When Coordinating Finger Tapping to a Variable Beat the Variability Scaling Structure of the Movement and the Cortical BOLD Signal are Both Entrained to the Auditory Stimuli

Rhythmic actions are characterizable as a repeating invariant pattern of movement together with variability taking the form of cycle-to-cycle fluctuations. Variability in behavioral measures is atypically random, and often exhibits serial temporal dependencies and statistical self-similarity in the scaling of variability magnitudes across timescales. Self-similar (i.e. fractal) variability scaling is evident in measures of both brain and behavior. Variability scaling structure can be quantified via the scaling exponent (α) from detrended fluctuation analysis (DFA). Here we study the task of coordinating thumb-finger tapping to the beats of constructed auditory stimuli. We test the hypothesis that variability scaling evident in tap-to-tap intervals as well as in the fluctuations of cortical hemodynamics will become entrained to (i.e. drawn toward) manipulated changes in the variability scaling of a stimulus’s beat-to-beat intervals. Consistent with this hypothesis, manipulated changes of the exponent α of the experimental stimuli produced corresponding changes in the exponent α of both tap-to-tap intervals and cortical hemodynamics. The changes in hemodynamics were observed in both motor and sensorimotor cortical areas in the contralateral hemisphere. These results were observed only for the longer timescales of the detrended fluctuation analysis used to measure the exponent α. These findings suggest that complex auditory stimuli engage both brain and behavior at the level of variability scaling structures

Exploring the role of primary and supplementary motor areas in simple motor tasks with fNIRS

Studies employing functional magnetic resonance imaging (fMRI) have highlighted a covariation between the amplitude of hemodynamic responses recorded in primary and supplementary motor areas (M1 and SMA) and the duration of a motor task. A subset of these studies have hinted to a possible functional dissociation between processing carried out in these areas, with SMA primarily involved in action preparation, while M1 involved in action execution. This proposed functional dissociation was explored in the present study using a different technique—functional near-infrared spectroscopy—which enabled a finer-grained monitoring of the temporal characteristics of the hemodynamic response compared to fMRI. Here, hemodynamic responses in M1 and SMA were recorded in 7 participants during a right-finger tapping task of short (1 s) or long (3 s) duration. Hemodynamic responses of larger amplitude were recorded from both contralateral M1 and SMA during long-duration than short-duration tapping. Furthermore, the analysis of the temporal profiles of these responses revealed a more sustained and prolonged activity for long-duration versus short-duration tapping in M1, but not in SMA. Rather than functionally dissociable areas, the present results are more compatible with the hypothesis that M1 and SMA subserve different, though strongly interacting, functional subroutines subtended in motor task preparation and execution

Exploring the role of primary and supplementary motor areas in simple motor tasks with fNIRS

Studies employing functional magnetic resonance imaging (fMRI) have highlighted a covariation between the amplitude of hemodynamic responses recorded in primary and supplementary motor areas (M1 and SMA) and the duration of a motor task. A subset of these studies have hinted to a possible functional dissociation between processing carried out in these areas, with SMA primarily involved in action preparation, while M1 involved in action execution. This proposed functional dissociation was explored in the present study using a different technique—functional near-infrared spectroscopy—which enabled a finer-grained monitoring of the temporal characteristics of the hemodynamic response compared to fMRI. Here, hemodynamic responses in M1 and SMA were recorded in 7 participants during a right-finger tapping task of short (1 s) or long (3 s) duration. Hemodynamic responses of larger amplitude were recorded from both contralateral M1 and SMA during long-duration than short-duration tapping. Furthermore, the analysis of the temporal profiles of these responses revealed a more sustained and prolonged activity for long-duration versus short-duration tapping in M1, but not in SMA. Rather than functionally dissociable areas, the present results are more compatible with the hypothesis that M1 and SMA subserve different, though strongly interacting, functional subroutines subtended in motor task preparation and execution

Frequency domain high density diffuse optical tomography for functional brain imaging

