Human Somatosensory Cortex Research Articles

Gamma oscillations in the human somatosensory cortex reflect facial affect discrimination

Event Abstract Back to Event Gamma oscillations in the human somatosensory cortex reflect facial affect discrimination Tzvetan Popov1*, Nathan Weisz1, Thomas Elbert1, Gregory M. Miller2 and Brigitte Rockstroh1 1 University of Konstanz, Germany 2 University of Illinois at Urbana-Champaign, United States Embodiment theories suggest that reproduction of a certain (emotional) state in one’s own mind is crucial for understanding the emotional states of others. The face area in the somatosensory cortex (SC) may be involved in such reproduction, as indicated by transcranial magnetic stimulation (TMS) studies on the processing of facial expression. Oscillatory activity in the gamma frequency range may be a measure of such processing, as it is thought to reflect the neuronal interaction within neocortical networks subserving functions such as perceptual binding. The present magnetoencephalographic study tested the hypothesis that the recognition of a change in facial affect from neutral to emotional was associated with synchronization in the gamma frequency band in the SC. Thirty healthy subjects monitored 120 face morphing videos of 5s length, each starting with a face exhibiting a neutral expression which changed into either fearful or happy expression, or with respect to a facial feature (e.g., nose length) but not emotional expression. Changes of facial expression from neutral to emotional evoked gamma frequency band synchronization (20-40Hz) relative to changes with facial expression remaining identical. Beamformer source localization confirmed the origin of this gamma band synchronization in bilateral somatosensory cortical areas. Parallel ratings showed that subjects successfully recognized the change in emotional expression at 33-66% morphing – and maximum gamma band synchronization (GBS) was found at the time this proportion of change was achieved. Results suggest that the processing of facial expression, which results in the recognition of emotional expression, is reflected in neuronal synchronization in the gamma frequency band within the somatosensory face area. Funding: Research was supported by the German Research Foundation (Deutsche Forschungsgemeinschaft DFG, Ro805/14). Keywords: emotion, TMS Conference: XI International Conference on Cognitive Neuroscience (ICON XI), Palma, Mallorca, Spain, 25 Sep - 29 Sep, 2011. Presentation Type: Poster Presentation Topic: Poster Sessions: Emotion, Motivation and the Social Brain Citation: Popov T, Weisz N, Elbert T, Miller GM and Rockstroh B (2011). Gamma oscillations in the human somatosensory cortex reflect facial affect discrimination. Conference Abstract: XI International Conference on Cognitive Neuroscience (ICON XI). doi: 10.3389/conf.fnhum.2011.207.00157 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: 18 Nov 2011; Published Online: 28 Nov 2011. * Correspondence: Dr. Tzvetan Popov, University of Konstanz, Konstanz, Germany, tzvetan.popov@uni-konstanz.de 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 Tzvetan Popov Nathan Weisz Thomas Elbert Gregory M Miller Brigitte Rockstroh Google Tzvetan Popov Nathan Weisz Thomas Elbert Gregory M Miller Brigitte Rockstroh Google Scholar Tzvetan Popov Nathan Weisz Thomas Elbert Gregory M Miller Brigitte Rockstroh PubMed Tzvetan Popov Nathan Weisz Thomas Elbert Gregory M Miller Brigitte Rockstroh 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.

P18-13 Differential responses to attended and non attended deviant somatosensory stimuli and stimulus omissions in human somatosensory cortex: an fMRI study

P18-13 Differential responses to attended and non attended deviant somatosensory stimuli and stimulus omissions in human somatosensory cortex: an fMRI study

P33-3 Change-related responses in the human somatosensory cortex: an MEG study

P33-3 Change-related responses in the human somatosensory cortex: an MEG study

ML1 Cortical representation of attention focus: short-term plasticity in the human somatosensory and auditory cortices

ML1 Cortical representation of attention focus: short-term plasticity in the human somatosensory and auditory cortices

P33-6 Subjective distinctness of tactile sensation is represented in the activity of human secondary somatosensory cortex (SII)

P33-6 Subjective distinctness of tactile sensation is represented in the activity of human secondary somatosensory cortex (SII)

