Spatial inhibition of return promotes changes in Response-related mu and beta oscillatory patterns

The possible role that response processes play in Inhibition of Return (IOR), traditionally associated with reduced or inhibited attentional processing of spatially cued target stimuli presented at cue-target intervals longer than 300 ms, is still under debate. Previous psychophysiological studies on response-related Electroencephalographic (EEG) activity and IOR have found divergent results. Considering that the ability to optimize our behavior not only resides in our capacity to inhibit the focus of attention from irrelevant information but also to inhibit or reduce motor activation associated with responses to that information, it is conceivable that response processes are also affected by IOR. In the present study, time–frequency (T–F) analyses were performed on EEG oscillatory activity between 2 and 40 Hz to check whether spatial IOR affects response preparation and execution during a visuospatial attention task. To avoid possible spatial stimulus–response compatibility effects and their interaction with the IOR effects, the stimuli were presented along the vertical meridian of the visual field. The results differed between lower and upper visual fields. In the lower visual field spatial IOR was related to a synchronization in the pre-movement mu band at bilateral precentral and central electrodes, and in the post-movement beta band at contralateral precentral and central electrodes, which may be associated with an attention-driven reduction of somatomotor processing prior to the execution of responses to relevant stimuli presented at previously cued locations followed by a post-movement deactivation of motor areas. In the upper visual field, spatial IOR was associated with a decrease in desynchronization around response execution in the beta band at contralateral postcentral electrodes that might indicate a late (last moment) reduction of motor activation when responding to spatially cued targets. The present results suggest that different response processes are affected by spatial IOR depending on the visual field where the target is presented. 2015 IBRO. Published byThis study was supported by grants from the Spanish MICINN (PSI2010-21427), Spanish MINECO (PSI2014-53743-P), and Xunta de Galicia (10PXIB211220PR)S

The effect of salient stimuli on neural oscillations, isometric force, and their coupling.

Survival in a suddenly-changing environment requires animals not only to detect salient stimuli, but also to promptly respond to them by initiating or revising ongoing motor processes. We recently discovered that the large vertex brain potentials elicited by sudden supramodal stimuli are strongly coupled with a multiphasic modulation of isometric force, a phenomenon that we named cortico-muscular resonance (CMR). Here, we extend our investigation of the CMR to the time-frequency domain. We show that (i) both somatosensory and auditory stimuli evoke a number of phase-locked and non-phase-locked modulations of EEG spectral power. Remarkably, (ii) some of these phase-locked and non-phase-locked modulations are also present in the Force spectral power. Finally, (iii) EEG and Force time-frequency responses are correlated in two distinct regions of the power spectrum. An early, low-frequency region (∼4 Hz) reflects the previously-described coupling between the phase-locked EEG vertex potential and force modulations. A late, higher-frequency region (beta-band, ∼20 Hz) reflects a second coupling between the non-phase-locked increase of power observed in both EEG and Force. In both time-frequency regions, coupling was maximal over the sensorimotor cortex contralateral to the hand exerting the force, suggesting an effect of the stimuli on the tonic corticospinal drive. Thus, stimulus-induced CMR occurs across at least two different types of cortical activities, whose functional significance in relation to the motor system should be investigated further. We propose that these different types of corticomuscular coupling are important to alter motor behaviour in response to salient environmental events

L’influence de l'anticipation sur les modulations de puissance dans la bande de fréquence bêta durant la préparation du mouvement et L'effet de la variance dans les rétroactions sensorielles sur la rétention à court terme

