Combined modulation of pulse width and pulse amplitude to enhance functional selectivity of neural stimulation

Advances in neural electrode designs have produced electrodes capable of interacting with small subsets of the axon population. To take full advantage of this intimate contact, it is necessary to use stimulating parameters that generate highly localized excitation fields. Previous studies have investigated modulation of either amplitude or pulse width while fixing the other at a value that either maximized a threshold difference or minimized a charge injection. The authors´ results suggest that combined modulation of both pulse width and amplitude can provide enhanced neural stimulation selectivity and augment the functional capabilities of neural electrodes. These results support the hypothesis that pulse amplitude determines the spatial extent of a stimulation field and pulse width determines the percentage of recruitment within that field. The authors conclude by discussing functional and design advantages suggested by their results and possible mechanisms currently being investigated to explain the observed phenomenon