Human cortical dynamics during full-body heading changes

The retrosplenial complex (RSC) plays a crucial role in spatial orientation by computing heading direction and translating between distinct spatial reference frames based on multi-sensory information. While invasive studies allow investigating heading computation in moving animals, established non-invasive analyses of human brain dynamics are restricted to stationary setups. To investigate the role of the RSC in heading computation of actively moving humans, we used a Mobile Brain/Body Imaging approach synchronizing electroencephalography with motion capture and virtual reality. Data from physically rotating participants were contrasted with rotations based only on visual flow. During physical rotation, varying rotation velocities were accompanied by pronounced wide frequency band synchronization in RSC, the parietal and occipital cortices. In contrast, the visual flow rotation condition was associated with pronounced alpha band desynchronization, replicating previous findings in desktop navigation studies, and notably absent during physical rotation. These results suggest an involvement of the human RSC in heading computation based on visual, vestibular, and proprioceptive input and implicate revisiting traditional findings of alpha desynchronization in areas of the navigation network during spatial orientation in movement-restricted participants.TU Berlin, Open-Access-Mittel – 202

LFP and oscillations - what do they tell us?

This review surveys recent trends in the use of local field potentials—and their non-invasive counterparts—to address the principles of functional brain architectures. In particular, we treat oscillations as the (observable) signature of context-sensitive changes in synaptic efficacy that underlie coordinated dynamics and message-passing in the brain. This rich source of information is now being exploited by various procedures—like dynamic causal modelling—to test hypotheses about neuronal circuits in health and disease. Furthermore, the roles played by neuromodulatory mechanisms can be addressed directly through their effects on oscillatory phenomena. These neuromodulatory or gain control processes are central to many theories of normal brain function (e.g. attention) and the pathophysiology of several neuropsychiatric conditions (e.g. Parkinson's disease)

A Meta-Analysis of Mental Imagery Effects on Post-Injury Functional Mobility, Perceived Pain, and Self-Efficacy

Objectives: We used meta-analysis to examine the effects of mental imagery (MI) on three bio-psycho-social factors, namely functional mobility, perceived pain, and self-efficacy. Method: Ten studies were included in the meta-analytical review. Cohen’s d effect sizes (ES) and Hedge's g weighted mean ES (WES) were computed for all dependent variables. Results: The analysis revealed that the effect of imagery interventions was (1) small and positive for functional mobility (g =.16), (2) large and negative for perceived pain (g = -.86), and (3) large and positive for self-efficacy (g = .99). These effects were all non-significant, probably because the interventions administered and populations sampled in the studies were mostly heterogeneous. Hence, the effects of MI on bio-psycho-social variables warrant continued empirical investigation. Conclusions: Given the observed statistical trends, MI interventions are likely to be beneficial for athletes recovering from injury, as they may serve to decrease negative affect and promote gains in mobility and positive affect

The Parkinsonian subthalamic network: measures of power, linear, and non-linear synchronization and their relationship to L-DOPA treatment and OFF state motor severity

In this paper we investigated the dopaminergic modulation of neuronal interactions occurring in the subthalamic nucleus (STN) during Parkinson's disease (PD). We utilized linear measures of local and long range synchrony such as power and coherence, as well as Detrended Fluctuation Analysis for Phase Synchrony (DFA-PS)- a recently developed non-linear method that computes the extent of long tailed autocorrelations present in the phase interactions between two coupled signals. Through analysis of local field potentials (LFPs) taken from the STN we seek to determine changes in the neurodynamics that may underpin the pathophysiology of PD in a group of 12 patients who had undergone surgery for deep brain stimulation. We demonstrate up modulation of alpha-theta (5–12 Hz) band power in response to L-DOPA treatment, whilst low beta band power (15–20 Hz) band-power is suppressed. We also find evidence for significant local connectivity within the region surrounding STN although there was evidence for its modulation via administration of L-DOPA. Further to this we present evidence for a positive correlation between the phase ordering of bilateral STN interactions and the severity of bradykinetic and rigidity symptoms in PD. Although, the ability of non-linear measures to predict clinical state did not exceed standard measures such as beta power, these measures may help identify the connections which play a role in pathological dynamics

