Altered Auditory Feedback In-The-Ear Devices

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 behavior related to struggle, avoidance and expectancy associated with stuttering was examined in Experiment 2. In Experiment 3, naive 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. Naive 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

Dynamic auditory contributions to error detection revealed in the discrimination of Same and Different syllable pairs

During speech production auditory and motor regions within the sensorimotor dorsal stream operate in concert to facilitate online error detection. As the dorsal stream also is known to activate in speech perception, the purpose of the current study was to probe the role of auditory regions in error detection during auditory discrimination tasks as stimuli are encoded and maintained in working memory. A priori assumptions are that sensory mismatch (i.e., error) occurs during the discrimination of Different (mismatched) but not Same (matched) syllable pairs. Independent component analysis was applied to raw EEG data recorded from 42 par-ticipants to identify bilateral auditory alpha rhythms, which were decomposed across time and frequency to reveal robust patterns of event related synchronization (ERS; inhibition) and desynchronization (ERD; pro-cessing) over the time course of discrimination events. Results were characterized by bilateral peri-stimulus alpha ERD transitioning to alpha ERS in the late trial epoch, with ERD interpreted as evidence of working memory encoding via Analysis by Synthesis and ERS considered evidence of speech-induced-suppression arising during covert articulatory rehearsal to facilitate working memory maintenance. The transition from ERD to ERS occurred later in the left hemisphere for Different trials than for Same trials, with ERD and ERS temporally overlapping during the early post-stimulus window. Results were interpreted to suggest that the sensory mismatch (i.e., error) arising from the comparison of the first and second syllable elicits further processing in the left hemisphere to support working memory encoding and maintenance. Results are consistent with auditory contributions to error detection during both encoding and maintenance stages of working memory, with encoding stage error detection associated with stimulus concordance and maintenance stage error detection associated with task-specific retention demands

Sensorimotor contributions to working memory differ between the discrimination of Same and Different syllable pairs

Sensorimotor activity during speech perception is both pervasive and highly variable, changing as a function of the cognitive demands imposed by the task. The purpose of the current study was to evaluate whether the discrimination of Same (matched) and Different (unmatched) syllable pairs elicit different patterns of sensorimotor activity as stimuli are processed in working memory. Raw EEG data recorded from 42 participants were decomposed with independent component analysis to identify bilateral sensorimotor mu rhythms from 36 subjects. Time frequency decomposition of mu rhythms revealed concurrent event related desynchronization (ERD) in alpha and beta frequency bands across the peri- and post-stimulus time periods, which were interpreted as evidence of sensorimotor contributions to working memory encoding and maintenance. Left hemisphere alpha/beta ERD was stronger in Different trials than Same trials during the post-stimulus period, while right hemisphere alpha/beta ERD was stronger in Same trials than Different trials. A between-hemispheres contrast revealed no differences during Same trials, while post-stimulus alpha/beta ERD was stronger in the left hemisphere than the right during Different trials. Results were interpreted to suggest that predictive coding mechanisms lead to repetition suppression effects in Same trials. Mismatches arising from predictive coding mechanisms in Different trials shift subsequent working memory processing to the speech-dominant left hemisphere. Findings clarify how sensorimotor activity differentially supports working memory encoding and maintenance stages during speech discrimination tasks and have potential to inform sensorimotor models of speech perception and working memory.•Sensorimotor activity differs for Same/Different pairs during speech discrimination.•Different stimulus pairs elicit stronger late left hemisphere sensorimotor activity.•Same stimulus pairs elicit weaker late right hemisphere sensorimotor activity.•Same syllable pairs elicit repetition suppression in the anterior dorsal stream.•Mu oscillations encode sensorimotor contributions to working memory

Sex differences in early sensorimotor processing for speech discrimination

Sensorimotor activity in speech perception tasks varies as a function of context, cognitive load, and cognitive ability. This study investigated listener sex as an additional variable. Raw EEG data were collected as 21 males and 21 females discriminated /ba/ and /da/ in quiet and noisy backgrounds. Independent component analyses of data from accurately discriminated trials identified sensorimotor mu components with characteristic alpha and beta peaks from 16 members of each sex. Time-frequency decompositions showed that in quiet discrimination, females displayed stronger early mu-alpha synchronization, whereas males showed stronger mu-beta desynchronization. Findings indicate that early attentional mechanisms for speech discrimination were characterized by sensorimotor inhibition in females and predictive sensorimotor activation in males. Both sexes showed stronger early sensorimotor inhibition in noisy discrimination conditions versus in quiet, suggesting sensory gating of the noise. However, the difference in neural activation between quiet and noisy conditions was greater in males than females. Though sex differences appear unrelated to behavioral accuracy, they suggest that males and females exhibit early sensorimotor processing for speech discrimination that is fundamentally different, yet similarly adaptable to adverse conditions. Findings have implications for understanding variability in neuroimaging data and the male prevalence in various neurodevelopmental disorders with inhibitory dysfunction

