Hippocampal Lesions in Male Rats Produce Retrograde Memory Loss for Over‐Trained Spatial Memory but Do Not Impact Appetitive‐Contextual Memory: Implications for Theories of Memory Organization in the Mammalian Brain
Bibliographic record
Abstract
Evidence suggests that hippocampal (HPC) disruption following learning produces retrograde amnesia on a range of tasks. Many of these tasks do not require HPC function in the anterograde direction suggesting that, in the intact brain, the HPC is actively involved during all forms of learning. However, prior work has also demonstrated double dissociations of HPC and amygdala function, which is inconsistent with this view. Here, we aim to understand this discrepancy by assessing the effects of neurotoxic lesions of the HPC on anterograde and retrograde amnesia for conditioned place preference (CPP). This task is dependent on a network centered on the basolateral amygdala and not the HPC. The results show that extensive HPC damage had no impact on the acquisition or expression of CPP. One explanation for this result is that the task requires multiple, distributed training sessions for conditioning to emerge, and it has been proposed that this parameter may eliminate the need for HPC to support memory. To test this, we completed experiments to probe place learning in the Morris water task, which is thought to always require HPC function, but implemented an over-training procedure before HPC damage. We found that rats were severely impaired suggesting that this task parameter does not always allow non-HPC networks to support learning. Finally, an experiment was designed to test whether memories acquired by distinct memory networks on the same days, within hours of one another, would be linked in HPC. The results showed that they remained independent of one another.
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How this classification was reachedexpand
Full frame distilled prediction
Teacher imitationNot calibrated prevalence, not ground truth. Human validation pending. Learned from the 10,348 direct Codex labels and 10,348 direct Gemma labels. Candidate is the union of thresholded teacher heads; consensus is their intersection. These outputs are machine_predicted_unvalidated and are not human labels or direct frontier model labels.
Codex and Gemma teacher scores by category
| Category | Codex | Gemma |
|---|---|---|
| Metaresearch | 0.008 | 0.031 |
| Meta-epidemiology (narrow) | 0.000 | 0.000 |
| Meta-epidemiology (broad) | 0.001 | 0.000 |
| Bibliometrics | 0.001 | 0.004 |
| Science and technology studies | 0.001 | 0.001 |
| Scholarly communication | 0.000 | 0.001 |
| Open science | 0.002 | 0.000 |
| Research integrity | 0.000 | 0.001 |
| Insufficient payload (model declined to judge) | 0.000 | 0.000 |
Machine scores (provisional)
The two teacher heads of the student model, read on this work. A score orders the frame for review; it never asserts a category, and the validation status ships verbatim with every row.
Baseline scores from an immature model (maturity gate not passed, 7 training rounds). Scores rank; they never assert a category.
score_only:v0-immature-baseline · verbatim from the scoring run: score_only means the number may rank works, and no category label ships from itClassification
machine, unvalidatedMachine predicted; a candidate call from one teacher head, not a consensus.
How this classification was reached, model by model and score by score, is at the end of the page under "How this classification was reached".