(Dis-)attending to the body : action and self-experience in the active inference framework

Endogenous attention is crucial and beneficial for learning, selecting, and supervising actions. However, deliberately attending to action execution usually comes at the cost of decreased smoothness and slower performance, often severely impairs normal functioning, and in the worst case may result in pathological behavior and experience as in schizophrenic hyperreflexivity. These ambiguous modulatory effects of self-directed attention have been examined on phenomenological, computational, and implementational levels of description—a recent formalization within an active inference framework aims to accommodate all of these aspects. Here, I examine the active inference account of motor control as enabled by attentional modulation based on expected precisions of prediction errors in a brain’s hierarchical generative model of the environment. The implications of active inference fit well with a range of empirical results, they resonate well with ideomotor accounts of motor control, and they also tentatively reflect many insights from phenomenological analysis of the “lived body”. Thereby a particular strength of active inference is its hierarchical account of motor control in terms of adaptive behavior driven by the imperative to maintain the organism’s states within unsurprising boundaries. Phenomena ranging from the reflex arc to intentional, goal-directed action and the experience of oneself as an embodied agent are are thus proposed to rely on the same mechanisms operating universally throughout the brain’s hierarchical generative model. However, while the explanation of movement production and sensory attenuation in terms of low-level attentional modulation is quite elegant on the active inference view, there are some questions left open by its extension to higher levels of action control and the accompanying phenomenology of for example volition, effort, or agency. I suggest that conceptual guidance from recent accounts of phenomenal self- and world-modeling may help develop active inference into an interdisciplinary framework for investigating embodied agentive self-experience

Attentional Modulation of Vision Versus Proprioception During Action

To control our actions efficiently, our brain represents our body based on a combination of visual and proprioceptive cues, weighted according to how (un)reliable—how precise—each respective modality is in a given context. However, perceptual experiments in other modalities suggest that the weights assigned to sensory cues are also modulated “top-down” by attention. Here, we asked whether during action, attention can likewise modulate the weights (i.e., precision) assigned to visual versus proprioceptive information about body position. Participants controlled a virtual hand (VH) via a data glove, matching either the VH or their (unseen) real hand (RH) movements to a target, and thus adopting a “visual” or “proprioceptive” attentional set, under varying levels of visuo-proprioceptive congruence and visibility. Functional magnetic resonance imaging (fMRI) revealed increased activation of the multisensory superior parietal lobe (SPL) during the VH task and increased activation of the secondary somatosensory cortex (S2) during the RH task. Dynamic causal modeling (DCM) showed that these activity changes were the result of selective, diametrical gain modulations in the primary visual cortex (V1) and the S2. These results suggest that endogenous attention can balance the gain of visual versus proprioceptive brain areas, thus contextualizing their inf luence on multisensory areas representing the body for action

Minimal self-models and the free energy principle

The term “minimal phenomenal selfhood” (MPS) describes the basic, pre-reflective experience of being a self (Blanke and Metzinger, 2009). Theoretical accounts of the minimal self have long recognized the importance and the ambivalence of the body as both part of the physical world, and the enabling condition for being in this world (Gallagher, 2005a; Grafton, 2009). A recent account of MPS (Metzinger, 2004a) centers on the consideration that minimal selfhood emerges as the result of basic self-modeling mechanisms, thereby being founded on pre-reflective bodily processes. The free energy principle (FEP; Friston, 2010) is a novel unified theory of cortical function built upon the imperative that self-organizing systems entail hierarchical generative models of the causes of their sensory input, which are optimized by minimizing free energy as an approximation of the log-likelihood of the model. The implementation of the FEP via predictive coding mechanisms and in particular the active inference principle emphasizes the role of embodiment for predictive self-modeling, which has been appreciated in recent publications. In this review, we provide an overview of these conceptions and illustrate thereby the potential power of the FEP in explaining the mechanisms underlying minimal selfhood and its key constituents, multisensory integration, interoception, agency, perspective, and the experience of mineness. We conclude that the conceptualization of MPS can be well mapped onto a hierarchical generative model furnished by the FEP and may constitute the basis for higher-level, cognitive forms of self-referral, as well as the understanding of other minds.Peer Reviewe

