Mismatch negativity (MMN) is a negative component in the human event related potential that occurs in response to a change in the nature of a repeating stimulus. Since it occurs even in the absence of attention, it reflects an automatic cerebral process for detecting change. The MMN is clinically helpful in detecting sensory memory and central processing deficits in groups, but its use as a clinical tool in individual patients is yet to be established. Late Discriminative Negativity (LDN) is another recently reported second negativity that follows MMN and has been suggested to reflect the automatic processing of complex linguistic stimuli in children. The use of cochlear implants in profoundly deaf children is increasing with a trend towards earlier implantation. However the tools used at present to assess and predict outcome of cochlear implantation are primarily based on behavioural tests, which are difficult to use effectively in young children due to limitations in communication and cognitive skills in this age group. MMN has been proposed as a potential test which can be used to assess auditory memory and central auditory processing in cochlear implant patients. The main objective of this study was to assess the correlation of auditory event related potential (ERP) measures with behavioural assessment data to identify if ERPs including mismatch negativity (MMN) can be used to categorize cochlear implant patients into good and poor performers. We carried out an observational, cross sectional, non-randomized, cohort study investigating auditory event related potentials to speech stimuli in 35 cochlear implant patients between the ages of 7 and 17 years and compared the occurrence, latencies and amplitudes of P1, N2, MMN and LDN with overall behavioural outcome in these children. Behavioural measures included category of auditory performance scores (CAP) and speech intelligibility rating scores (SIR). Auditory ERPs in response to standard stimuli were identifiable in 30 out of 35 patients, demonstrating a major positive component (P1) followed by a negativity (N2) with absence of N1 in all patients. The P1 component in pre-lingually deaf patients showed a statistically significant reduction in its latency with increasing duration of implant use. MMN was recorded in 80-85% of star performers but in only 15-20% of poor performers. Patients with higher SIR scores demonstrated statistically significant longer duration of MMN compared to those with a lower SIR score. Patients with higher SIR and CAP scores also demonstrated a statistically significant inverse relationship with the duration of LDN. These results indicate that MMN can be used to assess the functional status of the auditory cortex in young children with cochlear implants and may provide an objective mechanism for differentiating good from poor performers.
| Identifer | oai:union.ndltd.org:bl.uk/oai:ethos.bl.uk:420636 |
| Date | January 2005 |
| Creators | Singh, Shomeshwar |
| Publisher | University College London (University of London) |
| Source Sets | Ethos UK |
| Detected Language | English |
| Type | Electronic Thesis or Dissertation |
| Source | http://discovery.ucl.ac.uk/1446730/ |
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