Long-range correlation properties in timing of skilled piano performance: the influence of auditory feedback and deep brain stimulation

Unintentional timing deviations during musical performance can be conceived of as timing errors. However, recent research on humanizing computer-generated music has demonstrated that timing fluctuations that exhibit long-range temporal correlations (LRTC) are preferred by human listeners. This preference can be accounted for by the ubiquitous presence of LRTC in human tapping and rhythmic performances. Interestingly, the manifestation of LRTC in tapping behavior seems to be driven in a subject-specific manner by the LRTC properties of resting-state background cortical oscillatory activity. In this framework, the current study aimed to investigate whether propagation of timing deviations during the skilled, memorized piano performance (without metronome) of 17 professional pianists exhibits LRTC and whether the structure of the correlations is influenced by the presence or absence of auditory feedback. As an additional goal, we set out to investigate the influence of altering the dynamics along the cortico-basal-ganglia-thalamo-cortical network via deep brain stimulation (DBS) on the LRTC properties of musical performance. Specifically, we investigated temporal deviations during the skilled piano performance of a non-professional pianist who was treated with subthalamic-deep brain stimulation (STN-DBS) due to severe Parkinson's disease, with predominant tremor affecting his right upper extremity. In the tremor-affected right hand, the timing fluctuations of the performance exhibited random correlations with DBS OFF. By contrast, DBS restored long-range dependency in the temporal fluctuations, corresponding with the general motor improvement on DBS. Overall, the present investigations demonstrate the presence of LRTC in skilled piano performances, indicating that unintentional temporal deviations are correlated over a wide range of time scales. This phenomenon is stable after removal of the auditory feedback, but is altered by STN-DBS, which suggests that cortico-basal ganglia thalamocortical circuits play a role in the modulation of the serial correlations of timing fluctuations exhibited in skilled musical performance

Neuronale Korrelate von verdeckten und offenen Bewegungen untersucht durch EEG/EMG mit Implikationen für Gehirn-Computer-Schnittstellen

