Amplitude-modulated Stimulation Research Articles

Characteristics of the Deconvolved Transient AEP from 80Hz Steady-State Responses to Amplitude Modulation Stimulation.

This study aimed to validate the existence and investigate the characteristics of the transient responses from conventional auditory steady-state responses (ASSRs) using deconvolution methods capable of dealing with amplitude modulated (AM) stimulation. Conventional ASSRs to seven stimulus rates were recorded from 17 participants. A deconvolution method was selected and modified to accommodate the AM stimulation. The calculated responses were examined in terms of temporal features with respect to different combinations of stimulus rates. Stable transient responses consisting of early stage brainstem responses and middle latency responses were reconstructed consistently for all rate combinations, which indicates that the superposition hypothesis is applicable to the generation of approximately 80Hz ASSRs evoked by AM tones (AM-ASSRs). The new transient responses are characterized by three pairs of peak-troughs named as n0p0, n1p1, and n2p2 within 40ms. Compared with conventional ABR-MLRs, the n0p0 indicates the first neural activity where p0 might represent the main ABR components; the n1 is the counterpart of N10; the p2 is corresponding to the robust Pa at about 30ms; the p1 and n2 are absent of real counterparts. The peak-peak amplitudes show a slight decrease with increasing stimulation rate from 75 to 95Hz whereas the peak latencies change differently, which is consistent with the known rate-effect on AEPs. This is direct evidence for a transient response derived from AM-ASSRs for the first time. The characteristic components offer insight into the constitution of AM-ASSRs and may be promising in clinical applications and fundamental studies.

Temporal interference stimulation targets deep brain regions by modulating neural oscillations

BackgroundTemporal interference (TI) stimulation of the brain generates amplitude-modulated electric fields oscillating in the kHz range with the goal of non-invasive targeted deep brain stimulation. Yet, the current intensities required in human (sensitivity) to modulate deep brain activity and if superficial brain region are spared (selectivity) at these intensities remains unclear. ObjectiveWe developed an experimentally constrained theory for TI sensitivity to kHz electric field given the attenuation by membrane low-pass filtering property, and for TI selectivity to deep structures given the distribution of modulated and unmodulated electric fields in brain. MethodsThe electric field threshold to modulate carbachol-induced gamma oscillations in rat hippocampal slices was determined for unmodulated 0.05–2 kHz sine waveforms, and 5 Hz amplitude-modulated waveforms with 0.1–2 kHz carrier frequencies. The neuronal effects are replicated with a computational network model to explore the underlying mechanisms, and then coupled to a validated current-flow model of the human head. ResultsAmplitude-modulated electric fields are stronger in deep brain regions, while unmodulated electric fields are maximal at the cortical regions. Both experiment and model confirmed the hypothesis that spatial selectivity of temporal interference stimulation depends on the phasic modulation of neural oscillations only in deep brain regions. Adaptation mechanism (e.g. GABAb) enhanced sensitivity to amplitude modulated waveform in contrast to unmodulated kHz and produced selectivity in modulating gamma oscillation (i.e. Higher gamma modulation in amplitude modulated vs unmodulated kHz stimulation). Selection of carrier frequency strongly affected sensitivity to amplitude modulation stimulation. Amplitude modulated stimulation with 100 Hz carrier frequency required ∼5 V/m (corresponding to ∼13 mA at the scalp surface), whereas, 1 kHz carrier frequency ∼60 V/m (∼160 mA) and 2 kHz carrier frequency ∼80 V/m (∼220 mA) to significantly modulate gamma oscillation. Sensitivity is increased (scalp current required decreased) for theoretical neuronal membranes with faster time constants. ConclusionThe TI sensitivity (current required at the scalp) depends on the neuronal membrane time-constant (e.g. axons) approaching the kHz carrier frequency. TI selectivity is governed by network adaption (e.g. GABAb) that is faster than the amplitude-modulation frequency. Thus, we show neuronal and network oscillations time-constants determine the scalp current required and the selectivity achievable with TI in humans.

