Forward masked excitation patterns in multielectrode electrical stimulation

Abstract

Across-channel interactions in multi-electrode cochlear implant patients may be critical to their performance in the natural auditory environment. One measure of channel interaction can be obtained using forward masking. The patterns of threshold shift were obtained as a function of the separation between masker and probe electrode pairs in four Nucleus-implanted patients with varying levels of speech recognition. In the three subjects with better speech recognition (N4, N7, and N13), the masking patterns showed the least parameter dependence. In the subject with the lowest speech scores (N3), the masking patterns showed the greatest dependence on masker level and on probe delay. Masking as a function of masker level also reflected these differences: N3's functions showed the greatest changes for different probe delays. Similar rates of recovery were observed in the three good performers (time constant approximately 70 ms). In contrast, subject N3's recovery function shows a more rapid recovery. These data indicate that channel interaction is individually variable and parameter dependent, both of which may play a role in the perception of dynamic stimuli in the natural auditory environment.

Excitation Patterns of Standard and Steered Partial Tripolar Stimuli in Cochlear Implants

“…The excitation patterns of steered pTP stimuli were measured psychophysically using a forward masking technique (e.g., Chatterjee and Shannon 1998;Chatterjee et al 2006;Kwon and van den Honert 2006). In this technique, thresholds of probes along the electrode array are measured with or without a forward masker.…”

Topographic Spread of Inferior Colliculus Activation in Response to Acoustic and Intracochlear Electric Stimulation

“…In addition to psychophysical studies of activation selectivity (Pauka 1989;Dorman et al 1990;Busby et al 1994;McDermott and McKay 1994;Nelson et al 1995;Chatterjee and Shannon 1998;McKay et al 1999;Pfingst et al 1999), several modeling studies have attempted to define the intracochlear spread of current in cochlear implants. The approaches used in these studies range from saline tank/resistive network models of voltage distributions within the cochlea (Strelioff 1973;Black and Clark 1980;Black et al 1981Black et al , 1983O'Leary et al 1985;Girizon 1987;Ifukbe and White 1987;Kasper et al 1991;Suesserman and Spelman 1993;Jolly et al 1996;Kral et al 1998) to 2D and 3D computer simulations of intracochlear stimulation.…”

“…Studies of the spread of auditory nerve activation in response to electric stimuli have involved clinical and psychophysical studies in humans (Tong and Clark 1986;Lim et al 1989;Chatterjee and Shannon 1998;Hanekom and Shannon 1997), electrophysiological studies in animals (Woolsey and Walzl 1943; Van den Honert and Stypulkowski 1987;Snyder et al 1990Snyder et al , 1991Leake et al 1991Leake et al , 1995Leake et al , 2000Kral et al 1998;Shepherd et al 1999;Rebscher et al 2001;Taniguchi et al 1997;Raggio and Schreiner. 1999;Bierer and Middlebrooks 2002;Middlebrooks and Bierer 2002), and theoretical modeling studies (Finley 1989;Finley et al 1987Finley et al , 1990Frijns et al 1994Frijns et al , 1995Frijns et al , 1996Rattay et al 2001a,b).…”

Current focusing and steering: Modeling, physiology, and psychophysics

“…4, σ = 0), it is usually maintained only as long as the amplitude of stimulation is less than 3-4 dB above threshold of the most sensitive fibers. However, for most human listeners, excitation patterns derived from forward masking do have a pronounced peak near the stimulation electrode even for relatively loud masker stimuli (Chatterjee and Shannon, 1998;Kwon and van den Honert, 2006a). In addition, extremely broad spread with monopoles is not consistent with successful use of monopolar stimulation in speech processing strategies (Pfingst et al, 2001).…”