La production du mouvement est un aspect primordial de la vie qui permet aux organismes vivants d'interagir avec l'environnement. En ce sens, pour être efficaces, tous les mouvements doivent être planifiés et mis à jour en fonction de la complexité et de la variabilité de l'environnement. Des chercheurs du domaine du contrôle moteur ont étudié de manière approfondie les processus de planification et d’adaptation motrice. Puisque les processus de planification et d'adaptation motrice sont influencés par la variabilité de l'environnement, le présent mémoire cherche à fournir une compréhension plus profonde de ces deux processus moteurs à cet égard. La première contribution scientifique présentée ici tire parti du fait que les temps de réaction (TR) sont réduits lorsqu'il est possible d'anticiper l’objectif moteur, afin de déterminer si les modulations de TR associées à l'anticipation spatiale et temporelle sont sous-tendues par une activité préparatoire similaire. Cela a été fait en utilisant l'électroencéphalographie (EEG) de surface pour analyser l'activité oscillatoire dans la bande de fréquence bêta (13 - 30 Hz) au cours de la période de planification du mouvement. Les résultats ont révélé que l'anticipation temporelle était associée à la désynchronisation de la bande bêta au-dessus des régions sensorimotrices controlatérales à la main effectrice, en particulier autour du moment prévu de l'apparition de la cible. L’ampleur de ces modulations était corrélée aux modulations de TR à travers les participants. En revanche, l'anticipation spatiale a augmenté de manière sélective la puissance de la bande bêta au-dessus des régions pariéto-occipitales bilatérales pendant toute la période de planification. Ces résultats suggèrent des états de préparation distinct en fonction de l’anticipation temporelle et spatiale. D’un autre côté, le deuxième projet traite de la façon dont la variabilité de la rétroaction sensorielle interfère avec la rétention à court terme dans l’étude de l’adaptation motrice. Plus précisément, une tâche d'adaptation visuomotrice a été utilisée au cours de laquelle la variance des rotations a été manipulée de manière paramétrique à travers trois groupes, et ce, tout au long de la période d’acquisition. Par la suite, la rétention de cette nouvelle relation visuomotrice a été évaluée. Les résultats ont révélé que, même si le processus d'adaptation était robuste à la manipulation de la variance, la rétention à court terme était altérée par des plus hauts niveaux de variance. Finalement, la discussion a d'abord cherché à intégrer ces deux contributions en revisitant l'interprétation des résultats sous un angle centré sur l'incertitude et en fournissant un aperçu des potentielles représentations internes de l'incertitude susceptibles de sous-tendre les résultats expérimentaux observés. Par la suite, une partie de la discussion a été réservée à la manière dont le champ du contrôle moteur migre de plus en plus vers l’utilisation de tâches et d’approches expérimentales plus complexes, mais écologiques aux dépends des tâches simples, mais quelque peu dénaturées que l’on retrouve dans les laboratoires du domaine. La discussion a été couronnée par une brève proposition allant dans ce sens.Abstract: Motor behavior is a paramount aspect of life that enables the living to interact with the environment through the production of movement. In order to be efficient, movements need to be planned and updated according to the complexity and the ever-changing nature of the environment. Motor control experts have extensively investigated the planning and adaptation processes. Since both motor planning and motor adaptation processes are influenced by variability in the environment, the present thesis seeks to provide a deeper understanding of both these motor processes in this regard. More specifically, the first scientific contribution presented herein leverages the fact that reaction times (RTs) are reduced when the anticipation of the motor goal is possible to elucidate whether the RT modulations associated with temporal and spatial anticipation are subtended by similar preparatory activity. This was done by using scalp electroencephalography (EEG) to analyze the oscillatory activity in the beta frequency band (13 – 30 Hz) during the planning period. Results revealed that temporal anticipation was associated with beta-band desynchronization over contralateral sensorimotor regions, specifically around the expected moment of target onset, the magnitude of which was correlated with RT modulations across participants. In contrast, spatial anticipation selectively increased beta-band power over bilateral parieto-occipital regions during the entire planning period, suggesting that distinct states of preparation are incurred by temporal and spatial anticipation. Additionally, the second project addressed how variance in the sensory feedback interferes with short-term retention of motor adaptation. Specifically, a visuomotor adaptation task was used during which the variance of exposed rotation was parametrically manipulated across three groups, and retention of the adapted visuomotor relationship was assessed. Results revealed that, although the adaptation process was robust to the manipulation of variance, the short-term retention was impaired. The discussion first sought to integrate these two projects by revisiting the interpretation of both projects under the scope of uncertainty and by providing an overview of the internal representation of uncertainty that might subtend the experimental results. Subsequently, a part of the discussion was reserved to allude how the motor control field is transitioning from laboratory-based tasks to more naturalistic paradigms by using approaches to move motor control research toward real-world conditions. The discussion culminates with a brief scientific proposal along those lines