Targeting alpha-band oscillations in a cortical model with amplitude-modulated high-frequency transcranial electric stimulation

Non-invasive brain stimulation to target specific network activity patterns, e.g. transcranial alternating current stimulation (tACS), has become an essential tool to understand the causal role of neuronal oscillations in cognition and behavior. However, conventional sinusoidal tACS limits the ability to record neuronal activity during stimulation and lacks spatial focality. One particularly promising new tACS stimulation paradigm uses amplitude-modulated (AM) high-frequency waveforms (AM-tACS) with a slow signal envelope that may overcome the limitations. Moreover. AM-tACS using high-frequency carrier signals is more tolerable than conventional tACS, e.g. in terms of skin irritation and occurrence of phosphenes, when applied at the same current intensities (e.g. 1–2 mA). Yet, the fundamental mechanism of neuronal target-engagement by AM-tACS waveforms has remained unknown. We used a computational model of cortex to investigate how AM-tACS modulates endogenous oscillations and compared the target engagement mechanism to the case of conventional (unmodulated) low-frequency tACS. Analysis of stimulation amplitude and frequency indicated that cortical oscillations were phase-locked to the envelope of the AM stimulation signal, which thus exhibits the same target engagement mechanism as conventional (unmodulated) low frequency tACS. However, in the computational model substantially higher current intensities were needed for AM-tACS than for low-frequency (unmodulated) tACS waveforms to achieve pronounced phase synchronization. Our analysis of the carrier frequency suggests that there might be a trade-off between the use of high-frequency carriers and the stimulation amplitude required for successful entrainment. Together, our computational simulations support the use of slow-envelope high frequency carrier AM waveforms as a tool for noninvasive modulation of brain oscillations. More empirical data will be needed to identify the optimal stimulation parameters and to evaluate tolerability and safety of both, AM- and conventional tACS.

Steady-State EEG and Psychophysical Measures of Multisensory Integration to Cross-Modally Synchronous and Asynchronous Acoustic and Vibrotactile AmplitudeModulation Rate.

According to the temporal principle of multisensory integration, cross-modal synchronisation of stimulus onset facilitates multisensory integration. This is typically observed as a greater response to multisensory stimulation relative to the sum of the constituent unisensory responses (i.e., superadditivity). The aim of the present study was to examine whether the temporal principle extends to the cross-modal synchrony of amplitude-modulation (AM) rate. It is well established that psychophysical sensitivity to AM stimulation is strongly influenced by AM rate where the optimum rate differs according to sensory modality. This rate-dependent sensitivity is also apparent from EEG steady-state response (SSR) activity, which becomes entrained to the stimulation rate and is thought to reflect neural processing of the temporal characteristics of AM stimulation. In this study we investigated whether cross-modal congruence of AM rate reveals both psychophysical and EEG evidence of enhanced multisensory integration. To achieve this, EEG SSR and psychophysical sensitivity to simultaneous acoustic and/or vibrotactile AM stimuli were measured at cross-modally congruent and incongruent AM rates. While the results provided no evidence of superadditive multisensory SSR activity or psychophysical sensitivity, the complex pattern of results did reveal a consistent correspondence between SSR activity and psychophysical sensitivity to AM stimulation. This indicates that entrained EEG activity may provide a direct measure of cortical activity underlying multisensory integration. Consistent with the temporal principle of multisensory integration, increased vibrotactile SSR responses and psychophysical sensitivity were found for cross-modally congruent relative to incongruent AM rate. However, no corresponding increase in auditory SSR or psychophysical sensitivity was observed for cross-modally congruent AM rates. This complex pattern of results can be understood in terms of the likely influence of the principle of inverse effectiveness where the temporal principle of multisensory integration was only evident in the context of reduced perceptual sensitivity for the vibrotactile but not the auditory modality.

