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S74: Limitations of visual mismatch negativity for clinical use
Abstracts of Speakers / Clinical Neurophysiology 125, Supplement 1 (2014) S1–S339
S73 Visual mismatch negativity to changes in facial expressions in depressed and control participants P. Astikainen, E. Latva-Nevala, F. Cong University of Jyvaeskylae, Department of Psychology, Jyvaeskylae, Finland We studied whether visual mismatch negativity (vMMN) can be elicited in an ignore condition when rarely presented “deviant” facial expressions violate regularity formed by repeated “standard” faces, and whether this component is modulated in depression. In the first study, ERPs to neutral, fearful, and happy faces in oddball condition and in equiprobable condition were recorded in healthy participants. Independent component analysis (ICA) applied to the differential response (emotional – neutral) revealed two prominent components within 200 ms latency of which the component peaking at 130 ms post stimulus showed a difference in scalp topography between the oddball and the equiprobable conditions, and might conform to vMMN. In the second study, depressed and control participants were presented with happy and fearful deviants interspersed with neutral standard faces. ICA for vMMN/N170 revealed that both groups showed amplitude differences between responses to standard and deviant faces bilaterally in parietal electrodes, but in depression group the differential response was diminished at right hemisphere. In the third experiment, depressed and control participants were exposed to sad and happy faces among neutral faces (both neutral and emotional faces as standards and deviants). Peak amplitude analysis showed that vMMN/N170 was evident only to the emotional deviants, not to the neutral deviants. Depressed participants showed altered facial processing for both happy and sad faces compared to controls. These results suggest that automatic processing of facial expressions is dysfunctional in depression. They also highlight the need to apply proper control conditions when tracing the group differences to the specific cognitions.
S74 Limitations of visual mismatch negativity for clinical use J. Kremlacek Faculty of Medicine in Hradec Kralove, Charles University in Prague, Pathological Physiology, Hradec Kralove, Czech Republic Almost twenty reports have used the visual mismatch negativity (vMMN) to study neurological or neuropsychiatric diseases, to find if perceptual mechanisms responsible for an unintentional prediction of visual temporal events are impaired. The aim of this contribution is to point out important methodical issues limiting the vMMN in current clinical use. Among published studies very different approaches were used to elicit the vMMN, which results to diverse vMMN components with various localizations in time and space. The amplitude of the vMMN component is usually less than 1 μV, comparable to brainstem auditory potentials, and therefore, high number of single vMMN should be acquired to get a reliable result. As the vMMN represents a difference between responses to the deviant and about five times more frequent standard stimuli, the minimum number of responses is about six times higher compared to the aforementioned brainstem potentials. An attentional component mimicking the vMMN further complicates the examination, thus another visual task has to be incorporated in examination. Beside the attention control the examination design should eliminate a sensory fatigue or refractoriness from the vMMN. The vMMN seems to be a valuable tool for its very specific neuropsychological background, however, the concept of the perceptual learning and the attention control requires a high number of responses and puts a distinct load on the patient’s cooperation and attention, which is usually limited. For translation of the vMMN to clinical testing also reproducibility, accuracy and feasibility has to be evaluated. Acknowledgements: Supported by the Charles Univ. project PRVOUK P37/07.
S75 Safety and ethics of transcranial stimulation 2014 P.M. Rossini Catholic University of The Sacred Heart, Neurology, Rome, Italy Non invasive brain stimulation (NIBS) has shown its potential to modulate brain plasticity in human subjects. Transcranial magnetic stimulation (TMS) is a painless procedure that involves a short strong electrical current that is
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delivered through an insulated coil of wire placed over the scalp (magnetic coil). Depending on the frequency, duration of the stimulation, the shape of the coil, and the strength of the magnetic field, TMS can upregulate or downregulate neural excitability under the stimulating coil.Transcranial direct-current stimulation (tDCS) is a procedure used to polarise brain regions through the application of weak direct currents. tDCS is applied through two surface electrodes placed on the skull and enhances or depresses excitability in the stimulated region depending on the polarity, strength, and duration of stimulation.During the last years we have seen a rapid increase of applications of NIBS in studying cognition, brainbehaviour relations and the pathophysiology of various neurologic and psychiatric disorders. Furthermore, a large number of studies and clinical trials have demonstrated a potential therapeutic application of NIBS, especially for TMS, in psychiatric disorders (i.e. depression, bipolar disorders, obsessions/compulsions, schizophrenia, post-traumatic stress disorder, or drug craving), movement disorders (Parkinson’s disease, dystonia, tics, spasticity, or epilepsy), chronic neurogenic pain and stroke rehabilitation. In 2009 a large panel of Experts have revised and developed a new set of guidelines for the safe administration of TMS. The considerations at the basis of new guidelines include ethical and regulatory aspects, stimulation parameters, physiological and neuropsychological monitoring of subjects, settings in which TMS can be done, composition and expertise of the rTMS team, management of potential adverse effects, and contraindications to TMS. O growing body of attention has been progressively focused by the international scientific community on the uses of NIBS in modulating cortical networks so as to produce “enhancements” of brain functional performances in healthy human subjects, from cognition, to motor and memory functions. Cognitive enhancement can be defined as any augmentation of core information processing systems in the brain, including the mechanisms underlying perception, attention, conceptualization, memory, reasoning and motor performance. To date several studies have reported significant improvements in different tasks involving perceptual, motor, and executive processing following for some time NIBS procedures. According to the WADA (World Anti Doping Agency), Doping is defined as “the occurrence of one or more of the anti-doping rule violations set forth in WADA Code”, one of which is “use or attempted use of a prohibited substance or a prohibited method, that has the potential to enhance or enhances human performances or that represent an active or potential health risk”. In relation to above, should we consider the eventual enhancement of brain performances in healthy subjects following NIBS procedures as a kind of “neurodoping”? Today ethic guidelines are urgently needed to integrate safety recommendations and to clarify these fundamental issues.
