Induction of Neocortical Long-Term Depression Results in Smaller Movement Representations, Fewer Excitatory Perforated Synapses, and More Inhibitory Synapses
Bibliographic record
Abstract
Long-term depression (LTD) is one of the most widely investigated models of the synaptic mechanisms underlying learning and memory. Previous research has shown that induction of LTD in the neocortex decreases measures of pyramidal cell dendritic morphology in both layers III and V. Here, we investigated the effects of LTD induction on 1) the time course of recovery of synaptic efficacy, 2) movement representations, 3) cortical thickness and layer V neuron density, and 4) the density of excitatory and inhibitory synapses in layer V of sensorimotor neocortex. Rats carried a stimulating electrode in the midline corpus callosum and a recording electrode in the right sensorimotor neocortex. Each rat received either low-frequency stimulation composed of 900 pulses at 1 Hz or handling daily for a total of 20-25 days. Callosal-neocortical evoked potentials were recorded in the right hemisphere before and after stimulation or handling. Our results show that LTD induction lasts for 3 weeks and results in smaller motor maps of the caudal forelimb area. We did not observe any reduction in neocortical thickness or neuron density. There was a reduction in the density of excitatory perforated synapses and an increase in the density of inhibitory synapses in layer V of the sensorimotor neocortex, thereby providing a general mechanism for the reduction in motor map size. This study sheds light on the interaction between an artificial model of learning, receptive field characteristics, and synaptic number in the sensorimotor cortex.
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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 | 0.000 | 0.000 |
| Meta-epidemiology (narrow) | 0.000 | 0.000 |
| Meta-epidemiology (broad) | 0.000 | 0.000 |
| Bibliometrics | 0.000 | 0.001 |
| Science and technology studies | 0.000 | 0.001 |
| Scholarly communication | 0.000 | 0.000 |
| Open science | 0.000 | 0.000 |
| Research integrity | 0.000 | 0.000 |
| 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".