The Application of EEG Mu Rhythm Measures to Neurophysiological Research in Stuttering

Deficits in basal ganglia-based inhibitory and timing circuits along with sensorimotor internal modeling mechanisms are thought to underlie stuttering. However, much remains to be learned regarding the precise manner how these deficits contribute to disrupting both speech and cognitive functions in those who stutter. Herein, we examine the suitability of electroencephalographic (EEG) mu rhythms for addressing these deficits. We review some previous findings of mu rhythm activity differentiating stuttering from non-stuttering individuals and present some new preliminary findings capturing stuttering-related deficits in working memory. Mu rhythms are characterized by spectral peaks in alpha (8–13 Hz) and beta (14–25 Hz) frequency bands (mu-alpha and mu-beta). They emanate from premotor/motor regions and are influenced by basal ganglia and sensorimotor function. More specifically, alpha peaks (mu-alpha) are sensitive to basal ganglia-based inhibitory signals and sensory-to-motor feedback. Beta peaks (mu-beta) are sensitive to changes in timing and capture motor-to-sensory (i.e., forward model) projections. Observing simultaneous changes in mu-alpha and mu-beta across the time-course of specific events provides a rich window for observing neurophysiological deficits associated with stuttering in both speech and cognitive tasks and can provide a better understanding of the functional relationship between these stuttering symptoms. We review how independent component analysis (ICA) can extract mu rhythms from raw EEG signals in speech production tasks, such that changes in alpha and beta power are mapped to myogenic activity from articulators. We review findings from speech production and auditory discrimination tasks demonstrating that mu-alpha and mu-beta are highly sensitive to capturing sensorimotor and basal ganglia deficits associated with stuttering with high temporal precision. Novel findings from a non-word repetition (working memory) task are also included. They show reduced mu-alpha suppression in a stuttering group compared to a typically fluent group. Finally, we review current limitations and directions for future research

Speech perception, production, and the sensorimotor mu rhythm

The EEG mu (μ) rhythm is considered a measure of sensorimotor integration. This rhythm is commonly identified by co-occuring peaks at ~10'Hz(alpha) and ~20 Hz (beta) across the sensorimotor cortex. Suppression of the power within peaks are thought to reflect somatosensory and motor aspects of processing respectively. Suppression of μ power (especially in the beta peak) has been found when performing, imagining or perceiving relevant action (e.g., while watching hand movements and oro-facial movements). μ suppression has also been found to visual speech perception, listening to speech in noise, and when mentally segmenting speech for auditory discrimination, suggesting that it is a sensitive measure of audio-motor integration in speech. The two main goals in this study are to bolster understanding of the timing and function of dorsal stream activity in speech perception by examining ERS/ERD patterns in quiet and noisy discrimination conditions and to provide initial evidence that, via the application of ICA / ERSP, the use of EEG can be extended effectively into speech production. 17 of 20 participants provided left and right p components that were common to perception and production tasks. The most probably source of these components was the premotor cortex (BA 6) with primary motor cortex (BA 4) and primary somatosensory (BA 2/3) cortex providing additional possible sources. Fewer (8 and 7 of 20) participants provided components with average equivalent dipoles emanating from BA 22 and BA 7, respectively, with alpha activity suggesting entrainment within the dorsal stream

On the Importance of Scientific Rhetoric in Stuttering: A Reply to Finn, Bothe, and Bramlett (2005)

Purpose: To refute the alleged practice of pseudoscience by P. Finn, A. K. Bothe, and R. E. Bramlett (2005) and to illustrate their experimental and systematic bias when evaluating the SpeechEasy, an altered auditory feedback device used in the management of stuttering. Method: We challenged the experimental design that led to the seemingly predetermined outcome of pseudoscience rather than science: Limited preselected literature was submitted to a purposely sampled panel of judges (i.e., their own students). Each criterion deemed pseudoscientific was contested with published peer-reviewed data illustrating the importance of good rhetoric, testability, and logical outcomes from decades of scientific research. Conclusions: Stuttering is an involuntary disorder that is highly resistant to therapy. Altered auditory feedback is a derivation of choral speech (nature\u27s most powerful stuttering inhibitor ) that can be synergistically combined with other methods for optimal stuttering inhibition. This approach is logical considering that in stuttering no single treatment is universally helpful. Also, caution is suggested when attempting to differentiate science from pseudoscience in stuttering treatments using the criteria employed by Finn et al. For example, evaluating behavioral therapy outcomes implements a post hoc or untestable system. Speech outcome (i.e., stuttered or fluent speech) determines success or failure of technique use, placing responsibility for failure on those who stutter