S76 The diagnostic utility of threshold tracking TMS in amyotrophic lateral sclerosis S. Vucic University of Sydney, Sydney, Australia Objective: The diagnosis of amyotrophic lateral sclerosis (ALS) may rely on stringent clinical criteria, resulting in diagnostic delay and inevitable the institution of appropriate therapy. Cortical hyperexcitability, as assessed by the novel threshold tracking transcranial magnetic stimulation (TTTMS) technique, appears as an early feature of ALS. Consequently, the present study assessed the diagnostic utility of threshold tracking TMS and developed algorithms to aid the diagnosis of ALS. Methods: Prospective studies were undertaken on a cohort of 156 consecutive patients with neuromuscular symptoms (104 ALS and 52 lower motor neuron syndrome, non-ALS syndrome, NALS) and 62 healthy controls. Results: Short-interval intracortical inhibition (SICI) was significantly reduced in ALS patients (2.4±0.9%) compared to NALS (8.7±0.8%, P<0.0001) and controls (10.6±0.8%, P<0.0001). The MEP amplitude and intracortical facilitation were increased, while the cortical silent period duration was reduced in ALS, all indicative of cortical hyperexcitability. Analysis of receiver operating characteristic curves suggested that threshold tracking TMS distinguished ALS from NALS, with averaged (area under curve 0.76, P<0.0001) and peak SICI 3 ms (area under curve 0.73, P<0.0001) being the most robust diagnostic markers. Conclusions: The presence of cortical hyperexcitability distinguishes ALS from mimic disorders. Significance: The threshold tracking TMS techniques may prove useful as a diagnostic investigation for ALS.
S73 Visual mismatch negativity to changes in facial expressions in depressed and control participants P. Astikainen, E. Latva-Nevala, F. Cong University of Jyvaeskylae, Department of Psychology, Jyvaeskylae, Finland We studied whether visual mismatch negativity (vMMN) can be elicited in an ignore condition when rarely presented “deviant” facial expressions violate regularity formed by repeated “standard” faces, and whether this component is modulated in depression. In the first study, ERPs to neutral, fearful, and happy faces in oddball condition and in equiprobable condition were recorded in healthy participants. Independent component analysis (ICA) applied to the differential response (emotional – neutral) revealed two prominent components within 200 ms latency of which the component peaking at 130 ms post stimulus showed a difference in scalp topography between the oddball and the equiprobable conditions, and might conform to vMMN. In the second study, depressed and control participants were presented with happy and fearful deviants interspersed with neutral standard faces. ICA for vMMN/N170 revealed that both groups showed amplitude differences between responses to standard and deviant faces bilaterally in parietal electrodes, but in depression group the differential response was diminished at right hemisphere. In the third experiment, depressed and control participants were exposed to sad and happy faces among neutral faces (both neutral and emotional faces as standards and deviants). Peak amplitude analysis showed that vMMN/N170 was evident only to the emotional deviants, not to the neutral deviants. Depressed participants showed altered facial processing for both happy and sad faces compared to controls. These results suggest that automatic processing of facial expressions is dysfunctional in depression. They also highlight the need to apply proper control conditions when tracing the group differences to the specific cognitions.
S74 Limitations of visual mismatch negativity for clinical use J. Kremlacek Faculty of Medicine in Hradec Kralove, Charles University in Prague, Pathological Physiology, Hradec Kralove, Czech Republic Almost twenty reports have used the visual mismatch negativity (vMMN) to study neurological or neuropsychiatric diseases, to find if perceptual mechanisms responsible for an unintentional prediction of visual temporal events are impaired. The aim of this contribution is to point out important methodical issues limiting the vMMN in current clinical use. Among published studies very different approaches were used to elicit the vMMN, which results to diverse vMMN components with various localizations in time and space. The amplitude of the vMMN component is usually less than 1 μV, comparable to brainstem auditory potentials, and therefore, high number of single vMMN should be acquired to get a reliable result. As the vMMN represents a difference between responses to the deviant and about five times more frequent standard stimuli, the minimum number of responses is about six times higher compared to the aforementioned brainstem potentials. An attentional component mimicking the vMMN further complicates the examination, thus another visual task has to be incorporated in examination. Beside the attention control the examination design should eliminate a sensory fatigue or refractoriness from the vMMN. The vMMN seems to be a valuable tool for its very specific neuropsychological background, however, the concept of the perceptual learning and the attention control requires a high number of responses and puts a distinct load on the patient’s cooperation and attention, which is usually limited. For translation of the vMMN to clinical testing also reproducibility, accuracy and feasibility has to be evaluated. Acknowledgements: Supported by the Charles Univ. project PRVOUK P37/07.