Multi-frequency phase locking in human somatosensory cortex

Cortical population responses to sensory input arise from the interaction between external stimuli and the intrinsic dynamics of the densely interconnected neuronal population. Although there is a large body of knowledge regarding single neuron responses to periodic stimuli, responses at the scale of cortical populations are incompletely understood. The characteristics of large-scale neuronal activity during periodic stimulation speak directly to the mechanisms underlying collective neuronal activity. Their accurate elucidation is hence a vital prelude to constructing and evaluating large-scale computational and biophysical models of the brain. Electroencephalographic data was recorded from eight human subjects while periodic vibrotactile stimuli were applied to the fingertip. Time–frequency decomposition was performed on the multi-channel data in order to investigate relative changes in the power and phase distributions at stimulus-related frequencies. We observed phase locked oscillatory activity at multiple stimulus-specific frequencies, in particular at ratios of 1:1, 2:1 and 2:3 to the stimulus frequency. These phase locked components were found to be modulated differently across the range of stimulus frequencies, with oscillatory responses most robustly sustained around 30Hz. In contrast, no robust frequency-locked responses were apparent in the power changes. These results demonstrate n:m phase synchronization between cortical oscillations in the somatosensory system and an external periodic signal. We argue that neuronal populations evidence a collective nonlinear response to periodic sensory input. The existence of n:m phase synchronization demonstrates the contribution of intrinsic cortical dynamics to stimulus encoding and provides a novel phenomenological criteria for the validation of large-scale models of the brain.

50. Change-related response in the human somatosensory cortex: An MEG study

50. Change-related response in the human somatosensory cortex: An MEG study

Effects of somatosensory stimulation and attention on human somatosensory cortex: An fMRI study

It is well known that primary and non-primary areas of human somatosensory cortex are involved in the processing of adequate deviant/rare stimuli and omission of frequent stimuli. However, the relative weight and interaction of these variables is poorly known. This functional magnetic resonance imaging (fMRI) study tested the hypothesis that somatosensory stimulus processing and attention especially interact in non-primary somatosensory areas including secondary somatosensory cortex (SII) and insula. To test this hypothesis, responses of somatosensory cortex were mapped during four conditions of an oddball paradigm: DELIVERED COUNT and IGNORE (count or ignore deviant/rare electrical stimuli, respectively); OMITTED COUNT and IGNORE (count or ignore the rare omission of frequent electrical stimuli, respectively). The deviant/rare and frequent electrical stimuli were delivered to median and ulnar nerve, respectively. It was observed that contralateral (left) primary somatosensory responses were not markedly modulated by the mentioned deviant/rare events. Furthermore, contralateral SII and insula responded to all but not OMITTED IGNORE (purely attentive) condition, whereas ipsilateral (right) SII responded to all conditions. Finally, ipsilateral insula responded to the COUNT (attentive) conditions, regardless of the physical presence of the deviant/rare stimuli. The results suggest that in somatosensory modality, bilateral SII and left (contralateral) insula reflect complex integrative processes of stimulus elaboration and attention, whereas right (ipsilateral) insula mainly sub-serves active attention to deviance within a sequence of somatosensory stimuli.

Somatosensory evoked potentials and high frequency oscillations are differently modulated by theta burst stimulation over primary somatosensory cortex in humans

Objective The effects of theta burst stimulation (TBS) have been extensively investigated in primary motor cortex, where it leads to long-lasting LTP/LTD-like effects on synaptic plasticity. This study aimed to extend these observations to sensory cortex. Methods Fourteen healthy subjects participated in the study. Conditioning 600-pulse intermittent TBS (iTBS) and continuous TBS (cTBS) were delivered to left somatosensory cortex (S1) with an intensity of 80% active motor threshold. Somatosensory evoked potentials (SEPs) were evoked by median nerve electrical stimulation at right wrist. High frequency oscillations (HFOs) were obtained by digital filtering of original SEPs and divided into early and late subcomponents, relative to N20 peak latency. Results Repeated-measures ANOVA showed that iTBS facilitated N20 onset–N20 peak at 15 min and N20 peak–P25 at 15 and 30 min after conditioning, whereas cTBS did not. iTBS left the early and late HFOs unchanged. Conversely, cTBS facilitated the early HFOs, whereas it inhibited the late HFOs at 15 min after conditioning. Conclusions S1-iTBS facilitated SEPs without changes in HFOs whereas cTBS modulated early and late HFOs without changes in SEPs. Significance S1-TBS produces lasting changes in the excitability of intracortical circuits generating SEPs and HFOs differentially through mechanisms of LTP/LTD-like synaptic plasticity.