The present thesis investigates neural correlates of covert movements, i.e., motor imagery and the novel phenomenon quasi-movements, and overt movement execution in the human brain utilizing electroencephalography (EEG), electromyography (EMG), and neurofeedback. Although covert movements do not imply muscle contraction, yet there are distinct correlates of neural activity in sensorimotor networks in the brain. Investigating neural correlates of overt and covert movements is crucial for so-called "locked-in" patients, where the conscious mind is locked in a paralyzed body. Here communication and mobility can be (partially) restored with the help of a brain-computer interface (BCI) which, e.g., is operated via motor imagery. The present thesis comprises three studies, with the following key findings: Study 1: Covert and overt movements have been frequently shown to engage common neural substrates (e.g., sensorimotor cortex). However, it is an open question whether this similarity is also present during early stages of stimulus-processing. The present study demonstrates that "real" overt movements and "movements in the mind" differ already 120 ms after visual stimulus onset – the rapid activation of the contralateral sensorimotor cortex (EEG lateralized readiness potentials) is present only in the case of subsequent overt movements. This result indicates that the prior action intention differentially routes early stimulus-processing in the sensorimotor system, which in turn might contribute to later behavioral outcomes, i.e., movement generation or inhibition. Study 2: Per definition a true BCI must not rely on overt muscle contraction. However, covert movements occasionally are associated with weak, transient motor responses. Therefore, monitoring the target muscle and identifying contaminated trials is crucial for data interpretation. In contrast to previous studies we compared automatic and statistical procedures with visual inspection. The results show that visual inspection of EMG recordings from the target muscle was most sensitive for identifying contaminated trials (mean ~ 3 %), which were not detected by the other methods. Study 3: "Repetition suppression" (RS) denotes the decrease of neural responses to repeated external sensory stimuli. We hypothesize that RS can be triggered also by internal processes alone, i.e., in the absence of external sensory stimuli during the performance of a repetitive cognitive task. When subjects performed repetitive covert movements for 1 min, there was a significant recovery of oscillatory EEG alpha and beta dynamics over sensorimotor cortices back to resting baseline level. These results suggest that repeated cerebral activations, internally or externally triggered, are associated with RS, which presumably reflects the adaptation to stereotyped activation in neural networks. The results have crucial implications for designing experimental paradigms for BCI in order to overcome signal loss due to RS effects.Die vorliegende Dissertation untersucht im menschlichen Gehirn neuronale Korrelate offener Bewegungsausführung und von verdeckten Bewegungen, d.h. motorische Imagination und das neue motorisch-kognitive Phänomen "Quasi- Bewegungen", mittels der Elektroenzephalographie (EEG), Elektromyographie (EMG) und Neurofeedback. Obwohl verdeckte Bewegungen keine messbare Muskelaktivität involvieren, werden sie dennoch von spezifischer neuronaler Gehirnaktivität in sensomotorischen Netzwerken begleitet. Die Untersuchung der neuronalen Realisierung von offenen und verdeckten Bewegungen ist von fundamentaler Bedeutung für "locked-in" Patienten, die bei vollem Bewusstsein in ihren vollständig gelähmten Körper eingeschlossen sind. In diesem Fall können Kommunikation und Mobilität (partiell) mit Hilfe einer Gehirn-Computer- Schnittstelle (Brain-Computer Interface, BCI) wiederhergestellt werden, welche beispielsweise mittels motorischer Imagination kontrolliert wird. Die Dissertationsarbeit umfasst drei Studien mit folgenden Hauptbefunden: Studie 1: Es wurde bereits sehr häufig gezeigt, dass offene und verdeckte Bewegungen mit der Aktivierung ähnlicher oder gleicher neuronaler Substrate im Gehirn assoziiert sind. Die Studie hinterfragt diese Annahme jedoch in Hinblick auf sehr frühe Stadien der neuronalen Informationsverarbeitung und zeigt signifikante Unterschiede bereits 120 ms nach dem visuellen Stimulus: Nur für nachfolgende offene Bewegungen zeigte sich diese sehr frühe Aktivierung der kontralateralen sensomotorischen Kortizes (EEG lateralisierte Bereitschaftspotentiale). Dieses Ergebnis impliziert, dass bereits die vorausgehende Handlungsintention die frühe neuronale Verarbeitung moduliert und möglicherweise dadurch zu späteren Handlungsfolgen (Bewegungsausführung oder –hemmung) beiträgt. Studie 2: Eine wichtige Voraussetzung für BCI ist die Abwesenheit von Muskelaktivität. Somit wird eine EMG-Überwachung und sorgfältige Datenanalyse auf Bewegungsartefakte benötigt, zumal verdeckte Bewegungen durchaus von gelegentlichen Muskelkontraktionen begleitet werden können. Im Unterschied zu früheren Studien verglichen wir die Eignung verschiedener Verfahren (automatische und statistische Auswertung sowie visuelle Inspektion). Die Ergebnisse zeigen, dass nur die visuelle EMG- Inspektion des Zielmuskels die Datensegmente mit Bewegungsartefakten (~ 3 %) identifizieren konnte. Studie 3: Das Phänomen "repetition suppression" (RS; wörtlich "Wiederholungsunterdrückung") kennzeichnet die Abnahme neuronaler Aktivität bei wiederholter externer sensorischer Stimulation. Die Studie untersucht, ob RS ebenfalls präsent ist, wenn keine externe Stimulation vorliegt, d.h. während der wiederholten Ausführung von kognitiven Aufgaben (z. B. motorische Imagination). In der Tat zeigen die Ergebnisse, dass bei verdeckter Bewegungsausführung (Imagination oder Quasi-Bewegungen) über die Dauer von 1 Minute die Aktivierung sensomotorischer Netzwerke im EEG (alpha- und beta-Oszillationen) bei zunehmender Performanz-Dauer nachließ. Dies impliziert, dass RS auch in Abwesenheit von externer wiederholter Stimulation hervorgerufen werden kann, z. B. durch motorische Imagination und möglicherweise auch durch andere kognitive Aufgaben. RS indiziert höchstwahrscheinlich neuronale Adaption, deren Verständnis von fundamentaler Bedeutung ist für die Optimierung von Gehirn-Computer-Schnittstellen

