Posterodorsal septal lesions impair performance on both shift and stay working memory tasks


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Abstract

Two groups of male Long-Evans rats (N = 42) were trained preoperatively on either a shift or a stay problem in a T-maze. Training trials consisted of 2 runs, an “information run” in which S was forced to go down 1 of the 2 arms of the T-maze, followed immediately by a “choice run” in which S could choose either arm. In the shift condition, Ss were rewarded with wet mash only for choosing the arm opposite the one they entered on the information run. In the stay condition, Ss were rewarded for entering the arm that was entered on the information run. The shift group reached 100% performance accuracy after fewer trials than the stay group. Choice accuracy in both groups declined as the delay increased and returned to 100% at the 0-sec delay. Half of the Ss in each condition then received either lesions of the posterodorsal septum–aimed at disconnecting the septum and hippocampus–or control surgery. Results indicate that deficits in maze performance by Ss with septo-hippocampal damage were not restricted to tasks that require alternation of spatial locations. This finding falsifies the notion that maze deficits reflect a spontaneous alternation deficit or changed “spatial strategy,” but it supports the hypothesis of a working memory deficit in these Ss. (4 ref) (PsycINFO Database Record (c) 2006 APA, all rights reserved)

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