Overall, data from the placebo group suggest speech tracking scores in adult cochlear implant users improve on average 13% as a function of an 8-week aural habilitation program designed to enhance speech tracking abilities. These improvements are evident in both V+A and A-only speech tracking conditions suggesting aural habilitation provides a positive benefit for adult cochlear implant users. Considerable variation, however, occurred in the individual speech tracking performance of the placebo group with one subject achieving minimal performance changes for V+A and A-only presentations, two participants achieving increases in performance for V+A and A-only stimuli, and one subject increasing performance for V + A stimuli but not A-only stimuli.
Variability in the placebo group may be related to several factors including the demographic characteristics of the group which were intentionally not controlled, as part of the larger feasability study. For example, the two subjects demonstrating the greatest changes in V+ A speech tracking scores were bilaterally implanted. One of the bilaterally implanted subjects (Subject P4) also demonstrated substantial increases in A-only speech tracking performance whereas the second subject (Subject P3) did not. Inspection of the individual session speech tracking performance for subject P3 indicates their performance hovered around 70 and 60 words-per-minute for V+A and A-only presentations, respectively. Similarly, high performance levels are evident in the individual session data for subject P4 who achieves approximately 80 words-per-minute scores in V+A conditions and 70 words-per-minute under A-only conditions. Changes in speech tracking scores for V+A and A-only presentations were poorest for Subject P2 whose V+A and A-only performance hovered around 50 words-per-minute. However, subject P2 also had the least experience using their implant (.92 years). Subject P1 who had the lowest CVC and HINT performance demonstrated V+A speech tracking scores during the individual sessions of around 70 words-per-minute while A-only tracking hovered at 30 words-per-minute.
Comparisons of the speech tracking intervention sessions relative to the “ceiling” performances achieved when participants were allowed to also read the stimuli, as well as listen and see the examiner, are also revealing regarding sources of individual variability. During the intervention program, the two bilaterally implanted participants preformed nearly at ceiling levels for both V+A and A-only stimuli. Subject P2 appeared to be slightly below ceiling levels during the intervention program. Subject P1 remained substantially below ceiling levels for A-only stimuli. Although his V+A tracking scores were higher than his A-only scores during the intervention program, they, too, remained below his ceiling level. These observations suggest the intervention program designed with reading materials of approximately a fifth grade level allowed the majority of subjects to practice speech tracking at a fairly high level of success; thus, reducing frustration. However, it is not clear if higher performance levels would be achieved if the program was longer than 8-weeks, more intensive than two, 1.5 hour sessions per week, or designed to use more difficult reading materials. Manipulations of these variables may reduce the overall variance associated with aural habilitation as indicated by this small group of participants.
In contrast, the Treatment group displayed minimal changes in V+A speech tracking performance accompanied by substantial changes in A-only speech tracking scores following the intervention program. The percent change of A-only speech tracking performances was over three times as high as that observed for the placebo group, ranging from 22 to 79% across the individual participants in the treatment group. Interestingly, the two participants with the lowest CVC and HINT scores (subjects T2 and T4) demonstrated the greatest gains in A-only speech tracking scores (46.1% and 79.7%, respectively).
The speech tracking scores acquired across the treatment sessions relative to the ceiling levels acquired under conditions combining text, visual and auditory cues resemble the placebo group. For example, V+A speech tracking was typically higher than A-only tracking performance for all subjects across all sessions. As in the case of the placebo group, most of the subjects in the treatment group preformed below their ceiling performance again confirming fifth grade reading materials provided a reasonable stimulus for practicing speech tracking. Variability in speech tracking was evident in the measures acquired across treatment sessions in manners paralleling the placebo group, with some individuals achieving high levels of performance (i.e., subject T2) and others achieving fewer words-per-minute tracking scores (i.e., subject T4).
Differences between the groups were further confirmed by the functional brain imaging measures. Prior to intervention, the two groups demonstrated small reliable activations of the superior and middle temporal gyrus contralateral to the ear of implantation. Ipsilateral activation of the superior temporal gyrus also was evident in the two groups. Following the intervention program, no substantial improvement in brain activation occurred in the Placebo group, while both the extent and magnitude of primary auditory and association cortex increased significantly in the Treatment group. Increased responses were noted both contralateral and ipsilateral to the ear of implantation. These data support previous studies indicating SPECT rCBF is a sensitive measure of changes in cortical activity associated with adult cochlear implant users.