Slow Potentials of the Sensorimotor Cortex during Rhythmic Movements of the Ankle

The objective of this dissertation was to more fully understand the role of the human brain in the production of lower extremity rhythmic movements. Throughout the last century, evidence from animal models has demonstrated that spinal reflexes and networks alone are sufficient to propagate ambulation. However, observations after neural trauma, such as a spinal cord injury, demonstrate that humans require supraspinal drive to facilitate locomotion. To investigate the unique nature of lower extremity rhythmic movements, electroencephalography was used to record neural signals from the sensorimotor cortex during three cyclic ankle movement experiments. First, we characterized the differences in slow movement-related cortical potentials during rhythmic and discrete movements. During the experiment, motion analysis and electromyography were used characterize lower leg kinematics and muscle activation patterns. Second, a custom robotic device was built to assist in passive and active ankle movements. These movement conditions were used to examine the sensory and motor cortical contributions to rhythmic ankle movement. Lastly, we explored the differences in sensory and motor contributions to bilateral, rhythmic ankle movements. Experimental results from all three studies suggest that the brain is continuously involved in rhythmic movements of the lower extremities. We observed temporal characteristics of the cortical slow potentials that were time-locked to the movement. The amplitude of these potentials, localized over the sensorimotor cortex, revealed a reduction in neural activity during rhythmic movements when compared to discrete movements. Moreover, unilateral ankle movements produced unique sensory potentials that tracked the position of the movement and motor potentials that were only present during active dorsiflexion. In addition, the spatiotemporal patterns of slow potentials during bilateral ankle movements suggest similar cortical mechanisms for both unilateral and bilateral movement. Lastly, beta frequency modulations were correlated to the movement-related slow potentials within medial sensorimotor cortex, which may indicate they are of similar cortical origin. From these results, we concluded that the brain is continuously involved in the production of lower extremity rhythmic movements, and that the sensory and motor cortices provide unique contributions to both unilateral and bilateral movemen

The role of somatosensory afferences in Parkinson's disease

Parkinson’s disease (PD) is the second most common neurodegenerative disorder in the world. The primary motor symptom of PD is bradykinesia, a slowing and reduction in amplitude of voluntary movement. Here, I aim to test some neurophysiological aspects of PD. Furthermore, I explored the possibility to develop non-invasive treatment for this group of patients. The first two studies tested the contribution of a specific phenomenon labelled sensory attenuation or sensory gating in the motor symptoms of PD, especially bradykinesia. I found that the sensory attenuation is abnormal in this group of patients. Especially, PD patients OFF medications showed a reduced sensory attenuation measured as the amplitude of the somatosensory evoked potentials. Interestingly, I found that the sensory attenuation was equal to the healthy age matched controls when the patients were tested in ON pharmacological state. Additionally, this research tested a theory of the functional role of sensorimotor beta oscillations that could explain beta power modulations in healthy subjects and the increase in beta power observed in PD patients. My results were in line with the previous data presented in the literature. Indeed, I found the increase beta power in both my two cohorts of PD patients. Finally, I tested a potential correlation between the abnormalities of these two phenomena in PD: reduced sensory attenuation and increased beta oscillations. I did not find any significant correlation between the two phenomena. They might be two different neurophysiological mechanisms 5 underlying this disease. However, further studies are necessary to investigate this hypothesis. Having tested the influence of the somatosensory signal in some motor symptoms, the second part of the thesis was focused on the development of non-invasive treatments of bradykinesia in PD. I tested the impact of vibratory stimuli to improve these motor signs. In particular, several frequencies of vibration have been tested through different devices applied to the wrist. The device was called “Emma watch” and I found that the application of vibration with the modulation of 60 bpm improved the bradykinesia in PD patients Finally, I presented a case study regarding the benefit of vibratory stimulation on the freezing of gait thought shoe insoles generating vibration. The tested patient showed an improvement of the frequency of the freezing episodes after a week wearing the insoles, which generated vibration at 200 Hz

