- Email: [email protected]
Reply to the letter to the editor on “No modulatory effects by tSMS when delivered during a cognitive task”
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Brain Stimulation xxx (2017) 1e2
Contents lists available at ScienceDirect
Brain Stimulation journal homepage: http://www.journals.elsevier.com/brain-stimulation
Q1,6
Reply to the letter to the editor on “No modulatory effects by tSMS when delivered during a cognitive task”
Dear Editor:
Q3
We'd like to thank the authors for their comments [1] concering on our study [2]. We agree that the acoustic oddball task has to be considered as putative cause on modulatory effects in a cortical region. We first have to specify that we administered the oddball task only in the two motor experiments (experiment 1 and 2), but not in experiment 3 probing the somatosensory cortex. We explicitly instructed the subjects to count mentally only and not to use fingers. Nevertheless, it's quite plausible that counting numbers below 10 co-activates the motor system [3]. Our oddball task always went beyond this number, reaching 25e45 rare events in any run. It has been speculated that the representation of numbers above 10 causes less involvement of the motor system [e.g. Ref. [4]]. The influence of different cognitive activities on motor cortex excitability has been studied directly using MEPs as dependent variable. In a study reading aloud results in excitability changes of the hand area, but neither reading silently nor speaking loudly changed € el et al. [6] replicated the finding concerning excitability [5]. Flo reading aloud, but demonstrated that either speaking spontaneously or producing phonemes also increases excitability. Even silent reading had a moderate impact on corticospinal excitability. One of the control tasks they administered has similarities to an ordinary oddball task: Subjects read a text and had to count silently the occurrence of word pairs in which the first word ended with an “e” and the second word started with an “e”. After the task subjects had to report the number of “e - e” word pairs. Although the sensory channel was not auditory but visual, the attention to a certain event, as well as the request for counting silently, is similar to the acoustic oddball task we administered. Probing a small hand muscle they did not find any changes in cortical excitability during this control task [6]. A more indirect observation was made in our lab. In a study investigating the modulatory effect of temporal cortex tDCS on semantic processing, we applied the same acoustic oddball task during tDCS [7]. Since the dependent variable was reaction time, we controlled for possible motor cortex modulations, administering a choice reaction time task prior and after tDCS plus oddball task. We did not find any differences in choice reaction times.
Our rational to administer the oddball task was to control for attention and brain state in general, a requirement to improve experiments in plasticity induction, as mentioned previously [8]. In our experience, some subjects tend to fall asleep during a stimulation period of 10 minutes when nothing happens, causing a considerable decrease of motor cortex excitability [9,10]. In our opinion the evidence provided by the literature is not sufficient to clarify the specific impact of a continuous cognitive task, such as an acoustic oddball task, on modulatory interventions of the motor cortex. Only a direct experimental comparison could answer this question. Conflict of interest None.
References [1] Foffani G, Dileone M. No modulatory effects by tSMS when delivered during a cognitive task. Brain Stimul;in press. [2] Kufner M, Brückner S, Kammer T. No modulatory effects by transcranial static magnetic field stimulation of human motor and somatosensory cortex. Brain Stimul 2017. http://dx.doi.org/10.1016/j.brs.2017.03.001. [3] Tschentscher N, Hauk O, Fischer MH, Pulvermuller F. You can count on the motor cortex: finger counting habits modulate motor cortex activation evoked by numbers. Neuroimage 2012;59:3139e48. [4] Domahs F, Moeller K, Huber S, Willmes K, Nuerk HC. Embodied numerosity: implicit hand-based representations influence symbolic number processing across cultures. Cognition 2010;116:251e66. [5] Tokimura H, Tokimura Y, Oliviero A, Asakura T, Rothwell JC. Speech-induced changes in corticospinal excitability, 40; 1996. p. 628e34. €el A, Ellger T, Breitenstein C, Knecht S. Language perception activates the [6] Flo hand motor cortex: implications for motor theories of speech perception. Eur J Neurosci 2003;18:704e8. [7] Brückner S, Kammer T. Both anodal and cathodal transcranial direct current stimulation improves semantic processing. Neurosci 2017;343:269e75. [8] Ziemann U, Siebner HR. Inter-subject and inter-session variability of plasticity induction by non-invasive brain stimulation: boon or bane? Brain Stimul 2015;8:662e3. [9] Grosse P, Khatami R, Salih F, Kuhn A, Meyer BU. Corticospinal excitability in human sleep as assessed by transcranial magnetic stimulation. Neurology 2002;59:1988e91. [10] Manganotti P, Fuggetta G, Fiaschi A. Changes of motor cortical excitability in human subjects from wakefulness to early stages of sleep: a combined transcranial magnetic stimulation and electroencephalographic study. Neurosci Lett 2004;362:31e4.
