Stimulus processing and stimulus selection in rats with hippocampal lesions

Rickert, Edward J.; Lorden, Joan F.; Dawson, Ralph; Smyly, Elizabeth; Callahan, Michael F.

doi:10.1016/s0163-1047(79)92040-5

Cited by 57 publications

(29 citation statements)

References 15 publications

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“…Figure 4 shows that simulated normal, HPL, and CL cases exhibit overshadowing. Consistent with Rickert et al (1979) and Schmajuk et al (1983), but not with Garrud et al (1984), the model predicts that overshadowing is completely disrupted by HFL lesions. In addition, the model exhibits blocking in normal, HPL, and CL cases.…”

Section: Computation Of the Aggregate Predictionmentioning

confidence: 71%

Attention, configuration, and hippocampal function

Buhusi

Schmajuk

1996

Hippocampus

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Section: Computation Of the Aggregate Predictionmentioning

confidence: 71%

Attention, configuration, and hippocampal function

Buhusi

Schmajuk

1996

Hippocampus

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“…Relatively complex discrimination procedures such as this one have been examined only rarely in fear conditioning, and only then when freezing was taken as the measure of fear (Rickert et al 1979). It is not at all clear, therefore, whether the complex pattern of responsiveness to the A, B, X, and compound cues as predicted by Wagner and Rescorla will be evident in startle modulation.…”

Section: Experiments 3: Development Of a Conditioned Inhibition Trainimentioning

confidence: 99%

AX+, BX- Discrimination Learning in the Fear-Potentiated Startle Paradigm: Possible Relevance to Inhibitory Fear Learning in Extinction

Myers¹,

Davis²

2004

Learn. Mem.

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The neural mechanisms of fear suppression most commonly are studied through the use of extinction, a behavioral procedure in which a feared stimulus (i.e., one previously paired with shock) is nonreinforced repeatedly, leading to a reduction or elimination of the fear response. Although extinction is perhaps the most convenient index of fear inhibition, a great deal of behavioral work suggests that postextinction training conditioned stimuli are both excitatory and inhibitory, making it difficult to determine whether a neural manipulation affects inhibition, excitation, or some combination thereof. For this reason we sought to develop a behavioral procedure that would render a stimulus primarily inhibitory while at the same time avoiding some of the issues raised by the traditional conditioned inhibition paradigm, namely second-order conditioning, external inhibition, and configural learning. Using the fear-potentiated startle paradigm, we adapted an AX+, BX− training procedure in which stimuli A and X were presented simultaneously and paired with shock, and stimuli B and X were presented simultaneously in the absence of shock. In testing, high levels of fear-potentiated startle were seen in the presence of A and AX and much lower levels were seen in the presence of B and AB, as would be predicted if stimulus B were a conditioned inhibitor. We believe this method is a viable alternative to the traditional conditioned inhibition training procedure and will be useful for studying the neural mechanisms of fear inhibition.

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“…Rats were expected to freeze less to tone and more to context because tone signaled the absence of shock or a "safe" period while context indicated potential shock or a "non-safe" interval. In the paired condition, contextual cues tend to be overshadowed by phasic cues such as tone and thus, form weaker associations with the shock (Odling-Smee, 1975;Rickert et al, 1979). In the unpaired condition, context does not predict shock, but it does indicate when the shock is likely to occur and hence, the association between context and shock is stronger (Phillips and LeDoux, 1994).…”

Section: Control Studiesmentioning

confidence: 99%

Metyrapone Reveals That Previous Chronic Stress Differentially Impairs Hippocampal-dependent Memory

Conrad

Mauldin-Jourdain

Hobbs

2001

Stress

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Chronic stress facilitates fear conditioning in rats with hippocampal neuronal atrophy and in rats in which the atrophy is prevented with tianeptine, a serotonin re-uptake enhancer. The purpose of this study was to determine whether the lack of dissociation between fear conditioning performance and hippocampal integrity was masked by the presence of endogenous corticosteroids during training. As in previous studies, rats were stressed by daily restraint (6 h/day for 21 days), trained in the conditioning chamber (day 23), and then assessed for conditioned fear (day 25) at a time when hippocampal dendritic atrophy persists. On the training day, half of the control and stressed rats were injected with metyrapone to reduce corticosterone release. Two hours later, two paired or unpaired presentations of tone and footshock were delivered. Although metyrapone reduced conditioned fear in all rats, only stressed rats showed dissociated fear conditioning (i.e. tone conditioning was reduced while contextual conditioning was eliminated). Chronically stressed rats, regardless of metyrapone treatment displayed more rearing in the open field when tested immediately after the completion of fear conditioning. These data support the hypothesis that increased emotionality and enhanced fear conditioning exhibited by chronically stressed rats may be due to endogenous corticosterone secretion at the time of fear conditioned training. Moreover, these data suggest that chronic stress impairs hippocampal-dependent processes more robustly than hippocampal-independent processes after metyrapone to reduce corticosterone secretion during aversive training.

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Stimulus processing and stimulus selection in rats with hippocampal lesions

Cited by 57 publications

References 15 publications

Attention, configuration, and hippocampal function

Attention, configuration, and hippocampal function

AX+, BX- Discrimination Learning in the Fear-Potentiated Startle Paradigm: Possible Relevance to Inhibitory Fear Learning in Extinction

Metyrapone Reveals That Previous Chronic Stress Differentially Impairs Hippocampal-dependent Memory

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