Tactile expectation modulates pre-stimulus β-band oscillations in human sensorimotor cortex

Neuronal oscillations are postulated to play a fundamental role in top-down processes of expectation. We used magnetoencephalography (MEG) to investigate whether expectation of a tactile event involves a pre-stimulus modulation of neuronal oscillations in human somatosensory cortex. In a bimodal attention paradigm, participants were presented with a predictable spatio-temporal pattern of lateralized tactile stimulations and simultaneously occurring non-lateralized auditory stimuli. Before the onset of a series of such combined audio-tactile stimuli, a cue was presented that indicated the sensory stream that had to be attended. By investigating lateralized patterns of oscillatory activity, we were able to study both attentive (when the tactile stream was attended) and non-attentive (when the auditory stream was attended) tactile expectations. For both attention conditions, we observed a lateralized modulation of the amplitude of beta band oscillations prior to a predictable – and accordingly lateralized – tactile stimulus. As such, we show that anticipatory modulation of ongoing oscillatory activity is not restricted to attended sensory events. Attention did enlarge the size of this modulation. We argue that this modulation constitutes a suppression of beta oscillations that originate at least partly from primary somatosensory cortex (S1) contralateral to the expected stimulation. We discuss our results in the light of the hypothesis that ongoing beta oscillations over sensorimotor cortex reflect a brain state in which neuronal processing efficacy is low. Pre-stimulus suppression of these oscillations then prepares the system for future processing. This shows that perception is an active process that starts even prior to sensation.

Mapping Human Somatosensory Cortex in Individual Subjects With 7T Functional MRI

Functional magnetic resonance imaging (fMRI) is now routinely used to map the topographic organization of human visual cortex. Mapping the detailed topography of somatosensory cortex, however, has proven to be more difficult. Here we used the increased blood-oxygen-level-dependent contrast-to-noise ratio at ultra-high field (7 Tesla) to measure the topographic representation of the digits in human somatosensory cortex at 1 mm isotropic resolution in individual subjects. A "traveling wave" paradigm was used to locate regions of cortex responding to periodic tactile stimulation of each distal phalangeal digit. Tactile stimulation was applied sequentially to each digit of the left hand from thumb to little finger (and in the reverse order). In all subjects, we found an orderly map of the digits on the posterior bank of the central sulcus (postcentral gyrus). Additionally, we measured event-related responses to brief stimuli for comparison with the topographic mapping data and related the fMRI responses to anatomical images obtained with an inversion-recovery sequence. Our results have important implications for the study of human somatosensory cortex and underscore the practical utility of ultra-high field functional imaging with 1 mm isotropic resolution for neuroscience experiments. First, topographic mapping of somatosensory cortex can be achieved in 20 min, allowing time for further experiments in the same session. Second, the maps are of sufficiently high resolution to resolve the representations of all five digits and third, the measurements are robust and can be made in an individual subject. These combined advantages will allow somatotopic fMRI to be used to measure the representation of digits in patients undergoing rehabilitation or plastic changes after peripheral nerve damage as well as tracking changes in normal subjects undergoing perceptual learning.

Expectations about upcoming tactile events selectively modulate beta-band oscillations in human primary somatosensory cortex

Event Abstract Back to Event Expectations about upcoming tactile events selectively modulate beta-band oscillations in human primary somatosensory cortex Freek V. Ede1*, Ole Jensen1 and Eric Maris1 1 Radboud University Nijmegen, Donders Institute for Brain, Cognition and Behaviour, Netherlands Neuronal oscillations are postulated to play a fundamental role in top-down processes of expectation. We used magnetoencephalogaphy (MEG) to investigate whether expectation of a tactile event involves a pre-stimulus modulation of neuronal oscillations in human somatosensory cortex. In a bimodal attention paradigm, participants were presented with a predictable spatio-temporal pattern of tactile stimulations and simultaneously occurring non-lateralized auditory stimuli. By investigating lateralized patterns of oscillatory activity, we studied both attentive and non-attentive tactile expectation. For both, we observe a lateralized modulation of oscillatory activity in the beta-band prior to a predictable – and accordingly lateralized – tactile stimulus. Topography and lateralization imply an origin in primary somatosensory cortex (S1). We propose that beta – a dominant rhythm in S1 – drives neuronal excitability in an a-specific manner such that perceptual processing requires suppression of it. Expectation-induced suppression of beta then prepares the system for processing, leading the active process of perception to start even prior to sensation. Conference: Biomag 2010 - 17th International Conference on Biomagnetism , Dubrovnik, Croatia, 28 Mar - 1 Apr, 2010. Presentation Type: Poster Presentation Topic: Neurocognition and Functional Connectivity Citation: Ede FV, Jensen O and Maris E (2010). Expectations about upcoming tactile events selectively modulate beta-band oscillations in human primary somatosensory cortex. Front. Neurosci. Conference Abstract: Biomag 2010 - 17th International Conference on Biomagnetism . doi: 10.3389/conf.fnins.2010.06.00333 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: 06 Apr 2010; Published Online: 06 Apr 2010. * Correspondence: Freek V Ede, Radboud University Nijmegen, Donders Institute for Brain, Cognition and Behaviour, Nijmegen, Netherlands, f.vanede@donders.ru.nl 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 Freek V Ede Ole Jensen Eric Maris Google Freek V Ede Ole Jensen Eric Maris Google Scholar Freek V Ede Ole Jensen Eric Maris PubMed Freek V Ede Ole Jensen Eric Maris 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.

