reading skills later in life.