Active inference under visuo-proprioceptive conflict: Simulation and empirical results

It has been suggested that the brain controls hand movements via internal models that rely on visual and proprioceptive cues about the state of the hand. In active inference formulations of such models, the relative influence of each modality on action and perception is determined by how precise (reliable) it is expected to be. The 'top-down' affordance of expected precision to a particular sensory modality is associated with attention. Here, we asked whether increasing attention to (i.e., the precision of) vision or proprioception would enhance performance in a hand-target phase matching task, in which visual and proprioceptive cues about hand posture were incongruent. We show that in a simple simulated agent-based on predictive coding formulations of active inference-increasing the expected precision of vision or proprioception improved task performance (target matching with the seen or felt hand, respectively) under visuo-proprioceptive conflict. Moreover, we show that this formulation captured the behaviour and self-reported attentional allocation of human participants performing the same task in a virtual reality environment. Together, our results show that selective attention can balance the impact of (conflicting) visual and proprioceptive cues on action-rendering attention a key mechanism for a flexible body representation for action

Neuronal correlates of continuous manual tracking under varying visual movement feedback in a virtual reality environment

To accurately guide one's actions online, the brain predicts sensory action feedback ahead of time based on internal models, which can be updated by sensory prediction errors. The underlying operations can be experimentally investigated in sensorimotor adaptation tasks, in which moving under perturbed sensory action feedback requires internal model updates. Here we altered healthy participants’ visual hand movement feedback in a virtual reality setup, while assessing brain activity with functional magnetic resonance imaging (fMRI). Participants tracked a continually moving virtual target object with a photorealistic, three-dimensional (3D) virtual hand controlled online via a data glove. During the continuous tracking task, the virtual hand's movements (i.e., visual movement feedback) were repeatedly periodically delayed, which participants had to compensate for to maintain accurate tracking. This realistic task design allowed us to simultaneously investigate processes likely operating at several levels of the brain's motor control hierarchy. FMRI revealed that the length of visual feedback delay was parametrically reflected by activity in the inferior parietal cortex and posterior temporal cortex. Unpredicted changes in visuomotor mapping (at transitions from synchronous to delayed visual feedback periods or vice versa) activated biological motion-sensitive regions in the lateral occipitotemporal cortex (LOTC). Activity in the posterior parietal cortex (PPC), focused on the contralateral anterior intraparietal sulcus (aIPS), correlated with tracking error, whereby this correlation was stronger in participants with higher tracking performance. Our results are in line with recent proposals of a wide- spread cortical motor control hierarchy, where temporoparietal regions seem to evaluate visuomotor congruence and thus possibly ground a self-attribution of movements, the LOTC likely processes early visual prediction errors, and the aIPS computes action goal errors and possibly corresponding motor corrections

Cortical beta oscillations reflect the contextual gating of visual action feedback

In sensorimotor integration, the brain needs to decide how its predictions should accommodate novel evidence by 'gating' sensory data depending on the current context. Here, we examined the oscillatory correlates of this process by recording magnetoencephalography (MEG) data during a new task requiring action under intersensory conflict. We used virtual reality to decouple visual (virtual) and proprioceptive (real) hand postures during a task in which the phase of grasping movements tracked a target (in either modality). Thus, we rendered visual information either task-relevant or a (to-be-ignored) distractor. Under visuo-proprioceptive incongruence, occipital beta power decreased (relative to congruence) when vision was task-relevant but increased when it had to be ignored. Dynamic causal modelling (DCM) revealed that this interaction was best explained by diametrical, task-dependent changes in visual gain. These novel results suggest a crucial role for beta oscillations in the contextual gating (i.e., gain or precision control) of visual vs proprioceptive action feedback, depending on concurrent behavioral demands