Administration of d-amphetamine appears to enhance recovery of motor function, sensorimotor integration and binocular depth perception (Jonason, Lauber, Robbins, Meyer, & Meyer, 1970; Hurwitz, et al., 1991; Feeney, Gonzalez, & Law, 1982; Feeney & Hovda, 1985; Dietrich, et al., 1990; Crisostomo, Duncan, Propst, Dawson, & Davis, 1988). D-amphetamine-facilitated recovery appears to be greater when the pharmacologic treatment is paired with practice or training than when the drug is administered in isolation (Walker-Batson, 2000). Increase rate and extent of recovery is evident in hemiplegic patients following strokes when low dosages are administered during physical therapy conducted in the subacute recovery period (Crisostomo, Duncan, Propst, Dawson, & Davis, 1988). Administration of d-amphetamine paired with speech/language treatment during the subacute recovery period also accelerates communication abilities in stroke patients (Walker-Batson, 2000). Our data based on the preliminary reports of the first few participants enrolled in our feasibility study suggest d-amphetamine facilitates the development of A-only speech tracking scores in adult cochlear implant users. Although it is not entirely clear why greater changes are observed in the A-only conditions relative to the V + A conditions in the Treatment group, one can speculate that these differences reflect the emphasis of the intervention program on A-only speech tracking skills and may reflect the ability of the Treatment group to reach auditory-only speech tracking abilities more quickly than the placebo group. Achievement of these abilities, in turn, assures the group will receive a greater amount of practice in these skills during the intervention. Future studies with larger N’s will allow us to investigate these factors more clearly in order to specify the underlying relationships of factors contributing to these observations.
Although these initial observations are exciting and suggest new avenues for exploring how to enhance auditory performance in adult cochlear implant users, many questions remain to be addressed. For example, it is not clear precisely what dosage of d-amphetamine constitutes the ideal amount to enhance performance. Nor is it clear how long the treatment should last. When one considers the large increases in speech tracking performance acquired over 16 therapy sessions for 24 hours of aural habilitation, one must question if different dosages and a greater number of therapy sessions would further enhance performance. For example, the aphasia literature suggests a significant clinical change is indicated by a 15 point change in the Porch Index for Communication Disorders (Walker-Batson, 2000). One study reports a 16.7 point change when therapy is paired with d-amphetamine across 10 drug treatment sessions and 33 hours of therapy delivered in a 5-week period (Walker-Batson, 2000). Another study indicates patients made a 18.2 point recovery after 12 weeks of d-amphetamine-paired therapy that provided between 96 to 120 hours of therapy (Wertz et al., 1986). These issues will need to be carefully explored to determine the optimal habilitation intervals for adult cochlear implant users.
The composition and level of difficulty for tasks contained within the aural habilitation also needs to be explored to determine the ideal components necessary to increase performance in adult cochlear implant users. Several studies examining the treatment of phonological problems in young children suggest targeting more complex sounds results in a generalization of benefit to less complex sounds. It is not clear if such a concept can be applied to the development of effective aural habilitation programs for adult cochlear implant users.
Additionally, with the very small sample of participants described here, it is not yet possible to determine what type of patient will receive the most benefit. The subjects in this preliminary report used a variety of different implant devices, different speech processing strategies and different implantation characteristics (i.e., unilateral versus bilateral). Although the two bilateral patients (subjects P3 and P4) demonstrated the greatest percent change in performance for the placebo group, the percent changes in performance for two of the unilaterally implanted subjects in the treatment group with roughly similar lengths of implant experience (subjects T2 and T4) was higher. These four subjects also pinpoint another confounding issue, the chronological age of the subjects. Subjects in the placebo group are older than subjects in the treatment group. It remains unclear if the performance differences are related to the age and cognitive conditions of the groups. Finally, it is not clear how generalizable and long-lasting these findings may be. Future studies will attempt to more carefully match important demographic characteristics of subjects and to include a wide range of performance measures in order to better characterize the speech perception abilities of individuals participating in the intervention sessions. We intend to continue following these subjects to examine the stability of performance over time while we increase our pool of participants further examining these issues (Constable et al., 1978).
Portions of this work were presented at the International Meeting on Cochlear Implants held in Indianapolis, IN. Work on this project is sponsored by the Charles A. Dana Foundation Clinical Hypotheses Program in Imaging. (M. Devous, Sr., Principal Investigator) and the National Institute of Deafness and Other Communication Disorders (R01 DC04558, E. Tobey, Principal Investigator). We appreciate the assistance of Drs. Pam Kruger, Nathan Schwade and Peter Roland.
Bao, S., Chan, V. T., Merzenich, M. M. (2001). Cortical remodelling induced by activity of ventral tegmental dopamine neurons. Nature, 412
Boyeson, M. G., & Feeney, D. M. (1990). Intraventricular norepinephrine facilitates motor recovery following sensorimotor cortex injury. PharmacolBiochemBehav, 35
Clopton, B. M., Silverman, M. S., Webster, D. B., Webster, M., Neural responses to morphological, syntactic, and semantic properties of single words: an fMRI study.
