Hippocampal lesions impair rats’ performance of a nonspatial matching-to-sample task

Rats with excitotoxic hippocampal lesions were trained on delayed nonmatching-to-sample (DNMS) with small goal boxes, containing complex objects, presented on a pseudo trial-unique schedule. A series of experiments then tested performance on repeated presentation of either the small object or large empty goal boxes. All rats acquired the nonmatching rule, but hippocampal-lesioned rats performed less well than controls on choice accuracy for the final 2 blocks of acquisition. In the study's main phase, the lesions impaired choice accuracy when the large empty boxes were used as stimuli. This deficit was ameliorated when the rats were tested with the small object boxes, although the performance of the hippocampal-lesioned rats was still below that of controls. These results extend previous reports of box size-dependent effects of hippocampal aspiration lesions on DNMS and suggest that selective damage to the hippocampus, not neuronal loss in adjacent structures or fiber tracts, is critical for the effect.

Section: Discussionsupporting

confidence: 91%

mentioning

confidence: 99%

The effect of cytotoxic lesions of the hippocampus on recognition memory in the rat: Effects of stimulus size.

Higgs¹,

Bannerman²,

Rawlins³

2001

“…We have previously shown that, although lesions of the fornix or hippocampus do not necessarily impair nonspatial working memory performance when complex objects are used as the items to be remembered (Aggleton et al, 1986; Mumby et al, 1992; Rawlins et al, 1993), a clear lesion-induced impairment can be seen when large, relatively simple goalboxes are used instead of objects (Rawlins et al, 1993; Yee & Rawlins, 1994). The present results add to the body of evidence showing that these lesions can lead to performance impairments on DMS (Jagielo et al, 1990; Raffaele & Olton, 1988; Rawlins et al, 1993) and DNMS (Olton & Feustle, 1981; Yee & Rawlins, 1994) tasks that require working memory for goalbox or goal-arm stimuli. The presence of a lesion effect does not depend upon the need for animals to use allocentric spatial cues.…”

Section: Discussionsupporting

confidence: 67%

Fornix-fimbria section and working memory deficits in rats: Stimulus complexity and stimulus size.

Cassaday¹,

Rawlins²

1995

Rats were trained on delayed matching-to-sample (DMS) with goalboxes containing complex objects as stimuli. On reaching the preoperative learning criterion, the rats were allocated to conventional fornix-lesioned or control groups. In a series of postoperative DMS experiments, different kinds of stimuli were used, ranging from complex object boxes to large, simple black or white goalboxes, with 3 transitional types in between. Lesions impaired choice accuracy whenever the rats were tested with large, simple goalboxes, but not with smaller boxes of otherwise identical construction. A brief, final experiment showed no amelioration of the lesion-induced impairment when complex objects were added to large, simple goalboxes. The results are discussed in terms of spatial and nonspatial accounts of hippocampal function.

“…Similarly, Raffaele and Olton (1988) found that large, but not small, fimbria-fornix lesions impaired the ability of rats to select the goal box, irrespective of location, that was visibly identical to the goal box they had most recently entered. Finally, Jagielo, Nonneman, Issac, and Jackson-Smith (1990) found that rats with large hippocampal lesions failed to learn to select the goal box in a T maze that was the same color as the start box, even when there was no working memory requirement.…”

mentioning

confidence: 99%

Medial septal lesions disrupt spatial, but not nonspatial, working memory in rats.

Kelsey¹,

Vargas²

1993

In Experiment 1, rats with small medial septal lesions were less able than were control rats to remember the location of the arm of a Y maze they had been forced to enter on the preceding sample run. Moreover, as the retention interval between the sample and choice runs on this spatial delayed nonmatching-to-sample (DNMTS) task was increased to 1 and 2 min, the magnitude of the deficit increased. In contrast, these same lesioned rats were not deficient in Experiment 2 in their ability to remember the object they had encountered in the straight alley on the sample run. In fact, when the retention interval was increased to 1 min on this nonspatial DNMTS task, the rats with medial septal lesions were more accurate than were the controls. This pattern of results did not appear to be due to task difficulty, recovery of function, or sequence of training. Rather, these results indicate that damage to the septohippocampal system disrupts spatial working memory more than it disrupts nonspatial working memory.