DOIs of original article: http://dx.doi.org/10.1016/j.brs.2017.03.001, http://dx.doi. org/10.1016/j.brs.2017.04.121. http://dx.doi.org/10.1016/j.brs.2017.04.122 1935-861X/© 2017 Elsevier Inc. All rights reserved.
Please cite this article in press as: Kufner M, et al.Reply to the letter to the editor on “No modulatory effects by tSMS when delivered during a cognitive task”, Brain Stimulation (2017), http://dx.doi.org/10.1016/j.brs.2017.04.122
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M. Kufner et al. / Brain Stimulation xxx (2017) 1e2
Marco Kufner, Sabrina Brückner, Thomas Kammer* Section for Neurostimulation, Department of Psychiatry, University of Ulm, Germany *
6 7 8 9 10
E-mail address: [email protected] (T. Kammer). 11 April 2017 Available online xxx
Corresponding author.
Please cite this article in press as: Kufner M, et al.Reply to the letter to the editor on “No modulatory effects by tSMS when delivered during a cognitive task”, Brain Stimulation (2017), http://dx.doi.org/10.1016/j.brs.2017.04.122
Q5
BRS1050_proof ■ 18 April 2017 ■ 1/2
Brain Stimulation xxx (2017) 1e2
Contents lists available at ScienceDirect
Brain Stimulation journal homepage: http://www.journals.elsevier.com/brain-stimulation
Q1,6
Reply to the letter to the editor on “No modulatory effects by tSMS when delivered during a cognitive task”
Dear Editor:
Q3
We'd like to thank the authors for their comments [1] concering on our study [2]. We agree that the acoustic oddball task has to be considered as putative cause on modulatory effects in a cortical region. We first have to specify that we administered the oddball task only in the two motor experiments (experiment 1 and 2), but not in experiment 3 probing the somatosensory cortex. We explicitly instructed the subjects to count mentally only and not to use fingers. Nevertheless, it's quite plausible that counting numbers below 10 co-activates the motor system [3]. Our oddball task always went beyond this number, reaching 25e45 rare events in any run. It has been speculated that the representation of numbers above 10 causes less involvement of the motor system [e.g. Ref. [4]]. The influence of different cognitive activities on motor cortex excitability has been studied directly using MEPs as dependent variable. In a study reading aloud results in excitability changes of the hand area, but neither reading silently nor speaking loudly changed € el et al. [6] replicated the finding concerning excitability [5]. Flo reading aloud, but demonstrated that either speaking spontaneously or producing phonemes also increases excitability. Even silent reading had a moderate impact on corticospinal excitability. One of the control tasks they administered has similarities to an ordinary oddball task: Subjects read a text and had to count silently the occurrence of word pairs in which the first word ended with an “e” and the second word started with an “e”. After the task subjects had to report the number of “e - e” word pairs. Although the sensory channel was not auditory but visual, the attention to a certain event, as well as the request for counting silently, is similar to the acoustic oddball task we administered. Probing a small hand muscle they did not find any changes in cortical excitability during this control task [6]. A more indirect observation was made in our lab. In a study investigating the modulatory effect of temporal cortex tDCS on semantic processing, we applied the same acoustic oddball task during tDCS [7]. Since the dependent variable was reaction time, we controlled for possible motor cortex modulations, administering a choice reaction time task prior and after tDCS plus oddball task. We did not find any differences in choice reaction times.
