1
|
Orpella J, Flick G, Assaneo MF, Shroff R, Pylkkänen L, Poeppel D, Jackson ES. Reactive Inhibitory Control Precedes Overt Stuttering Events. NEUROBIOLOGY OF LANGUAGE (CAMBRIDGE, MASS.) 2024; 5:432-453. [PMID: 38911458 PMCID: PMC11192511 DOI: 10.1162/nol_a_00138] [Citation(s) in RCA: 0] [Impact Index Per Article: 0] [Reference Citation Analysis] [Abstract] [Key Words] [Grants] [Track Full Text] [Figures] [Subscribe] [Scholar Register] [Received: 08/21/2023] [Accepted: 02/06/2024] [Indexed: 06/25/2024]
Abstract
Research points to neurofunctional differences underlying fluent speech between stutterers and non-stutterers. Considerably less work has focused on processes that underlie stuttered vs. fluent speech. Additionally, most of this research has focused on speech motor processes despite contributions from cognitive processes prior to the onset of stuttered speech. We used MEG to test the hypothesis that reactive inhibitory control is triggered prior to stuttered speech. Twenty-nine stutterers completed a delayed-response task that featured a cue (prior to a go cue) signaling the imminent requirement to produce a word that was either stuttered or fluent. Consistent with our hypothesis, we observed increased beta power likely emanating from the right pre-supplementary motor area (R-preSMA)-an area implicated in reactive inhibitory control-in response to the cue preceding stuttered vs. fluent productions. Beta power differences between stuttered and fluent trials correlated with stuttering severity and participants' percentage of trials stuttered increased exponentially with beta power in the R-preSMA. Trial-by-trial beta power modulations in the R-preSMA following the cue predicted whether a trial would be stuttered or fluent. Stuttered trials were also associated with delayed speech onset suggesting an overall slowing or freezing of the speech motor system that may be a consequence of inhibitory control. Post-hoc analyses revealed that independently generated anticipated words were associated with greater beta power and more stuttering than researcher-assisted anticipated words, pointing to a relationship between self-perceived likelihood of stuttering (i.e., anticipation) and inhibitory control. This work offers a neurocognitive account of stuttering by characterizing cognitive processes that precede overt stuttering events.
Collapse
Affiliation(s)
- Joan Orpella
- Department of Neuroscience, Georgetown University Medical Center, Washington, DC, USA
- Department of Psychology, New York University, New York, NY, USA
- Department of Communicative Sciences and Disorders, New York University, New York, NY, USA
| | - Graham Flick
- Department of Psychology, New York University, New York, NY, USA
| | - M. Florencia Assaneo
- Institute of Neurobiology, National Autonomous University of Mexico, Mexico City, Mexico
| | - Ravi Shroff
- Department of Applied Statistics, Social Science, and Humanities, New York University, New York, NY, USA
| | - Liina Pylkkänen
- Department of Psychology, New York University, New York, NY, USA
- Department of Linguistics, New York University, New York, NY, USA
- NYUAD Institute, New York University Abu Dhabi, Abu Dhabi, United Arab Emirates
| | - David Poeppel
- Department of Psychology, New York University, New York, NY, USA
- Center for Language, Music and Emotion (CLaME), New York University, New York, NY, USA
- Ernst Strüngmann Institute (ESI) for Neuroscience, Frankfurt, Germany
| | - Eric S. Jackson
- Department of Communicative Sciences and Disorders, New York University, New York, NY, USA
| |
Collapse
|
2
|
Bayat M, Boostani R, Sabeti M, Yadegari F, Pirmoradi M, Rao KS, Nami M. Source Localization and Spectrum Analyzing of EEG in Stuttering State upon Dysfluent Utterances. Clin EEG Neurosci 2024; 55:371-383. [PMID: 36627837 DOI: 10.1177/15500594221150638] [Citation(s) in RCA: 0] [Impact Index Per Article: 0] [Reference Citation Analysis] [Abstract] [Key Words] [MESH Headings] [Track Full Text] [Journal Information] [Submit a Manuscript] [Subscribe] [Scholar Register] [Indexed: 01/12/2023]
Abstract
Purpose: The present study which addressed adults who stutter (AWS) attempted to investigate power spectral dynamics in the stuttering state by answering the questions using quantitative electroencephalography (qEEG). Method: A 64-channel electroencephalography (EEG) setup was used for data acquisition at 20 AWS. Since the speech, especially stuttering, causes significant noise in the EEG, 2 conditions of speech preparation (SP) and imagined speech (IS) were considered. EEG signals were decomposed into 6 bands. The corresponding sources were localized using the standard low-resolution electromagnetic tomography (sLORETA) tool in both fluent and dysfluent states. Results: Significant differences were noted after analyzing the time-locked EEG signals in fluent and dysfluent utterances. Consistent with previous studies, poor alpha and beta suppression in SP and IS conditions were localized in the left frontotemporal areas in a dysfluent state. This was partly true for the right frontal regions. In the theta range, disfluency was concurrence with increased activation in the left and right motor areas. Increased delta power in the left and right motor areas as well as increased beta2 power over left parietal regions was notable EEG features upon fluent speech. Conclusion: Based on the present findings and those of earlier studies, explaining the neural circuitries involved in stuttering probably requires an examination of the entire frequency spectrum involved in speech.
