Olfactory bulbectomy impairs the rat's radial-maze behavior.

Previous studies had shown that transection of the lateral olfactory tracts and lesions of the septohippocampal system were similar in the deficits they engendered in nest building and food piling or hoarding by hamsters. The present investigation asked whether olfactory lesions would also produce deficits in radial-maze behavior like those associated with septo-hippocampal lesions. Radical olfactory bulbectomy led to a marked deterioration in preoperatively trained behavior in an 8-arm radial maze. The behavioral changes resembled those resulting from septo-hippocampal lesions in three ways: (1) There were fewer choices of adjacent arms and more choices of more distant arms. (2) Choice accuracy as a function of successive choices within a trial declined more rapidly. (3) The probability of repeating choice sequences was abnormally high. Earlier studies had shown that the rat does not require olfactory cues to perform efficiently in radial mazes. It therefore seems likely that the deficits described here resulted from the disruption of interconnections between the olfactory and septo-hippocampal systems rather than from the loss of olfactory sensitivity.