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Bakhtiar M, Yeung TWY, Choi A. The application of neuronavigated rTMS of the supplementary motor area and rhythmic speech training for stuttering intervention. INTERNATIONAL JOURNAL OF LANGUAGE & COMMUNICATION DISORDERS 2024. [PMID: 38711376 DOI: 10.1111/1460-6984.13039] [Citation(s) in RCA: 0] [Impact Index Per Article: 0] [Reference Citation Analysis] [Abstract] [Key Words] [Grants] [Track Full Text] [Subscribe] [Scholar Register] [Received: 11/24/2023] [Revised: 04/10/2024] [Accepted: 04/11/2024] [Indexed: 05/08/2024]
Abstract
BACKGROUND Stuttering, a neurodevelopmental speech fluency disorder, is associated with intermittent disruptions of speech-motor control. Behavioural treatments for adults who stutter (AWS) concentrate on adopting speech patterns that enhance fluency, such as speaking rhythmically or prolonging speech sounds. However, maintaining these treatment benefits can be challenging. Neuroimaging studies suggest that supplementary motor area (SMA) which play a crucial role in speech initiation, planning and internal timing shows aberrant activation in speech production of AWS and may contribute to stuttering. Preliminary evidence suggests that brain stimulation may impact responsiveness to behavioural treatments. AIMS The present study aims to investigate whether excitatory repetitive transcranial magnetic stimulation (rTMS) of the SMA and rhythmic speech can consistently reduce stuttering severity across various measures. METHODS AND PROCEDURES Ten self-identified Cantonese-speaking AWS participated in this double-blinded, sham-controlled clinical trial study (NCT05472181). The participants underwent 10 sessions of rhythmic speech training across two phases, combined with either neuronavigated rTMS or sham, with a 2-week washout period between phases. The stuttering severity was assessed through various outcome measures, including the percentage of syllables stuttered, self-perceived stuttering severity, and the brief version of Unhelpful Thoughts and Beliefs About Stuttering before and after each treatment phase. OUTCOMES AND RESULTS Results demonstrated improved speech fluency in various speaking contexts, with no significant difference between rTMS and sham conditions immediately and 1 week post-treatment. Notably, rTMS specifically led to less stuttering in tongue twister production (d = -0.70). Both treatment conditions effectively reduced self-perceived stuttering severity and negative thoughts and beliefs about stuttering. CONCLUSIONS AND IMPLICATIONS The findings of this study indicate that stimulating the SMA reduced stuttering, only in the production of tongue twisters that may require greater motor control and coordination. Furthermore, it indicates that rhythmic speech might help alleviate negative beliefs and anxiety related to stuttering. This research contributes to our understanding of neuromodulation in stuttering treatment and the role of the SMA in speech motor control and emphasises the need for more research on the potential benefits and limitations of applying rTMS in this condition. WHAT THIS PAPER ADDS What is already known on the subject Behavioural treatments for adults who stutter concentrate on adopting speech patterns that enhance fluency, such as speaking rhythmically or prolonging speech sounds. However, maintaining these treatment benefits can be challenging. Neuroimaging studies indicate that aberrant neural activation in speech production regions, like the supplementary motor area (SMA), is involved in stuttering. The SMA plays a crucial role in initiating, planning, and sequencing motor behaviours. Preliminary evidence suggests that brain stimulation (e.g., transcranial direct current stimulation or transcranial magnetic stimulation) may impact responsiveness to behavioural treatments. What this paper adds to existing knowledge There is limited knowledge regarding the potential effects of stimulating the SMA to enhance speech fluency in people who stutter. Existing research primarily consists of single case studies that lack proper control conditions or involve only a single stimulation session. Due to their limited scope and power, these studies may not provide sufficient evidence. The current study expands upon existing research by investigating whether multiple sessions of repetitive transcranial magnetic stimulation over the SMA, combined with rhythmic speech, improve speech fluency in adults who stutter. Furthermore, it addresses the limitations of brain stimulation methods and proposes directions for future research. What are the potential or actual clinical implications of this work? This study implies that the stimulation of SMA reduced stuttering only in speaking contexts that may require greater motor control and coordination such as tongue twisters. Additionally, the research suggests that using rhythmic speech could potentially alleviate negative beliefs and anxiety associated with stuttering.
