Intact Behavioral Expression of Contextual Fear, Context Discrimination, and Object Discrimination Memories Acquired in the Absence of the Hippocampus
Bibliographic record
Abstract
We test the hypothesis that the stability and precision of context and visual discrimination memories depend on interactions between the hippocampus (HPC) and other memory storage networks. In four experiments we tested the properties of memories acquired in the absence of the HPC. Long–Evans male rats were exclusively used in all experiments. Experiment 1 evaluated acquisition and retention of context fear memories in rats with prior partial or complete HPC damage. Confirming an earlier report (Zelikowsky et al., 2012) a very small but statistically reliable slowing in a single session of context fear conditioning was found after HPC damage. In contrast, retention of context fear memory was normal after HPC damage up to 30 d after learning. In experiment 2, we found that discrimination between a context paired with foot shocks and a different context never paired with foot shock was retained normally for 15 d. In experiment 3, we replicated the finding of intact context discrimination for at least 15 d in rats who display a significant impairment in acquisition of place learning in the Morris water task (MWT). In final experiment using an appetitive object discrimination task, we showed normal retention of the discrimination for at least 30 d after training in rats with complete HPC damage. These finding score against the idea that non HPC memory storage requires a period of interaction with HPC to establish a stable, precise memory. SIGNIFICANCE STATEMENT Contrary to expectations from systems memory consolidation, we find that in the absence of a functional hippocampus (HPC) context and visual memories are formed rapidly and exhibit normal persistence and precision. The findings suggest that the HPC is not obligatory for these features of long-term memories.
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How this classification was reachedexpand
Full frame machine prediction
Teacher imitationNot calibrated prevalence, not ground truth. Human validation pending. The Gemma side is a direct model label for every work in the frame, read from the title-only record. The Codex side is a classifier learned from the 10,348 direct Codex labels and calibrated to design-weighted sample rates; fields without enough sample support carry no Codex call. Candidate is the union of the two sides; consensus is their intersection. These outputs are machine_predicted_unvalidated and are not human labels.
Distilled classifier scores by category (both heads)
| Category | Codex | Gemma |
|---|---|---|
| Metaresearch | 0.000 | 0.000 |
| Meta-epidemiology (narrow) | 0.001 | 0.000 |
| Meta-epidemiology (broad) | 0.001 | 0.000 |
| Bibliometrics | 0.001 | 0.000 |
| Science and technology studies | 0.000 | 0.001 |
| Scholarly communication | 0.000 | 0.001 |
| Open science | 0.001 | 0.001 |
| Research integrity | 0.000 | 0.001 |
| Insufficient payload (model declined to judge) | 0.001 | 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 source (direct Gemma or distilled Codex), 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".