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The effects of offline frontal δ-tACS on evoked endogenous oscillatory activity
382
Abstracts / Brain Stimulation 10 (2017) 346e540
Results: “Montage B” induces substantially higher electric field levels than “Montage A” and “Montage C” at the genital level. Moreover, the comparison between the two female models shows current density amplitudes and temperature increases higher in the younger subject than in the adult. However, the maxima levels found across the three models and the three montages are widely lower than the limits leading to tissue damage by heating. Significance: This modelling study represents the first contribution that gives quantitative information about genital safety during tsDCS. Keywords: tsDCS, computational modelling, neuromodulation, genital safety [0188] HIGHER TDCS GAIN IN LOW PERFORMERS IN A VERBAL EPISODIC MEMORY TASK € ppel 1, 2, J. Peter 1, 2. A. Habich*1, 2, S. Klo University of Bern, Switzerland
1
University of Freiburg, Germany;
2
Connecting information with a specific context (i.e. episodic memory) is highly relevant for the daily routine but also liable to decline in aging and neuropathological conditions. As the left dorsolateral prefrontal cortex (DLPFC) is involved in the encoding and retrieval of episodic memories, it is frequently targeted in brain stimulation paradigms. Anodal transcranial direct current stimulation (tDCS) that boosts neuronal excitability in stimulated cortical areas has been successfully applied to increase learning and memory performance. However, in view of the large inter-individual variety in performance it can be expected that participants profit from the treatment in a more differential manner. More precisely, we hypothesize that the benefit of the stimulation will depend on the participants' initial performance. In the present randomized, double-blind, parallel study, healthy young and older adults received either anodal tDCS or sham stimulation to their left DLPFC during the encoding phase of a verbal episodic memory task. Forty words were presented visually thrice in a pseudo-randomized order with immediate vocal retrieval after each block and an additional delayed recall. In the young cohort, participants receiving anodal tDCS outperformed participants of the sham group during the late recall while the stimulation effect for the three immediate retrievals was non-significant. A moderation analysis revealed that the number of remembered words in the first retrieval moderated the stimulation effect in such a way that initially low performers experienced the highest gain from the stimulation. These results suggest that the predicted stimulation effect is even greater in cognitively impaired cohorts, such as healthy elderly and patients suffering from neurodegenerative diseases, who are targeted in a clinical context. Keywords: transcranial direct current stimulation, verbal episodic memory [0189] BRAIN STATE DEPENDENCY OF CORTICOSPINAL EXCITABILITY U. Ziemann*, C. Zrenner, D. Desideri, P. Belardinelli. University of Tübingen, Germany Introduction: It is now relatively well known that the instantaneous state of brain has a substantial impact on responses evoked by non-invasive brain stimulation. Methods: Methods that trigger the TMS pulse based on the EEG signal are increasingly available. Using this EEG-TMS method, it is now possible to monitor the instantaneous brain state in real time and utilize the EEG signal to trigger TMS pulses upon specific states (e.g., specific phases of an endogenous oscillation such as the alpha-mu-rhythm of sensorimotor cortex). Results: This presentation will summarize the available data and address two fundamental questions: (1) How do phase and amplitude of the endogenous alpha-mu-rhythm of sensorimotor cortex influence the excitability of the corticospinal system, as measured by the amplitude of motor evoked potentials (MEP) in a contralateral hand muscle? (2) To what extent do instantaneous phase and amplitude of this rhythm influence the intertrial variability in MEP amplitude. Discussion: These questions are of fundamental importance for our understanding of what determines MEP amplitude and its variability.
