Adaptive place-pitch ranking procedure for optimizing performance of a multi-channel neural stimulator
View Patent ↗An adaptive place-pitch ranking procedure for use with a cochlear implant or other neural stimulation system provides a systematic method for quantifying the magnitude and direction of errors along the place-pitch continuum. The method may be conducted and completed in a relatively short period of time. In use, the implant user or listener is asked to rank the percepts obtained after a sequential presentation of monopolar stimulation pulses are applied to a selected spatially-defined electrode pair. The spatially-defined electrode pair may be a physical electrode pair or a virtual electrode pair. A virtual electrode pair includes at least one virtual electrode contact. Should the patient's judgment of pitch order be correct for all applied interrogations, then no further testing involving the tested electrode pair (two electrode contacts) is undertaken. However, should there be errors in the place-pitch ranking, which errors evidence perceptual place-confusions, then a search is undertaken for the spread of the perceptual confusion. This search for the spread of confusion continues until no errors are made in all directions. Identified channels wherein pitch confusion exists may be de-selected (not used) during normal operation of the cochlear implant or other neural stimulation system.
1. A method for measuring the spread of perception confusion between stimulus channels of a neural stimulation system comprising:
coarsely determining the spread of perception confusion using physical stimulus channels; and
finely determining the spread of perception confusion using at least one virtual stimulus channel;
wherein coarsely determining the spread of perception confusion using physical stimulus channels comprises
(a) sequentially applying monopolar stimulation pulses in a first order to a selected spatially-defined physical electrode pair representing adjacent stimulus channels;
(b) sequentially applying monopolar stimulation pulses in a second order to the selected spatially-defined physical electrode pair;
(c) ranking perceived sounds resulting from the stimulation pulses applied in the first order and the second order;
(d) determining whether the perceived sounds are correct, and if so, ceasing further testing involving the selected spatially-defined physical electrode pair, and
(e) if the perceived sounds are not correct, identifying a state of perceived confusion for the spatially-defined electrode pair, defining a new spatially-defined physical electrode pair representing stimulus channels that are one stimulus channel farther apart than the previously defined physical electrode pair, and
(f) repeating steps (a)-(e) as many times as necessary to determine the spread of confusion as measured in terms of a physical separation between stimulus channels.
2. The method of claim 1 wherein finely determining the spread of perception confusion using at least one virtual stimulus channel comprises
(a) sequentially applying monopolar stimulation pulses in a first order to a selected spatially-defined virtual electrode pair, said virtual electrode pair including at least one virtual electrode contact, said virtual electrode pair having a separation distance between electrode contacts, at least one of which electrode contacts is a virtual electrode contact, that is measured in terms of units that are fraction of the physical separation between stimulus channels;
(b) sequentially applying monopolar stimulation pulses in a second order to the selected spatially-defined virtual electrode pair;
(c) ranking perceived sounds resulting from the stimulation pulses applied in the first order and the second order;
(d) determining whether the perceived sounds are correct, and if so, ceasing further testing involving the selected spatially-defined virtual electrode pair, and
(e) if the perceived sounds are not correct, identifying a state of perceived confusion for the spatially-defined virtual electrode pair, defining a new spatially-defined virtual electrode pair and a new separation distance between electrode contacts of the virtual electrode pair that is a different distance than the separation distance of the previously defined virtual electrode pair, and
(f) repeating steps (a)-(e) as many times as necessary to determine the spread of confusion between stimulus channels as measured in terms of a virtual stimulus channel separation.
3. The method of claim 2 wherein finely determining the spread of perception confusion using at least one virtual stimulus channel includes recording responses obtained during application of the monopolar stimulation pulses on a grid table.
4. The method of claim 3 further including dividing each cell in the grid table into at least two subparts and recording responses obtained during application of the stimulation pulses in each subpart.
5. The method of claim 1 wherein coarsely determining the spread of perception confusion using physical stimulus channels includes recording responses obtained during application of the monopolar stimulation pulses on a grid table.
6. The method of claim 5 further including dividing each cell in the grid table into at least two subparts and recording responses obtained during application of the stimulation pulses in each subpart.