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Random Noise Stimulation of the Cortex: Stochastic Resonance Enhances Central Mechanisms of Perception
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Abstracts / Brain Stimulation 10 (2017) e1–e19
Purpose: The authors report a case of chronic oral-pharyngeal dystonia, and a resultant profound dysarthria, in a post-encephalitic young woman who demonstrated quantitative improvement during a two-week combined course of priming repetitive transcranial magnetic stimulation (rTMS) and speech therapy. Method: An oral-motor examination and assessment of intelligibility and language skills were customized by the speech-language pathologist (SLP). A personalized speech-language assessment was required due to the level of severity, which was profound. Single pulse TMS mapping was used to locate the left hemisphere motor cortex for the orbicularis oris muscle, to serve as a therapeutic rTMS stimulation site. For 10 consecutive weekdays, 30-minute rTMS sessions were given, immediately followed by 45 minutes of individualized speech therapy. Pre-, mid- and post-treatment videos were taken and presented randomly to a blinded group of 6 SLPs, each having no less than 5 years experience in the assessment and treatment of dysarthria. Each SLP was asked to rate levels of severity for all tasks in each video and judge which video was pre- or post-treatment. Additionally, an objective measurement was taken for the timing of lip closure during verbal production of the phoneme /m/. Results: 5 of the 6 SLPs accurately judged which video was post-treatment. The timing of the patient’s lip closure for /m/ improved, from 61 seconds pre-treatment to 12 seconds post-treatment. Conclusion: This case provides preliminary support for tolerability and efficacy using non-invasive brain stimulation priming for the therapeutic retraining of oro-motor control in acquired dystonia.
11 OPEN EPHYS ELECTROENCEPHALOGRAPHY: A NOVEL METHOD FOR REAL-TIME RECORDING DURING TRANSCRANIAL ALTERNATING CURRENT STIMULATION Chris J. Black a,b,*, Jakob Voigts a,c, Chris I. Moore a, Stephanie R. Jones a. a Department of Neuroscience, Brown University, Providence, RI, USA; b Department of Biomedical Engineering, Brown University, Providence, RI, USA; c Department of Brain and Cognitive Science, Massachusetts Institute of Technology, Cambridge, MA, USA * Corresponding author. Transcranial alternating current stimulation (tACS) is a frequency dependent, non-invasive stimulation technique used to treat an array of neurological disorders. While the therapeutic effects of tACS are clear the mechanism of action is poorly understood. Electroencephalography (EEG), a neural recording technique with high temporal resolution, offers a non-invasive method to study the effects of tACS on neural activity. Currently, stimulation from tACS obscures EEG signals and produces irregularities in bio amplifier operations, hindering the ability to simultaneously stimulate and record. Post-processing techniques can extract signals from noisy recordings but also results in data loss. Alternatively, EEG can be done post-stimulation but powering up electronics causes delays for signal acquisition. We have addressed these issues by developing EEG compatibility on the open-electrophysiology platform, Open Ephys. By recording EEG on the Open Ephys platform we can reduce the time lag in data acquisition. Open ephys employs an Intan Technologies RHD2000 amplifier chip that provides an amplifier fast settle function. Amplifier output can be set and held at zero, and then reset to normal operation within 200 microseconds. Implementing this low-latency, fast settle function during tACS inhibits amplifier saturation from high voltage inputs allowing for reliable EEG recording immediately following stimulation. Monitoring this resulting neural activity
has strong implications in optimizing stimulation based therapies and neural-interface technologies. We are currently applying this system to study the impact of tACS on somatosensation and pain. Acknowledgements: We thank Reid Harrison of Intan Technologies, everyone who has contributed to Open Ephys, and the Rhode Island NASA Space Grant Consortium for their support.