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Affiliation(s)
- Mehdi Bakhtiar
- Speech and Neuromodulation Laboratory, Unit of Human Communication, Learning and Development, Faculty of Education, The University of Hong Kong, Hong Kong
| | - Tegan Wai Yee Yeung
- Speech and Neuromodulation Laboratory, Unit of Human Communication, Learning and Development, Faculty of Education, The University of Hong Kong, Hong Kong
| | - Angela Choi
- Speech Science Laboratory, Unit of Human Communication, Learning and Development, Faculty of Education, The University of Hong Kong, Hong Kong
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Balduin-Philipps LS, Weiss S, Mueller H. Supporting auditory word recognition with transcranial direct current stimulation: effects in elderly individuals with and without objective memory complaints. NEUROPSYCHOLOGY, DEVELOPMENT, AND COGNITION. SECTION B, AGING, NEUROPSYCHOLOGY AND COGNITION 2022; 29:237-259. [PMID: 33432880 DOI: 10.1080/13825585.2020.1861203] [Citation(s) in RCA: 1] [Impact Index Per Article: 0.5] [Reference Citation Analysis] [Abstract] [Key Words] [MESH Headings] [Track Full Text] [Subscribe] [Scholar Register] [Received: 04/19/2020] [Accepted: 12/03/2020] [Indexed: 06/12/2023]
Abstract
Healthy elderly people often experience a subjective loss of daily memory performance whereas an objective decrease in memory performance is often observed in patients with memory complaints. In this paper, we investigate the influence of a single session of "anodal" transcranial direct current stimulation (a-tDCS) on auditory word recognition performance in a decision time experiment. Three groups of participants (>64 years of age) with and without memory complaints underwent a word recognition task, in which they had to recognize words previously encoded among several distractors (semantically or phonologically related words) via a button press. In this double-blinded study, the participants completed two sessions (sham/a-tDCS), counterbalanced between subjects with a washout period of at least 10 days. Twenty minutes of 1.5 mA a-tDCS was applied over the left temporal cortex during the memorizing and decision phases. Overall, our results demonstrated that the participants, independent of their memory performance, were faster in word recognition during a-tDCS. As expected, older participants with memory complaints recognized significantly less words correctly compared to other participants. However, tDCS did not have a beneficial effect on the extent of successful word recognition. These results suggest a general effect of a single session of a-tDCS over the left temporal cortex, with participants becoming faster in their word recognition, thus having easier access to encoded words.
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Affiliation(s)
- Larissa S Balduin-Philipps
- Experimental Neurolinguistics Group, Bielefeld University, Bielefeld, Germany
- Cluster of Excellence "Cognitive Interaction Technology" (CITEC), Bielefeld University, Bielefeld, Germany
| | - Sabine Weiss
- Experimental Neurolinguistics Group, Bielefeld University, Bielefeld, Germany
- Cluster of Excellence "Cognitive Interaction Technology" (CITEC), Bielefeld University, Bielefeld, Germany
- Clinical Linguistics, Bielefeld University, Bielefeld, Germany
| | - Horst Mueller
- Experimental Neurolinguistics Group, Bielefeld University, Bielefeld, Germany
- Cluster of Excellence "Cognitive Interaction Technology" (CITEC), Bielefeld University, Bielefeld, Germany
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Anodal tDCS over Broca's area improves fast mapping and explicit encoding of novel vocabulary. Neuropsychologia 2022; 168:108156. [PMID: 35026217 DOI: 10.1016/j.neuropsychologia.2022.108156] [Citation(s) in RCA: 0] [Impact Index Per Article: 0] [Reference Citation Analysis] [Abstract] [Key Words] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 04/30/2021] [Revised: 12/09/2021] [Accepted: 01/08/2022] [Indexed: 11/24/2022]
Abstract