Constable, R. T., Pugh, K. R., Berroya, E., Mencl, W. E., Westerveld, M., Ni, W., Shankweiler, D., Guenther, F. H., Nieto-Castanon, A., Ghosh, S. S., & Tourville, J. A. (1978). Sentence complexity and input modality effects in sentence comprehension: an fMRI studyRepresentation of sound categories in auditory cortical maps. ExpBrain Res, 32
Crisostomo, E. A., Duncan, P. W., Propst, M., Dawson, D. V., & Davis, J. N. (1988). Evidence that amphetamine with physical therapy promotes recovery of motor function in stroke patients. Ann Neurol, 23
De Filippo, C. L., & Scott, B. L. (1978). A method for training and evaluating the reception of ongoing speech. JAcoustSocAm, 63
Delanoy, R. L., Tucci, D. L., Gold, P. E. (1983). Amphetamine effects on long term potentiation in dentate granule cells. Pharmacol Biochem Behavior, 18
Dietrich, W. D., Alonso, O., Busto, R., Watson, B. D., Loor, Y., & Ginsberg, M. D. (1990). Influence of amphetamine treatment on somatosensory function of the normal and infarcted rat brain. Stroke, 21
Dinse H.R., Ragert, P., Pleger, B., Schwenkreis, P., Tegenthoff, M. (2003). Pharmacological Modulation of Perceptual Learning and Associated Cortical Reorganization. Science, 301
Feeney, D. M., Gonzalez, A., & Law, W. A. (1982). Amphetamine, haloperidol, and experience interact to affect rate of recovery after motor cortex injury. Science, 217
Feeney, D. M., & Hovda, D. A. (1985). Reinstatement of binocular depth perception by amphetamine and visual experience after visual cortex ablation. Brain Res, 342
Friston, K. (1994). Statistical parametric mapping. In R.W.E.H.M.E.e.al.Thatcher (Ed.), Functional neuroimaging: Technical foundations
(pp. 79–93). San Diego, CA, Academic Press, Inc.
Fujiki, N., Naito, Y., Hirano, S., Kojima, H., Shiomi, Y., Nishizawa, S., Konishi, J., & Honjo, I. (1999). Correlation between rCBF and speech perception in cochlear implant users. Auris Nasus Larynx, 26
Fujiki, N., Naito, Y., Hirano, S., Kojima, H., Shiomi, Y., Nishizawa, S., Konishi, J., & Honjo, I. (2000). Cortical activity and speech perception performance in cochlear implant users. AdvOtorhinolaryngol, 57
Giraud, A. L., & Truy, E. (2002). The contribution of visual areas to speech comprehension: a PET study in cochlear implants patients and normal-hearing subjects. Neuropsychologia, 40
Giraud, A. L., Truy, E., Frackowiak, R. S., Gregoire, M. C., Pujol, J. F., & Collet, L. (2000). Differential recruitment of the speech processing system in healthy subjects and rehabilitated cochlear implant patients. Brain, 123 ( Pt 7)
Herzog, H., Lamprecht, A., Kuhn, A., Roden, W., Vosteen, K. H., & Feinendegen, L. E. (1991). Cortical activation in profoundly deaf patients during cochlear implant stimulation demonstrated by H2(15)O PET. J ComputAssistTomogr, 15
Hurwitz, B. E., Dietrich, W. D., McCabe, P. M., Alonso, O., Watson, B. D., Ginsberg, M. D., & Schneiderman, N. (1991). Amphetamine promotes recovery from sensory-motor integration deficit after thrombotic infarction of the primary somatosensory rat cortex. Stroke, 22
Ito, J., Sakakibara, J., Iwasaki, Y., & Yonekura, Y. (1993). Positron emission tomography of auditory sensation in deaf patients and patients with cochlear implants. Ann Otol Rhinol Laryngol, 102
Jancke, L., Gaab, N., Wustenberg, T., Scheich, H., & Heinze, H. J. (2001). Short-term functional plasticity in the human auditory cortex: an fMRI study. Brain ResCogn Brain Res, 12
Jonason, K. R., Lauber, S. M., Robbins, M. J., Meyer, P. M., & Meyer, D. R. (1970). Effects of amphetamine upon relearning pattern and black-white discriminations following neocortical lesions in rats. J Comp Physiol Psychol, 73
Kral, A., Tillein, J., Heid, S., Hartmann, R., & Klinke, R. (2004). Postnatal Cortical Development in Congenital Auditory Deprivation. Cereb. Cortex