Keywords: EEG-TMS, Brain state dependent stimulation, MEP amplitude, Alpha-mu-rhythm [0190] THE EFFECTS OF OFFLINE FRONTAL d-TACS ON EVOKED ENDOGENOUS OSCILLATORY ACTIVITY M. Wischnewski*, D.J.L.G. Schutter. Donders Institute, The Netherlands Introduction: Transcranial alternating current stimulation (tACS) has been shown to enhance endogenous oscillatory activity that can outlast the duration of stimulation. However, the majority of research on tACS after-effects has been done investigated during resting state. Here we investigated the effects of d-tACS and q-tACS on evoked endogenous deltatheta activity. Methods: In a double blind within-subjects study twenty-four participants received d-tACS (2.5 Hz), q-tACS (5 Hz) or sham tACS for 12 minutes with an intensity of 1 mA peak-to-peak. Afterwards participants performed a simple decision making task with feedback consisting of rewards and punishments, while an electroencephalogram was recorded from 13 electrodes (sampling rate 1000 Hz, online band-pass filter 0.1-70 Hz). From previous studies it is known that this task evokes delta-theta oscillations 150-600 ms after feedback onset. TACS induced effects on the feedback evoked oscillatory activity were compared to sham. Results: Compared to sham, d-tACS decreased endogenous oscillatory activity between 2.0 and 2.3 Hz. This decrease in oscillatory activity was related to a shift in peak delta-theta peak frequency. In contrast, q-tACS had no effect on oscillatory activity. Discussion: These results show that tACS can decrease, rather than increase, endogenous evoked oscillatory activity. This contrasts findings of studies investigating oscillatory activity at rest, which showed that tACS enhances oscillatory activity. This may suggest that tACS after-effects are state-dependent. Keywords: Delta Oscillations, Offline tACS
[0191] THE COMPLEX RELATIONSHIP BETWEEN PAIN AND MOTOR CORTEX J.P. Lefaucheur*1, 2. 1 Henri Mondor Hospital, Creteil, France; Medicine, Creteil, France
2
Faculty of
Introduction: Pain is a highly disabling condition that interacts with multiple sensori-motor, emotional, and cognitive factors. The aim of this talk is to focus on the complex relationship between pain and motor cortex. Methods: All clinical, neurophysiological, and neuroimaging data corresponding to the interaction between pain (acute experimentally provoked pain or chronic spontaneous pain) and the motor cortex (control of movements, exercise, motor skill learning, or cortical stimulation) have been reviewed. Results: First, acute pain can interfere with motor activities and motor learning capacities. Second, movement can provoke pain at the origin of disability, incapacity, or handicap. Third, chronic pain can induce motor cortex plasticity. Fourth, motor cortex reorganization can, conversely, contribute to chronic pain. Fifth, motor training or exercise can be used to control chronic pain syndromes. Sixth, stimulation of the motor cortex, using invasive or non-invasive techniques, can produce analgesia. All these issues will be addressed according to experimental data and current evidence from the clinical practice in neurology and rehabilitation medicine. Neurophysiological results provided by brain stimulation techniques, especially using transcranial magnetic stimulation (TMS) methods (motor evoked potentials, cortical excitability studies, navigated TMS motor mapping, repetitive TMS), will be emphasized. Discussion: In summary, there is a relationship between chronic pain and motor cortex reorganization, one influencing the other and vice-versa. This relationship needs to be further studied in various pain conditions and to be better exploited to deliver therapeutic solutions for patients with pain, as well as to develop innovative rehabilitative strategies. Keywords: Pain, Motor cortex
Abstracts / Brain Stimulation 10 (2017) 346e540
Results: “Montage B” induces substantially higher electric field levels than “Montage A” and “Montage C” at the genital level. Moreover, the comparison between the two female models shows current density amplitudes and temperature increases higher in the younger subject than in the adult. However, the maxima levels found across the three models and the three montages are widely lower than the limits leading to tissue damage by heating. Significance: This modelling study represents the first contribution that gives quantitative information about genital safety during tsDCS. Keywords: tsDCS, computational modelling, neuromodulation, genital safety [0188] HIGHER TDCS GAIN IN LOW PERFORMERS IN A VERBAL EPISODIC MEMORY TASK € ppel 1, 2, J. Peter 1, 2. A. Habich*1, 2, S. Klo University of Bern, Switzerland
1
University of Freiburg, Germany;
2
Connecting information with a specific context (i.e. episodic memory) is highly relevant for the daily routine but also liable to decline in aging and neuropathological conditions. As the left dorsolateral prefrontal cortex (DLPFC) is involved in the encoding and retrieval of episodic memories, it is frequently targeted in brain stimulation paradigms. Anodal transcranial direct current stimulation (tDCS) that boosts neuronal excitability in stimulated cortical areas has been successfully applied to increase learning and memory performance. However, in view of the large inter-individual variety in performance it can be expected that participants profit from the treatment in a more differential manner. More precisely, we hypothesize that the benefit of the stimulation will depend on the participants' initial performance. In the present randomized, double-blind, parallel study, healthy young and older adults received either anodal tDCS or sham stimulation to their left DLPFC during the encoding phase of a verbal episodic memory task. Forty words were presented visually thrice in a pseudo-randomized order with immediate vocal retrieval after each block and an additional delayed recall. In the young cohort, participants receiving anodal tDCS outperformed participants of the sham group during the late recall while the stimulation effect for the three immediate retrievals was non-significant. A moderation analysis revealed that the number of remembered words in the first retrieval moderated the stimulation effect in such a way that initially low performers experienced the highest gain from the stimulation. These results suggest that the predicted stimulation effect is even greater in cognitively impaired cohorts, such as healthy elderly and patients suffering from neurodegenerative diseases, who are targeted in a clinical context. Keywords: transcranial direct current stimulation, verbal episodic memory [0189] BRAIN STATE DEPENDENCY OF CORTICOSPINAL EXCITABILITY U. Ziemann*, C. Zrenner, D. Desideri, P. Belardinelli. University of Tübingen, Germany Introduction: It is now relatively well known that the instantaneous state of brain has a substantial impact on responses evoked by non-invasive brain stimulation. Methods: Methods that trigger the TMS pulse based on the EEG signal are increasingly available. Using this EEG-TMS method, it is now possible to monitor the instantaneous brain state in real time and utilize the EEG signal to trigger TMS pulses upon specific states (e.g., specific phases of an endogenous oscillation such as the alpha-mu-rhythm of sensorimotor cortex). Results: This presentation will summarize the available data and address two fundamental questions: (1) How do phase and amplitude of the endogenous alpha-mu-rhythm of sensorimotor cortex influence the excitability of the corticospinal system, as measured by the amplitude of motor evoked potentials (MEP) in a contralateral hand muscle? (2) To what extent do instantaneous phase and amplitude of this rhythm influence the intertrial variability in MEP amplitude. Discussion: These questions are of fundamental importance for our understanding of what determines MEP amplitude and its variability.