Single photon detection and signal analysis for high sensitivity dosimetry based on optically stimulated luminescence with beryllium oxide

Single photon detection applied to optically stimulated luminescence (OSL) dosimetry is a promising approach due to the low level of luminescence light and the known statistical behavior of single photon events. Time resolved detection allows to apply a variety of different and independent data analysis methods. Furthermore, using amplitude modulated stimulation impresses time- and frequency information into the OSL light and therefore allows for additional means of analysis. Considering the impressed frequency information, data analysis by using Fourier transform algorithms or other digital filters can be used for separating the OSL signal from unwanted light or events generated by other phenomena. This potentially lowers the detection limits of low dose measurements and might improve the reproducibility and stability of obtained data. In this work, an OSL system based on a single photon detector, a fast and accurate stimulation unit and an FPGA is presented. Different analysis algorithms which are applied to the single photon data are discussed.

Independent component analysis for cochlear implant artifacts attenuation from electrically evoked auditory steady-state response measurements

Objective. Electrically evoked auditory steady-state responses (EASSRs) are potentially useful for objective cochlear implant (CI) fitting and follow-up of the auditory maturation in infants and children with a CI. EASSRs are recorded in the electro-encephalogram (EEG) in response to electrical stimulation with continuous pulse trains, and are distorted by significant CI artifacts related to this electrical stimulation. The aim of this study is to evaluate a CI artifacts attenuation method based on independent component analysis (ICA) for three EASSR datasets. Approach. ICA has often been used to remove CI artifacts from the EEG to record transient auditory responses, such as cortical evoked auditory potentials. Independent components (ICs) corresponding to CI artifacts are then often manually identified. In this study, an ICA based CI artifacts attenuation method was developed and evaluated for EASSR measurements with varying CI artifacts and EASSR characteristics. Artifactual ICs were automatically identified based on their spectrum. Main results. For 40 Hz amplitude modulation (AM) stimulation at comfort level, in high SNR recordings, ICA succeeded in removing CI artifacts from all recording channels, without distorting the EASSR. For lower SNR recordings, with 40 Hz AM stimulation at lower levels, or 90 Hz AM stimulation, ICA either distorted the EASSR or could not remove all CI artifacts in most subjects, except for two of the seven subjects tested with low level 40 Hz AM stimulation. Noise levels were reduced after ICA was applied, and up to 29 ICs were rejected, suggesting poor ICA separation quality. Significance. We hypothesize that ICA is capable of separating CI artifacts and EASSR in case the contralateral hemisphere is EASSR dominated. For small EASSRs or large CI artifact amplitudes, ICA separation quality is insufficient to ensure complete CI artifacts attenuation without EASSR distortion.

Do Cross-Modal Phase Differences between Acoustic and Vibrotactile AM Stimuli Influence Audio-Tactile Integration? A Psychophysical and EEG Investigation