An accumulating body of evidence suggests that transcranial direct current stimulation (tDCS) can be used to modulate speech processing both in healthy individuals and in patients with speech disorders. There has been, however, no comprehensive study of effects of tDCS of the core language areas in relation to the main word-learning mechanisms. Two principal strategies have been posited as important for natural word acquisition: explicit encoding (EE) which relies on direct instructions and repetition of material, and fast mapping (FM) which operates implicitly, via context-based inference or deduction. We used anodal and cathodal tDCS of Broca's and Wernicke's areas to assess effects of stimulation site and polarity on novel word acquisition in both EE and FM regimes. 160 participants, divided into five groups, received 15 min of cathodal or anodal tDCS over one of the two areas or a sham (placebo) stimulation before learning eight novel words, presented ten times each in a short naturalistic audio-visual word-picture association session, fully counterbalanced across different learning regimes. Behavioural outcome of novel word acquisition was measured immediately after the training in a free recall task, which showed elevated accuracy in all real stimulation groups in comparison with sham stimulation; however, this effect only reached full significance after anodal tDCS of Broca's area. Comparisons between the two learning modes indicated that Broca's anodal tDCS significantly improved both implicit and explicit acquisition of novel vocabulary in comparison with sham tDCS, without, however, any significant differences between EE and FM regimes as such. The results indicate involvement of the left inferior-frontal neocortex in the learning of novel vocabulary and suggest a possibility to promote different types of word acquisition using anodal tDCS of this area.
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Wiltshire CEE, Watkins KE. Failure of tDCS to modulate motor excitability and speech motor learning. Neuropsychologia 2020; 146:107568. [PMID: 32687836 PMCID: PMC7534039 DOI: 10.1016/j.neuropsychologia.2020.107568] [Citation(s) in RCA: 6] [Impact Index Per Article: 1.5] [Reference Citation Analysis] [Abstract] [Key Words] [MESH Headings] [Grants] [Track Full Text] [Download PDF] [Figures] [Journal Information] [Subscribe] [Scholar Register] [Received: 02/24/2020] [Revised: 05/25/2020] [Accepted: 07/15/2020] [Indexed: 12/25/2022]
Abstract
Transcranial direct current stimulation (tDCS) modulates cortical excitability in a polarity-specific way and, when used in combination with a behavioural task, it can alter performance. TDCS has the potential, therefore, for use as an adjunct to therapies designed to treat disorders affecting speech, including, but not limited to acquired aphasias and developmental stuttering. For this reason, it is important to conduct studies evaluating its effectiveness and the parameters optimal for stimulation. Here, we aimed to evaluate the effects of bi-hemispheric tDCS over speech motor cortex on performance of a complex speech motor learning task, namely the repetition of tongue twisters. A previous study in older participants showed that tDCS could modulate performance on a similar task. To further understand the effects of tDCS, we also measured the excitability of the speech motor cortex before and after stimulation. Three groups of 20 healthy young controls received: (i) anodal tDCS to the left IFG/LipM1 and cathodal tDCS to the right hemisphere homologue; or (ii) cathodal tDCS over the left and anodal over the right; or (iii) sham stimulation. Participants heard and repeated novel tongue twisters and matched simple sentences before, during and 10 min after the stimulation. One mA tDCS was delivered concurrent with task performance for 13 min. Motor excitability was measured using transcranial magnetic stimulation to elicit motor-evoked potentials in the lip before and immediately after tDCS. The study was double-blind, randomized, and sham-controlled; the design and analysis were pre-registered. Performance on the task improved from baseline to after stimulation but was not significantly modulated by tDCS. Similarly, a small decrease in motor excitability was seen in all three stimulation groups but did not differ among them and was unrelated to task performance. Bayesian analyses provide substantial evidence in support of the null hypotheses in both cases, namely that tongue twister performance and motor excitability were not affected by tDCS. We discuss our findings in the context of the previous positive results for a similar task. We conclude that tDCS may be most effective when brain function is sub-optimal due to age-related declines or pathology. Further study is required to determine why tDCS failed to modulate excitability in the speech motor cortex in the expected ways.
