ELECTROENCEPHALOGRAPHIC STUDIES OF HOMING SALMON.

When adult spawning salmon (Oncorhynchus tshawytscha, 0. kisutch) arrive at the "home" pond, most regions of the brain are electrically inactive, but the olfactory bulbs and posterior cerebellum are relatively highly active. Infusion of various natural waters from nearby sources other than the home pond into the olfactory sac produces little or no change in spontaneous electroencephalographic patterns recorded from the olfactory bulbs. Water from the home pond, however, produces a vigorous response of high amplitude. These findings suggest that olfaction is an important factor in guidance during the final phases of homeward migration of salmon, and that olfactory discrimination occurs at the level of either the olfactory bulbs or the olfactory epithelium.