Hub gene selection methods for the reconstruction of transcription networks

Transcription control networks have a scale-free topological structure: While most genes are involved in a reduced number of links, a few hubs or key regulators are connected to a significantly large number of nodes. Several methods have been developed for the reconstruction of these networks from gene expression data, e.g. ARACNE. However, few of them take into account the scale-free structure of transcription networks. In this paper, we focus on the hubs that commonly appear in scale-free networks. First, three feature selection methods are proposed for the identification of those genes that are likely to be hubs and second, we introduce an improvement in ARACNE so that this technique can take into account the list of hub genes generated by the feature selection methods. Experiments with synthetic gene expression data validate the accuracy of the feature selection methods in the task of identifying hub genes. When ARACNE is combined with the output of these methods, we achieve up to a 62% improvement in performance over the original reconstruction algorithm. Finally, the best method for identifying hub genes is validated on a set of expression profiles from yeast. © 2010 Springer-Verlag Berlin Heidelberg

The learning hearing aid: common-sense reasoning in hearing aid circuits

This article discusses how hearing aid engineers have applied the Bayesian probability theory approach to the problem of hearing aid fitting. Currently more an art than a science, it is likely that probability theory will play a large role in future generations of fitting software used by dispensing professionals. We will show that probability theory is consistent with common-sense reasoning, a feature that is not shared by alternative mathematical frameworks for intelligent reasoning. While probability theory gets to the same answers as a consistently reasoning human expert, it can deal with larger problems than a typical human is capable of handling. Since human expertise cannot be replaced by a mathematical system, we expect that mathematical reasoning systems, like the one described here, will serve as an assistant to the dispenser in difficult fitting tasks

Efficient evaluation of hearing ability

A system for establishing a hearing ability model of a hearing ability of a person, includes a data storage configured to store a representation of a distribution of a hearing ability of a population of individuals, and a processor configured to establish a hearing ability model representing a hearing ability of the person based at least in part on (i) information regarding a person's response to a stimulus of a hearing evaluation event, and (ii) the representation of the distribution of the hearing ability of the population. Also published as: EP2238899 (A1

Optimal Control of a Hybrid Rhythmic-Discrete Task: The Bouncing Ball Revisited

Rhythmically bouncing a ball with a racket is a hybrid task that combines continuous rhythmic actuation of the racket with the control of discrete impact events between racket and ball. This study presents experimental data and a two-layered modeling framework that explicitly addresses the hybrid nature of control: a first discrete layer calculates the state to reach at impact and the second continuous layer smoothly drives the racket to this desired state, based on optimality principles. The testbed for this hybrid model is task performance at a range of increasingly slower tempos. When slowing the rhythm of the bouncing actions, the continuous cycles become separated into a sequence of discrete movements interspersed by dwell times and directed to achieve the desired impact. Analyses of human performance show increasing variability of performance measures with slower tempi, associated with a change in racket trajectories from approximately sinusoidal to less symmetrical velocity profiles. Matching results of model simulations give support to a hybrid control model based on optimality, and therefore suggest that optimality principles are applicable to the sensorimotor control of complex movements such as ball bouncing

Frequency dependence of the action-perception cycle for postural control in a moving visual environment: relative phase dynamics

Contains fulltext : 103984.pdf (publisher's version ) (Open Access

Control of Bimanual Rhythmic Movements: Trading Efficiency for Robustness Depending on the Context

This paper investigates how the efficiency and robustness of a skilled rhythmic task compete against each other in the control of a bimanual movement. Human subjects juggled a puck in 2D through impacts with two metallic arms, requiring rhythmic bimanual actuation. The arms kinematics were only constrained by the position, velocity and time of impacts while the rest of the trajectory did not influence the movement of the puck. In order to expose the task robustness, we manipulated the task context in two distinct manners: the task tempo was assigned at four different values (hence manipulating the time available to plan and execute each impact movement individually); and vision was withdrawn during half of the trials (hence reducing the sensory inflows). We show that when the tempo was fast, the actuation was rhythmic (no pause in the trajectory) while at slow tempo, the actuation was discrete (with pause intervals between individual movements). Moreover, the withdrawal of visual information encouraged the rhythmic behavior at the four tested tempi. The discrete versus rhythmic behavior give different answers to the efficiency/robustness trade-off: discrete movements result in energy efficient movements, while rhythmic movements impact the puck with negative acceleration, a property preserving robustness. Moreover, we report that in all conditions the impact velocity of the arms was negatively correlated with the energy of the puck. This correlation tended to stabilize the task and was influenced by vision, revealing again different control strategies. In conclusion, this task involves different modes of control that balance efficiency and robustness, depending on the context

Postural Coordination Dynamics in Standing Humans

Human stance requires the coordination of multiple joints. This article examines the dynamics of postural coordination modes involving the torso and legs in the control of stance and stance-related activities. Based on data obtained in various experiments using the same postural tracking task, we provide evidence that postural modes (i) emerge out of the coalescence of multiple constraints, (ii) exhibit persistence and changes that are characteristic of self-organized systems, (iii) are modulated by the actors intention, and (iv) can be learned by modifying the intrinsic dynamics of the postural system. Similarities between postural phase transitions in humans or non-biological phenomena suggest the existence of general and common principles governing pattern formation and flexibility in complex systems, and circumscribe the generality of neurophysiologically-based theories of postural behavior. Postural Coordination Dynamics in Standing Humans One of the major problems facing movement scientists is how humans and other animals coordinate the multitude of degrees of freedom of their bodies, constraining them to act as a single unit in accomplishing behavioral tasks. Standing, walking, reaching, or hitting a moving object are prosaic examples in which successful performance is based upon, and severely constrained by, a set of neuro