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Affiliation(s)
- Charlotte E E Wiltshire
- Wellcome Centre for Integrative Neuroimaging, Department of Experimental Psychology, Radcliffe Observatory Quarter, University of Oxford, OX2 6GG, UK.
| | - Kate E Watkins
- Wellcome Centre for Integrative Neuroimaging, Department of Experimental Psychology, Radcliffe Observatory Quarter, University of Oxford, OX2 6GG, UK.
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Wong MN, Chan Y, Ng ML, Zhu FF. Effects of transcranial direct current stimulation over the Broca's area on tongue twister production. INTERNATIONAL JOURNAL OF SPEECH-LANGUAGE PATHOLOGY 2019; 21:182-188. [PMID: 29642741 DOI: 10.1080/17549507.2017.1417480] [Citation(s) in RCA: 2] [Impact Index Per Article: 0.4] [Reference Citation Analysis] [Abstract] [Key Words] [MESH Headings] [Track Full Text] [Subscribe] [Scholar Register] [Received: 11/08/2016] [Revised: 10/01/2017] [Accepted: 12/07/2017] [Indexed: 06/08/2023]
Abstract
PURPOSE The present study aimed to explore the short-term effect of anodal transcranial direct current stimulation (tDCS) on tongue twister production. METHOD Thirty healthy native Cantonese adult speakers were randomly assigned to the anodal tDCS group or the sham tDCS group. Anodal tDCS of 2 mA was applied over the Broca's area of the brain. The stimulation lasted for 20 min for the anodal tDCS group and 30 s for the sham tDCS group. The participants were instructed to produce a list of tongue twisters before, immediately after and 4 h after tDCS. RESULT Speech rate and response accuracy measured immediately after stimulation were significantly faster and higher, respectively, than before stimulation. Although there was no change in speech rate measured at 4 h after stimulation, response accuracy at that time point was significantly lower than that measured immediately after stimulation. However, there were no significant differences between the anodal tDCS and sham tDCS groups in either speech rate or response accuracy. CONCLUSION The findings revealed that a single session of anodal tDCS over the Broca's area did not significantly improve speech production during tongue twister production.
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Affiliation(s)
- Min Ney Wong
- a Department of Chinese and Bilingual Studies , The Hong Kong Polytechnic University , Hung Hom, Kowloon , Hong Kong
- b Speech Science Laboratory, Division of Speech and Hearing Sciences, Faculty of Education , The University of Hong Kong , Pokfulam , Hong Kong
- c Centre for Communication Disorders , The University of Hong Kong , Pokfulam , Hong Kong
| | - Yanky Chan
- b Speech Science Laboratory, Division of Speech and Hearing Sciences, Faculty of Education , The University of Hong Kong , Pokfulam , Hong Kong
- c Centre for Communication Disorders , The University of Hong Kong , Pokfulam , Hong Kong
| | - Manwa L Ng
- b Speech Science Laboratory, Division of Speech and Hearing Sciences, Faculty of Education , The University of Hong Kong , Pokfulam , Hong Kong
- c Centre for Communication Disorders , The University of Hong Kong , Pokfulam , Hong Kong
| | - Frank F Zhu
- d Faculty of Education , The University of Hong Kong , Pokfulam , Hong Kong
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Fiori V, Nitsche MA, Cucuzza G, Caltagirone C, Marangolo P. High-Definition Transcranial Direct Current Stimulation Improves Verb Recovery in Aphasic Patients Depending on Current Intensity. Neuroscience 2019; 406:159-166. [PMID: 30876982 DOI: 10.1016/j.neuroscience.2019.03.010] [Citation(s) in RCA: 20] [Impact Index Per Article: 4.0] [Reference Citation Analysis] [Abstract] [Key Words] [MESH Headings] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 12/04/2018] [Revised: 02/24/2019] [Accepted: 03/06/2019] [Indexed: 12/28/2022]