Our rational to administer the oddball task was to control for attention and brain state in general, a requirement to improve experiments in plasticity induction, as mentioned previously [8]. In our experience, some subjects tend to fall asleep during a stimulation period of 10 minutes when nothing happens, causing a considerable decrease of motor cortex excitability [9,10]. In our opinion the evidence provided by the literature is not sufficient to clarify the specific impact of a continuous cognitive task, such as an acoustic oddball task, on modulatory interventions of the motor cortex. Only a direct experimental comparison could answer this question. Conflict of interest None.
References [1] Foffani G, Dileone M. No modulatory effects by tSMS when delivered during a cognitive task. Brain Stimul;in press. [2] Kufner M, Brückner S, Kammer T. No modulatory effects by transcranial static magnetic field stimulation of human motor and somatosensory cortex. Brain Stimul 2017. http://dx.doi.org/10.1016/j.brs.2017.03.001. [3] Tschentscher N, Hauk O, Fischer MH, Pulvermuller F. You can count on the motor cortex: finger counting habits modulate motor cortex activation evoked by numbers. Neuroimage 2012;59:3139e48. [4] Domahs F, Moeller K, Huber S, Willmes K, Nuerk HC. Embodied numerosity: implicit hand-based representations influence symbolic number processing across cultures. Cognition 2010;116:251e66. [5] Tokimura H, Tokimura Y, Oliviero A, Asakura T, Rothwell JC. Speech-induced changes in corticospinal excitability, 40; 1996. p. 628e34. €el A, Ellger T, Breitenstein C, Knecht S. Language perception activates the [6] Flo hand motor cortex: implications for motor theories of speech perception. Eur J Neurosci 2003;18:704e8. [7] Brückner S, Kammer T. Both anodal and cathodal transcranial direct current stimulation improves semantic processing. Neurosci 2017;343:269e75. [8] Ziemann U, Siebner HR. Inter-subject and inter-session variability of plasticity induction by non-invasive brain stimulation: boon or bane? Brain Stimul 2015;8:662e3. [9] Grosse P, Khatami R, Salih F, Kuhn A, Meyer BU. Corticospinal excitability in human sleep as assessed by transcranial magnetic stimulation. Neurology 2002;59:1988e91. [10] Manganotti P, Fuggetta G, Fiaschi A. Changes of motor cortical excitability in human subjects from wakefulness to early stages of sleep: a combined transcranial magnetic stimulation and electroencephalographic study. Neurosci Lett 2004;362:31e4.
DOIs of original article: http://dx.doi.org/10.1016/j.brs.2017.03.001, http://dx.doi. org/10.1016/j.brs.2017.04.121. http://dx.doi.org/10.1016/j.brs.2017.04.122 1935-861X/© 2017 Elsevier Inc. All rights reserved.
Please cite this article in press as: Kufner M, et al.Reply to the letter to the editor on “No modulatory effects by tSMS when delivered during a cognitive task”, Brain Stimulation (2017), http://dx.doi.org/10.1016/j.brs.2017.04.122
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BRS1050_proof ■ 18 April 2017 ■ 2/2
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M. Kufner et al. / Brain Stimulation xxx (2017) 1e2
Marco Kufner, Sabrina Brückner, Thomas Kammer* Section for Neurostimulation, Department of Psychiatry, University of Ulm, Germany *
6 7 8 9 10
E-mail address: [email protected] (T. Kammer). 11 April 2017 Available online xxx
Corresponding author.
Please cite this article in press as: Kufner M, et al.Reply to the letter to the editor on “No modulatory effects by tSMS when delivered during a cognitive task”, Brain Stimulation (2017), http://dx.doi.org/10.1016/j.brs.2017.04.122
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