Performance of hippocampectomized rats in a reference/working-memory task: Effects of preoperative versus postoperative training

Abstract

Hippocampectomized and sham-operated male rats were pre-or postoperatively trained to perform a reference/working-memory task in a standard radial eight-arm maze. On each trial, three arms were baited. These "correct" arms formed one of two configurations, which changed between conditions. The remaining arms were never baited. The rats' task was to enter each of the baited arms only once, and to refrain from entering any of the unbaited arms. Incorrect choices were punished with a brief period of confinement. Preoperatively trained groups were tested postoperatively for retention, and then trained on a new reference-memory task in which the baited arms formed the second configuration. Postoperatively trained groups were also trained on two such tasks in succession. Order of training on the two configurations was counterbalanced between groups. Postoperatively trained hippocampal groups were severely impaired in acquisition of the tasks. Preoperatively trained hippocampal groups were unimpaired, relative to shamoperated groups, in all measures of performance.

Effects of medial septal or unilateral hippocampal inactivations on reference and working spatial memory in rats

“…In contrast, they fail to provide any evidence that the hippocampus would be specifically concerned with working or reference memory. This result contrasts with previous reports of specific working memory impairments following hippocampal damage (Olton et al, 1979) or hippocampal inactivations (Barea et al, 1988), but is in agreement with others that show both working and reference memory to be impaired in rats sustaining hippocam-pal lesions (e.g., Gage, 1985;Nadel and MacDonald, 1980). The observation that reference memory in the radial maze was affected following either septal or unilateral ventral hippocampal inactivations also contrasts with our previous report of an unimpaired performance in a spatial reference memory task see Introduction).…”

Preoperative training modifies radial maze performance in rats with ischemic hippocampal injury.

“…[17][18][19][20][21][22] - 24 Nevertheless, the results of the current study raise the question of whether this degree of ischemic injury and functional impairment have clinical relevance. Ischemic hippocampal injury occurs in patients, perhaps most often because of the selectively vulnerable nature of neurons in the subregions of the cornu ammonis.…”

Early protein malnutrition changes learning and memory in spaced but not in condensed trials in the Morris water-maze

“…This attention in spatial learning is justified by the well documented literature showing that early malnutrition affects the morphology (Lewis et al 1979, Jordan et al 1982, Ahmed et al 1987, Cintra et al 1990, Tonkiss et al 2000 neurochemistry (Chen et al 1992, Blatt et al 1994, Almeida et al 1996 and neurophysiology (Bronzino et al 1990(Bronzino et al , 1991a(Bronzino et al , 1991b of the hippocampal formation, a structure believed to be implicated in functions such as learning and memory, especially those of spatial characteristics (O'Keefe and Nadel 1978). Furthermore, deficits in learning and spatial memory have been shown after lesions of the hippocampal formation (Olton and Papas 1978, Morris et al 1982, Gage 1985, Whishaw 1998, Maaswinkel et al 1999, Xavier et al 1999, emphasizing the importance of this structure for spatial learning.…”