Brain Stem Evoked Response in the Assessment of Learning Disabilities

Abstract

Evidence has accumulated rapidly to support the hypothesis that neurological anomalies underlie specific forms of learning disability (LD). This article reviews recent studies directed at the electrophysiological assessment of LD children, with emphasis on the brain stem evoked response(BSER) methodology. Child studies appear to indicate that there are significant differences in BSERs between LD and age-matched normal controls. The methodological and statistical differences among these studies, which have clouded the findings and made replication difficult, are reviewed. Improvements in sampling and empirical procedures are suggested, including the use of discriminant analysis to explore BSER asymmetries in LD children. Future inquiry into the measurement and analysis of BSER activity in LD populations is warranted on the basis of these preliminary findings. New information may bring professionals closer to an understanding of the neurological causes of specific subtypes of LD and permit earlier identification of these "at risk" populations.

Evidence for aberrant auditory anatomy in developmental dyslexia.

“…Moreover, the results are not the same for both the hemispheres, which would imply that the cells in only one hemisphere were cut at an unfavorable angle, also an unlikely situation. Several studies (5)(6)(7)(8)(9)(10)(11)(12)(13)(14)(15)(16)(17)(18)(19)(27)(28)(29) We find that the brains of dyslexics show an abnormal MGN asymmetry. We cannot distinguish between changes in numbers of different types of neurons versus changes in size of particular neuronal populations to explain the changes we see in the distributions.…”

“…These findings provide a physiological basis for behavioral findings that developmental dyslexics do poorly in tests requiring rapid visual processing (3,4). Because reports of abnormally slow auditory processing in dyslexics (5)(6)(7)(8)(9)(10)(11)(12)(13)(14)(15)(16)(17)(18)(19) suggest that a similar fast subsystem defect might be present in the auditory system as well, we measured cross-sectional neuronal areas in the medial geniculate nuclei (MGNs) of five dyslexic and seven control brains.…”

Induced Microgyria and Auditory Temporal Processing in Rats: A Model for Language Impairment?

“…While normal children are able to discriminate two 75 msec tones separated by as little as 8 msec, language-impaired children require over a 350 msec in-terval to perform this same basic discrimination (Tallal and Piercy, 1973). These and other findings (Bakker, 1971;Tallal, 1980;Shucard et al, 1984;Byring and Jarvilehto, 1985;Obrzut et al, 1987;Pinkerton et al, 1989;Reed, 1989;Ortiz Alonso et al, 1990;Watson, 1992) strongly suggest a fundamental dysfunction of the basic ability to perform rapid auditory discriminations in individuals with LI. Subsequent studies have demonstrated similar temporal integration deficits in the visual and tactile modalities, as well as in the performance of sequential motor functions (Johnston et al, 1981;Tallal et al, 1981Tallal et al, , 1985Katz et al, 1992).…”