A novel method using EEG to characterize the cortical processes involved in active and passive touch

International audienceWe present a novel method to compare brain responses to identical tactile stimuli in active and passive touch. Using electroencephalography (EEG) to record steady-state evoked brain potentials (SS-EPs), our goal was to characterize the cortical activity related to the tactile exploration of a textured surface. For this purpose, we used a novel tactile display, which is able to produce tactile texture experiences using ultrasonic stationary waves to transiently modulate tangential friction between the finger and the display. Because the change in friction depends on the amplitude of the ultrasonic vibrations, modulation of ultrasonic vibration amplitude was used to periodically modulate friction at a frequency of 11 Hz, producing a tactile percept resembling that of a square-wave grating. After recording the exact motion of the fingertip and normal force used for each trial while one participant freely explored the surface (active touch condition), the same motion and normal force was reproduced by a high-precision robotic device with force feedback (passive touch condition). Frequency analysis of the recorded EEG signals showed that, for both active and passive touch conditions, the interactions between the fingertip and the plate elicited a robust SS-EP at 11 Hz, corresponding to the frequency of friction modulation, maximal over the parietal region contralateral to the stimulated finger. Our results suggest that the cortical activity related to active and passive touch can be characterized in humans by combining the recording of SS-EPs with an ultrasonic device generating a periodic tactile experience whose frequency is independent of finger movements

Neural Mechanisms of Intermodal Sustained Selective Attention with Concurrently Presented Auditory and Visual Stimuli

We investigated intermodal attention effects on the auditory steady-state response (ASSR) and the steady-state visual evoked potential (SSVEP). For this purpose, 40-Hz amplitude-modulated tones and a stream of flickering (7.5 Hz) random letters were presented concurrently. By means of an auditory or visual target detection task, participants’ attention was directed to the respective modality for several seconds. Attention to the auditory stream led to a significant enhancement of the ASSR compared to when the visual stream was attended. This attentional modulation was located mainly in the right superior temporal gyrus. Vice versa, attention to the visual stream especially increased the second harmonic response of the SSVEP. This modulation was focused in the inferior occipital and lateral occipitotemporal gyrus of both hemispheres. To the best of our knowledge, this is the first demonstration of amplitude modulation of the ASSR and the SSVEP by intermodal sustained attention. Our results open a new avenue of research to understand the basic neural mechanisms of intermodal attention in the human brain

Performance of Brain-Computer Interfacing Based on Tactile Selective Sensation and Motor Imagery

© 2017 IEEE.Personal use of this material is permitted. Permission from IEEE must be obtained for all other uses, in any current or future media, including reprinting/republishing this material for advertising or promotional purposes,creating new collective works, for resale or redistribution to servers or lists, or reuse of any copyrighted component of this work in other works.A large proportion of users do not achieve adequate control using current non-invasive Brain-computer Interfaces (BCI). This issue has being coined “BCI-Illiteracy”, and is observed among BCI modalities. Here, we compare the performance and BCI-illiteracy rate of tactile selective sensation (SS) and motor imagery (MI) BCI, for large subject samples. We analyzed 80 experimental sessions from 57 subjects with two-class SS protocols. For SS, the group average performance was 79.8±10.6%, with 43 out of the 57 subjects (75.4%) exceeding the 70% BCI-illiteracy threshold for left and right hand SS discrimination. When compared to previous results, this tactile BCI outperformed all other tactile BCIs currently available. We also analyzed 63 experiment sessions from 43 subjects with two-class MI BCI protocols, where the group average performance was 77.2±13.3%, with 69.7% of the subjects exceeded the 70% performance threshold for left and right hand MI. For within-subject comparison, the 24 subjects who participated to both the SS and MI experiments, the BCI performance was superior with SS than MI especially in beta frequency band (p<0.05), with enhanced R2 discriminative information in the somatosensory cortex for the SS modality. Both SS and MI showed a functional dissociation between lower alpha ([8 10] Hz) and upper alpha ([10 13] Hz) bands, with BCI performance significantly better in the upper alpha than the lower alpha (p<0.05) band. In summary, we demonstrated that SS is a promising BCI modality with low BCI illiteracy issue, and has great potential in practical applications reaching large population.University Starter Grant of the University of Waterloo [No. 203859]National Natural Science Foundation of China [Grant No. 51620105002