Covert movements trigger repetition suppression of electroencephalography in sensorimotor cortex

‘Repetition suppression’ (RS) denotes the decrease of neural responses to repeated external sensory stimuli. Weshowed that RS can be also triggered by internal processes alone. When individuals perform repetitive covert movements, that is, motor imagery or quasi-movements, both of which are associated with pericentral cortical activity without muscle activations, there was asignificant recovery of electroencephalographic oscillations over sensorimotor cortices back to resting baseline level. After 58 s of task performance only 20% of[alpha]and 5% of [beta] suppressions remained (overt movements: 34% remaining in [alpha], complete recovery in [beta]). This result suggests that various, possibly all, repeated cerebral activations are associated with RS, presumably reflecting the adaptation to stereotyped activation in neuralnetworks

Visual stimuli evoke rapid activation (120 ms) of sensorimotor cortex for overt but not for covert movements

Overt and covert movements (e.g., motor imagery) have been frequently demonstrated to engage common neuronal substrates in the motor system. However, it is an open question whether this similarity is also present during early stages of stimulus-processing. We utilized the high temporal resolution of multi-channel electroencephalography (EEG) in order to test whether the prior action intention (overt vs. covert movements) differentially modulates early stimulus-processing stages in the cortical sensorimotor system. The subjects performed overt or covert movements contingent upon an instructive visual stimulus (indicating left or right hand performance). We introduced a novel measure, LRPrect, calculated as Lateralized Readiness Potentials from rectified EEG signals. This measure overcomes a problem related to the EEG signal variability due to polarity differences in the spatial distribution of neuronal sources. The LRPrect showed an activation already at 120 ms after stimulus onset (latN120) focally over sensorimotor cortices contralateral to the upcoming hand movement, yet only for overt but not covert movements. Thus the prior action intention differentially routes early stimulus-processing into the sensorimotor system, which might contribute to significantly different behavioral outcomes, i.e., movement generation or inhibition. The present results have implications for studies of motor inhibition and action intention