Collapse
Affiliation(s)
- Masoumeh Bayat
- Department of Neuroscience, School of Advanced Medical Sciences and Technologies, Shiraz University of Medical Sciences, Shiraz, Iran
| | - Reza Boostani
- Department of Computer Sciences and Engineering, School of Engineering, Shiraz University, Shiraz, Iran
| | - Malihe Sabeti
- Department of Computer Engineering, Islamic Azad University, North Tehran Branch, Tehran, Iran
| | - Fariba Yadegari
- Department of Speech and Language Pathology, University of Social Welfare and Rehabilitation Sciences, Tehran, Iran
| | - Mohammadreza Pirmoradi
- Department of Clinical Psychology, School of Behavioral Sciences and Mental Health, Iran University of Medical Sciences, Tehran, Iran
| | - K S Rao
- Neuroscience Center, INDICASAT-AIP, Panama City, Republic of Panama
| | - Mohammad Nami
- Department of Neuroscience, School of Advanced Medical Sciences and Technologies, Shiraz University of Medical Sciences, Shiraz, Iran
- Neuroscience Center, INDICASAT-AIP, Panama City, Republic of Panama
- Dana Brain Health Institute, Iranian Neuroscience Society-Fars Chapter, Shiraz, Iran
- Academy of Health, Senses Cultural Foundation, Sacramento, CA, USA
| |
Collapse
|
3
|
Liu X, Howell P. Can listeners predict whether or not a stutter follows a stretch of fluent speech? JOURNAL OF FLUENCY DISORDERS 2024; 79:106038. [PMID: 38290224 DOI: 10.1016/j.jfludis.2024.106038] [Citation(s) in RCA: 0] [Impact Index Per Article: 0] [Reference Citation Analysis] [Abstract] [Key Words] [MESH Headings] [Track Full Text] [Subscribe] [Scholar Register] [Received: 05/16/2023] [Revised: 01/12/2024] [Accepted: 01/17/2024] [Indexed: 02/01/2024]
Abstract
PURPOSE Neurophysiological studies report that people who stutter (PWS) exhibit enhanced motor preparation before they stutter. This motor preparation pattern raises the possibility of detecting upcoming stutter moments before they actually occur. This study examined whether these motor preparation differences are detectable by listeners in the corresponding acoustic signal, thereby allowing them to predict upcoming stuttering moments. If so, features in these acoustic patterns could potentially be employed by computational procedures to automate detection of upcoming stutters and to target auditory feedback alterations specifically on these locations. METHODS Forty healthy normal-hearing participants (aged 18-30) listened to seemingly fluent speech extracts each of which was either followed by a fluent (control condition) or stuttered (experimental condition) moment after the fluent extract. Participants listened to each extract and rated the likelihood of the speaker stuttering on the next word on a scale of 1 (very unlikely) to 7 (very likely) as to whether they thought there was a subsequent stutter. Several measures were made on the speech extracts which were examined either as control requirements to ensure no differences between experimental and control material or as covariates to assess any effects they had on judgments between the two conditions. RESULTS Listeners gave significantly higher stutter-likelihood ratings for speech originally followed by a stuttered moment although effects were small. CONCLUSIONS Naive listeners rated speech extracts that were subsequently followed by stuttered moments as more likely to be followed by a stutter than those that were followed by fluent words after the effects of significant covariates were excluded.
Collapse
Affiliation(s)
- Xena Liu
- Department of Experimental Psychology, University College London, 26 Bedford Way, London WC1H 0AP, UK.
| | - Peter Howell
- Department of Experimental Psychology, University College London, 26 Bedford Way, London WC1H 0AP, UK.
| |
Collapse
|
4
|
Caruso VC, Wray AH, Lescht E, Chang SE. Neural oscillatory activity and connectivity in children who stutter during a non-speech motor task. J Neurodev Disord 2023; 15:40. [PMID: 37964200 PMCID: PMC10647051 DOI: 10.1186/s11689-023-09507-8] [Citation(s) in RCA: 0] [Impact Index Per Article: 0] [Reference Citation Analysis] [Abstract] [Key Words] [MESH Headings] [Grants] [Track Full Text] [Journal Information] [Submit a Manuscript] [Subscribe] [Scholar Register] [Received: 11/18/2022] [Accepted: 10/25/2023] [Indexed: 11/16/2023] Open
Abstract
BACKGROUND Neural motor control rests on the dynamic interaction of cortical and subcortical regions, which is reflected in the modulation of oscillatory activity and connectivity in multiple frequency bands. Motor control is thought to be compromised in developmental stuttering, particularly involving circuits in the left hemisphere that support speech, movement initiation, and timing control. However, to date, evidence comes from adult studies, with a limited understanding of motor processes in childhood, closer to the onset of stuttering. METHODS We investigated the neural control of movement initiation in children who stutter and children who do not stutter by evaluating transient changes in EEG oscillatory activity (power, phase locking to button press) and connectivity (phase synchronization) during a simple button press motor task. We compared temporal changes in these oscillatory dynamics between the left and right hemispheres and between children who stutter and children who do not stutter, using mixed-model analysis of variance. RESULTS We found reduced modulation of left hemisphere oscillatory power, phase locking to button press and phase connectivity in children who stutter compared to children who do not stutter, consistent with previous findings of dysfunction within the left sensorimotor circuits. Interhemispheric connectivity was weaker at lower frequencies (delta, theta) and stronger in the beta band in children who stutter than in children who do not stutter. CONCLUSIONS Taken together, these findings indicate weaker engagement of the contralateral left motor network in children who stutter even during low-demand non-speech tasks, and suggest that the right hemisphere might be recruited to support sensorimotor processing in childhood stuttering. Differences in oscillatory dynamics occurred despite comparable task performance between groups, indicating that an altered balance of cortical activity might be a core aspect of stuttering, observable during normal motor behavior.
Collapse
Affiliation(s)
- Valeria C Caruso
- Department of Psychiatry, University of Michigan, Ann Arbor, MI, USA.
