Auditory Pattern Perception in 'Split Brain' Patients

Three “split brain” subjects with normal peripheral hearing were tested on identifying monaurally presented auditory intensity and frequency patterns. One subject was tested before commissurotomy, ten days later, and one year after surgery. Results indicated that sectioning the corpus callosum dramatically affects the ability to verbally report both intensity and frequency patterns. However, the ability of the subjects to correctly "hum" frequency patterns was not impaired. Thus, it appears for a correct verbal report of an auditory pattern, interhemispheric transfer of acoustic information is required, while "humming" the pattern does not. Further application of this finding implicates auditory pattern tasks as a potentially valuable test for detecting problems of higher auditory processing, particularly those affecting interhemispheric interaction.