Model of Gamma Frequency Burst Discharge Generated by Conditional Backpropagation
Bibliographic record
Abstract
Pyramidal cells of the electrosensory lateral line lobe (ELL) of the weakly electric fish Apteronotus leptorhynchus have been shown to produce oscillatory burst discharge in the gamma-frequency range (20-80 Hz) in response to constant depolarizing stimuli. Previous in vitro studies have shown that these bursts arise through a recurring spike backpropagation from soma to apical dendrites that is conditional on the frequency of action potential discharge ("conditional backpropagation"). Spike bursts are characterized by a progressive decrease in inter-spike intervals (ISIs), and an increase of dendritic spike duration and the amplitude of a somatic depolarizing afterpotential (DAP). The bursts are terminated when a high-frequency somatic spike doublet exceeds the dendritic spike refractory period, preventing spike backpropagation. We present a detailed multi-compartmental model of an ELL basilar pyramidal cell to simulate somatic and dendritic spike discharge and test the conditions necessary to produce a burst output. The model ionic channels are described by modified Hodgkin-Huxley equations and distributed over both soma and dendrites under the constraint of available immunocytochemical and electrophysiological data. The currents modeled are somatic and dendritic sodium and potassium involved in action potential generation, somatic and proximal apical dendritic persistent sodium, and K(V)3.3 and fast transient A-like potassium channels distributed over the entire model cell. The core model produces realistic somatic and dendritic spikes, differential spike refractory periods, and a somatic DAP. However, the core model does not produce oscillatory spike bursts with constant depolarizing stimuli. We find that a cumulative inactivation of potassium channels underlying dendritic spike repolarization is a necessary condition for the model to produce a sustained gamma-frequency burst pattern matching experimental results. This cumulative inactivation accounts for a frequency-dependent broadening of dendritic spikes and results in a conditional failure of backpropagation when the intraburst ISI exceeds dendritic spike refractory period, terminating the burst. These findings implicate ion channels involved in repolarizing dendritic spikes as being central to the process of conditional backpropagation and oscillatory burst discharge in this principal sensory output neuron of the ELL.
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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 | 0.001 |
| Bibliometrics | 0.000 | 0.000 |
| Science and technology studies | 0.000 | 0.001 |
| Scholarly communication | 0.001 | 0.001 |
| Open science | 0.002 | 0.001 |
| Research integrity | 0.001 | 0.001 |
| Insufficient payload (model declined to judge) | 0.002 | 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".