Elsevier

Neuropsychologia

Volume 31, Issue 10, October 1993, Pages 1055-1066
Neuropsychologia

Additive effects of forgetting and fornix transection in the temporal gradient of retrograde amnesia

https://doi.org/10.1016/0028-3932(93)90032-UGet rights and content

Abstract

Nine Rhesus monkeys (Macaca mulatta) learned to discriminate among 320 complex naturalistic scenes (Set A) for food reward. Six months later they learned to discriminate among a further 192 scenes (Set B). Immediately after learning Set B the animals were given a preoperative retention test of both sets, consisting of a single trial with every scene they had learned. Three monkeys were then operated upon to transect the fornix, the other six forming an unoperated control group. Two weeks after operation the scenes were presented once each in a postoperative retention test. The animals with fornix transection showed significantly poorer memory than the control animals at the postoperative retention test. Furthermore, within the fornix-transected animals' performance, postoperative amnesia for Set B was more marked than amnesia for Set A, by comparison with the animals' own preoperative retention of the two sets. However, a similar pattern of performance was also seen within the control animals' results, in that they forgot more of Set B than of Set A in the interval between the preoperative and postoperative retention tests. There was no significant difference between the groups in the gradient of forgetting, defined as the difference between forgetting of Set B and forgetting of Set A in the interval between the preoperative and postoperative retention tests. These results give no support to the idea that the severity of retrograde amnesia is graded as a function of the remoteness of the memory at the onset of amnesia, and they give some indication of possible reasons why the impression of such a gradient is frequently reported clinically.

References (15)

There are more references available in the full text version of this article.

Cited by (43)

  • A computational theory of hippocampal function, and tests of the theory: New developments

    2015, Neuroscience and Biobehavioral Reviews
    Citation Excerpt :

    This raises the issue of the possible gradient of retrograde amnesia following hippocampal damage, and of whether information originally hippocampus-dependent for acquisition gradually becomes “consolidated” in the neocortex and thereby become hippocampus-independent over time (Debiec et al., 2002; McGaugh, 2000). The issue of whether memories stored some time before hippocampal damage are less impaired than more recent memories, and whether the time course is minutes, hours, days, weeks or years is a debated issue (Gaffan, 1993; Squire, 1992). ( In humans, there is evidence for a gradient of retrograde amnesia; in rats and monkeys, hippocampal damage in many studies appears to impair previously learned hippocampal-type memories, suggesting that in these animals, at least with the rather limited numbers of different memories that need to be stored in the tasks used, the information remains in the hippocampus for long periods).

  • Alternative conceptions of memory consolidation and the role of the hippocampus at the systems level in rodents

    2011, Current Opinion in Neurobiology
    Citation Excerpt :

    The simpler idea that there are multiple memory storage sites, each with its own acquisition and consolidation process, was widely rejected in the mid-1990s, because of influential experiments with nonhuman animals (for example [8,9]) showing that HPC damage disrupted recent memories much more than more remote memories formed by the same learning episodes. Yet, demonstrations were in hand of equivalent disruption of recent and remote memories, referred to as flat gradients [10,11]. Reports with human patients appeared where even remote memories seemed to be impaired.

  • The volumes of the fornix in schizophrenia and affective disorders: A post-mortem study

    2008, Psychiatry Research - Neuroimaging
    Citation Excerpt :

    However, only one post-mortem study by Chance et al. (1999) considered the cross-sectional areas and the total fiber number of the fornix in schizophrenia. The fornix plays a major role in functions that are assumed to be disturbed in schizophrenia such as memory retrieval (Gaffan, 1993; Calabrese et al., 1995), verbal memory (Calabrese et al., 1995; McMackin et al., 1995), spatial memory (Gaffan, 1994; Parker and Gaffan, 1997; Murray et al., 1998; Galani et al., 2002; Buckley et al., 2004), increased motor activity (Weiner et al., 1998) and transitive inference (Dusek and Eichenbaum, 1997). Morphologically, near the splenium of the corpus callosum the fimbria of the hippocampus becomes the crus of the fornix which sends fibers forward at the inferior edge of the septum pellucidum to the interventricular foramen.

  • A computational theory of hippocampal function, and empirical tests of the theory

    2006, Progress in Neurobiology
    Citation Excerpt :

    This raises the issue of the possible gradient of retrograde amnesia following hippocampal damage, and of whether information originally hippocampus-dependent for acquisition gradually becomes “consolidated” in the neocortex and thereby becomes hippocampus-independent over time (Debiec et al., 2002; McGaugh, 2000). The issue of whether memories stored some time before hippocampal damage are less impaired than more recent memories, and whether the time course is minutes, hours, days, weeks or years is a debated issue (Gaffan, 1993; Squire, 1992). ( In humans, there is evidence for a gradient of retrograde amnesia; in rats and monkeys, hippocampal damage in many studies appears to impair previously learned hippocampal-type memories, suggesting that in these animals, at least with the rather limited numbers of different memories that need to be stored in the tasks used, the information remains in the hippocampus for long periods.)

View all citing articles on Scopus
View full text