Tim Saltuklaroglu

Investigations of the impact of altered auditory feedback in‐the‐ear devices on the speech of people who stutter: initial fitting and 4‐month follow‐up

BACKGROUND Self-contained ear-level devices delivering altered auditory feedback (AAF) for the application with those who stutter have only been recently developed. AIMS The paper examines the first therapeutic application of self-contained ear-level devices in three experiments. The effect of the device on the proportion of stuttered syllables and speech naturalness was investigated following initial fitting and at 4 months post-fitting. METHODS & PROCEDURES Three experiments were undertaken: In Experiment 1, the effect of a self-contained in-the-ear device delivering AAF was investigated with those who stutter during reading and monologue. Two adolescents and five adults who stuttered read and produced monologue with and without a device fit monaurally. The device provided a frequency shift of +500 Hz in combination with a delayed auditory feedback of 60 ms. Custom-made ITC and CIC devices were fabricated for four adults and four youths in Experiment 2. The effect of group (i.e. youth versus adult), time (i.e. initial fitting versus 4-month follow-up), speech task (i.e. reading versus monologue), and device (i.e. present versus absent) on stuttering rate was examined. In Experiment 3, 15 naïve listeners rated the speech naturalness of speech produced by the participants in Experiment 2. Speech samples from six conditions were rated: reading and monologue without the device at the initial visit, reading and monologue with the device at the initial visit, and reading and monologue with the device at 4 months. OUTCOMES & RESULTS In Experiment 1, the proportion of stuttered syllables was significantly (p=0.011) reduced by approximately 90% during reading and 67% during monologue with the device relative to no device. Only a significant main effect of device (p=0.0028) was found in Experiment 2. That is, stuttering rate was significantly reduced with the device in place regardless of speech task or group and remained so 4 months later. In Experiment 3, speech samples generated while wearing the device were judged to be more natural sounding than those without the device (p<0.0001) for reading and monologue with both adults and youths. There was no significant difference between the mean naturalness ratings of speech samples generated during the initial fitting with the device relative to that at 4 months with the device (p>0.05) in all cases except with the youths while engaged in monologue. For that condition, raters judged the speech produced at the initial fitting as more natural. CONCLUSIONS These findings support the notion that a self-contained in-the-ear device delivering AAF assists those who stutter. With the device in place, stuttering is reduced and speech produced is judged to be more natural than with out the device.

Investigations of the impact of altered auditory feedback in-the-ear devices on the speech of people who stutter: One-year follow-up

Purpose. This study examined objective and subjective measures of the effect of a self-contained ear-level device delivering altered auditory feedback (AAF) for those who stutter 12 months following initial fitting with and without the device. Method. Nine individuals with developmental stuttering participated. In Experiment 1, the proportion of stuttering was examined during reading and monologue. A self-report inventory inquiring about behaviour related to struggle, avoidance and expectancy associated with stuttering was examined in Experiment 2. In Experiment 3, naïve listeners rated the speech naturalness of speech produced by the participants during reading and monologue. Results. The proportions of stuttering events were significantly ( p < 0.05) reduced at initial fitting and remained so 12 months post follow-up. After using the device for 12 months, self-reported perception of struggle, avoidance and expectancy were significantly (p < 0.05) reduced relative to pre-fitting. Naïve listeners rated the speech samples produced by those who stutter while wearing the device significantly more natural sounding than those produced without the device for both reading and monologue (p < 0.0001). Conclusions. These findings support the notion that a device delivering AAF is a viable therapeutic alternative in the treatment of stuttering.

Differential levels of speech and manual dysfluency in adults who stutter during simultaneous drawing and speaking tasks.

We examined the disruptive effects of stuttering on manual performance during simultaneous speaking and drawing tasks. Fifteen stuttering and fifteen non-stuttering participants drew continuous circles with a pen on a digitizer tablet under three conditions: silent (i.e., neither reading nor speaking), reading aloud, and choral reading (i.e., reading aloud in unison with another reader). We counted the frequency of stuttering events in the speaking tasks and measured pen stroke duration and pen stroke dysfluency (normalized jerk) in all three tasks. The control group was stutter-free and did not increase manual dysfluency in any condition. In the silent condition, the stuttering group performed pen movements without evidence of dysfluency, similar to the control group. However, in the reading aloud condition, the stuttering group stuttered on 12% of the syllables and showed increased manual dysfluency. In the choral reading condition stuttering was virtually eliminated (reduced by 97%), but manual dysfluency was reduced by only 47% relative to the reading aloud condition. Trials where more stuttered events were generally positively correlated with higher manual dysfluency. The results are consistent with a model in which episodes of stuttering and motor dysfluency are related to neural interconnectivity between manual and speech processes.

Suppression of the µ rhythm during speech and non-speech discrimination revealed by independent component analysis: implications for sensorimotor integration in speech processing.