- Department of Psychology, University of Michigan, Ann Arbor, MI, USA.
| | - Amanda Hampton Wray
- Department of Communication Science & Disorders, University of Pittsburgh, Pittsburgh, PA, USA
| | - Erica Lescht
- Department of Communication Science & Disorders, University of Pittsburgh, Pittsburgh, PA, USA
| | - Soo-Eun Chang
- Department of Psychiatry, University of Michigan, Ann Arbor, MI, USA
- Department of Communication Disorders, Ewha Womans University, Seoul, South Korea
| |
Collapse
|
5
|
Sheikh SA, Sahidullah M, Hirsch F, Ouni S. Machine learning for stuttering identification: Review, challenges and future directions. Neurocomputing 2022. [DOI: 10.1016/j.neucom.2022.10.015] [Citation(s) in RCA: 2] [Impact Index Per Article: 1.0] [Reference Citation Analysis] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 11/13/2022]
|
6
|
Kidwai J, Brumberg JS, Marsh BM. A Neural Marker of Speech Intention: Evidence From Contingent Negative Variation. JOURNAL OF SPEECH, LANGUAGE, AND HEARING RESEARCH : JSLHR 2021; 64:2392-2399. [PMID: 33684301 PMCID: PMC8758324 DOI: 10.1044/2020_jslhr-20-00277] [Citation(s) in RCA: 0] [Impact Index Per Article: 0] [Reference Citation Analysis] [Abstract] [MESH Headings] [Grants] [Track Full Text] [Subscribe] [Scholar Register] [Received: 05/21/2020] [Revised: 08/06/2020] [Accepted: 10/19/2020] [Indexed: 06/12/2023]
Abstract
Purpose This study investigated whether changes in brain activity preceding spoken words can be used as a neural marker of speech intention. Specifically, changes in the contingent negative variation (CNV) were examined prior to speech production in three different study designs to determine a method that maximizes signal detection in a speaking task. Method Electroencephalography data were collected in three different protocols to elicit the CNV in a spoken word task that varied the timing and type of linguistic information. The first protocol provided participants with the word to be spoken before the instruction of whether or not to speak, the second provided both the word and the instruction to speak, and the third provided the instruction to speak before the word. Participants (N = 18) were split into three groups (one for each protocol) and were instructed to either speak (Go) or refrain from speaking (NoGo) each word according to task instructions. The CNV was measured by analyzing the difference in slope between Go and NoGo trials. Results Statistically significant effects of hemispheric laterality on the CNV slope confirm the third protocol where the participants know they will speak in advance of the word, as the paradigm that reliably elicits a CNV response related to speech intention. Conclusions The maximal CNV response when the instruction is known before the word indicates the neural processing measured in this protocol may reflect a generalized speech intention process in which the speech-language systems become prepared to speak and then execute production once the word information is provided. Further analysis of the optimal protocol identified in this study requires additional experimental investigation to confirm its role in eliciting an objective marker of speech intention. Supplemental Material https://doi.org/10.23641/asha.14111468.
Collapse
Affiliation(s)
- Juhi Kidwai
- Department of Speech-Language-Hearing: Sciences & Disorders, The University of Kansas, Lawrence
| | - Jonathan S. Brumberg
- Department of Speech-Language-Hearing: Sciences & Disorders, Neuroscience Graduate Program, The University of Kansas, Lawrence
| | | |
Collapse
|
7
|
Tezel-Bayraktaroglu O, Bayraktaroglu Z, Demirtas-Tatlidede A, Demiralp T, Oge AE. Neuronavigated rTMS inhibition of right pars triangularis anterior in stuttering: Differential effects on reading and speaking. BRAIN AND LANGUAGE 2020; 210:104862. [PMID: 32979643 DOI: 10.1016/j.bandl.2020.104862] [Citation(s) in RCA: 1] [Impact Index Per Article: 0.3] [Reference Citation Analysis] [Abstract] [Key Words] [MESH Headings] [Track Full Text] [Subscribe] [Scholar Register] [Received: 11/03/2019] [Revised: 09/09/2020] [Accepted: 09/10/2020] [Indexed: 06/11/2023]
Abstract
Functional neuroimaging studies show an overactivation of speech and language related homologous areas of the right hemisphere in persons who stutter. In this study, we inhibited Broca's homologues using 1 Hz repetitive transcranial magnetic stimulation (rTMS) and assessed its effects on stuttering severity. The investigated cortical areas included pars opercularis (BA44), anterior and posterior pars triangularis (BA45), mouth area on the primary motor cortex (BA4). We collected reading and speaking samples before and after rTMS sessions and calculated the percentage of syllables stuttered. Only right anterior pars triangularis stimulation induced significant changes in speech fluency. Notably, the effects were differential for reading and speaking conditions. Overall, our results provide supportive evidence that right anterior BA45 may be a critical region for stuttering. The observed differential effects following the inhibition of right anterior BA45 merits further study of contributions of this region on different language domains in persons who stutter.
Collapse
Affiliation(s)
| | - Zubeyir Bayraktaroglu
- Istanbul Medipol University, International School of Medicine, Department of Physiology, 34815 Beykoz, Istanbul, Turkey; Istanbul Medipol University, Research Institute for Health Sciences and Technologies (SABITA), Restorative and Regenerative Medicine Research Center (REMER), functional Imaging and Cognitive Affective Neuroscience Laboratory (fINCAN), 34810 Beykoz, Istanbul, Turkey
| | - Asli Demirtas-Tatlidede
- Istanbul University, Istanbul Faculty of Medicine, Department of Neurology, 34093 Capa, Istanbul, Turkey; Bahcesehir University, School of Medicine, Department of Neurology, 34734 Kadikoy, Istanbul, Turkey
| | - Tamer Demiralp
- Istanbul University, Hulusi Behcet Life Sciences Research Laboratory-Neuroimaging Unit, 34093 Capa, Istanbul, Turkey; Istanbul University, Istanbul Faculty of Medicine, Department of Physiology, 34093 Capa, Istanbul, Turkey
| | - A Emre Oge
- Istanbul University, Istanbul Faculty of Medicine, Department of Neurology, 34093 Capa, Istanbul, Turkey
| |
Collapse
|
8
|
Busan P. Developmental stuttering and the role of the supplementary motor cortex. JOURNAL OF FLUENCY DISORDERS 2020; 64:105763. [PMID: 32361030 DOI: 10.1016/j.jfludis.2020.105763] [Citation(s) in RCA: 13] [Impact Index Per Article: 3.3] [Reference Citation Analysis] [Abstract] [Key Words] [MESH Headings] [Track Full Text] [Subscribe] [Scholar Register] [Received: 06/05/2018] [Revised: 04/05/2020] [Accepted: 04/08/2020] [Indexed: 06/11/2023]
Abstract
Developmental stuttering is a frequent neurodevelopmental disorder with a complex neurobiological basis. Robust neural markers of stuttering include imbalanced activity of speech and motor related brain regions, and their impaired structural connectivity. The dynamic interaction of cortical regions is regulated by the cortico-basal ganglia-thalamo-cortical system with the supplementary motor area constituting a crucial cortical site. The SMA integrates information from different neural circuits, and manages information about motor programs such as self-initiated movements, motor sequences, and motor learning. Abnormal functioning of SMA is increasingly reported in stuttering, and has been recently indicated as an additional "neural marker" of DS: anatomical and functional data have documented abnormal structure and activity of the SMA, especially in motor and speech networks. Its connectivity is often impaired, especially when considering networks of the left hemisphere. Compatibly, recent data suggest that, in DS, SMA is part of a poorly synchronized neural network, thus resulting in a likely substrate for the appearance of DS symptoms. However, as evident when considering neural models of stuttering, the role of SMA has not been fully clarified. Herein, the available evidence is reviewed, which highlights the role of the SMA in DS as a neural "hub", receiving and conveying altered information, thus "gating" the release of correct or abnormal motor plans.