Abstract
High-definition transcranial direct current stimulation (HD-tDCS) is a variant of tDCS, which produces more focal stimulation, delimiting brain current flow to a defined region compared to conventional tDCS. To date, only one study has been conducted to investigate HD-tDCS effects on language recovery in aphasia. Here, we aimed to assess the effects of cathodal HD-tDCS on verb naming by comparing two current intensities: 1 vs 2 mA. In a double-blinded cross over study, two groups of 10 aphasic individuals were submitted to active cathodal HD-tDCS and sham stimulation over the right homolog of Broca's area, while performing a verb naming task. Indeed, we reasoned that, by applying inhibitory current over the right Broca's area, we would decrease the inhibitory impact from the right hemisphere to the left perilesional cortex, thus boosting language recovery. The groups differed in the intensity of the active stimulation (1 mA or 2 mA). In both groups, each condition was carried out in five consecutive daily sessions with one week of interval between the two experimental conditions. A significant improvement in verb naming was found only after cathodal HD-tDCS at 2 mA, which endured one week after the end of treatment. The improvement was not observed on the group receiving cathodal HD-tDCS at 1 mA. Our findings showed that HD-tDCS applied to the right intact hemisphere are efficacious for language recovery. These results indicate that HD-tDCS represents a promising new technique for language rehabilitation. However, systematic determination of stimulation intensity appears to be crucial for obtaining relevant effects.
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Affiliation(s)
| | - Michael A Nitsche
- Department Psychology and Neurosciences, Leibniz Research Center for Working Environment and Human Factors, Dortmund, Germany; Department of Neurology, BG University Hospital Bergmannsheil, Bochum, Germany
| | | | - Carlo Caltagirone
- IRCCS, Fondazione Santa Lucia, Rome, Italy; Università degli Studi di Tor Vergata, Rome, Italy
| | - Paola Marangolo
- IRCCS, Fondazione Santa Lucia, Rome, Italy; Università Federico II, Naples, Italy.
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Klaus J, Schutter DJLG. Putting focus on transcranial direct current stimulation in language production studies. PLoS One 2018; 13:e0202730. [PMID: 30138361 PMCID: PMC6107198 DOI: 10.1371/journal.pone.0202730] [Citation(s) in RCA: 7] [Impact Index Per Article: 1.2] [Reference Citation Analysis] [Abstract] [MESH Headings] [Grants] [Track Full Text] [Download PDF] [Figures] [Journal Information] [Subscribe] [Scholar Register] [Received: 06/15/2018] [Accepted: 08/08/2018] [Indexed: 11/24/2022] Open
Abstract
Previous language production studies targeting the inferior frontal and superior temporal gyrus using anodal tDCS have provided mixed results. Part of this heterogeneity may be explained by limited target region focality of conventionally used electrode montages. We examined the focality of conventionally and alternative electrode montages. Electrical field distributions of anodal tDCS targeting IFG and pSTG were simulated in conventional setups (anodal electrode over left IFG/pSTG, reference electrode over right supraorbital region) and an alternative electrode montage in four different brains. Conventional montages showed maximum field strengths outside of the target regions. Results from alternative electrode montages showed that focality of tDCS could be improved by adjustments in electrode placement. Heterogeneity of findings of language production studies deploying conventional montages may in part be explained by diffuse electrical field distributions. Alternative montages may improve focality and provide more unequivocal results.