12 RANDOM NOISE STIMULATION OF THE CORTEX: STOCHASTIC RESONANCE ENHANCES CENTRAL MECHANISMS OF PERCEPTION Onno van der Groen *, Nicole Wenderoth. Neural Control of Movement Lab, Department of Health Sciences and Technology, ETH Zurich, Switzerland * Corresponding author. It has been demonstrated that detection thresholds decrease by adding random noise to the peripheral nervous system (Simonotto et al., 1996, Collins et al., 1996) in accordance to a stochastic resonance (SR) phenomenon. Psychophysical experiments in humans suggest that SR in the visual system can occur in the primary visual cortex (Aihara et al., 2008). In an EEG (electroencephalography) study in humans, it was shown that when a small amount of tactile random noise was applied to a tactile signal on the fingertip signal-to-noise ratio of the EEG signals decreased for the optimal level of peripheral noise, which is a characteristic of SR (Manjarrez et al., 2003). In previous work, signal and noise were always applied to the peripheral nervous system and not directly to the central nervous system. The question arises as to whether SR-like behavior occurs if noise is added to cortical areas. Here subjects performed a visual perception task while different levels of noise were added either to the peripheral or central nervous system. Peripheral noise was zero-mean Gaussian noise represented on the screen. Central noise was applied via transcranial random noise stimulation (tRNS, 100-640 Hz, intensity varying between 0 and 1.5 mA) with one electrode overlying the visual cortex. Our results indicate that a small amount of peripheral as well as central noise induces a SR effect for sub-threshold stimuli, i.e. the detection threshold is reduced for optimal noise levels. Increasing the noise beyond the optimal amount does not benefit perception.
13 EFFECTS OF TDCS ON STEPPING REACTION IN HEALTHY ADULTS AND INDIVIDUALS WITH CHRONIC STROKE Shuo-Hsiu Chang a,*, Joshua Choi b, Shih-Chiao Tseng c. a Department of Physical Medicine and Rehabilitation, UT Health, Houston, TX, USA; b Department of Bioengineering, Rice University, Houston, TX, USA; c School of Physical Therapy, Texas Women’s University, Houston, TX, USA * Corresponding author. Stepping is an important protective reaction to prevent falls and fall related injuries and this ability is usually impaired in elderly and individuals with stroke. This impaired stepping reaction is characterized by prolong reaction time and decrease neuromuscular control. Transcranial direct current stimulation (tDCS) has been applied in human to enhance cortical excitability and in turn
Abstracts / Brain Stimulation 10 (2017) e1–e19
Purpose: The authors report a case of chronic oral-pharyngeal dystonia, and a resultant profound dysarthria, in a post-encephalitic young woman who demonstrated quantitative improvement during a two-week combined course of priming repetitive transcranial magnetic stimulation (rTMS) and speech therapy. Method: An oral-motor examination and assessment of intelligibility and language skills were customized by the speech-language pathologist (SLP). A personalized speech-language assessment was required due to the level of severity, which was profound. Single pulse TMS mapping was used to locate the left hemisphere motor cortex for the orbicularis oris muscle, to serve as a therapeutic rTMS stimulation site. For 10 consecutive weekdays, 30-minute rTMS sessions were given, immediately followed by 45 minutes of individualized speech therapy. Pre-, mid- and post-treatment videos were taken and presented randomly to a blinded group of 6 SLPs, each having no less than 5 years experience in the assessment and treatment of dysarthria. Each SLP was asked to rate levels of severity for all tasks in each video and judge which video was pre- or post-treatment. Additionally, an objective measurement was taken for the timing of lip closure during verbal production of the phoneme /m/. Results: 5 of the 6 SLPs accurately judged which video was post-treatment. The timing of the patient’s lip closure for /m/ improved, from 61 seconds pre-treatment to 12 seconds post-treatment. Conclusion: This case provides preliminary support for tolerability and efficacy using non-invasive brain stimulation priming for the therapeutic retraining of oro-motor control in acquired dystonia.
