Fundamental studies of the Latency Mapping of auditory brainstem response (ABR)

Abstract

Brain electrical mappings of ABR components by latency measurement were studied in cats.Topographic mappngs of the scalp were made by two methods.In the first one, the latency was measured from the base line which was the middle line between the fastest latency and the slowest latency in 16 electrodes on the scalp of normal cats. It was called “Base Line Method”.The other is called as SPM (Significance probability mapping) Method, reported by Duffy in 1981 in his lesion experiments.The lesions were experimentally made by pentobarbital, anoxia, freezing the inferior colliculus.The results were as follows.1) Mappings by Base Line Method did not clearly show the changes on the scalp, when ABR were recorded by the sampling time of 50μ seconds in normal cats.2) Mappings by SPM Method were better than mappings by Base Line Method to show very small changes of the latency distribution on the scalp.3) The continuous discrepancy between the mappings by the administration of pentobarbital and anoxia was similar, but it was deffered with modality mappings following freezing the inferior colliculus.4) SPM Method is acceptable for the demonstration of continuous discrepancy of the mapping.