Collapse
|
9
|
Jenson D, Bowers AL, Hudock D, Saltuklaroglu T. The Application of EEG Mu Rhythm Measures to Neurophysiological Research in Stuttering. Front Hum Neurosci 2020; 13:458. [PMID: 31998103 PMCID: PMC6965028 DOI: 10.3389/fnhum.2019.00458] [Citation(s) in RCA: 19] [Impact Index Per Article: 4.8] [Reference Citation Analysis] [Abstract] [Key Words] [Grants] [Track Full Text] [Download PDF] [Figures] [Journal Information] [Subscribe] [Scholar Register] [Received: 08/01/2019] [Accepted: 12/13/2019] [Indexed: 11/29/2022] Open
Abstract
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.
Collapse
Affiliation(s)
- David Jenson
- Department of Speech and Hearing Sciences, Elson S. Floyd College of Medicine, Washington State University, Spokane, WA, United States
| | - Andrew L. Bowers
- Epley Center for Health Professions, Communication Sciences and Disorders, University of Arkansas, Fayetteville, AR, United States
| | - Daniel Hudock
- Department of Communication Sciences and Disorders, Idaho State University, Pocatello, ID, United States
| | - Tim Saltuklaroglu
- College of Health Professions, Department of Audiology and Speech-Pathology, University of Tennessee Health Science Center, Knoxville, TN, United States
| |
Collapse
|
10
|
Sengupta R, Yaruss JS, Loucks TM, Gracco VL, Pelczarski K, Nasir SM. Theta Modulated Neural Phase Coherence Facilitates Speech Fluency in Adults Who Stutter. Front Hum Neurosci 2019; 13:394. [PMID: 31798431 PMCID: PMC6878001 DOI: 10.3389/fnhum.2019.00394] [Citation(s) in RCA: 3] [Impact Index Per Article: 0.6] [Reference Citation Analysis] [Abstract] [Key Words] [Track Full Text] [Download PDF] [Figures] [Journal Information] [Subscribe] [Scholar Register] [Received: 06/24/2019] [Accepted: 10/22/2019] [Indexed: 12/03/2022] Open
Abstract
Adults who stutter (AWS) display altered patterns of neural phase coherence within the speech motor system preceding disfluencies. These altered patterns may distinguish fluent speech episodes from disfluent ones. Phase coherence is relevant to the study of stuttering because it reflects neural communication within brain networks. In this follow-up study, the oscillatory cortical dynamics preceding fluent speech in AWS and adults who do not stutter (AWNS) were examined during a single-word delayed reading task using electroencephalographic (EEG) techniques. Compared to AWNS, fluent speech preparation in AWS was characterized by a decrease in theta-gamma phase coherence and a corresponding increase in theta-beta coherence level. Higher spectral powers in the beta and gamma bands were also observed preceding fluent utterances by AWS. Overall, there was altered neural communication during speech planning in AWS that provides novel evidence for atypical allocation of feedforward control by AWS even before fluent utterances.
Collapse
Affiliation(s)
- Ranit Sengupta
- Department of Communication Sciences and Disorders, Northwestern University, Evanston, IL, United States
| | - J Scott Yaruss
- Department of Communicative Sciences and Disorders, Michigan State University, East Lansing, MI, United States
| | - Torrey M Loucks
- Department of Communication Sciences and Disorders, Faculty of Rehabilitation Medicine, University of Alberta, Edmonton, AB, Canada.,Institute for Stuttering Treatment and Research, Faculty of Rehabilitation Medicine, University of Alberta, Edmonton, AB, Canada
| | | | - Kristin Pelczarski
- School of Family Studies and Human Services, Kansas State University, Manhattan, KS, United States
| | - Sazzad M Nasir
- Haskins Laboratories, New Haven, CT, United States.,Indiana Academy, Ball State University, Muncie, IN, United States
| |
Collapse
|
11
|
Vreeswijk SME, Hoang TNL, Korzeczek A, Neef NE, Wolff von Gudenberg A, Paulus W, Sommer M. No Evidence for Dystonia-Like Sensory Overflow of Tongue Representations in Adults Who Stutter. Front Hum Neurosci 2019; 13:336. [PMID: 31636553 PMCID: PMC6787140 DOI: 10.3389/fnhum.2019.00336] [Citation(s) in RCA: 1] [Impact Index Per Article: 0.2] [Reference Citation Analysis] [Abstract] [Key Words] [Track Full Text] [Download PDF] [Figures] [Journal Information] [Subscribe] [Scholar Register] [Received: 06/05/2019] [Accepted: 09/12/2019] [Indexed: 11/13/2022] Open
Abstract
Persistent developmental stuttering (PDS) disrupts speech fluency in about 1% of adults. Although many models of speech production assume an intact sensory feedback from the speech organs to the brain, very little is actually known about the integrity of their sensory representation in PDS. Here, we studied somatosensory evoked potentials (SEPs) in adults who stutter (AWS), with the aim of probing the integrity of sensory pathways. In addition, we tested the processing of dual sensory input to address a putative link between stuttering and focal dystonia. In 15 AWS (aged 15-55 years; three females) and 14 matched fluent speaking adults (ANS), we recorded SEPs at C5' and C6' induced by stimulating separately or simultaneously the tongue or the cheek at the corner of the mouth. We determined latencies (N13, P19, and N27) and peak-to-peak amplitudes (N13-P19, P19-N27). We divided amplitudes from simultaneous stimulation by the sum of those from separate stimulation. Amplitude ratios did not differ between groups, indicating normal processing of dual sensory input. This does not support a clinical analogy between focal dystonia and persistent stuttering. SEP latencies as a measure of transmission speed in sensory pathways were significantly shorter in stuttering subjects than in fluent speaking participants, however, this might have been related to a trend for a height difference between groups, and was not confirmed in a replication dataset. In summary, we did not find evidence for dystonia-like sensory overflow of tongue representations in AWS.