11 OPEN EPHYS ELECTROENCEPHALOGRAPHY: A NOVEL METHOD FOR REAL-TIME RECORDING DURING TRANSCRANIAL ALTERNATING CURRENT STIMULATION Chris J. Black a,b,*, Jakob Voigts a,c, Chris I. Moore a, Stephanie R. Jones a. a Department of Neuroscience, Brown University, Providence, RI, USA; b Department of Biomedical Engineering, Brown University, Providence, RI, USA; c Department of Brain and Cognitive Science, Massachusetts Institute of Technology, Cambridge, MA, USA * Corresponding author. Transcranial alternating current stimulation (tACS) is a frequency dependent, non-invasive stimulation technique used to treat an array of neurological disorders. While the therapeutic effects of tACS are clear the mechanism of action is poorly understood. Electroencephalography (EEG), a neural recording technique with high temporal resolution, offers a non-invasive method to study the effects of tACS on neural activity. Currently, stimulation from tACS obscures EEG signals and produces irregularities in bio amplifier operations, hindering the ability to simultaneously stimulate and record. Post-processing techniques can extract signals from noisy recordings but also results in data loss. Alternatively, EEG can be done post-stimulation but powering up electronics causes delays for signal acquisition. We have addressed these issues by developing EEG compatibility on the open-electrophysiology platform, Open Ephys. By recording EEG on the Open Ephys platform we can reduce the time lag in data acquisition. Open ephys employs an Intan Technologies RHD2000 amplifier chip that provides an amplifier fast settle function. Amplifier output can be set and held at zero, and then reset to normal operation within 200 microseconds. Implementing this low-latency, fast settle function during tACS inhibits amplifier saturation from high voltage inputs allowing for reliable EEG recording immediately following stimulation. Monitoring this resulting neural activity
has strong implications in optimizing stimulation based therapies and neural-interface technologies. We are currently applying this system to study the impact of tACS on somatosensation and pain. Acknowledgements: We thank Reid Harrison of Intan Technologies, everyone who has contributed to Open Ephys, and the Rhode Island NASA Space Grant Consortium for their support.
12 RANDOM NOISE STIMULATION OF THE CORTEX: STOCHASTIC RESONANCE ENHANCES CENTRAL MECHANISMS OF PERCEPTION Onno van der Groen *, Nicole Wenderoth. Neural Control of Movement Lab, Department of Health Sciences and Technology, ETH Zurich, Switzerland * Corresponding author. It has been demonstrated that detection thresholds decrease by adding random noise to the peripheral nervous system (Simonotto et al., 1996, Collins et al., 1996) in accordance to a stochastic resonance (SR) phenomenon. Psychophysical experiments in humans suggest that SR in the visual system can occur in the primary visual cortex (Aihara et al., 2008). In an EEG (electroencephalography) study in humans, it was shown that when a small amount of tactile random noise was applied to a tactile signal on the fingertip signal-to-noise ratio of the EEG signals decreased for the optimal level of peripheral noise, which is a characteristic of SR (Manjarrez et al., 2003). In previous work, signal and noise were always applied to the peripheral nervous system and not directly to the central nervous system. The question arises as to whether SR-like behavior occurs if noise is added to cortical areas. Here subjects performed a visual perception task while different levels of noise were added either to the peripheral or central nervous system. Peripheral noise was zero-mean Gaussian noise represented on the screen. Central noise was applied via transcranial random noise stimulation (tRNS, 100-640 Hz, intensity varying between 0 and 1.5 mA) with one electrode overlying the visual cortex. Our results indicate that a small amount of peripheral as well as central noise induces a SR effect for sub-threshold stimuli, i.e. the detection threshold is reduced for optimal noise levels. Increasing the noise beyond the optimal amount does not benefit perception.
13 EFFECTS OF TDCS ON STEPPING REACTION IN HEALTHY ADULTS AND INDIVIDUALS WITH CHRONIC STROKE Shuo-Hsiu Chang a,*, Joshua Choi b, Shih-Chiao Tseng c. a Department of Physical Medicine and Rehabilitation, UT Health, Houston, TX, USA; b Department of Bioengineering, Rice University, Houston, TX, USA; c School of Physical Therapy, Texas Women’s University, Houston, TX, USA * Corresponding author. Stepping is an important protective reaction to prevent falls and fall related injuries and this ability is usually impaired in elderly and individuals with stroke. This impaired stepping reaction is characterized by prolong reaction time and decrease neuromuscular control. Transcranial direct current stimulation (tDCS) has been applied in human to enhance cortical excitability and in turn