Mobile Brain/Body Imaging Data Heading Computation

This is Mobile Brain/Body Imaging data from 20 healthy adult participants in a heading computation experiment. Participants performed a spatial orientation task in a sparse virtual environment (WorldViz Vizard, Santa Barbara, USA) consisting of an infinite floor granulated in green and black. The experiment was self-paced and participants advanced the experiment by starting and ending each trial with a button press using the index finger of the dominant hand. A trial started with the onset of a red pole, which participants had to face and align with. Once the button was pressed the pole disappeared and was immediately replaced by a red sphere floating at eye level. The sphere automatically started to move around the participant along a circular trajectory at a fixed distance (30m) with one of two different velocity profiles. Participants were asked to rotate on the spot and to follow the sphere, keeping it in the center of their visual field (outward rotation). The sphere stopped unpredictably at varying eccentricity between 30° and 150° and turned blue, which indicated that participants had to rotate back to the initial heading (backward rotation). When participants had reproduced their estimated initial heading, they confirmed their heading with a button press and the red pole reappeared for reorientation. To ensure that the floor could not be used as an external landmark during the trials, it was faded out, turned randomly, and faded back in after each outward and backward rotation. The participants completed the experimental task twice, using i) a traditional desktop 2D setup (visual flow controlled through joystick movement; “joyR”), and ii) equipped with a MoBI setup (visual flow controlled through active physical rotation with the whole body; “physR”). The condition order was balanced across participants. To ensure the comparability of both rotation conditions, participants carried the full motion capture system at all times. In the joyR condition participants stood in the dimly lit experimental hall in front of a standard TV monitor (1.5m viewing distance, HD resolution, 60Hz refresh rate, 40″ diagonal size) and were instructed to move as little as possible. They followed the sphere by tilting the joystick and were thus only able to use visual flow information to complete the task. In the physical rotation condition participants were situated in a 3D virtual reality environment using a head-mounted display (HTC Vive; 2x1080x1200 resolution, 90 Hz refresh rate, 110° field of view). Participants’ movements were unconstrained, i.e., in order to follow the sphere they physically rotated on the spot, thus enabling them to use motor and kinesthetic information (i.e., vestibular input and proprioception) in addition to the visual flow for completing the task. If participants diverged from the center position as determined through motion capture of the head position, the task automatically halted and participants were asked to regain center position, indicated by a yellow floating sphere, before continuing with the task. Each movement condition was preceded by recording a three-minute baseline, during which the participants were instructed to stand still and to look straight ahead. The starting condition (visual flow only or physical rotation) was also counterbalanced for participants with different reference frame proclivities, such that five egocentric, four allocentric, and two mixed-strategy participants started with the joyR condition, and four egocentric, five allocentric participants started with the physR condition. In each rotation condition, participants practiced the experiment in three learning trials with instructions presented on screen. Subsequently, the main experiment started, including 140 experimental trials per rotation condition. The experimental trials in each condition were randomized and split into five blocks of 28 trials each. The breaks were self-paced and the next block was initiated with the push of a button. The sphere moved either clockwise or anticlockwise around the participant; this movement was either slow or fast (randomized), depending on two different velocity profiles. The eccentricities of the sphere’s end positions were clustered from -15° to +15° around the mean eccentric end positions of 45°, 90°, and 135° in steps of 3° (e.g., the cluster 45° eccentricity ranged from 30° and 60° with 11 trials covering all eccentricities). In addition, eccentricities of 67° and 112° (2 x 8 trials) were used to achieve a near-continuous distribution of end positions for the outward rotation in both rotation directions. Mobile Brain/Body Imaging (MoBI) setup. To allow for a meaningful interpretation of the data modalities and to preserve their temporal context, the EEG data, motion capture data from different sources, and experiment event marker data were time-stamped, streamed, recorded, and synchronized using the Lab Streaming Layer. Data Recordings: EEG. EEG data was recorded from 157 active electrodes with a sampling rate of 1000 Hz and band-pass filtered from 0.016 Hz to 500 Hz (BrainAmp Move System, Brain Products, Gilching, Germany). Using an elastic cap with an equidistant design (EASYCAP, Herrsching, Germany), 129 electrodes were placed on the scalp, and 28 electrodes were placed around the neck using a custom neckband (EASYCAP, Herrsching, Germany) in order to record neck muscle activity. Data were referenced to an electrode located closest to the standard position FCz. Impedances were kept below 10kΩ for standard locations on the scalp, and below 50kΩ for the neckband. Electrode locations were digitized using an optical tracking system (Polaris Vicra, NDI, Waterloo, ON, Canada). Data Recordings: Motion Capture. Two different motion capture data sources were used: 19 red active light-emitting diodes (LEDs) were captured using 31 cameras of the Impulse X2 System (PhaseSpace Inc., San Leandro, CA, USA) with a sampling rate of 90 Hz. They were placed on the feet (2 x 4 LEDs), around the hips (5 LEDs), on the shoulders (4 LEDs), and on the HTC Vive (2 LEDs; to account for an offset in yaw angle between the PhaseSpace and the HTC Vive tracking). Except for the two LEDs on the HTC Vive, they were subsequently grouped together to form rigid body parts of feet, hip, and shoulders, enabling tracking with six degrees of freedom (x, y, and z position and roll, yaw, and pitch orientation) per body part. Head motion capture data (position and orientation) was acquired using the HTC Lighthouse tracking system with 90Hz sampling rate, since it was also used for the positional tracking of the virtual reality view. Because the main focus of the study concerned the head movement-related modulation of neural dynamics in RSC, only data streams from the head motion capture data were used for the analysis.DFG, 240600905, Mobiles Bildgebungssyste