Measurements of dynamic near-infrared (NIR) light attenuation across the human head together with model-based image reconstruction algorithms allow the recovery of three-dimensional spatial brain activation maps. Previous studies using high-density diffuse optical tomography (HD-DOT) systems have reported improved image quality over sparse arrays. Modulated NIR light, known as Frequency Domain (FD) NIR, enables measurements of phase shift along with amplitude attenuation. It is hypothesised that the utilization of these two sets of complementary data (phase and amplitude) for brain activity detection will result in an improvement in reconstructed image quality within HD-DOT. However, parameter recovery in DOT is a computationally expensive algorithm, especially when FD-HD measurements are required over a large and complex volume, as in the case of brain functional imaging. Therefore, computational tools for the light propagation modelling, known as the forward model, and the parameter recovery, known as the inverse problem, have been developed, in order to enable FD-HD-DOT. The forward model, within a diffusion approximation-based finite-element modelling framework, is accelerated by employing parallelization. A 10-fold speed increase when GPU architectures are available is achieved while maintaining high accuracy. For a very high-resolution finite-element model of the adult human head with ∼600,000 nodes, light propagation can be calculated at ∼0.25s per excitation source. Additionally, a framework for the sparse formulation of the inverse model, incorporating parallel computing, is proposed, achieving a 10-fold speed increase and a 100-fold memory efficiency, whilst maintaining reconstruction quality. Finally, to evaluate image reconstruction with and without the additional phase information, point spread functions have been simulated across a whole-scalp field of view in 24 subject-specific anatomical models using an experimentally derived noise model. The addition of phase information has shown to improve the image quality by reducing localization error by up to 59%, effective resolution by up to 21%, and depth penetration up to 5mm, as compared to using the intensity attenuation measurements alone. In addition, experimental data collected during a retinotopic experiment reveal that the phase data contains unique information about brain activity and enables images to be resolved for deeper brain regions

DESIGN AND IMPLEMENTATION OF A NOVEL LAPLACE-DOMAIN DIFFUSE OPTICAL TOMOGRAPHY AND ITS APPLICATION FOR BRAIN IMAGING

Ph.DDOCTOR OF PHILOSOPH

Der Einfluss der transkraniellen Gleichstromstimulation auf den Motorcortex: Eine Untersuchung mittels Nahinfrarotspektroskopie

