Abstract
1. Bilateral ablation of cortical acoustic areas or sub-areas was performed on the dogs and functional roles of these areas were investigated by salivary conditioned reflex method.
2. On the other hand, the levels of the central nervous system required to establish and to preserve the acoustic conditioned reflexes were examined.
3. In all cases, the positive conditioned reflexes as excitatory processes were essentially unimpaired.
4. On the contrary, the differential inhibition was affected. The disturbance in its postoperative formation was more marked than impairment due to cortical destruction of pre-established differential inhibition, though no essential difference was found between them. In the case of the successive removal of the acoustic sub-areas, the differential inhibition was most affected after the bilateral ablation of posterior ectosylvian gyrus which is generally regarded as a secondary acoustic area.
5. From these results, it is suggested that the excitatory process in the acoustic conditioned reflexes can be compensated by remaining cortical areas or subcortical centers, but in respect to satisfactory fulfilment of the inhibitory process especially of the differential inhibition, the presence of the acoustic area is indispensable.
