Internal states as a source of subject-dependent movement variability and their representation by large-scale networks

AbstractA human’s ability to adapt and learn relies on reflecting on past performance. Such reflections form latent factors called internal states that induce variability of movement and behavior to improve performance. Internal states are critical for survival, yet their temporal dynamics and neural substrates are less understood. Here, we link internal states with motor performance and neural activity using state-space models and local field potentials captured from depth electrodes in over 100 brain regions. Ten human subjects performed a goal-directed center-out reaching task with perturbations applied to random trials, causing subjects to fail goals and reflect on their performance. Using computational methods, we identified two internal states, indicating that subjects kept track of past errors and perturbations, that predicted variability in reaction times and speed errors. These states granted access to latent information indicative of how subjects strategize learning from trial history, impacting their overall performance. We further found that large-scale brain networks differentially encoded these internal states. The dorsal attention network encoded past errors in frequencies above 100 Hz, suggesting a role in modulating attention based on tracking recent performance in working memory. The default network encoded past perturbations in frequencies below 15 Hz, suggesting a role in achieving robust performance in an uncertain environment. Moreover, these networks more strongly encoded internal states and were more functionally connected in higher performing subjects, whose learning strategy was to respond by countering with behavior that opposed accumulating error. Taken together, our findings suggest large-scale brain networks as a neural basis of strategy. These networks regulate movement variability, through internal states, to improve motor performance.Key pointsMovement variability is a purposeful process conjured up by the brain to enable adaptation and learning, both of which are necessary for survival.The culmination of recent experiences—collectively referred to as internal states—have been implicated in variability during motor and behavioral tasks.To investigate the utility and neural basis of internal states during motor control, we estimated two latent internal states using state-space representation that modeled motor behavior during a goal-directed center-out reaching task in humans with simultaneous whole-brain recordings from intracranial depth electrodes.We show that including these states—based on error and environment uncertainty—improves the predictability of subject-specific variable motor behavior and reveals latent information related to task performance and learning strategies where top performers counter error scaled by trial history while bottom performers maintain error tendencies.We further show that these states are encoded by the large-scale brain networks known as the dorsal attention network and default network in frequencies above 100 Hz and below 15 Hz but found neural differences between subjects where network activity closely modulates with states and exhibits stronger functional connectivity for top performers.Our findings suggest the involvement in large-scale brain networks as a neural basis of motor strategy that orchestrates movement variability to improve motor performance.</jats:list-item

Le compartiment sauvage de la carotte en France : des ressources génétiques importantes et pourtant méconnues

La France est considérée comme centre secondaire de diversification de la carotte, du fait de l’activité importante de sélection (par des maraîchers ou semenciers), ce qui justifie les actions de conservation et connaissance des variétés anciennes menées par le réseau de ressources génétiques « Carotte et autres Daucus ». Par contre, le compartiment sauvage est méconnu et sous-exploité, alors qu’il s’agit d’une espèce pour laquelle de nombreuses populations existent sur le territoire français, avec une situation très contrastée. Si la carotte sauvage D. carota spp carota n’est pas en danger, d’autres sous espèces sont protégées (ssp gadecaei) ou menacées du fait de la dégradation de leur milieux naturels notamment en zone littorale ou de possibles introgressions avec la sous-espèce carota. Le travail présenté porte donc sur : i/ la sauvegarde et la mise à disposition des ressources génétiques sauvages, à travers l’inventaire de populations in situ et la constitution de collections ex-situ ; ii/ l’approfondissement de la connaissance et de l’identification taxonomique des sous-espèces sauvages ; iii/ la connaissance de la diversité au sein du compartiment sauvage (marqueurs SSR et données écologiques) ; et iv/ l’évaluation des ressources génétiques sauvages de carotte pour permettre leur exploitation (fertilité, croisements avec le compartiment cultivé, tolérance à différents bioagresseurs). Ce programme fait l’objet du soutien d’un contrat de branche du ministère de l’agriculture et implique les membres du réseau « Carotte et autres Daucus ».

The Bolund Experiment, Part I: Flow Over a Steep, Three-Dimensional Hill

We present an analysis of data from a measurement campaign performed at the Bolund peninsula in Denmark in the winter of 2007–2008. Bolund is a small isolated hill exhibiting a significantly steep escarpment in the main wind direction. The physical shape of Bolund represents, in a scaled-down form, a typical wind turbine site in complex terrain. Because of its small size the effect of atmospheric stratification can be neglected, which makes the Bolund experiment ideal for the validation of neutral flow models and hence model scenarios most relevant to wind energy. We have carefully investigated the upstream conditions. With a 7-km fetch over water, the incoming flow is characterized as flow over flat terrain with a local roughness height based on the surface momentum flux. The nearly perfect upstream conditions are important in forming a meaningful quantitative description of the flow over the Bolund hill. Depending on the wind direction, we find a maximum speed-up of 30% at the hill top accompanied by a maximum 300% enhancement of turbulence intensity. A closer inspection reveals transient behaviour with recirculation zones. From the wind energy context, this implies that the best site for erecting a turbine based on resource constraints unfortunately also imposes a penalty of high dynamic loads. On the lee side of Bolund, recirculation occurs with the turbulence intensity remaining significantly enhanced even at one hill length downstream. Its transient behaviour and many recirculation zones place Bolund in a category in which the linear flow theory is not applicable

On the use of Fourier averages to compute the global isochrons of (quasi)periodic dynamics

The concept of isochrons is crucial for the analysis of asymptotically periodic systems. Roughly, isochrons are sets of points that partition the basin of attraction of a limit cycle according to the asymptotic behavior of the trajectories. The computation of global isochrons (in the whole basin of attraction) is however difficult, and the existing methods are inefficient in high-dimensional spaces. In this context, we present a novel (forward integration) algorithm for computing the global isochrons of high-dimensional dynamics, which is based on the notion of Fourier time averages evaluated along the trajectories. Such Fourier averages in fact produce eigenfunctions of the Koopman semigroup associated with the system, and isochrons are obtained as level sets of those eigenfunctions. The method is supported by theoretical results and validated by several examples of increasing complexity, including the 4-dimensional Hodgkin-Huxley model. In addition, the framework is naturally extended to the study of quasiperiodic systems and motivates the definition of generalized isochrons of the torus. This situation is illustrated in the case of two coupled Van der Pol oscillators. © 2012 American Institute of Physics