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Affiliation(s)
- Jana Klaus
- Donders Institute for Brain, Cognition and Behaviour, Radboud University, Nijmegen, The Netherlands
- * E-mail:
| | - Dennis J. L. G. Schutter
- Donders Institute for Brain, Cognition and Behaviour, Radboud University, Nijmegen, The Netherlands
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Simione M, Fregni F, Green JR. The Effect of Transcranial Direct Current Stimulation on Jaw Motor Function Is Task Dependent: Speech, Syllable Repetition and Chewing. Front Hum Neurosci 2018; 12:33. [PMID: 29487512 PMCID: PMC5816739 DOI: 10.3389/fnhum.2018.00033] [Citation(s) in RCA: 3] [Impact Index Per Article: 0.5] [Reference Citation Analysis] [Abstract] [Grants] [Track Full Text] [Download PDF] [Figures] [Journal Information] [Subscribe] [Scholar Register] [Received: 09/15/2017] [Accepted: 01/19/2018] [Indexed: 11/13/2022] Open
Abstract
Motor cortex transcranial direct current stimulation (tDCS) has been shown to enhance motor learning in healthy adults as well as various neurological conditions. However, there has been limited data on whether tDCS enhances jaw motor performance during different oral behaviors such as speech, maximum syllable repetition, and chewing. Because the effects of anodal and cathodal stimulation are known to be dependent on task demands, we hypothesized that tDCS would have a distinct effect on the jaw motor performance during these disparate oral behaviors. Ten healthy adults completed speech, maximum syllable repetition, and chewing tasks as their jaw movements were recorded using 3D optical motion capture during sham, anodal, and cathodal tDCS. Our findings showed that compared to the sham condition, jaw displacements during speech and syllable repetition were smaller during anodal stimulation, but larger during cathodal stimulation for syllable repetition and chewing indicating improved performance during anodal tDCS. On the other hand, there were no effects of anodal tDCS during chewing. These results confirm our hypotheses that: (1) tDCS induces a significant effect on jaw motor function; (2) its effects are polarity dependent; and (3) its effects are dependent on the task demands on jaw motor function. These findings support future studies exploring the effects of tDCS on persons with oral sensorimotor impairments and the development of therapeutic protocols.
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Affiliation(s)
- Meg Simione
- Department of Pediatrics, MassGeneral Hospital for Children, Boston, MA, United States
| | - Felipe Fregni
- Spaulding-Labuschagne Neuromodulation Center, Spaulding Rehabilitation Hospital, Boston, MA, United States
| | - Jordan R. Green
- Speech and Feeding Disorders Laboratory, MGH Institute of Health Professions, Boston, MA, United States
- *Correspondence: Jordan R. Green
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Fiori V, Nitsche M, Iasevoli L, Cucuzza G, Caltagirone C, Marangolo P. Differential effects of bihemispheric and unihemispheric transcranial direct current stimulation in young and elderly adults in verbal learning. Behav Brain Res 2017; 321:170-175. [DOI: 10.1016/j.bbr.2016.12.044] [Citation(s) in RCA: 30] [Impact Index Per Article: 4.3] [Reference Citation Analysis] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 11/16/2016] [Revised: 12/29/2016] [Accepted: 12/31/2016] [Indexed: 12/19/2022]
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Berthier ML, Moreno-Torres I. Commentary: Visual Feedback of Tongue Movement for Novel Speech Sound Learning. Front Hum Neurosci 2017; 10:662. [PMID: 28066219 PMCID: PMC5179538 DOI: 10.3389/fnhum.2016.00662] [Citation(s) in RCA: 1] [Impact Index Per Article: 0.1] [Reference Citation Analysis] [Key Words] [Track Full Text] [Download PDF] [Figures] [Journal Information] [Subscribe] [Scholar Register] [Received: 09/19/2016] [Accepted: 12/12/2016] [Indexed: 11/13/2022] Open
Affiliation(s)
- Marcelo L Berthier
- Cognitive Neurology and Aphasia Unit and Cathedra ARPA of Aphasia, Centro de Investigaciones Médico-Sanitarias, Instituto de Investigación Biomédica de Málaga, University of Malaga Malaga, Spain