Background Constructivist theories propose that articulatory hypotheses about incoming phonetic targets may function to enhance perception by limiting the possibilities for sensory analysis. To provide evidence for this proposal, it is necessary to map ongoing, high-temporal resolution changes in sensorimotor activity (i.e., the sensorimotor μ rhythm) to accurate speech and non-speech discrimination performance (i.e., correct trials.) Methods Sixteen participants (15 female and 1 male) were asked to passively listen to or actively identify speech and tone-sweeps in a two-force choice discrimination task while the electroencephalograph (EEG) was recorded from 32 channels. The stimuli were presented at signal-to-noise ratios (SNRs) in which discrimination accuracy was high (i.e., 80–100%) and low SNRs producing discrimination performance at chance. EEG data were decomposed using independent component analysis and clustered across participants using principle component methods in EEGLAB. Results ICA revealed left and right sensorimotor µ components for 14/16 and 13/16 participants respectively that were identified on the basis of scalp topography, spectral peaks, and localization to the precentral and postcentral gyri. Time-frequency analysis of left and right lateralized µ component clusters revealed significant (pFDR<.05) suppression in the traditional beta frequency range (13–30 Hz) prior to, during, and following syllable discrimination trials. No significant differences from baseline were found for passive tasks. Tone conditions produced right µ beta suppression following stimulus onset only. For the left µ, significant differences in the magnitude of beta suppression were found for correct speech discrimination trials relative to chance trials following stimulus offset. Conclusions Findings are consistent with constructivist, internal model theories proposing that early forward motor models generate predictions about likely phonemic units that are then synthesized with incoming sensory cues during active as opposed to passive processing. Future directions and possible translational value for clinical populations in which sensorimotor integration may play a functional role are discussed.

Voluntary stuttering suppresses true stuttering: a window on the speech perception-production link.

In accord with a proposed innate link between speech perception and production (e.g., motor theory), this study provides compelling evidence for the inhibition of stuttering events in people who stutter prior to the initiation of the intended speech act, via both the perception and the production of speech gestures. Stuttering frequency during reading was reduced in 10 adults who stutter by approximately 40% in three of four experimental conditions: (1) following passive audiovisual presentation (i.e., viewing and hearing) of another person producing pseudostuttering (stutter-like syllabic repetitions) and following active shadowing of both (2) pseudostuttered and (3) fluent speech. Stuttering was not inhibited during reading following passive audiovisual presentation of fluent speech. Syllabic repetitions can inhibit stuttering both when produced and when perceived, and we suggest that these elementary stuttering forms may serve as compensatory speech gestures for releasing involuntary stuttering blocks by engaging mirror neuronal systems that are predisposed for fluent gestural imitation.

Jobs, Sex, Love and Lifestyle: When Nonstutterers Assume the Roles of Stutterers

Purpose: This study assessed the impact of stuttering via a questionnaire in which fluent individuals were asked to assume the mindset of persons who stutter (PWS) in various life aspects, including vocation, romance, daily activities, friends/social life, family and general lifestyle. The perceived impact of stuttering through the mind’s eyes of nonstutterers is supposed to reflect respondents’ abilities to impart ‘theory of mind’ in addressing social penalties related to stuttering. Method: Ninety-one university students answered a questionnaire containing 56 statements on a 7-point Likert scale. Forty-four participants (mean age = 20.4, SD = 4.4) were randomly selected to assume a stuttering identity and 47 respondents (mean age = 20.5, SD = 3.1) to assume their normally fluent identity. Results: Significant differences between groups were found in more than two thirds of items regarding employment, romance, and daily activities, and in fewer than half of items regarding family, friend/social life, and general life style (p <0.001). Conclusions: The social penalties associated with stuttering appear to be apparent to fluent individuals, especially in areas of vocation, romance, and daily activities, suggesting that nonstuttering individuals, when assuming the role of PWS, are capable of at least temporarily feeling the negative impact of stuttering.

Towards a common neural substrate in the immediate and effective inhibition of stuttering.

Stuttering can be effectively inhibited via exogenous sensory signals (e.g., speaking in unison or using altered auditory feedback) or by using endogenous motoric strategies (e.g., singing or therapeutically implementing long vowel prolongations to reduce speech rates). We propose that these channels, which superficially appear to be diametrically opposite, centrally converge in the engagement of mirror neurons for fluent gestural productions. Sensory changes incurred via exogenous speech signals allow for direct engagement of mirror systems, while endogenous motor strategies appear to require significant departures from normal speech production (e.g., highly unnatural or droned speech) to engage mirror systems. Thus, paradoxically, stuttering is prone to resurface during attempts to impose naturalness upon therapeutic speech

