抄録
The localization of the gustation center was investigated in white rats by examining the results of the preference method and the electrical response of the cerebral cortex to chemical stimulation of the gustatory end-organs. An objective observation and quantitative measurment of the acuity of gustation of white rats by the preference method were effected by the use of a liquid supplier, a graduated test tube, devised for the purpose by Hirakawa and Ueno. The first step in the first experiment was the determination of the gustatory threshold for each test solution by the preference method; and the next the symmetrical destruction by bilateral operation of one small area of the cerebral cortex, for observation of the postoperative change in the taste ability of each animal deprived of the local cerebral function, and for eventual identification of the area of the cortex concerned in gustation. The results of this experiment in 45 cases led to the conclusion that the destruction of a certain small area of the lowest portion of the parietal lobe, lying near where the frontal lobe meets the temporal, is invariably followed by an enduring drop in the gustation threshold, i. e., permanent gustatory impairment. The other experiment, performed alongside of the first in the hope that the result might throw some sidelight on the problem, was an examination of the accompanying electric phenomena produced in the cerebral cortex by gustatory stimulation. The result of this experiment showed that the electrical effect of gustatory stimulation on the cerebral cortex was divisible into : (1) inhibition of α waves and (2) multiplication of β waves and an increase and periodic appearance of attack waves. The former change appeared over a fairly extensive area of the cortex and the extent of the area where the change could be induced was not finally definable. Whereas the latter changes (2) were demonstrable exclusively in a limited area of the cortex, an area embracing in the center the lowest portion of the region identified as the gustation center in the first experiment, indicating presumably that the changes are manifestations of a central nervous excitation caused by gustatory stimulation. Experiments in electric stimulation of the cerebral cortex showed that the area of the cortex where the latter changes (2) could be induced to the utmost extent was identical with the area controlling the movements of the mouth and jaws. This was also the very area where the changes in the cortical brain wave associated with the movements of the lips, tongue and jaws are inducible to the highest degree, and what was more, these changes bore a close temporary resemblance in the shape of wave to those (2) induced by gustatory stimulaton. The results of the foregoing two experiments coincide with each other in locating the gustation center in one identical area of the cerebral cortex. It is therefore conceivable that in white rats the gustation center is located in a small limited area of the lowest portion of the parietal lobe, abutting on the boundary line of the frontal and the temporal lobe. It is also presumable that the cortical taste area may be either identical with, or located in close proximity to, the sensorimotor area for the mouth, tongue and jaws.