Event Abstract Back to Event Do Cross-Modal Phase Differences between Acoustic and Vibrotactile AM Stimuli Influence Audio-Tactile Integration? A Psychophysical and EEG Investigation Justin Timora1* and Timothy Budd1 1 University of Newcastle, Psychology, Australia Previous research has found that cross-modal temporal correspondence enhances behavioural and neurophysiological responses to multisensory, relative to unisensory stimulation. It is also well established that the dynamic temporal characteristics of sensory stimulation, such as amplitude modulation (AM), play an important role in unisensory perception. The aim of the present study was to extend previous research by examining the influence of cross-modal phase correspondence on simultaneous auditory and vibrotactile AM stimulation on both perceptual sensitivity and the steady-state response, an EEG measure of oscillatory activity associated with auditory and tactile temporal processing. To achieve this, psychophysical AM detection thresholds and EEG power at EEG frequencies corresponding to the AM rates of stimulation were measured across three cross-modal phase conditions: None (AM stimuli in the target modality alone); Same (AM in modalities/no phase difference) and Different (AM in both modalities/180? phase difference). Analysis of the detection thresholds revealed that vibrotactile and auditory thresholds were significantly lower for None conditions relative to both Same and Different conditions. SSR results showed that multisensory AM stimulation significantly increased EEG power at the frequency of stimulation. The increased psychophysical thresholds in the simultaneous AM stimulation conditions suggest that multisensory AM stimulation decrease sensitivity to AM stimuli. Increases in the magnitude of SSR activity for simultaneous AM stimulation conditions indicate that multisensory AM stimulation enhances the entrainment of oscillatory cortical activity associated with temporal processing. The differences found between the psychophysical and SSR results question the role of oscillatory activity underlying the SSR in audio-tactile multisensory integration. Keywords: amplitude modulation, multisensory integration, temporal processing, Steady-state response, Temporal correspondence Conference: XII International Conference on Cognitive Neuroscience (ICON-XII), Brisbane, Queensland, Australia, 27 Jul - 31 Jul, 2014. Presentation Type: Poster Topic: Sensation and Perception Citation: Timora J and Budd T (2015). Do Cross-Modal Phase Differences between Acoustic and Vibrotactile AM Stimuli Influence Audio-Tactile Integration? A Psychophysical and EEG Investigation. Conference Abstract: XII International Conference on Cognitive Neuroscience (ICON-XII). doi: 10.3389/conf.fnhum.2015.217.00371 Copyright: The abstracts in this collection have not been subject to any Frontiers peer review or checks, and are not endorsed by Frontiers. They are made available through the Frontiers publishing platform as a service to conference organizers and presenters. The copyright in the individual abstracts is owned by the author of each abstract or his/her employer unless otherwise stated. Each abstract, as well as the collection of abstracts, are published under a Creative Commons CC-BY 4.0 (attribution) licence (https://creativecommons.org/licenses/by/4.0/) and may thus be reproduced, translated, adapted and be the subject of derivative works provided the authors and Frontiers are attributed. For Frontiers’ terms and conditions please see https://www.frontiersin.org/legal/terms-and-conditions. Received: 19 Feb 2015; Published Online: 24 Apr 2015. * Correspondence: Mr. Justin Timora, University of Newcastle, Psychology, Newcastle, Australia, justin.timora@uon.edu.au Login Required This action requires you to be registered with Frontiers and logged in. To register or login click here. Abstract Info Abstract The Authors in Frontiers Justin Timora Timothy Budd Google Justin Timora Timothy Budd Google Scholar Justin Timora Timothy Budd PubMed Justin Timora Timothy Budd Related Article in Frontiers Google Scholar PubMed Abstract Close Back to top Javascript is disabled. Please enable Javascript in your browser settings in order to see all the content on this page.

Steady state responses to temporally congruent and incongruent auditory and vibrotactile amplitude modulated stimulation

Recent research suggests that multisensory integration may occur at an early phase in sensory processing and within cortical regions traditionally though to be exclusively unisensory. Evidence from perceptual and electrophysiological studies indicate that the cross modal temporal correspondence of multisensory stimuli plays a fundamental role in the cortical integration of information across separate sensory modalities. Further, oscillatory neural activity in sensory cortices may provide the principle mechanism whereby sensory information from separate modalities is integrated.In the present study we aimed to extend this prior research by using the steady-state EEG response (SSR) to examine whether variations in the cross-modality temporal correspondence of amplitude modulated auditory and vibrotactile stimulation are apparent in SSR activity to multisensory stimulation. To achieve this we varied the cross-modal congruence of modulation rate for passively and simultaneously presented amplitude modulated auditory and vibrotactile stimuli. In order to maximise the SSR response in both modalities 21 and 40Hz modulation rates were selected. Consistent with prior SSR studies, the present results showed clear evidence of phase-locking for EEG frequencies corresponding to the modulation rate of auditory and vibrotactile stimulation. As also found previously, the optimal modulation rate for SSR activity differed according to the modality, being greater at 40Hz for auditory responses and greater at 21Hz for vibrotactile responses. Despite consistent and reliable changes in SSR activity with manipulations of modulation rate within modality, the present study failed to provide strong evidence of multisensory interactions in SSR activity for temporally congruent, relative to incongruent, cross modal conditions. The results are discussed in terms of the role of attention as a possible factor in reconciling inconsistencies in SSR studies of multisensory integration.

Cross-Modal Modulation Masking: A Psychophysical and EEG Investigation of Simultaneous Acoustic and Vibrotactile Amplitude Modulation.