Lacaille, J. C., Harley, C. W. (1985). The action of norepinephrine in the dentate gyrus: beta-mediated facilitation of evoked potentials in vitro. Brain Res, 358
Montague, P. R., Dayan, P., Sejnowski, T. J. (1996). A framework for mesencephalic dopamine systems based on predictive Hebbian learning. J Neurosci, 16
Morita, T., Naito, Y., Tsuji, J., Nakamura, T., Yamaguchi, S., & Ito, J. (2004). Relationship between cochlear implant outcome and the diameter of the cochlear nerve depicted on MRI. Acta Otolaryngol. Suppl
Naito, Y., Hirano, S., Fujiki, N., Nishizawa, S., Takahashi, H., Kojima, H., Yamaguchi, S., Kawano, M., Konishi, J., & Honjo, I. (2000a). Development and plasticity of the auditory cortex in cochlear implant users: a follow-up study by positron emission tomography. AdvOtorhinolaryngol, 57
Naito, Y., Hirano, S., Honjo, I., Okazawa, H., Ishizu, K., Takahashi, H., Fujiki, N., Shiomi, Y., Yonekura, Y., & Konishi, J. (1997). Sound-induced activation of auditory cortices in cochlear implant users with post- and prelingual deafness demonstrated by positron emission tomography. Acta Otolaryngol, 117
Naito, Y., Okazawa, H., Honjo, I., Takahashi, H., Kawano, M., Ishizu, K., & Yonekura, Y. (1995). Cortical activation during sound stimulation in cochlear implant users demonstrated by positron emission tomography. Ann Otol Rhinol Laryngol Suppl, 166
Naito, Y., Tateya, I., Fujiki, N., Hirano, S., Ishizu, K., Nagahama, Y., Fukuyama, H., & Kojima, H. (2000b). Increased cortical activation during hearing of speech in cochlear implant users. Hear Res, 143
Nicoll, R. A., Malenka, R. C. (1995). Contrasting properties of two forms of long-term potentiation in the hippocampus. Nature, 377
Nilsson, M., Soli, S. D., & Sullivan, J. A. (1994). Development of the Hearing in Noise Test for the measurement of speech reception thresholds in quiet and in noise. JAcoustSocAm, 95
Nishimura, H., Doi, K., Iwaki, T., Hashikawa, K., Oku, N., Teratani, T., Hasegawa, T., Watanabe, A., Nishimura, T., & Kubo, T. (2000). Neural plasticity detected in short- and long-term cochlear implant users using PET. Neuroreport, 11
Okazawa, H., Naito, Y., Yonekura, Y., Sadato, N., Hirano, S., Nishizawa, S., Magata, Y., Ishizu, K., Tamaki, N., Honjo, I., & Konishi, J. (1996). Cochlear implant efficiency in pre- and postlingually deaf subjects. A study with H2(15)O and PET. Brain, 119 ( Pt 4)
Roland, P. S., Tobey, E. A., & Devous, M. D., Sr. (2001). Preoperative functional assessment of auditory cortex in adult cochlear implant users. Laryngoscope, 111
Shiomi, Y., Naito, Y., Honjo, I., Fujiki, N., Kaneko, K., Takahashi, H., Yamashita, M., & Kawano, M. (1999). Cochlear implant in patients with residual hearing. Auris Nasus Larynx, 26
Talairach, J. & Tournoux, P. (1988). Co-Planar Stereotaxic Atlas of the Human Brain
. New York: Thieme Medical Publishers.
Truy, E., Deiber, M. P., Cinotti, L., Mauguiere, F., Froment, J. C., & Morgon, A. (1995). Auditory cortex activity changes in long-term sensorineural deprivation during crude cochlear electrical stimulation: evaluation by positron emission tomography. Hear Res, 86
Walker-Batson, D. (2000). Use of pharmacotherapy in the treatment of aphasia. Brain Lang, 71
Webster, D. B., & Webster, M. (1977). Neonatal sound deprivation affects brain stem auditory nuclei. ArchOtolaryngol, 103
Wertz, R. T., Weiss, D. G., Aten, J. L., Brookshire, R. H., Garcia-Bunuel, L., Holland, A. L., Kurtzke, J. F., LaPointe, L. L., Milianti, F. J., Brannegan, R. (1986). Comparison of clinic, home, and deferred language treatment for aphasia. A Veterans Administration Cooperative Study. Arch. Neurol, 43
Wong, D., Miyamoto, R. T., Pisoni, D. B., Sehgal, M., & Hutchins, G. D. (1999). PET imaging of cochlear-implant and normal-hearing subjects listening to speech and nonspeech. Hear Res, 132