Collapse
Affiliation(s)
- Sarah M E Vreeswijk
- Department of Clinical Neurophysiology, University Medical Center Göttingen, Georg-August-University, Göttingen, Germany
| | - T N Linh Hoang
- Department of Clinical Neurophysiology, University Medical Center Göttingen, Georg-August-University, Göttingen, Germany
| | - Alexandra Korzeczek
- Department of Clinical Neurophysiology, University Medical Center Göttingen, Georg-August-University, Göttingen, Germany
| | - Nicole E Neef
- Department of Neuropsychology, Max Planck Institute for Human Cognitive and Brain Sciences, Leipzig, Germany
| | | | - Walter Paulus
- Department of Clinical Neurophysiology, University Medical Center Göttingen, Georg-August-University, Göttingen, Germany
| | - Martin Sommer
- Department of Clinical Neurophysiology, University Medical Center Göttingen, Georg-August-University, Göttingen, Germany
| |
Collapse
|
12
|
Chang SE, Garnett EO, Etchell A, Chow HM. Functional and Neuroanatomical Bases of Developmental Stuttering: Current Insights. Neuroscientist 2018; 25:566-582. [PMID: 30264661 DOI: 10.1177/1073858418803594] [Citation(s) in RCA: 38] [Impact Index Per Article: 6.3] [Reference Citation Analysis] [Abstract] [Key Words] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 12/28/2022]
Abstract
Affecting 5% of all preschool-aged children and 1% of the general population, developmental stuttering-also called childhood-onset fluency disorder-is a complex, multifactorial neurodevelopmental disorder characterized by frequent disruption of the fluent flow of speech. Over the past two decades, neuroimaging studies of both children and adults who stutter have begun to provide significant insights into the neurobiological bases of stuttering. This review highlights convergent findings from this body of literature with a focus on functional and structural neuroimaging results that are supported by theoretically driven neurocomputational models of speech production. Updated views on possible mechanisms of stuttering onset and persistence, and perspectives on promising areas for future research into the mechanisms of stuttering, are discussed.
Collapse
Affiliation(s)
- Soo-Eun Chang
- Department of Psychiatry, University of Michigan, Ann Arbor, MI, USA
| | - Emily O Garnett
- Department of Psychiatry, University of Michigan, Ann Arbor, MI, USA
| | - Andrew Etchell
- Department of Psychiatry, University of Michigan, Ann Arbor, MI, USA
| | - Ho Ming Chow
- Nemours/Alfred I. DuPont Hospital for Children, Wilmington, DE, USA
| |
Collapse
|
13
|
Jenson D, Reilly KJ, Harkrider AW, Thornton D, Saltuklaroglu T. Trait related sensorimotor deficits in people who stutter: An EEG investigation of μ rhythm dynamics during spontaneous fluency. Neuroimage Clin 2018; 19:690-702. [PMID: 29872634 PMCID: PMC5986168 DOI: 10.1016/j.nicl.2018.05.026] [Citation(s) in RCA: 10] [Impact Index Per Article: 1.7] [Reference Citation Analysis] [Abstract] [MESH Headings] [Track Full Text] [Download PDF] [Figures] [Journal Information] [Subscribe] [Scholar Register] [Received: 10/13/2017] [Revised: 03/28/2018] [Accepted: 05/20/2018] [Indexed: 01/09/2023]
Abstract
Stuttering is associated with compromised sensorimotor control (i.e., internal modeling) across the dorsal stream and oscillations of EEG mu (μ) rhythms have been proposed as reliable indices of anterior dorsal stream processing. The purpose of this study was to compare μ 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 μ components from 24/27 PWS and matched TFS that localized over premotor cortex. Time-frequency analysis of the left hemisphere μ clusters demonstrated significantly reduced μ-α and μ-β ERD (pCLUSTER < 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.
Collapse
Affiliation(s)
- David Jenson
- University of Tennessee Health Science Center, Dept. of Audiology and Speech Pathology, United States.
| | - Kevin J Reilly
- University of Tennessee Health Science Center, Dept. of Audiology and Speech Pathology, United States
| | - Ashley W Harkrider
- University of Tennessee Health Science Center, Dept. of Audiology and Speech Pathology, United States
| | - David Thornton
- University of Tennessee Health Science Center, Dept. of Audiology and Speech Pathology, United States
| | - Tim Saltuklaroglu
- University of Tennessee Health Science Center, Dept. of Audiology and Speech Pathology, United States
| |
Collapse
|
14
|
Sengupta R, Shah S, Loucks TMJ, Pelczarski K, Scott Yaruss J, Gore K, Nasir SM. Cortical dynamics of disfluency in adults who stutter. Physiol Rep 2018; 5:5/9/e13194. [PMID: 28483857 PMCID: PMC5430117 DOI: 10.14814/phy2.13194] [Citation(s) in RCA: 10] [Impact Index Per Article: 1.7] [Reference Citation Analysis] [Abstract] [Key Words] [Track Full Text] [Download PDF] [Figures] [Journal Information] [Subscribe] [Scholar Register] [Received: 01/18/2017] [Accepted: 01/27/2017] [Indexed: 01/21/2023] Open
Abstract
Stuttering is a disorder of speech production whose origins have been traced to the central nervous system. One of the factors that may underlie stuttering is aberrant neural miscommunication within the speech motor network. It is thus argued that disfluency (any interruption in the forward flow of speech) in adults who stutter (AWS) could be associated with anomalous cortical dynamics. Aberrant brain activity has been demonstrated in AWS in the absence of overt disfluency, but recording neural activity during disfluency is more challenging. The paradigm adopted here took an important step that involved overt reading of long and complex speech tokens under continuous EEG recording. Anomalies in cortical dynamics preceding disfluency were assessed by subtracting out neural activity for fluent utterances from their disfluent counterparts. Differences in EEG spectral power involving alpha, beta, and gamma bands, as well as anomalies in phase-coherence involving the gamma band, were observed prior to the production of the disfluent utterances. These findings provide novel evidence for compromised cortical dynamics that directly precede disfluency in AWS.
