Stimulation parameter space

The high-dimensional set of controllable variables that define an ICMS stimulus: pulse amplitude, pulse frequency, pulse width, train duration, which electrode or electrodes, the current fractionalization across them, waveform shape and polarity, and the temporal pattern of the train. Each dimension can influence the intensity, quality and location of the evoked percept, and they do so non-independently, so the mapping from parameters to perception is a coupled, nonlinear function.

This coupling makes exhaustive search intractable and makes disciplined psychophysics essential: one characterizes the perceptual effect of each dimension and their interactions, rather than assuming, say, that amplitude sets intensity while frequency sets quality. Practical encoding designs therefore reduce the space to a few well-understood, behaviourally validated control axes instead of exploiting its full dimensionality.