Fredagsseminar: Galina Kovalchuk

Fredagsseminar:
Galina Kovalchuk
University of Bergen

Mismatch negativity (MMN) – a useful method for accessing auditory discrimination in individuals with language impairments?

Abstract

Representative literature on the auditory mismatch negativity (MMN) will be reviewed in this presentation. MMN is noted for being a useful tool to study cortical auditory discrimination in children with specific language impairments (SLI). Recently, MMN component of the event-related potential (ERP) has become a popular objective measure to study the brain’s ability to discriminate sounds. As a matter of fact, individuals with SLI have difficulties interpreting, storing and accessing auditory information. Consequently, it leads to language acquisition disorders in children who otherwise show adequate intelligence if tested using non-verbal measures. SLI has a strong genetic component, affecting about 7% of pre-school children, mainly male. Hence, the disorder is quite common and has wide-range social and educational consequences.
Examined literature on the subject revealed highly inconsistent results to report on statistically significant MMN differences in the SLI and normally developing groups. Most of the reports found a trend for reduced MMN amplitude and longer latency in the clinical group compare to the control group. Indeed these results were most likely to be found in studies using rapidly presented stimuli supporting the hypothesis that children with SLI experience difficulties identifying brief and rapidly presented tones. Overall literature review doesn’t show a strong support for the hypothesis that auditory temporal processing is impaired in language and literacy disorders. This may be due to the fact that the field is plagued by a large number of positive and negative findings, which sometimes contradicts each other.
There exists two major theoretical frameworks that try to explain the difficulties experienced by children with SLI. Non-modular theories attribute SLI to non-linguistic deficiencies such as: delayed auditory processing, reduced phonological short memory, general processing limitation, as well as problems with procedural learning. They claim a slow processing speed would consequently lead to difficulties in perceiving sounds and phonemes. According to the alternative modular hypothesis, SLI disorder regards to deficits in grammatical knowledge, namely parts of grammar responsible for tense and agreement making. Thus, opposing to it theory argues that the core deficit in SLI is in the structural complexity of the grammatical components. The hypothesis further suggests that the main problem within syntax is in accessing syntactic dependencies between words, as a part of the whole sentence. All current theories explain the SLI phenomenon to a certain extend while the debate between modular and non-modular perspectives remains open