High-resolution optical functional mapping of the human somatosensory cortex

Non-invasive optical imaging of brain function has been promoted in a number of fields in which functional magnetic resonance imaging (fMRI) is limited due to constraints induced by the scanning environment. Beyond physiological and psychological research, bedside monitoring and neurorehabilitation may be relevant clinical applications that are yet little explored. A major obstacle to advocate the tool in clinical research is insufficient spatial resolution. Based on a multi-distance high-density optical imaging setup, we here demonstrate a dramatic increase in sensitivity of the method. We show that optical imaging allows for the differentiation between activations of single finger representations in the primary somatosensory cortex (SI). Methodologically our findings confirm results in a pioneering study by Zeff et al. (2007) and extend them to the homuncular organization of SI. After performing a motor task, eight subjects underwent vibrotactile stimulation of the little finger and the thumb. We used a high-density diffuse-optical sensing array in conjunction with optical tomographic reconstruction. Optical imaging disclosed three discrete activation foci one for motor and two discrete foci for vibrotactile stimulation of the first and fifth finger, respectively. The results were co-registered to the individual anatomical brain anatomy (MRI) which confirmed the localization in the expected cortical gyri in four subjects. This advance in spatial resolution opens new perspectives to apply optical imaging in the research on plasticity notably in patients undergoing neurorehabilitation.

Cortical dynamics of selective attention to somatosensory events

Recent studies have shown evidence of somatosensory deficits in individuals with attentional difficulties yet relatively little is known about the role of attention in the processing of somatosensory input. Neuromagnetic imaging studies have shown that rhythmic oscillations within the human somatosensory cortex are strongly modulated by somatosensory stimulation and may reflect the normal processing of such stimuli. However, few studies have examined how attention influences these cortical oscillations. We examined attentional effects on human somatosensory oscillations during median nerve stimulation by conducting time–frequency analyses of neuromagnetic recordings in healthy adults. We found that selective attention modulated somatosensory oscillations in the alpha, beta, and gamma bands that were both phase-locked and non-phase-locked to the stimulus. In the primary somatosensory cortex (SI), directing the subject's attention toward the somatosensory stimulus resulted in increased gamma band power (30–55 Hz) that was phase-locked to stimulus onset. Directed attention also produced an initial suppression (desynchrony) followed by enhancement (synchrony) of beta band power (13–25 Hz) that was not phase-locked to the stimulus. In the secondary somatosensory cortex (SII), directing attention towards the stimulus increased phase-locked alpha (7–9 Hz) power approximately 30 ms after onset of phase-locked gamma in SI, followed by a non-phase-locked increase in alpha power. We suggest that earlier phase-locked oscillatory power may reflect the relay of input from SI to SII, whereas later non-phase-locked rhythms reflect stimulus-induced oscillations that are modulated by selective attention and may thus reflect enhanced processing of the stimulus underlying the perception of somatosensory events.

High-density optical mapping of the human somatosensory cortex to vibrotactile stimulation

stimulation Stefan P. Koch1, Jan Mehnert1,2, Christoph Schmitz1,3, Susanne Holtze1, Arno Villringer1,2,4, Hellmuth Obrig1,2,5 1Berlin NeuroImaging Center, Charite Berlin, Germany/2Max-Planck Institute for Human Cognitive and Brain Science Leipzig, Germany/3NIRx Medizintechnik GmbH, Berlin, Germany/ 4Berlin School of Mind and Brain, Humboldt-University/ 5Day Clinic for Cognitive Neurology, University Hospital Leipzig, Germany

Sights of touching activates the somatosensory cortex in humans

Sights of touching activates the somatosensory cortex in humans

Sights of touching activates the somatosensory cortex in humans

We report our observations of cross-modal interactions between sight and touch using functional magnetic resonance imaging (fMRI). Experiments were devised to show that sight and touch are linked in a cross-modal arrangement, and two separate experiments were done in an MRI scanner. In the first, the subject's right hand was stimulated with a brush; in the second, a video sequence was presented to the subject inside the scanner through video goggles in visual three-dimensional stereo, showing one brushstroke every second on a hand in the same manner as the subject had just previously experienced. The result was that both the primary and the secondary somatosensory cortexes were activated in the participants when the hands were touched, and when the subjects saw only a hand being touched in the same manner. The results indicated cross-modal links between sight and touch of the hand in humans.

