Auditory Cortex, Altered Auditory Feedback and Developmental Stuttering
Initial studies of SpeechEasy
Anne L. Foundas, M.D. and Edward G. Conture, Ph.D.
From the Stuttering Foundation's fall 2007 newsletter
Editor's note: The Stuttering Foundation is pleased to support this new research.
Our knowledge of the biological bases of developmental stuttering has been greatly enhanced by recent results of brain imaging and physiological studies. Taken together, these complementary methods have begun to provide converging evidence about the brain regions that may be affected in individuals who stutter. For example, there is strong evidence that dysfunctions in auditory cortical brain regions may contribute to developmental stuttering. Related to these findings, numerous investigators have studied how altered auditory feedback may influence speech fluency in individuals with developmental stuttering (e.g., Armson, Kiefte, Mason, & DeCroos, 2006; Stuart, Kalinowski, Armson, Stenstrom & Jones, 1996; Van Riper, 1973, pp. 116-139). These alterations have involved such procedures as low-pass and high-pass auditory masking (e.g., Conture, 1974), delayed auditory feedback (DAF) (Van Riper, 1973), and frequency altered feedback (FAF) (Armson et al., 2006). To greater or lesser degrees, these various alterations in speaker's auditory feedback for speech have been shown to reduce stuttering during reading as well as conversational speech. However, what is still unknown is whether there are predictable relationships between auditory cortical brain regions (structure and function) and changes in stuttering to altered auditory feedback.
In our first volumetric MRI study of developmental stuttering we found structural anomalies within a discrete brain region " a portion of auditory temporal cortex (Foundas et al, 2001). Other studies have found atypical activation-deactivation in this same brain region and atypical physiological responses when adults who stutter are compared to adults who do not stutter (for review, Brown et al, 2005). In a subsequent study we found that adults with developmental stuttering and atypical auditory temporal anatomy had enhanced fluency with DAF, but adults with developmental stuttering and typical anatomy showed less improvement under conditions of DAF (Foundas et al, 2004).
Although alteration in auditory feedback for speech appears effective, at least in the short term, for some individuals who stutter, there is a limited understanding of the means by which stuttering changes as a result of alterations in speakers" air-borne auditory feedback for speech and language. With recent advances in digital technology, however, one such device has been widely marketed and empirically studied, that is, the SpeechEasy (2001).
The SpeechEasy is a small device which looks and fits like a hearing aid. This device works in essence by "playing a copy" of the person's own speech in their ear after shifting the pitch as well as creating a temporal delay in the acoustic output of their speech production. According to SpeechEasy's associated marketing literature, such adjustments or alterations in auditory feedback for speech supposedly mimic the effects of choral reading. One empirical study (Armson et al., 2006) showed that the SpeechEasy reduced stuttering events by 49%, 36%, and 74% respectively for conversation, monologue, and reading. Fluency was even more enhanced in all speaking conditions with the instruction to deliberately prolong vowels.
At present, there are several unanswered questions: How does the SpeechEasy device work at the level of the auditory cortex? How does the SpeechEasy device relate to brain anatomy and function? Our research group is interested in investigating these important questions. Our research group at Tulane, in collaboration with Dr. Edward G. Conture and colleagues at Vanderbilt, are conducting pilot studies to objectively examine the SpeechEasy in a small group of adults with persistent developmental stuttering.
Overall, results of this study should provide crucial, objective information for further, larger-scale study of this device, particularly relative to how cortical activity and structure relates to those who do versus those who do not benefit from using the device. The proposed studies have considerable theoretical and clinical significance. The proposed studies should provide a biological framework that will allow us to learn more about the structure and function of auditory cortical regions in adults who do and do not stutter. Furthermore, it is thought that such studies may lead to more targeted interventions using the SpeechEasy to help those individuals with developmental stuttering seeming most able to receive benefit from such treatment.
Armson, J., Kiefte, M., Mason, J., De Croos, D. (2006). The effects of SpeechEasy on stuttering frequency in laboratory conditions. Journal of Fluency Disorders, 31, 137-152.
Brown S., Ingham R.J., Ingham, J.C., Laird, A.R., Fox, P.T. (2005). Stuttered and fluent speech production: an ALE meta-analysis of functional neuroimaging studies. Human Brain Mapping, 25, 105-17.
Conture, E. (1974). Some effects of noise on the speaking behavior of stutterers. Journal of Speech and Hearing Research, 17, 714-723.
Foundas, A.L., Bollich AM, Corey, D., Hurley, M., Heilman, K. (2001).Anomalous anatomy of speech-language areas in adults with persistent developmental stuttering. Neurology, 57, 207-215.
Foundas, A.L., Bollich, A.M., Feldman. J., Corey, D.M., Hurley, M., Heilman, K.M. (2004). Atypical planum temporale anatomy in stuttering: Relationship to delayed auditory feedback. Neurology. 63: 1640-1646.
Stuart, A., Kalinowski, J., Armson, J., Strenstrom, R., Jones, K. (1996). Fluency effect of frequency alternations of plus/minus one-half and one-quarter octave shifts in auditory feedback of people who stutter. Journal of Speech and Hearing Research, 39, 396-401.
Van Riper, C. (1973). The Treatment of Stuttering. Englewood Cliffs, NJ: Prentice Hall, Inc.