[Neuropsychological studies of two subjects after the transection of the splenium of the corpus callosum. (Part 2. The auditory recognition by the dichotic listening test) (author's transl)].

We made the neuropsychological auditory studies of two right-handed subjects who had undergone the transection of the splenium of the corpus callosum for the pineal operation (the teratoma by the histopathological examination). The transection grades were 2.0 cm and 2.5 cm. The truncus and splenium of the second subject were flat by the compression of the tumor. We examined these subjects by the some audiolocigal methods. 1. Pure tone audiometry. 2. Fixed frequency Békésy audiometry. 3. SISI test (short increment sensitivity index test). 4. Speech audiometry. 5. Distorted speech test (filtered speech test). 6. Binaural fusion test. 7. Dichotic listening test. The tasks used for the dichotic listening test were following. Different digits (one pair, three pairs), different words (from two to four syllables) and different vowels and consonants were presented simultaneously to the two ears by means of a dual-channel tape recorder with stereophonic earphone. The result shows that the first subject (whose section of the spelenium was 2.0 cm) shows a slight but not significant superiority on the right ear to the one pair digits and words (p less than 0.1), and the second subject (whose section of the splenium was 2.5 cm and whose splenium and truncus of the corpus callusum were flatten by the compression of the tumor) shows a significant superiority on the right ear to the one pair digits, words, three pairs digits and vowels (p less than 0.05). But there was no definitive abnormalities at the pure tone audiometry, the fixed frequency Békésy audiometry, SISI test, distorted speech test and binaural fusion test of two cases. The result shows that the commissure fibres of the auditory perception of the speech of two hemispheres connect through from splenium to the truncus of the corpus callosum.