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Chesters J, Watkins KE, Möttönen R. Investigating the feasibility of using transcranial direct current stimulation to enhance fluency in people who stutter. BRAIN AND LANGUAGE 2017; 164:68-76. [PMID: 27810647 PMCID: PMC5240850 DOI: 10.1016/j.bandl.2016.10.003] [Citation(s) in RCA: 9] [Impact Index Per Article: 1.3] [Reference Citation Analysis] [Abstract] [MESH Headings] [Grants] [Track Full Text] [Subscribe] [Scholar Register] [Received: 12/30/2015] [Revised: 10/17/2016] [Accepted: 10/23/2016] [Indexed: 05/02/2023]
Abstract
Developmental stuttering is a disorder of speech fluency affecting 1% of the adult population. Long-term reductions in stuttering are difficult for adults to achieve with behavioural therapies. We investigated whether a single session of transcranial direct current stimulation (TDCS) could improve fluency in people who stutter (PWS). In separate sessions, either anodal TDCS (1mA for 20min) or sham stimulation was applied over the left inferior frontal cortex while PWS read sentences aloud. Fluency was induced during the stimulation period by using choral speech, that is, participants read in unison with another speaker. Stuttering frequency during sentence reading, paragraph reading and conversation was measured at baseline and at two outcome time points: immediately after the stimulation period and 1h later. Stuttering was reduced significantly at both outcome time points for the sentence-reading task, presumably due to practice, but not during the paragraph reading or conversation tasks. None of the outcome measures were significantly modulated by anodal TDCS. Although the results of this single-session study showed no significant TDCS-induced improvements in fluency, there were some indications that further research is warranted. We discuss factors that we believe may have obscured the expected positive effects of TDCS on fluency, such as heterogeneity in stuttering severity for the sample and variations across sessions. Consideration of such factors may inform future studies aimed at determining the potential of TDCS in the treatment of developmental stuttering.
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Affiliation(s)
- Jennifer Chesters
- Department of Experimental Psychology, South Parks Road, University of Oxford, Oxford, UK.
| | - Kate E Watkins
- Department of Experimental Psychology, South Parks Road, University of Oxford, Oxford, UK
| | - Riikka Möttönen
- Department of Experimental Psychology, South Parks Road, University of Oxford, Oxford, UK
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Sandars M, Cloutman L, Woollams AM. Taking Sides: An Integrative Review of the Impact of Laterality and Polarity on Efficacy of Therapeutic Transcranial Direct Current Stimulation for Anomia in Chronic Poststroke Aphasia. Neural Plast 2015; 2016:8428256. [PMID: 26819777 PMCID: PMC4706968 DOI: 10.1155/2016/8428256] [Citation(s) in RCA: 20] [Impact Index Per Article: 2.2] [Reference Citation Analysis] [Abstract] [MESH Headings] [Track Full Text] [Download PDF] [Figures] [Journal Information] [Subscribe] [Scholar Register] [Received: 04/16/2015] [Revised: 08/10/2015] [Accepted: 08/24/2015] [Indexed: 11/18/2022] Open
Abstract
Anomia is a frequent and persistent symptom of poststroke aphasia, resulting from damage to areas of the brain involved in language production. Cortical neuroplasticity plays a significant role in language recovery following stroke and can be facilitated by behavioral speech and language therapy. Recent research suggests that complementing therapy with neurostimulation techniques may enhance functional gains, even amongst those with chronic aphasia. The current review focuses on the use of transcranial Direct Current Stimulation (tDCS) as an adjunct to naming therapy for individuals with chronic poststroke aphasia. Our survey of the literature indicates that combining therapy with anodal (excitatory) stimulation to the left hemisphere and/or cathodal (inhibitory) stimulation to the right hemisphere can increase both naming accuracy and speed when compared to the effects of therapy alone. However, the benefits of tDCS as a complement to therapy have not been yet systematically investigated with respect to site and polarity of stimulation. Recommendations for future research to help determine optimal protocols for combined therapy and tDCS are outlined.