Event Abstract Back to Event Cross-Modal Modulation Masking: A Psychophysical and EEG Investigation of Simultaneous Acoustic and Vibrotactile Amplitude Modulation. Justin R. Timora1* and Timothy W. Budd1 1 University of Newcastle, Australia Aims: Modulation masking refers to a disruption in the ability to detect amplitude modulation (AM) in sound in the presence of an auditory masker with a similar temporal pattern. Previously, we have shown that multisensory presentations of acoustic and vibrotactile AM stimuli increase auditory and vibrotactile AM detection thresholds, suggesting a cross-modal modulation masking effect. Prior psychoacoustic research suggests that this masking effect is dependent on the phase of the AM masker. This study aimed to determine whether cross-modal phase differences for simultaneously presented acoustic and vibrotactile AM stimuli increase AM detection thresholds and whether this is reflected in the steady-state response (SSR) elicited by the same multisensory stimulus combinations. Method: A 2I-3AFC psychophysical procedure was used to estimate AM detection thresholds for auditory and vibrotactile stimuli at two AM rates (27 and 40 Hz) and three cross-modal phase conditions: None (AM stimulation in the target modality only); Same (AM in both modalities /no cross-modal phase difference); Different (AM stimulation in both modalities/180˚ phase difference). In a separate EEG session SSR activity was measured to the same stimulus combinations. Results: Vibrotactile AM thresholds significantly varied according to Phase F(2,28)= 4.81,p = .02. Thresholds for the Same condition were higher relative to None F(1,14) = 8.06, p =.01. Differences between None and Different were non-significant. The influence of Phase on auditory 27 and 40 Hz SSR activity significantly varied according to AM rate F(2,16) = 8.65, p =.003, F(2,16) = 6.43, p=.01, with greater increases in activity at the EEG frequency corresponding to the AM rate. Conclusions: The increased sensitivity to vibrotactile AM stimuli resulting from a cross-modal phase difference suggests a release from masking and provides further evidence of cross-modal modulation masking. Cross-modal AM stimulation increases auditory SSR activity at the frequency of stimulation but has no effect on vibrotactile SSR activity which suggests a dissociation between SSR activity and AM detection. Keywords: amplitude modulation, auditory steady-state responses (ASSRs), vibrotactile steady-state responses, cross-modal modulation masking, temporal processing Conference: ASP2013 - 23rd Annual meeting of the Australasian Society for Psychophysiology, Wollongong, Australia, 20 Nov - 22 Nov, 2013. Presentation Type: Poster Presentation Topic: Perception Citation: Timora JR and Budd TW (2013). Cross-Modal Modulation Masking: A Psychophysical and EEG Investigation of Simultaneous Acoustic and Vibrotactile Amplitude Modulation.. Conference Abstract: ASP2013 - 23rd Annual meeting of the Australasian Society for Psychophysiology. doi: 10.3389/conf.fnhum.2013.213.00006 Copyright: The abstracts in this collection have not been subject to any Frontiers peer review or checks, and are not endorsed by Frontiers. They are made available through the Frontiers publishing platform as a service to conference organizers and presenters. The copyright in the individual abstracts is owned by the author of each abstract or his/her employer unless otherwise stated. Each abstract, as well as the collection of abstracts, are published under a Creative Commons CC-BY 4.0 (attribution) licence (https://creativecommons.org/licenses/by/4.0/) and may thus be reproduced, translated, adapted and be the subject of derivative works provided the authors and Frontiers are attributed. For Frontiers’ terms and conditions please see https://www.frontiersin.org/legal/terms-and-conditions. Received: 31 Oct 2013; Published Online: 05 Nov 2013. * Correspondence: Mr. Justin R Timora, University of Newcastle, Newcastle, Australia, justin.timora@uon.edu.au Login Required This action requires you to be registered with Frontiers and logged in. To register or login click here. Abstract Info Abstract The Authors in Frontiers Justin R Timora Timothy W Budd Google Justin R Timora Timothy W Budd Google Scholar Justin R Timora Timothy W Budd PubMed Justin R Timora Timothy W Budd Related Article in Frontiers Google Scholar PubMed Abstract Close Back to top Javascript is disabled. Please enable Javascript in your browser settings in order to see all the content on this page.

