104 samples measured by 29 quality variables with 81 categories including bradyacusia andtinnitus due to head injury were analyzed by the QUANTIFICATION THEORY TYPE III, and then 5 axes were obtained. The first axis shows the degree of total lesion by the head injury, bradyacusia and tinnitus. In the axis, the following variables-the degree of tinnitus, the existence or not of bradyacusia, the starting time of the tinnitus and the abnormality of the eardrum-have the large range of quantities of categories, that is to say, they have big influence to the quantities of samples. The quantities of almost all the categories show the monotonity, and some of them show even the linearity. This means the possibility of analyzing them as the continuous quantity variables. In the 2nd, 3rd, 4th, 5th axes, the starting time of the tinnitus and the frequency of the sound of the tinnitus have the large range of quantities of categories.
A human study of the compound action potential (AP) to frequency-modulated tone (FM tone) was achieved in order to obtain frequency-specific APs using the transtympanic electrode. Clearly recognizable APs were elicited by a downward shift of 20% in the frequency of 515Hz, 1150Hz or 2230Hz pure tone. The latency is greater for lower frequency tones and this latency increase agrees with the traveling delay for the intensity range used in this study. The latency-intensity curves of these three frequencies did not show the convergence with increase in the intensity of tones. The latency at moderate intensity of the FM tone was similar to that for the short tone burst at threshold intenisty. These findings suggest that the FM tone in downward direction can be a frequency-specific stimulus even at relatively high intensities.
An animal experiement previously performed indicated that the ABR was considered to be consisted of at least two components; one is the fast component (wave I, II, III, IV, V, VI, VII) and the other is the positive slow component with the peak observed within the latency of the IV or V waves. In order to investigate the origin of the slow component, in this study the evoked potentials were recorded at various points in the inferior colliculus, and the field map was consecutively made at the frontal and the sagittal sections. Acoustic stimuli evoked a large negative potential, and there observed the electrical positive field surrounding the negative potential and this positive field was recorded as a positive potential from the surface of the cortex. Therefore, the slow wave of the ABR is considered to have a close relation to the activity of the inferior colliculus evoked by acoustic stimuli. The origin of the fast waves, however, can not be estimated by this experiment.
ABR seems to be a composite of both several sequential fast waves and a slowly shifting vertex-positive potential (positive slow wave of the ABR). The relation of the positive slow wave and the inferior colliculus was studied by two different experiments in rats: (1) observation of the evoked potentials in the inferior colliculus and the ABR changes in different places of the scalp before and after destruction of unilateral cochlea, and (2) observation of the evoked potentials and the wave forms of the ABRs before and after destructions of the inferior colliculus. As the results, the central nucleus of the inferior colliculus was found to play an important part of the positive slow component of the ABR, however, it might not be essential for generation of the several sequential fast waves of the ABR.