Immunohistochemical studies on brain nitric oxide synthase (bNOS) in the male genital accessory glands of the rat during postnatal development

The aim of the study was to investigate the presence, localisation and function of brain nitric oxide synthase (bNOS) in the male genital accessory glands of rats in the course of their postnatal development. Localisation of the bNOS was immunocytochemically investigated in the epididymis, seminal vesicle and ventral prostate of male Wistar strain rats at 1, 5, 10, 20, 28, 35, 45 and 59 days of age. The method employed involved mouse monoclonal antibodies against rat bNOS in combination with tyramide signal amplification (CSA). The intensity of the reaction in the organs studied was determined using computer software to demonstrate the optical density of the reaction product obtained. In the epididymis a weak reaction was observed in the connective tissue/muscular sublayer on the 28th and 45th days of life. In the seminal vesicle and ventral prostate a positive reaction appeared in the epinuclear portions of glandular epithelial cells on the 20th day of life, reaching a maximum intensity on the 28th day and thus before the rats reached maturity. The results obtained allow the conclusion to be drawn that nitric oxide resulting from bNOS-activity participates in the processes of differentiation and of function in the epididymis, seminal vesicle and ventral prostate

Die Haftung des Staates für Verletzungen der Berufsfreiheit

Die Reformbedürftigkeit des Staatshaftungsrechts lässt sich an keinem Grundrecht so eindrücklich verdeutlichen wie an der Berufsfreiheit. Während der Staat immer stärker reguliert und agiert, kann der Bürger nur durch die defizitäre Amtshaftung Kompensation für rechtswidrige Eingriffe erlangen. Der Autor zeichnet die Lücke im Haftungssystem nach und untersucht mit Hilfe einer Rechtsprechungsanalyse ihre weiten praktischen Auswirkungen. Anhand dieser Erkenntnisse überprüft er hergebrachte Lösungsansätze und arbeitet die bisher unterrepräsentierte Idee einer originären Grundrechtshaftung als dogmatisch und praktisch tragfähiges Fundament heraus, auf dem weiter aufgebaut wird. Mit einer Rückbeziehung auf die praktischen Problemfälle entkräftet der Autor unter Zuhilfenahme der allgemeinen Kausalitäts- und Eingriffsdogmatik und einer genauen Schadensberechnung die Befürchtungen einer grenzenlosen Haftung, um abschließend die mögliche Umsetzung des Konzepts durch Gesetz oder Richterrecht zu beleuchten.»The Liability of the State for Violations of Occupational Freedom«Based on a case law analysis, the author identifies systematic gaps of state liability in the field of occupational freedom. The idea of a state liability derived directly from fundamental rights serves as a dogmatically and practically sustainable foundation to close these gaps. Fears of unlimited liability can be refuted by using the requirements of causality of the state act as well as the precise calculation of damages. Both Parliament and the courts might implement this concept

The computational neurology of movement under active inference

We propose a computational neurology of movement based on the convergence of theoretical neurobiology and clinical neurology. A significant development in the former is the idea that we can frame brain function as a process of (active) inference, in which the nervous system makes predictions about its sensory data. These predictions depend upon an implicit predictive (generative) model used by the brain. This means neural dynamics can be framed as generating actions to ensure sensations are consistent with these predictions-and adjusting predictions when they are not. We illustrate the significance of this formulation for clinical neurology through simulating a clinical examination of the motor system; i.e. an upper limb coordination task. Specifically, we show how tendon reflexes emerge naturally under the right kind of generative model. Through simulated perturbations, pertaining to prior probabilities of this model's variables, we illustrate the emergence of hyperreflexia and pendular reflexes, reminiscent of neurological lesions in the corticospinal tract and cerebellum. We then turn to the computational lesions causing hypokinesia and deficits of coordination. This in silico lesion-deficit analysis provides an opportunity to revisit classic neurological dichotomies (e.g. pyramidal versus extrapyramidal systems) from the perspective of modern approaches to theoretical neurobiology-and our understanding of the neurocomputational architecture of movement control based on first principles