Dysfluency levels during repeated readings, choral readings, and readings with altered auditory feedback in two cases of acquired neurogenic stuttering

We investigated how conditions that are known to be fluency-enhancing for individuals with persistent developmental stuttering (PDS) affect the speech of individuals with acquired neurogenic stuttering (ANS). Based on others' claims that the overt speech dysfluencies of PDS and ANS are difficult to distinguish, as well as the derived hypothesis that similar neural mechanisms—or even similar neural deficits—may underlie both disorders, the purpose of the present work was to examine whether speakers with ANS experience the same improvements in speech fluency as do speakers with PDS during (a) repeated readings of the same material, (b) choral readings with a second speaker, and (c) readings with delayed or frequency-altered auditory feedback. Two individuals with ANS read passages out loud in each of these conditions. Results differed from those typically reported for individuals with PDS and, instead, showed (a) only a small amount of adaptation during repeated readings, (b) a small improvement for choral reading that never reached nearly fluent speech, and (c) an increase, rather than decrease, in dysfluency in the conditions with altered auditory feedback. These findings are consistent with those for another case of ANS previously reported by our own group. Possible reasons for the lack of facilitation of fluent speech under these experimental conditions in cases of ANS are discussed.