Die Verarbeitung vibrotaktiler Stimulation mit subliminaler Stimulationslücke und der Einfluss von Aufmerksamkeit auf diese:eine magnetenzephalographische Grundlagenstudie

Die permanente Aufmerksamkeit auf kleine Schwankungen in Körpersensationen scheint ein zentraler Faktor in der Pathogenese der Somatisierungsstörung zu sein. Im Sinne der Grundlagenforschung wurde der Einfluss von Aufmerksamkeit auf die Verarbeitung minimaler Schwankungen in somatosensiblen Reizen anhand von subliminalen Lücken in vibrotaktilen Stimuli an 16 gesunden Probanden mittels Magnetenzephalographie untersucht. Die Probanden erhielten simultan vibrotaktile und visuelle Reize. Zur Aufmerksamkeitsgenerierung sollten die Probanden eine vibrotaktile Aufgabe lösen. Um von der vibrotaktilen Stimulation abzulenken, erhielten die Probanden eine Aufgabe bezüglich einer simultanen visuellen Stimulation. Die Ergebnisse dieser Arbeit zeigen, dass subliminale Lücken in vibrotaktilen Reizen im kontralateralen primären somatosensiblen Kortex (SI) Änderungen neuronaler Erregung hervorrufen und dass Aufmerksamkeit eine deutliche Erhöhung der neuronalen Aktivität im SI verursacht

Processing resources and interplay among sensory modalities: an EEG investigation

The primary aim of the present thesis was to investigate how the human brain handles and distributes limited processing resources among different sensory modalities. Two main hypothesis have been conventionally proposed: (1) common processing resources shared among sensory modalities (supra-modal attentional system) or (2) independent processing resources for each sensory modality. By means of four EEG experiments, we tested whether putative competitive interactions between sensory modalities – regardless of attentional influences – are present in early sensory areas. We observed no competitive interactions between sensory modalities, supporting independent processing resources in early sensory areas. Consequently, we tested the influence of top-down attention on a cross-modal dual task. We found evidence for shared attentional resources between visual and tactile modalities. Taken together, our results point toward a hybrid model of inter-modal attention. Attentional processing resources seem to be controlled by a supra-modal attentional system, however, in early sensory areas, the absence of competitive interactions strongly reduces interferences between sensory modalities, thus providing a strong processing resource independence

The in vivo functional neuroanatomy and neurochemistry of vibrotactile processing

Touch is a sense with which humans are able to actively explore the world around them. Primary somatosensory cortex (S1) processing has been studied to differing degrees at both the macroscopic and microscopic levels in both humans and animals. Both levels of enquiry have their advantages, but attempts to combine the two approaches are still in their infancy. One mechanism that is possibly involved in determining the reponse properties of neurons that are involved in sensory discrimination is inhibition by γ-aminobutyric acid (GABA). Several studies have shown that inhibition is an important mechanism to “tune” the response of neurons. Recently it has become possible to measure the concentration of GABA in vivo using edited Magnetic Resonance Spectroscopy (MRS), whereas magnetoencephalography (MEG) offers the possibility to look at changes in neuromagnetic activation with millisecond accuracy. With these methods we aimed to establish whether in vivo non-invasive neuroimaging can elucidate the underlying neuronal mechanisms of human tactile behaviour and to determine how such findings can be integrated with what is currently known from invasive methods. Edited GABA-MRS has shown that individual GABA concentration in S1 correlates strongly with tactile frequency discrimination. MEG was used to investigate the neuromagnetic correlates of a frequency discrimination paradigm in which we induced adaptation to a 25 Hz frequency. We showed that S1 is driven by the adapting stimulus and shows that neural rhythms are modulated as a result of adaptation. This is the first time that behavioural psychophysics of tactile adaptation has been investigated using complimentary neuroimaging methods. We combined different methods to complement both physiological and behavioural studies of tactile processing in S1 to investigate the factors involved in the neural dynamics of tactile processing and we show that non-invasive studies on humans can be used to understand physiological underpinnings of somatosensory processing.EThOS - Electronic Theses Online ServiceGBUnited Kingdo