Die vorliegende Studie untersucht mittels Nahinfrarotspektroskopie (NIRS) den Einfluss einer tDCS auf die Blutflussantwort im primär motorischen Cortex. Auf Grundlage der neurovaskulären Kopplung lassen sich Durchblutungsänderungen hierbei als Ausdruck cerebraler Aktivitätsänderungen interpretieren. Gemäß den Ergebnissen bisheriger Studien zum Einfluss der tDCS auf die Erregbarkeit des Motorcortex, wurde die Hypothese aufgestellt, dass eine anodale Stimulation zu einer vermehrten und eine kathodale Stimulation zu einer verminderten regionalen cerebralen Durchblutung (rCBF) führt. Es wurden 36 gesunde, rechtshändige Probanden in drei randomisierte Untersuchungsgruppen aufgeteilt. Gruppe A erhielt eine unipolare anodale tDCS, den Probanden der Gruppe B wurde eine unipolare kathodale tDCS appliziert und in Gruppe C erfolgte eine Sham-Stimulation. Die Stimulationselektrode wurde jeweils über dem linken primär motorischen Cortex positioniert, die Referenzelektrode wurde jeweils über der rechten Orbita platziert. Auf Grundlage einer im Vorfeld der Studie durchgeführten Voruntersuchung wurde während der Bildgebung von den Probanden eine Zeigefingertapping-Aufgabe ausgeführt, deren Frequenz und Ausführungsseite (rechts oder links) in randomisierter Reihenfolge durch einen visuellen Impuls vorgegeben wurden. Die Bildgebung mittels Nahinfrarotspektroskopie erfolgte unter Ausführung dieser motorischen Aufgabe zu insgesamt 5 verschiedenen Messzeitpunkten: Unmittelbar vor der Stimulation sowie schnellstmöglich (5-7 Minuten), 15, 25 und 45 Minuten nach erfolgter tDCS über beiden Motorcortices. Nach anodaler tDCS war eine signifikante Abnahme der Durchblutung in Form einer O2Hb-Konzentrationsabnahme im linken und rechten primären motorischen Cortex unmittelbar nach erfolgter Stimulation messbar. Diese ließ sich in abgeschwächter Form bis zum Messzeitpunkt 15 Minuten nach Stimulationsende beobachten. Eine Veränderung der HHb-Konzentration blieb aus. Nach kathodaler tDCS und Sham-Stimulation waren keine signifikanten Änderungen der Blutflussantwort feststellbar. Ursachen für dieses Ergebnis könnten aufgabenabhängige und zustandsabhängige Interaktionen sein. In der vorliegenden Arbeit könnten sowohl die Ausführung der Tapping-Aufgabe als auch ungewollte motorische oder kognitive Tätigkeiten den Stimulationseffekt beeinflusst haben. Auch der neuronale Zustand, auf den die tDCS trifft und der physiologischen zirkadianen, hormonellen und metabolischen Schwankungen unterliegt, könnte die Untersuchungsergebnisse mitbedingt haben. Es ist denkbar, dass auch interindividuelle Merkmalsunterschiede anatomischer und physiologischer Merkmale – wie z. B. die Passung des Referenzpunktes C3 (des zur Elektrodenpositionierung genutzten 10-20-Systems) zum primären Motorcortexareal, die Dicke der Kopfschwarte oder der Schädelkalotte – den Stimulationseffekt beeinflussten. Die isolierte Veränderung der O2Hb-Konzentration bei gleichzeitigem Ausbleiben der erwarteten gegenläufigen HHb-Konzentrationsänderung deckt sich mit Beobachtungen vorhergehender Studien und könnte als Ausdruck der höheren Sensitivität des O2Hb für Durchblutungsänderungen gedeutet werden und somit auf eine relativ gering ausgeprägte Blutflussabnahme nach anodaler tDCS hinweisen. Da HHb corticale Blutflussänderungen spezifischer abzubilden scheint als O2Hb, könnte die isolierte Konzentrationsänderung des O2Hb alternativ auch als Ausdruck einer Erfassung nichtcorticaler hämodynamischer Veränderungen wie z. B. der lokalen Hautdurchblutung interpretiert werden

Somatics Research Bibliography: A Working Tool for Somatics and Somatic Psychology

Many years ago when Somatics magazine was young, it occurred to me that it would be valuable to collect and publish research article references in Somatics magazine that were relevant to the different somatics disciplines to encourage the development of the field. There were next to no studies devoted to Somatics itself, but there were many studies devoted to the elements of somatic practices. Somatics is a multidisciplinary field. It builds on the research findings from many fields, such as anatomy, physiology, neurophysiology, psychology, dance, biomechanics, and education. The references are selected to be suggestive to the interested researcher and practitioner for their purposes and of the many possible research avenues that are yet to be explored. I have collected these research references for more than four decades. I worked originally with Psychological Abstracts, then PsychInfo, and finally, PubMed. Over that time there has been more research done on the somatic disciplines themselves. The greatest amount of research has been done on yoga (the oldest and largest of the somatic disciplines) and yoga therapy. These studies are examples of the research that can be done with the other somatics disciplines as well. We are in an era that appreciates evidence-based practice and practice-based evidence. This is evidence. These research articles are selected according to the following criteria: The article combines both body and mind either in its research design or theoretical perspective; the research design incorporates convergent measures—that is, it includes physiological, behavioral, and psychological measures; subjective and objective measures; and the research focuses on the whole organism (human) from a somatic perspective—that is, the effect of a body therapy on a psychological state. Topics addressed include biofeedback, body psychotherapy, consciousness states, electrophysiology, kinesiology, mind and body, motor processes, neural basis of motor control, neuroscience, posture and emotion, psychophysiology, and yoga/yoga therapy