Kanokporn Kitisupornpun. A comparasion study of middle latency response between learning disabilities and normal children aged 8-12 years . Master's Degree(Communication Disorders). Mahidol University. : Mahidol University, 2003.
A comparasion study of middle latency response between learning disabilities and normal children aged 8-12 years
Abstract:
The purpose of this research was to compare middle latency response (MLR)
in waveform morphology, latency, and amplitude between children with learning disabilities
and normal children. The study was conducted by using 28 normal children (15 boys, 13
girls) and 13 boys with learning disabilities. Subjects were between 8-12 years of age. The
MLR responses were recorded with a Nicolet Spirit 2000. The stimuli were click 500-1000
sweeps with 0.1 ms duration, alternating polarity, applied at a rate of 3.7 / sec, and at 70
dBnHL intensity to both ears. The filter bandpass was 5 -100 Hz. The electrode sites were
placed on the vertex (Cz), each mastoid (A1, A2), and forehead (ground). All subjects were
kept alert and awake by watching a video cartoon without sound during the test.
The results of this study showed that MLR waveform morphology could be
classified into three types of Pa. Type 1 showed a sharp, distinct peak for wave Pa and Pb,
Type 2 showed a broad Pa component with two rounded peaks with a minimal trough between
the two peaks, Type 3 showed a clear wave Pa which had a sharp peak or rounded peak with a
broad base, and which might be followed with either a deep Nb trough or no apparent negative
trough although it was not followed by a Pb component. The results showed that the largest
percentage of identifiable MLR waveforms in the learning disabilities group were Type 1,
while a high percentage of identifiable MLR waveforms in the normal group were Type 2.
The percentage of detectability of Pa in 8 years old subjects was 66.67 %, and for those who
were older than 8 years it was 100%.
There were statistically non significant differences in MLR latency (Na, Pa,
Nb, and Pb) and MLR amplitude (Pa and Pb) in both ears between children with learning
disabilities and normal children. These findings indicated that, first, the variations of MLR
waveform morphology were the results of multiple overlapping cortical sources that
contributed to the generation of MLR. Second, there could be different types of MLR
waveform identification. Third, there could be different measurement parameters of MLR
recording used by other researchers.
The results of this study may be used as guidelines for the further study of
MLR in order to evaluate other groups of subjects or to develop a test. Further, MLR testing
should be conducted by using larger groups of normal children and other children with
learning disabilities. In addition, different parameters should be considered for future MLR
research.