Ipsilateral Versus Contralateral Extinction in Dichotic Listening Resulting from Hemisphere Lesions

This ipsilateral extinction is presented as being less paradoxical by a model which postulates that competition between signals received by both ears occurs in the left hemisphere.

Abstract

A study is presented of verbal dichotic listening by twenty-eight left brain-injured aphasic patients and twenty right brain-injured non-aphasic patients. The total population of the study was right-handed. The results reveal that the right hemisphere damaged group demonstrated exclusive extinction of the signals received by the contralateral left ear. The left hemisphere damaged group was divided between those who demonstrated extinction of the contralateral right ear and a significant number of subjects who demonstrated. what. might appear to be paradoxical extinction of the ipsilateral left ear. This ipsilateral extinction is presented as being less paradoxical by a model which postulates that competition between signals received by both ears occurs in the left hemisphere. The signal from the right ear arrives there directly via the more important decussating route but the information from the left ear reaches the left hemisphere via the stronger decussating route to the right hemisphere and anterior commissural fibers. By this model only a left hemisphere lesion can affect the information from either the contralateral or ipsilateral ear.