Collapse
Affiliation(s)
- Ranit Sengupta
- Department of Communication Sciences and Disorders, Northwestern University, Evanston, Illinois
| | - Shalin Shah
- Department of Communication Sciences and Disorders, Northwestern University, Evanston, Illinois
| | - Torrey M J Loucks
- Department of Speech and Hearing Science, University of Illinois at Urbana-Champaign, Champaign, Illinois
| | - Kristin Pelczarski
- School of Family Studies and Human Services, Kansas State University, Manhattan, Kansas
| | - J Scott Yaruss
- Department of Communication Sciences and Disorders, University of Pittsburgh, Pittsburgh, Pennsylvania
| | | | - Sazzad M Nasir
- Department of Communication Sciences and Disorders, Northwestern University, Evanston, Illinois
| |
Collapse
|
15
|
Etchell AC, Civier O, Ballard KJ, Sowman PF. A systematic literature review of neuroimaging research on developmental stuttering between 1995 and 2016. JOURNAL OF FLUENCY DISORDERS 2018; 55:6-45. [PMID: 28778745 DOI: 10.1016/j.jfludis.2017.03.007] [Citation(s) in RCA: 73] [Impact Index Per Article: 12.2] [Reference Citation Analysis] [Abstract] [Key Words] [MESH Headings] [Track Full Text] [Subscribe] [Scholar Register] [Received: 07/23/2016] [Revised: 01/25/2017] [Accepted: 03/06/2017] [Indexed: 05/14/2023]
Abstract
PURPOSE Stuttering is a disorder that affects millions of people all over the world. Over the past two decades, there has been a great deal of interest in investigating the neural basis of the disorder. This systematic literature review is intended to provide a comprehensive summary of the neuroimaging literature on developmental stuttering. It is a resource for researchers to quickly and easily identify relevant studies for their areas of interest and enable them to determine the most appropriate methodology to utilize in their work. The review also highlights gaps in the literature in terms of methodology and areas of research. METHODS We conducted a systematic literature review on neuroimaging studies on developmental stuttering according to the PRISMA guidelines. We searched for articles in the pubmed database containing "stuttering" OR "stammering" AND either "MRI", "PET", "EEG", "MEG", "TMS"or "brain" that were published between 1995/01/01 and 2016/01/01. RESULTS The search returned a total of 359 items with an additional 26 identified from a manual search. Of these, there were a total of 111 full text articles that met criteria for inclusion in the systematic literature review. We also discuss neuroimaging studies on developmental stuttering published throughout 2016. The discussion of the results is organized first by methodology and second by population (i.e., adults or children) and includes tables that contain all items returned by the search. CONCLUSIONS There are widespread abnormalities in the structural architecture and functional organization of the brains of adults and children who stutter. These are evident not only in speech tasks, but also non-speech tasks. Future research should make greater use of functional neuroimaging and noninvasive brain stimulation, and employ structural methodologies that have greater sensitivity. Newly planned studies should also investigate sex differences, focus on augmenting treatment, examine moments of dysfluency and longitudinally or cross-sectionally investigate developmental trajectories in stuttering.
Collapse
Affiliation(s)
- Andrew C Etchell
- Department of Psychiatry, University of Michigan, MI, United States; Department of Cognitive Science, Macquarie University, Sydney, Australia.
| | - Oren Civier
- The Gonda Multidisciplinary Brain Research Center, Bar-Ilan University, Ramat-Gan, Israel; Department of Computer Science and Applied Mathematics, Weizmann Institute of Science, Rehovot, Israel
| | - Kirrie J Ballard
- Faculty of Health Sciences, University of Sydney, Sydney, Australia
| | - Paul F Sowman
- Department of Cognitive Science, Macquarie University, Sydney, Australia
| |
Collapse
|
16
|
Mersov A, Cheyne D, Jobst C, De Nil L. A preliminary study on the neural oscillatory characteristics of motor preparation prior to dysfluent and fluent utterances in adults who stutter. JOURNAL OF FLUENCY DISORDERS 2018; 55:145-155. [PMID: 28577876 DOI: 10.1016/j.jfludis.2017.05.003] [Citation(s) in RCA: 7] [Impact Index Per Article: 1.2] [Reference Citation Analysis] [Abstract] [Key Words] [MESH Headings] [Track Full Text] [Subscribe] [Scholar Register] [Received: 07/28/2016] [Revised: 04/14/2017] [Accepted: 05/14/2017] [Indexed: 06/07/2023]
Abstract
PURPOSE Recent literature on speech production in adults who stutter (AWS) has begun to investigate the neural mechanisms characterizing speech-motor preparation prior to speech onset. Compelling evidence has suggested that stuttering is associated with atypical processing within cortical and sub-cortical motor networks, particularly in the beta frequency range, that is effective before speech production even begins. Due to low stuttering frequency in experimental settings, however, the literature has so far predominantly reported on fluent speech production in AWS. Consequently, we have limited understanding of the way in which fluent speech processing in AWS is disturbed leading to a dysfluency. This preliminary study aims to characterize neural motor preparation prior to stuttered utterances in AWS. METHODS Eight AWS participated in the study. A total of 336 stuttered utterances were compared to the participants' own fluent utterance productions. Beta oscillatory activity was analyzed with magnetoencephalography (MEG) and localized using minimum-variance beamforming. RESULTS Preparation for speech production induced beta suppression in the bilateral premotor and motor cortex prior to speech onset. Although the data revealed some interesting trends, no significant differences between fluent and stuttered utterances were present. This may be due to a relatively low and variable number of stuttered trials analyzed in individual subjects. CONCLUSION While the lack of significant differences may have resulted from the relatively low numbers of stuttered utterances across subjects, the observed trends demonstrated that the proposed methodology and experimental paradigm is a promising approach for future studies aiming to characterize differences between stuttered and fluent speech.