Stuttering inhibition via visual feedback at normal and fast speech rates

BACKGROUND Immediate and drastic reductions in stuttering are found when speech is produced in conjunction with a variety of second signals (for example, auditory choral speech and its permutations, and delayed auditory feedback). Initially, researchers suggested a decreased speech rate as a plausible explanation for the reduction in stuttering as people who stutter produced speech under second signals. However, this explanation was refuted by research findings that demonstrated reductions in stuttering at both normal and fast speech rates under second signals. Recent studies have also demonstrated significant reductions in stuttering from second signals delivered via the visual modality. However, the question as to whether stuttering can be substantially reduced at normal and fast speech rates under visual speech feedback conditions has yet to be answered. AIMS The current study investigated stuttering frequency reduction at normal and fast speech rates across different visual speech feedback conditions relative to a no-visual feedback condition. METHODS & PROCEDURES Ten adults who stutter recited memorized tokens of eight to 13 syllables under five visual speech feedback conditions at both normal and fast speech rates. Visual speech feedback conditions consisted of participants viewing the lower portion of their face (that is, lips, jaw, and base of the nose) on a monitor as they produced the aforementioned utterances. Conditions consisted of (1) no-visual feedback condition, (2) 0 ms (simultaneous visual speech feedback), (2) a 50-ms delay, (3) a 200-ms delay, and (4) a 400-ms delay. OUTCOMES & RESULTS A significant main effect of visual speech feedback on stuttering frequency was found (p= 0.001) with no significant main effect of speech rate or the interaction between speech rate and visual speech feedback. Relative to the no-visual feedback condition, the feedback conditions produced reductions in stuttering ranging from 27% (0 ms) to 62% (400 ms). Post-hoc comparisons revealed that all of the delay conditions differed significantly from the simultaneous feedback (p= 0.017) and the no-visual feedback conditions (p= 0.0002) while no significant differences between delay conditions (that is, 50, 200, and 400 ms) were observed. CONCLUSIONS & IMPLICATIONS The current findings demonstrate the capabilities of visual speech feedback signals to reduce stuttering frequency that is independent of the speakers rate of speech. Possible strategies are suggested to transfer these findings into naturalistic and clinical settings, though further research is warranted.

Gaze Aversion to Stuttered Speech: A Pilot Study Investigating Differential Visual Attention to Stuttered and Fluent Speech.

BACKGROUND People who stutter are often acutely aware that their speech disruptions, halted communication, and aberrant struggle behaviours evoke reactions in communication partners. Considering that eye gaze behaviours have emotional, cognitive, and pragmatic overtones for communicative interactions and that previous studies have indicated increased physiological arousal in listeners in response to stuttering, it was hypothesized that stuttered speech incurs increased gaze aversion relative to fluent speech. The possible importance in uncovering these visible reactions to stuttering is that they may contribute to the social penalty associated with stuttering. AIMS To compare the eye gaze responses of college students while observing and listening to fluent and severely stuttered speech samples produced by the same adult male who stutters. METHODS & PROCEDURES Twelve normally fluent adult college students watched and listened to three 20-second audio-video clips of the face of an adult male stuttering and three 20-second clips of the same male producing fluent speech. Their pupillary movements were recorded with an eye-tracking device and mapped to specific regions of interest (that is, the eyes, the nose and the mouth of the speaker). OUTCOMES & RESULTS Participants spent 39% more time fixating on the speakers eyes while witnessing fluent speech compared with stuttered speech. In contrast, participants averted their direct eye gaze more often and spent 45% more time fixating on the speakers nose when witnessing stuttered speech compared with fluent speech. These relative time differences occurred as a function of the number of fixations in each area of interest. Thus, participants averted their gaze from the eyes of the speaker more frequently during the stuttered stimuli than the fluent stimuli. CONCLUSIONS & IMPLICATIONS This laboratory study provides pilot data suggesting that gaze aversion is a salient response to the breakdown in communication that occurs during stuttering. This response may occur as a result of emotional, cognitive, and pragmatic factors in communication partners. Regardless of the factors contributing to the response, its primary importance may be that gaze aversion is a visible communication partner signal informing the person stuttering that something is amiss in the interaction and hence, may contribute to inducing negative emotions in the persons stuttering, via engagement of the mirror neuron system. We suggest that witnessing and interpreting communication partner responses to stuttering may play a role when a person who stutters engages in future interactions, perhaps contributing to the development of covert strategies to hide stuttering.

Say it with me: Stuttering inhibited

This study examined fluency enhancement in people who stutter via the concomitant presentation of silently mouthed visual speech. Ten adults who stutter recited memorized text while watching another speaker silently mouth linguistically equivalent and linguistically different material. Relative to a control condition, in which no concomitant stimulus was provided, stuttering was reduced by 71% in the linguistically equivalent condition versus only 35% in the linguistically different condition. Despite being an ‘incomplete’ second speech signal, visual speech possesses the capacity to immediately and substantially enhance fluency when it is linguistically equivalent to the intended utterance. It is suggested that fluency enhancement via concomitantly presented external speech is achieved through the extraction of relevant speech gestures from the external speech signal that compliment the intended production, thereby compensating for possible internal inconsistencies in the matching of speech codes in people who stutter. As visual speech perception relies on fewer redundant cues to demarcate the intended gestures, when used as an external stuttering inhibitor, higher degrees of linguistic equivalence seem to be necessary for optimal stuttering inhibition.