Cortical Sensorimotor Mechanisms for Neural Control of Skilled Manipulation

abstract: The human hand is a complex biological system. Humans have evolved a unique ability to use the hand for a wide range of tasks, including activities of daily living such as successfully grasping and manipulating objects, i.e., lifting a cup of coffee without spilling. Despite the ubiquitous nature of hand use in everyday activities involving object manipulations, there is currently an incomplete understanding of the cortical sensorimotor mechanisms underlying this important behavior. One critical aspect of natural object grasping is the coordination of where the fingers make contact with an object and how much force is applied following contact. Such force-to-position modulation is critical for successful manipulation. However, the neural mechanisms underlying these motor processes remain less understood, as previous experiments have utilized protocols with fixed contact points which likely rely on different neural mechanisms from those involved in grasping at unconstrained contacts. To address this gap in the motor neuroscience field, transcranial magnetic stimulation (TMS) and electroencephalography (EEG) were used to investigate the role of primary motor cortex (M1), as well as other important cortical regions in the grasping network, during the planning and execution of object grasping and manipulation. The results of virtual lesions induced by TMS and EEG revealed grasp context-specific cortical mechanisms underlying digit force-to-position coordination, as well as the spatial and temporal dynamics of cortical activity during planning and execution. Together, the present findings provide the foundation for a novel framework accounting for how the central nervous system controls dexterous manipulation. This new knowledge can potentially benefit research in neuroprosthetics and improve the efficacy of neurorehabilitation techniques for patients affected by sensorimotor impairments.Dissertation/ThesisDoctoral Dissertation Neuroscience 201

Cortical oscillatory changes associated with cognitive effort, value of effort, and incentive.

Cognitive effort is conceptualised as being deployed relative to the SV of its associated outcomes. The SV of incentives should therefore directly modulate effortful performance, as well as cortical processes associated with effortful engagement. However, the relationship between incentive value and modality, and effortful engagement remains unclear. The current thesis aimed to elaborate on the deployment of cognitive effort in response to incentives of differing magnitude and valence using preparatory ERD/ERS measures in tandem with discounting procedures. ERD/ERS in the alpha and beta bands was used to untangle cortical activation from inhibition during effortful engagement, as well as separating anticipatory attention from approach/avoidance motor responses under rewards of differing magnitudes and valence. Further, a COGED discounting task was used to estimate effort discounting rates, and to compare the SV of gains and losses. The results presented in the three experimental chapters showed that rewards lead to different modulations in pre-movement ERD/ERS depending on the task-structure used. Losses were more motivating than gains, but were associated with slower RTs, as well as deteriorations in alpha-band ERD. Further, individual SVs of effort were not significantly associated with changes in RT or ERD under differing incentives. The current thesis showed that cognitive effort is deployed through patterns of strategic cortical activation and inhibition, rather than a sustained increase in cortical activation. Further, the divergent effect of losses and gains was revealed to likely be due to attentional effects not the previously hypothesised approach/avoidance associations. Finally, the SV of effort does not appear to directly inform effortful engagement