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Affiliation(s)
- Margaret Sandars
- Neuroscience and Aphasia Research Unit, School of Psychological Sciences, 3rd Floor, Zochonis Building, University of Manchester, Brunswick Street, Manchester M13 9PL, UK
| | - Lauren Cloutman
- Neuroscience and Aphasia Research Unit, School of Psychological Sciences, 3rd Floor, Zochonis Building, University of Manchester, Brunswick Street, Manchester M13 9PL, UK
| | - Anna M. Woollams
- Neuroscience and Aphasia Research Unit, School of Psychological Sciences, 3rd Floor, Zochonis Building, University of Manchester, Brunswick Street, Manchester M13 9PL, UK
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Hartwigsen G. The neurophysiology of language: Insights from non-invasive brain stimulation in the healthy human brain. BRAIN AND LANGUAGE 2015; 148:81-94. [PMID: 25468733 DOI: 10.1016/j.bandl.2014.10.007] [Citation(s) in RCA: 45] [Impact Index Per Article: 5.0] [Reference Citation Analysis] [Abstract] [Key Words] [MESH Headings] [Track Full Text] [Subscribe] [Scholar Register] [Received: 08/29/2014] [Revised: 10/20/2014] [Accepted: 10/21/2014] [Indexed: 06/04/2023]
Abstract
With the advent of non-invasive brain stimulation (NIBS), a new decade in the study of language has started. NIBS allows for testing the functional relevance of language-related brain activation and enables the researcher to investigate how neural activation changes in response to focal perturbations. This review focuses on the application of NIBS in the healthy brain. First, some basic mechanisms will be introduced and the prerequisites for carrying out NIBS studies of language are addressed. The next section outlines how NIBS can be used to characterize the contribution of the stimulated area to a task. In this context, novel approaches such as multifocal transcranial magnetic stimulation and the condition-and-perturb approach are discussed. The third part addresses the combination of NIBS and neuroimaging in the study of plasticity. These approaches are particularly suited to investigate short-term reorganization in the healthy brain and may inform models of language recovery in post-stroke aphasia.
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Affiliation(s)
- Gesa Hartwigsen
- Department of Psychology, Christian-Albrechts-University Kiel, Germany.
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Nozari N, Arnold JE, Thompson-Schill SL. The effects of anodal stimulation of the left prefrontal cortex on sentence production. Brain Stimul 2014; 7:784-92. [PMID: 25129401 DOI: 10.1016/j.brs.2014.07.035] [Citation(s) in RCA: 21] [Impact Index Per Article: 2.1] [Reference Citation Analysis] [Abstract] [Key Words] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 04/03/2014] [Revised: 07/14/2014] [Accepted: 07/14/2014] [Indexed: 10/25/2022] Open
Abstract
BACKGROUND Most studies in which Anodal Transcranial Direct Current Stimulation (A-tDCS) has been used to improve language production have focused on single words. Yet sentence production requires more than lexical retrieval. For example, successful suppression of the past and careful planning of the future are two critical requirements for producing a correct sentence. Can A-tDCS improves those, and by extension, production at the sentence level? OBJECTIVE/HYPOTHESIS Given that many aspects of sentence production beyond word retrieval require frontally-mediated operations, we hypothesized that A-tDCS to the left prefrontal cortex should benefit various operation involved in producing sentences, two of which, suppression of the past and planning of the future, were targeted in this study. METHODS We used a paradigm that elicited construction of sentences through event description, but was structured enough to allow for between-subject comparison, clear error identification, and implementation of experimental manipulations to probe certain aspects of production. RESULTS We showed that A-tDCS to the left PFC reliably decreased the number of incomplete and errorful sentences. When the origin of this improvement was probed, we found that A-tDCS significantly decreased errors due to premature commitment to the future word (insufficient internal monitoring), and had a marginal effect on errors of perseverations (insufficient suppression of the past). CONCLUSION We conclude that A-tDCS is a promising tool for improving production at the sentence level, and that improvement can be expected when internal monitoring and control over verbal responses is impaired, or for certain cases of perseveratory errors.
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Affiliation(s)
- Nazbanou Nozari
- Department of Neurology, Johns Hopkins University School of medicine, 1629 Thames Street, Suite 350, Baltimore, MD 21231, USA.
| | - Jennifer E Arnold
- Department of Psychology, University of North Carolina at Chapel-Hill, USA
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