Collapse
Affiliation(s)
- Anna Mersov
- Department of Speech-Language Pathology, University of Toronto, Toronto, ON, Canada.
| | - Douglas Cheyne
- Department of Speech-Language Pathology, University of Toronto, Toronto, ON, Canada; Program in Neurosciences and Mental Health, Hospital for Sick Children Research Institute, Toronto, Ontario M5G 0A4, Canada; Department of Medical Imaging, University of Toronto, Toronto, Ontario M5T 1W7, Canada
| | - Cecilia Jobst
- Program in Neurosciences and Mental Health, Hospital for Sick Children Research Institute, Toronto, Ontario M5G 0A4, Canada
| | - Luc De Nil
- Department of Speech-Language Pathology, University of Toronto, Toronto, ON, Canada
| |
Collapse
|
17
|
Furini J, Picoloto LA, Marconato E, Bohnen AJ, Cardoso ACV, Oliveira CMCD. The role of auditory temporal cues in the fluency of stuttering adults. REVISTA CEFAC 2017. [DOI: 10.1590/1982-021620171954417] [Citation(s) in RCA: 1] [Impact Index Per Article: 0.1] [Reference Citation Analysis] [Abstract] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 11/22/2022] Open
Abstract
ABSTRACT Purpose: to compare the frequency of disfluencies and speech rate in spontaneous speech and reading in adults with and without stuttering in non-altered and delayed auditory feedback (NAF, DAF). Methods: participants were 30 adults: 15 with Stuttering (Research Group - RG), and 15 without stuttering (Control Group - CG). The procedures were: audiological assessment and speech fluency evaluation in two listening conditions, normal and delayed auditory feedback (100 milliseconds delayed by Fono Tools software). Results: the DAF caused a significant improvement in the fluency of spontaneous speech in RG when compared to speech under NAF. The effect of DAF was different in CG, because it increased the common disfluencies and the total of disfluencies in spontaneous speech and reading, besides showing an increase in the frequency of stuttering-like disfluencies in reading. The intergroup analysis showed significant differences in the two speech tasks for the two listening conditions in the frequency of stuttering-like disfluencies and in the total of disfluencies, and in the flows of syllable and word-per-minute in the NAF. Conclusion: the results demonstrated that delayed auditory feedback promoted fluency in spontaneous speech of adults who stutter, without interfering in the speech rate. In non-stuttering adults an increase occurred in the number of common disfluencies and total of disfluencies as well as reduction of speech rate in spontaneous speech and reading.
Collapse
|
18
|
Metzger FL, Auer T, Helms G, Paulus W, Frahm J, Sommer M, Neef NE. Shifted dynamic interactions between subcortical nuclei and inferior frontal gyri during response preparation in persistent developmental stuttering. Brain Struct Funct 2017; 223:165-182. [PMID: 28741037 PMCID: PMC5772149 DOI: 10.1007/s00429-017-1476-1] [Citation(s) in RCA: 13] [Impact Index Per Article: 1.9] [Reference Citation Analysis] [Abstract] [Key Words] [Track Full Text] [Download PDF] [Figures] [Journal Information] [Subscribe] [Scholar Register] [Received: 09/23/2016] [Accepted: 07/07/2017] [Indexed: 11/29/2022]
Abstract
Persistent developmental stuttering is associated with basal ganglia dysfunction or dopamine dysregulation. Here, we studied whole-brain functional connectivity to test how basal ganglia structures coordinate and reorganize sensorimotor brain networks in stuttering. To this end, adults who stutter and fluent speakers (control participants) performed a response anticipation paradigm in the MRI scanner. The preparation of a manual Go/No-Go response reliably produced activity in the basal ganglia and thalamus and particularly in the substantia nigra. Strikingly, in adults who stutter, substantia nigra activity correlated positively with stuttering severity. Furthermore, functional connectivity analyses yielded altered task-related network formations in adults who stutter compared to fluent speakers. Specifically, in adults who stutter, the globus pallidus and the thalamus showed increased network synchronization with the inferior frontal gyrus. This implies dynamic shifts in the response preparation-related network organization through the basal ganglia in the context of a non-speech motor task in stuttering. Here we discuss current findings in the traditional framework of how D1 and D2 receptor activity shapes focused movement selection, thereby suggesting a disproportional involvement of the direct and the indirect pathway in stuttering.
Collapse
Affiliation(s)
- F Luise Metzger
- Department of Clinical Neurophysiology, Georg August University, Göttingen, Germany
| | - Tibor Auer
- Biomedizinische NMR Forschungs GmbH am Max-Planck-Institut für Biophysikalische Chemie, Göttingen, Germany.,MRC Cognition and Brain Sciences Unit, Cambridge, UK.,Department of Psychology, Royal Holloway, University of London, Egham, UK
| | - Gunther Helms
- Department of Medical Radiation Physics, Lund University, Lund, Sweden
| | - Walter Paulus
- Department of Clinical Neurophysiology, Georg August University, Göttingen, Germany
| | - Jens Frahm
- Biomedizinische NMR Forschungs GmbH am Max-Planck-Institut für Biophysikalische Chemie, Göttingen, Germany
| | - Martin Sommer
- Department of Clinical Neurophysiology, Georg August University, Göttingen, Germany
| | - Nicole E Neef
- Department of Clinical Neurophysiology, Georg August University, Göttingen, Germany. .,Department of Neuropsychology, Max Planck Institute for Human Cognitive and Brain Sciences, Stephanstraße 1a, 04103, Leipzig, Germany.