Keywords: EEG-TMS, Brain state dependent stimulation, MEP amplitude, Alpha-mu-rhythm [0190] THE EFFECTS OF OFFLINE FRONTAL d-TACS ON EVOKED ENDOGENOUS OSCILLATORY ACTIVITY M. Wischnewski*, D.J.L.G. Schutter. Donders Institute, The Netherlands Introduction: Transcranial alternating current stimulation (tACS) has been shown to enhance endogenous oscillatory activity that can outlast the duration of stimulation. However, the majority of research on tACS after-effects has been done investigated during resting state. Here we investigated the effects of d-tACS and q-tACS on evoked endogenous deltatheta activity. Methods: In a double blind within-subjects study twenty-four participants received d-tACS (2.5 Hz), q-tACS (5 Hz) or sham tACS for 12 minutes with an intensity of 1 mA peak-to-peak. Afterwards participants performed a simple decision making task with feedback consisting of rewards and punishments, while an electroencephalogram was recorded from 13 electrodes (sampling rate 1000 Hz, online band-pass filter 0.1-70 Hz). From previous studies it is known that this task evokes delta-theta oscillations 150-600 ms after feedback onset. TACS induced effects on the feedback evoked oscillatory activity were compared to sham. Results: Compared to sham, d-tACS decreased endogenous oscillatory activity between 2.0 and 2.3 Hz. This decrease in oscillatory activity was related to a shift in peak delta-theta peak frequency. In contrast, q-tACS had no effect on oscillatory activity. Discussion: These results show that tACS can decrease, rather than increase, endogenous evoked oscillatory activity. This contrasts findings of studies investigating oscillatory activity at rest, which showed that tACS enhances oscillatory activity. This may suggest that tACS after-effects are state-dependent. Keywords: Delta Oscillations, Offline tACS
[0191] THE COMPLEX RELATIONSHIP BETWEEN PAIN AND MOTOR CORTEX J.P. Lefaucheur*1, 2. 1 Henri Mondor Hospital, Creteil, France; Medicine, Creteil, France
2
Faculty of
Introduction: Pain is a highly disabling condition that interacts with multiple sensori-motor, emotional, and cognitive factors. The aim of this talk is to focus on the complex relationship between pain and motor cortex. Methods: All clinical, neurophysiological, and neuroimaging data corresponding to the interaction between pain (acute experimentally provoked pain or chronic spontaneous pain) and the motor cortex (control of movements, exercise, motor skill learning, or cortical stimulation) have been reviewed. Results: First, acute pain can interfere with motor activities and motor learning capacities. Second, movement can provoke pain at the origin of disability, incapacity, or handicap. Third, chronic pain can induce motor cortex plasticity. Fourth, motor cortex reorganization can, conversely, contribute to chronic pain. Fifth, motor training or exercise can be used to control chronic pain syndromes. Sixth, stimulation of the motor cortex, using invasive or non-invasive techniques, can produce analgesia. All these issues will be addressed according to experimental data and current evidence from the clinical practice in neurology and rehabilitation medicine. Neurophysiological results provided by brain stimulation techniques, especially using transcranial magnetic stimulation (TMS) methods (motor evoked potentials, cortical excitability studies, navigated TMS motor mapping, repetitive TMS), will be emphasized. Discussion: In summary, there is a relationship between chronic pain and motor cortex reorganization, one influencing the other and vice-versa. This relationship needs to be further studied in various pain conditions and to be better exploited to deliver therapeutic solutions for patients with pain, as well as to develop innovative rehabilitative strategies. Keywords: Pain, Motor cortex