Dynamic large-scale network synchronization from perception to action

Sensory-guided actions entail the processing of sensory information, generation of perceptual decisions, and the generation of appropriate actions. Neuronal activity underlying these processes is distributed into sensory, fronto-parietal, and motor brain areas, respectively. How the neuronal processing is coordinated across these brain areas to support functions from perception to action remains unknown. We investigated whether phase synchronization in large-scale networks coordinate these processes. We recorded human cortical activity with magnetoencephalography (MEG) during a task in which weak somatosensory stimuli remained unperceived or were perceived. We then assessed dynamic evolution of phase synchronization in large-scale networks from source-reconstructed MEG data by using advanced analysis approaches combined with graph theory. Here we show that perceiving and reporting of weak somatosensory stimuli is correlated with sustained strengthening of large-scale synchrony concurrently in delta/theta (3-7 Hz) and gamma (40-60 Hz) frequency bands. In a data-driven network localization, we found this synchronization to dynamically connect the task-relevant, that is, the fronto-parietal, sensory, and motor systems. The strength and temporal pattern of interareal synchronization were also correlated with the response times. These data thus show that key brain areas underlying perception, decision-making, and actions are transiently connected by large-scale dynamic phase synchronization in the delta/theta and gamma bands.Peer reviewe

The effect of salient stimuli on neural oscillations, isometric force, and their coupling

Survival in a suddenly-changing environment requires animals not only to detect salient stimuli, but also to promptly respond to them by initiating or revising ongoing motor processes. We recently discovered that the large vertex brain potentials elicited by sudden supramodal stimuli are strongly coupled with a multiphasic modulation of isometric force, a phenomenon that we named cortico-muscular resonance (CMR). Here, we extend our investigation of the CMR to the time-frequency domain. We show that (i) both somatosensory and auditory stimuli evoke a number of phase-locked and non-phase-locked modulations of EEG spectral power. Remarkably, (ii) some of these phase-locked and non-phase-locked modulations are also present in the Force spectral power. Finally, (iii) EEG and Force time-frequency responses are correlated in two distinct regions of the power spectrum. An early, low-frequency (∼4 Hz) region reflects the previously-described coupling between the phase-locked EEG vertex potential and force modulations. A late, higher-frequency (beta-band, ∼20 Hz) region reflects a second coupling between the non-phase-locked increase of power observed in both EEG and Force. In both time-frequency regions, coupling was maximal over the sensorimotor cortex contralateral to the hand exerting the force, suggesting an effect of the stimuli on the tonic corticospinal drive. Thus, stimulus-induced CMR occurs across at least two different types of cortical activities, whose functional significance in relation to the motor system should be investigated further. We propose that these different types of corticomuscular coupling are important to alter motor behavior in response to salient environmental events

The Effects of Reward and Risk Level Associated with Speeded Actions: Evidence from Behavior and Electroencephalography

Choosing a course of action in our daily lives requires an accurate assessment of the associated risks as well as the potential rewards. The present two studies investigated the mechanism of how reward and risk level influence the motor decisions of speeded actions (Chapter 2) and its neural dynamics (Chapter 3) by focusing on the beta band (15-30 Hz) oscillation patterns reflected in the EEG signals. Participants performed a modified version of the Go-NoGo task, in which they earned reward points based on the speed and accuracy of response. On each trial, the reward points at stake (120 vs. 6) and the probability that a Go signal would follow (Go-probability) were presented prior to a Go/NoGo signal (Trial Information Period). The behavioral results (from both Chapters 2 and 3) showed that larger amount of rewards can motivate people to respond faster, and this effect was modulated by the assessed risk, suggesting that decisions for actions are based on a systematic trade-off between rewards and risks. The EEG data showed that motor beta oscillations from the two studied brain regions reflected different levels of motivation towards a motor response across different reward and risk levels. Specifically, the lower beta power associated with higher reward and lower risk level. Collectively, the results provide a mechanistic understanding of how motivational cues are translated into action outcomes via modulating patterns of brain oscillations