| |
Collapse
|
19
|
Busan P, Battaglini P, Sommer M. Transcranial magnetic stimulation in developmental stuttering: Relations with previous neurophysiological research and future perspectives. Clin Neurophysiol 2017; 128:952-964. [DOI: 10.1016/j.clinph.2017.03.039] [Citation(s) in RCA: 9] [Impact Index Per Article: 1.3] [Reference Citation Analysis] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 09/25/2016] [Revised: 03/14/2017] [Accepted: 03/22/2017] [Indexed: 10/19/2022]
|
20
|
Silva PBD, Fabron EMG, Picoloto LA, Oliveira CMCD. Prolongamentos na fala de adultos com e sem gagueira. REVISTA CEFAC 2016. [DOI: 10.1590/1982-021620161856116] [Citation(s) in RCA: 0] [Impact Index Per Article: 0] [Reference Citation Analysis] [Abstract] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 11/21/2022] Open
Abstract
RESUMO Objetivo: realizar uma análise quantitativa e qualitativa dos prolongamentos de adultos com e sem gagueira. Métodos: os participantes foram divididos em: Grupo de Pesquisa (GP, 15 adultos com gagueira) e Grupo Controle (GC, 15 fluentes). Os procedimentos utilizados foram: avaliação da fluência, Instrumento de Gravidade da Gagueira e análises quantitativa e qualitativa dos prolongamentos. Resultados: GP mostrou maior número de prolongamentos não hesitativos, enquanto que GC mostrou maior ocorrência de prolongamentos hesitativos em relação ao total das disfluências. Prolongamentos não hesitativos ocorreram com maior frequência na palavra inicial e monossilábica, bem como na posição medial da frase para GP. Em relação à tensão muscular e duração, observou-se diferença apenas para a tensão muscular nos prolongamentos não hesitativos com maior média de ocorrência para GP. Conclusão: os prolongamentos não hesitativos ocorreram com maior frequência no GP, nas palavras iniciais, monossílabos e na posição medial da frase. Qualitativamente a tensão muscular foi uma característica típica dos prolongamentos não hesitativos no GP. Com relação aos prolongamentos hesitativos houve semelhança entre os adultos dos dois grupos quanto à frequência em relação ao total da fala, a posição dos prolongamentos nas palavras e nas frases e nos aspectos qualitativos, relacionados a tensão muscular e duração.
Collapse
|
21
|
Neef NE, Bütfering C, Anwander A, Friederici AD, Paulus W, Sommer M. Left posterior-dorsal area 44 couples with parietal areas to promote speech fluency, while right area 44 activity promotes the stopping of motor responses. Neuroimage 2016; 142:628-644. [PMID: 27542724 DOI: 10.1016/j.neuroimage.2016.08.030] [Citation(s) in RCA: 46] [Impact Index Per Article: 5.8] [Reference Citation Analysis] [Abstract] [Key Words] [MESH Headings] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 06/05/2016] [Revised: 08/03/2016] [Accepted: 08/15/2016] [Indexed: 01/03/2023] Open
Abstract
Area 44 is a cytoarchitectonically distinct portion of Broca's region. Parallel and overlapping large-scale networks couple with this region thereby orchestrating heterogeneous language, cognitive, and motor functions. In the context of stuttering, area 44 frequently comes into focus because structural and physiological irregularities affect developmental trajectories, stuttering severity, persistency, and etiology. A remarkable phenomenon accompanying stuttering is the preserved ability to sing. Speaking and singing are connatural behaviours recruiting largely overlapping brain networks including left and right area 44. Analysing which potential subregions of area 44 are malfunctioning in adults who stutter, and what effectively suppresses stuttering during singing, may provide a better understanding of the coordination and reorganization of large-scale brain networks dedicated to speaking and singing in general. We used fMRI to investigate functionally distinct subregions of area 44 during imagery of speaking and imaginary of humming a melody in 15 dextral males who stutter and 17 matched control participants. Our results are fourfold. First, stuttering was specifically linked to a reduced activation of left posterior-dorsal area 44, a subregion that is involved in speech production, including phonological word processing, pitch processing, working memory processes, sequencing, motor planning, pseudoword learning, and action inhibition. Second, functional coupling between left posterior area 44 and left inferior parietal lobule was deficient in stuttering. Third, despite the preserved ability to sing, males who stutter showed bilaterally a reduced activation of area 44 when imagine humming a melody, suggesting that this fluency-enhancing condition seems to bypass posterior-dorsal area 44 to achieve fluency. Fourth, time courses of the posterior subregions in area 44 showed delayed peak activations in the right hemisphere in both groups, possibly signaling the offset response. Because these offset response-related activations in the right hemisphere were comparably large in males who stutter, our data suggest a hyperactive mechanism to stop speech motor responses and thus possibly reflect a pathomechanism, which, until now, has been neglected. Overall, the current results confirmed a recently described co-activation based parcellation supporting the idea of functionally distinct subregions of left area 44.
Collapse
Affiliation(s)
- Nicole E Neef
- Department of Clinical Neurophysiology, Georg-August-University, Robert-Koch-Straße 40, 37075 Göttingen, Germany; Department of Neuropsychology, Max Planck Institute for Human Cognitive and Brain Sciences, Stephanstraße 1a, 03104 Leipzig, Germany.
| | - Christoph Bütfering
- Department of Clinical Neurophysiology, Georg-August-University, Robert-Koch-Straße 40, 37075 Göttingen, Germany.
| | - Alfred Anwander
- Department of Neuropsychology, Max Planck Institute for Human Cognitive and Brain Sciences, Stephanstraße 1a, 03104 Leipzig, Germany.
| | - Angela D Friederici
- Department of Neuropsychology, Max Planck Institute for Human Cognitive and Brain Sciences, Stephanstraße 1a, 03104 Leipzig, Germany.
| | - Walter Paulus
- Department of Clinical Neurophysiology, Georg-August-University, Robert-Koch-Straße 40, 37075 Göttingen, Germany.
| | - Martin Sommer
- Department of Clinical Neurophysiology, Georg-August-University, Robert-Koch-Straße 40, 37075 Göttingen, Germany.
| |
Collapse
|