EEG Mu (µ) rhythm spectra and oscillatory activity differentiate stuttering from non-stuttering adults

Stuttering is linked to sensorimotor deficits related to internal modeling mechanisms. This study compared spectral power and oscillatory activity of EEG mu (μ) rhythms between persons who stutter (PWS) and controls in listening and auditory discrimination tasks. EEG data were analyzed from passive listening in noise and accurate (same/different) discrimination of tones or syllables in quiet and noisy backgrounds. Independent component analysis identified left and/or right μ rhythms with characteristic alpha (α) and beta (β) peaks localized to premotor/motor regions in 23 of 27 people who stutter (PWS) and 24 of 27 controls. PWS produced μ spectra with reduced β amplitudes across conditions, suggesting reduced forward modeling capacity. Group time-frequency differences were associated with noisy conditions only. PWS showed increased μ-β desynchronization when listening to noise and early in discrimination events, suggesting evidence of heightened motor activity that might be related to forward modeling deficits. PWS also showed reduced μ-α synchronization in discrimination conditions, indicating reduced sensory gating. Together these findings indicate spectral and oscillatory analyses of μ rhythms are sensitive to stuttering. More specifically, they can reveal stuttering-related sensorimotor processing differences in listening and auditory discrimination that also may be influenced by basal ganglia deficits

Auditory cortical deactivation during speech production and following speech perception An EEG investigation of the temporal dynamics of the auditory alpha rhythm

Sensorimotor integration (SMI) across the dorsal stream enables online monitoring of speech. Jenson et al. (2014) used independent component analysis (ICA) and event related spectral perturbation (ERSP) analysis of electroencephalography (EEG) data to describe anterior sensorimotor (e.g., premotor cortex, PMC) activity during speech perception and production. The purpose of the current study was to identify and temporally map neural activity from posterior (i.e., auditory) regions of the dorsal stream in the same tasks. Perception tasks required "active" discrimination of syllable pairs Vba/ and /da/) in quiet and noisy conditions. Production conditions required overt production of syllable pairs and nouns. ICA performed on concatenated raw 68 channel EEG data from all tasks identified bilateral "auditory" alpha (a) components in 15 of 29 participants localized to pSTG (left) and pMTG (right). ERSP analyses were performed to reveal fluctuations in the spectral power of the is rhythm clusters across time. Production conditions were characterized by significant is event related synchronization (ERS; pFDR < 0.05) concurrent with EMG activity from speech production, consistent with speechinduced auditory inhibition. Discrimination conditions were also characterized by is ERS following stimulus offset. Auditory is ERS in all conditions temporally aligned with PMC activity reported in Jenson et al. (2014). These findings are indicative of speechinduced suppression of auditory regions, possibly via efference copy. The presence of the same pattern following stimulus offset in discrimination conditions suggests that sensorimotor contributions following speech perception reflect covert replay, and that covert replay provides one source of the motor activity previously observed in some speech perception tasks. To our knowledge, this is the first time that inhibition of auditory regions by speech has been observed in real-time with the ICA/ERSP technique

Trait related sensorimotor deficits in people who stutter An EEG investigation of mu rhythm dynamics during spontaneous fluency

Stuttering is associated with compromised sensorimotor control (i.e., internal modeling) across the dorsal stream and oscillations of EEG mu (mu) rhythms have been proposed as reliable indices of anterior dorsal stream processing. The purpose of this study was to compare mu rhythm oscillatory activity between (PWS) and matched typically fluent speakers (TFS) during spontaneously fluent overt and covert speech production tasks. Independent component analysis identified bilateral mu components from 24/27 PWS and matched TFS that localized over premotor cortex. Time-frequency analysis of the left hemisphere mu clusters demonstrated significantly reduced mu-alpha and mu-beta ERD (p(CLUSTER) < 0.05) in PWS across the time course of overt and covert speech production, while no group differences were found in the right hemisphere in any condition. Results were interpreted through the framework of State Feedback Control. They suggest that weak forward modeling and evaluation of sensory feedback across the time course of speech production characterizes the trait related sensorimotor impairment in PWS. This weakness is proposed to represent an underlying sensorimotor instability that may predispose the speech of PWS to breakdown