Cross-excitation in dorsal root ganglia redistributes coding capacity from stimulus intensity to stimulus location

Abstract

The phenomenon of cross-excitation between neurons of dorsal root ganglia (DRGs) of mammals is widely known, yet its exact mechanism remains underexplored. In this work, we analyze the phenomenon as part of the signal processing performed by the body's somatosensory system. We argue that, if the mechanism is indeed as prevalent as it is reported in experimental works, it should provide a significant computational advantage. Here, we created a model network in which sensory A-type neurons are interconnected only via a chemical agent and showed that such a connection, when fitted with parameters similar to those observed in experiments, improves the stimulus-localization properties of the ganglia at the expense of intensity-encoding accuracy. Although this exchange is near-neutral in raw bits, it becomes favorable once the logarithmic compression of intensity perception - the Weber--Fechner law - is taken into account, since the sacrificed intensity capacity is largely perceptually redundant. We therefore propose that cross-excitation is not an imperfection of somatic isolation but an effective, chemically mediated pre-processing stage that sharpens spatial localization.