Computation predicts rapidly adapting mechanotransduction currents cannot account for tactile encoding in Merkel cell-neurite complexes
Fig 1
A computational model of mechanotransduction in the slowly adapting type I cutaneous afferent.
Shown is current over a ramp and hold stimulus for multiple sub-components, including a slowly inactivating (SI) current modeled as originating from the Merkel cell and rapidly inactivating (RI) and ultra-slowly inactivating (USI) currents modeled as originating from the neurite terminal. All three currents are included within the generator function, which receives input of compressive stress from a finite element model. The finite element model takes probe force, as shown in the upper panel, as its input. The generated trace of compressive stress interior to the skin’s layers, as shown in Fig 2, exhibits time-dependent viscoelastic relaxation. The currents that the generator function represents, in modeling one Merkel cell—neurite complex, are summed across a cluster of eight Merkel cell-neurite complexes feeding a heminode. It is this current, upon entering into a leaky integrate and fire model, which gives rise to predicted spike firing times. Note that for the sake of the simulation here, the irregular inter-spike intervals were unimportant so noise was removed from the model.