Multisensory integration of temporal processing in the auditory and somatosensory modalities: A psychophysical and EEG study.

Event Abstract Back to Event Multisensory integration of temporal processing in the auditory and somatosensory modalities: A psychophysical and EEG study. Justin Timora1* and Timothy Budd1 1 University of Newcastle, Australia Prior research examining multisensory integration has established the importance of the cross modal correspondence of temporal information. In the present study we examine the perceptual and neurophysiological impact of cross modal variations in amplitude modulation (AM) rate of acoustic and vibrotactile stimulation. To achieve this 33 participants completed separate psychophysical and EEG recording sessions where the cross modal correspondence of AM rate was varied. For the psychophysical session AM detection thresholds were estimated for 21 and 40 Hz auditory and vibrotactile stimuli where AM rate varied across modalities in one of three different cross modal correspondence (CMC) conditions, being either the SAME, DIFFERENT or NONE (i.e. unmodulated). For the EEG session identical stimulation conditions were presented and an FFT analysis carried out to determine whether EEG entrainment at each AM rate varied according to cross modal correspondence of temporal stimulation. The psychophysical results showed significant decreases in AM detection thresholds for conditions where the non-target modality was amplitude modulated at the same rate as the target modality (i.e. SAME), indicating reduced perceptual sensitivity when stimuli in both modalities were amplitude modulated. In contrast the results of the EEG analysis showed the opposite relationship, where EEG activity at the stimulation rate (i.e. entrainment) showed increases in EEG power for stimulus conditions where cross modal correspondence for AM stimulation was the same (i.e. SAME). These results suggest a potential dissociation between perception and EEG activity and are discussed in terms of the relationship between oscillatory neural activity and multisensory integration. Keywords: multisensory integration, multisensory processing, steady state, amplitude modulation, temporal processing Conference: ACNS-2012 Australasian Cognitive Neuroscience Conference, Brisbane, Australia, 29 Nov - 2 Dec, 2012. Presentation Type: Poster Presentation Topic: Sensation and Perception Citation: Timora J and Budd T (2012). Multisensory integration of temporal processing in the auditory and somatosensory modalities: A psychophysical and EEG study.. Conference Abstract: ACNS-2012 Australasian Cognitive Neuroscience Conference. doi: 10.3389/conf.fnhum.2012.208.00173 Copyright: The abstracts in this collection have not been subject to any Frontiers peer review or checks, and are not endorsed by Frontiers. They are made available through the Frontiers publishing platform as a service to conference organizers and presenters. The copyright in the individual abstracts is owned by the author of each abstract or his/her employer unless otherwise stated. Each abstract, as well as the collection of abstracts, are published under a Creative Commons CC-BY 4.0 (attribution) licence (https://creativecommons.org/licenses/by/4.0/) and may thus be reproduced, translated, adapted and be the subject of derivative works provided the authors and Frontiers are attributed. For Frontiers’ terms and conditions please see https://www.frontiersin.org/legal/terms-and-conditions. Received: 14 Oct 2012; Published Online: 17 Nov 2012. * Correspondence: Mr. Justin Timora, University of Newcastle, Newcastle, Australia, justin.timora@uon.edu.au Login Required This action requires you to be registered with Frontiers and logged in. To register or login click here. Abstract Info Abstract The Authors in Frontiers Justin Timora Timothy Budd Google Justin Timora Timothy Budd Google Scholar Justin Timora Timothy Budd PubMed Justin Timora Timothy Budd Related Article in Frontiers Google Scholar PubMed Abstract Close Back to top Javascript is disabled. Please enable Javascript in your browser settings in order to see all the content on this page.

Vibrotactile Sensory Substitution for Object Manipulation: Amplitude Versus Pulse Train Frequency Modulation

Incorporating sensory feedback with prosthetic devices is now possible, but the optimal methods of providing such feedback are still unknown. The relative utility of amplitude and pulse train frequency modulated stimulation paradigms for providing vibrotactile feedback for object manipulation was assessed in 10 participants. The two approaches were studied during virtual object manipulation using a robotic interface as a function of presentation order and a simultaneous cognitive load. Despite the potential pragmatic benefits associated with pulse train frequency modulated vibrotactile stimulation, comparison of the approach with amplitude modulation indicates that amplitude modulation vibrotactile stimulation provides superior feedback for object manipulation.

