Speaker
Description
Cross-excitation (CE) – non-synaptic coupling between somata of primary sensory neurons in dorsal root ganglia – is highly prevalent among A-type (mechanoreceptive) fibers but nearly absent in C-type (nociceptive) fibers, hinting at a functional role in somatosensory processing. Its computational contribution, however, remains unclear, as well as underlying biophysical mechanisms. We built a leaky integrate-and-fire network (N=400 neurons) in which neurons interact solely through a diffusible chemical agent, with coupling parameters (degradation constant τ=220 ms, effect on membrane potential from concentration g=0.22) fitted to reported CE-induced depolarization kinetics. Network performance was assessed with a spatio-temporal Intersection-over-Union metric and relative mutual information, across stimulation frequencies (2–200 Hz), CE coupling range, sensory noise levels, afferent recruitment failure, and degree of somatotopic disorganization, under both low-noise ("ideal") and high-noise ("noisy") afferent input regimes.
Overall spatio-temporal accuracy gains from CE were small (≤0.02), but this masked a consistent dissociation: CE reliably improved spatial localization accuracy (up to +0.23 under noisy input) while degrading temporal accuracy, an effect that became severe when somatotopy was disrupted (median gain −0.49). The spatial benefit of CE was consistently larger under degraded/noisy input than under ideal conditions across every manipulation tested – matching an analytical result showing that CE-driven gains in effective firing probability scale with baseline unreliability. An information-theoretic analysis further showed that CE redistributes bandwidth from information about intensity of stimulation (which is perceived logarithmically by the brain) to localization (which is perceived linearly, therefore each extra bit linearly increases the amount of perceived information).
These results suggest that DRG cross-excitation is not a general signal-quality booster but a targeted, noise-dependent enhancement of spatial resolution, achieved by trading off temporal fidelity – offering a plausible computational rationale for an otherwise poorly understood non-synaptic interaction.
| Preferred Presentation | Poster Presentation |
|---|