S75 Safety and ethics of transcranial stimulation 2014 P.M. Rossini Catholic University of The Sacred Heart, Neurology, Rome, Italy Non invasive brain stimulation (NIBS) has shown its potential to modulate brain plasticity in human subjects. Transcranial magnetic stimulation (TMS) is a painless procedure that involves a short strong electrical current that is
S17
delivered through an insulated coil of wire placed over the scalp (magnetic coil). Depending on the frequency, duration of the stimulation, the shape of the coil, and the strength of the magnetic field, TMS can upregulate or downregulate neural excitability under the stimulating coil.Transcranial direct-current stimulation (tDCS) is a procedure used to polarise brain regions through the application of weak direct currents. tDCS is applied through two surface electrodes placed on the skull and enhances or depresses excitability in the stimulated region depending on the polarity, strength, and duration of stimulation.During the last years we have seen a rapid increase of applications of NIBS in studying cognition, brainbehaviour relations and the pathophysiology of various neurologic and psychiatric disorders. Furthermore, a large number of studies and clinical trials have demonstrated a potential therapeutic application of NIBS, especially for TMS, in psychiatric disorders (i.e. depression, bipolar disorders, obsessions/compulsions, schizophrenia, post-traumatic stress disorder, or drug craving), movement disorders (Parkinson’s disease, dystonia, tics, spasticity, or epilepsy), chronic neurogenic pain and stroke rehabilitation. In 2009 a large panel of Experts have revised and developed a new set of guidelines for the safe administration of TMS. The considerations at the basis of new guidelines include ethical and regulatory aspects, stimulation parameters, physiological and neuropsychological monitoring of subjects, settings in which TMS can be done, composition and expertise of the rTMS team, management of potential adverse effects, and contraindications to TMS. O growing body of attention has been progressively focused by the international scientific community on the uses of NIBS in modulating cortical networks so as to produce “enhancements” of brain functional performances in healthy human subjects, from cognition, to motor and memory functions. Cognitive enhancement can be defined as any augmentation of core information processing systems in the brain, including the mechanisms underlying perception, attention, conceptualization, memory, reasoning and motor performance. To date several studies have reported significant improvements in different tasks involving perceptual, motor, and executive processing following for some time NIBS procedures. According to the WADA (World Anti Doping Agency), Doping is defined as “the occurrence of one or more of the anti-doping rule violations set forth in WADA Code”, one of which is “use or attempted use of a prohibited substance or a prohibited method, that has the potential to enhance or enhances human performances or that represent an active or potential health risk”. In relation to above, should we consider the eventual enhancement of brain performances in healthy subjects following NIBS procedures as a kind of “neurodoping”? Today ethic guidelines are urgently needed to integrate safety recommendations and to clarify these fundamental issues.
S76 The diagnostic utility of threshold tracking TMS in amyotrophic lateral sclerosis S. Vucic University of Sydney, Sydney, Australia Objective: The diagnosis of amyotrophic lateral sclerosis (ALS) may rely on stringent clinical criteria, resulting in diagnostic delay and inevitable the institution of appropriate therapy. Cortical hyperexcitability, as assessed by the novel threshold tracking transcranial magnetic stimulation (TTTMS) technique, appears as an early feature of ALS. Consequently, the present study assessed the diagnostic utility of threshold tracking TMS and developed algorithms to aid the diagnosis of ALS. Methods: Prospective studies were undertaken on a cohort of 156 consecutive patients with neuromuscular symptoms (104 ALS and 52 lower motor neuron syndrome, non-ALS syndrome, NALS) and 62 healthy controls. Results: Short-interval intracortical inhibition (SICI) was significantly reduced in ALS patients (2.4±0.9%) compared to NALS (8.7±0.8%, P<0.0001) and controls (10.6±0.8%, P<0.0001). The MEP amplitude and intracortical facilitation were increased, while the cortical silent period duration was reduced in ALS, all indicative of cortical hyperexcitability. Analysis of receiver operating characteristic curves suggested that threshold tracking TMS distinguished ALS from NALS, with averaged (area under curve 0.76, P<0.0001) and peak SICI 3 ms (area under curve 0.73, P<0.0001) being the most robust diagnostic markers. Conclusions: The presence of cortical hyperexcitability distinguishes ALS from mimic disorders. Significance: The threshold tracking TMS techniques may prove useful as a diagnostic investigation for ALS.