Hindlimb movement in the cat induced by amplitude-modulated stimulation using extra-spinal electrodes

Hindlimb movement in the cat induced by electrical stimulation with an amplitude-modulated waveform of the dorsal surface of the L5-S1 spinal cord or the L5-S1 dorsal/ventral roots was investigated before and after acute spinal cord transection at the T13-L1 level. Stimulation of the spinal cord or dorsal/ventral root at the same spinal segment induced similar movements including coordinated multi-joint flexion or extension. The induced movements changed from flexion to extension when the stimulation was moved from rostral (L5) to caudal (S1) spinal segments. Stimulation of a dorsal or ventral root on one side induced only ipsilateral hindlimb movement. However, stimulation on the dorsal surface of the spinal cord along the midline or across the spinal cord induced bilateral movements. The extension induced by stimulation of L7 dorsal root produced the largest ground reaction force that was strong enough to support body weight. Dorsal root stimulation induced a larger ground reaction force than ventral root stimulation and produced a more graded recruitment curve. Stepping at different speeds could be generated by combined stimulation of the rostral (L5) and the caudal (L6/L7) spinal segments with an appropriate timing between the different stimulation channels. Acute transection of the spinal cord did not change the responses indicating that the induced movements did not require the involvement of the supraspinal locomotor centers. The methods and the stimulation strategy developed in this study might be utilized to restore locomotor function after spinal cord injury.

Closed-loop control of the cardiovascular system by means of an electronic baroreceptor analog

In baropacing (e.g. therapeutical electrical carotid sinus nerve stimulation in open loop, as well as in closed loop by means of a baroreceptor analog) an adaptation of stimulation parameters to the individual patients sensitivity is useful, regarding optimal stimulation patterns. An alternative method to closed loop frequency modulated stimulation has been developed: Amplitude modulated stimulation was compared to other methods in animal experiments and was found to be equally effective to frequency modulation with regard to depressor response. With regard to applied stimulation energy, amplitude modulation was found to be energetically more economic. A test unit, comprising currently available stimulation methods has been developed in order to adapt method and stimulation parameters to the needs of a patient to be equipped with a stimulator. An alternative use of the analog is proposed in the control of the artificial heart.

Modern Trends and Problems in Future on Low Frequency Electrotherapy in Japan

1) Statistics of electrotherapies in Japan (1961-1966): Questionnaires concerning on clinical application of low frequency electrotherapy were sent to 142 big clinics in all over the Japan. Answers were obtained from 70 clinics. The total number of the cases was 8973 who were treated for past five years.It is clarified from the analysis of this questionnaires and answers that low frequency electrotherapy have been applyed in many clinics by following the basis of neuro-physiological principles and some improvements were noticed on 56.4% of 8858 cases.2) Statistics of electrotherapy in our clinic during past five years:The principle in the treatment of the nervous system in our clinic were as follows;a) The diseases in the muscle and peripheral nerve fibers: They will be treated by the third effect of polarization.b) The disease in neuro-muscular junction: It will be treated by the post-tetanic potentiation on neuro-muscular junction.c) The disease in the spinal synapses:It will be treated by two theoretical bases; firstly post-tetanic potentiation on spinal mono-synaptic reflex and secondly the third effect of spinal polarization on the reflex action.3) Therapeutic application of low frequency current on progressive muscular dystrophy:Recent advancement in electrotherapy on progressive muscular dystrophy in our clinic was reported in the view point of electromyography and biochemistry. The best result was gained by the administration of post-tetanic potentiation on the spinal mono-synaptic pathway.4) Several problems in future:The size and shape of electrode, wave-form, amplitude modulation, frequency modulation, telemetry, mechanical vibration, electrical narcosis, and heart and bladder stimulation with pace maker and so on were discussed.