Reward Facilitates Tactile Judgments and Modulates Hemodynamic Responses in Human Primary Somatosensory Cortex

Reinforcing effects of reward on action are well established, but possible effects on sensory function are less well explored. Here, using functional magnetic resonance imaging, we assessed whether reward can influence somatosensory judgments and modulate activity in human somatosensory cortex. Participants discriminated electrical somatosensory stimuli on an index finger with correct performance rewarded financially at trial end, at one of four different anticipated levels. Higher rewards improved tactile performance and led to increased hemodynamic signals from ventral striatum on rewarded trials. Remarkably, primary somatosensory cortex contralateral to the judged hand was reactivated at the point of reward delivery, despite the absence of concurrent somatosensory input at that time point. This side-specific reactivation of primary somatosensory cortex increased monotonically with level of reward. Moreover, the level of reward received on a particular trial influenced somatosensory performance and neural activity on the subsequent trial, with better discrimination and enhanced hemodynamic response in contralateral primary somatosensory cortex for trials that followed higher rewards. These results indicate that rewards can influence not only classical reward-related regions, but also early somatosensory cortex when a decision is required for that modality.

Homeostatic Metaplasticity in the Human Somatosensory Cortex

Long-term potentiation (LTP) and long-term depression (LTD) are regulated by homeostatic control mechanisms to maintain synaptic strength in a physiological range. Although homeostatic metaplasticity has been demonstrated in the human motor cortex, little is known to which extent it operates in other cortical areas and how it links to behavior. Here we tested homeostatic interactions between two stimulation protocols -- paired associative stimulation (PAS) followed by peripheral high-frequency stimulation (pHFS) -- on excitability in the human somatosensory cortex and tactile spatial discrimination threshold. PAS employed repeated pairs of electrical stimulation of the right median nerve followed by focal transcranial magnetic stimulation of the left somatosensory cortex at an interstimulus interval of the individual N20 latency minus 15 msec or N20 minus 2.5 msec to induce LTD- or LTP-like plasticity, respectively [Wolters, A., Schmidt, A., Schramm, A., Zeller, D., Naumann, M., Kunesch, E., et al. Timing-dependent plasticity in human primary somatosensory cortex. Journal of Physiology, 565, 1039-1052, 2005]. pHFS always consisted of 20-Hz trains of electrical stimulation of the right median nerve. Excitability in the somatosensory cortex was assessed by median nerve somatosensory evoked cortical potential amplitudes. Tactile spatial discrimination was tested by the grating orientation task. PAS had no significant effect on excitability in the somatosensory cortex or on tactile discrimination. However, the direction of effects induced by subsequent pHFS varied with the preconditioning PAS protocol: After PAS(N20-15), excitability tended to increase and tactile spatial discrimination threshold decreased. After PAS(N20-2.5), excitability decreased and discrimination threshold tended to increase. These interactions demonstrate that homeostatic metaplasticity operates in the human somatosensory cortex, controlling both cortical excitability and somatosensory skill.

Oral structure representation in human somatosensory cortex

To clarify the topography of the areas representing whole intraoral structures and elucidate bilateral neuronal projection to those areas in the primary somatosensory (S1) cortex, we recorded somatosensory-evoked magnetic fields (SEFs), which reflect the earliest cortical responses to pure tactile stimulation, using magnetoencephalography and a piezo-driven tactile stimulation device. Subjects consisted of 10 healthy male adults. Following tactile stimulation of 6 sites on the oral mucosa (inferior/superior buccal mucosa, posterior/anterior tongue mucosa, and upper/lower lip mucosa), SEFs with a peak latency of 15 ms (1M) were identified bilaterally. In contrast, SEFs with a peak latency of 30 ms following right index finger tactile stimulation were identified only in the contralateral hemisphere. Equivalent current dipoles (ECDs) generating 15 ms components were found along the posterior wall of the central sulcus, bilaterally. The ECD locations for oral mucosa-representing areas were located inferiorly to those for the index finger, with the following pattern of organization from top to bottom along the central sulcus: index finger, upper or lower lip, anterior or posterior tongue and superior or inferior buccal mucosa, with a wide distribution, covering 30% of the S1 cortex. Source strength for 1M in the ipsilateral hemisphere was weaker than that in the contralateral hemisphere. These results clearly indicate that sensory afferents innervating the intraoral region project to both the contralateral and ipsilateral 3b areas via the trigeminothalamic tract, where contralateral projection is predominant. The results clarify the intraoral structure-representing areas in the S1 cortex, adding those areas to the classical “sensory homunculus”.