Thierry Pozzo

Bio: Thierry Pozzo is an academic researcher from Istituto Italiano di Tecnologia. The author has contributed to research in topics: Body movement & Kinematics. The author has an hindex of 47, co-authored 183 publications receiving 6545 citations. Previous affiliations of Thierry Pozzo include University of Burgundy & Centre national de la recherche scientifique.

Head stabilization during various locomotor tasks in humans. I. Normal subjects.

Abstract: Head kinematics were studied in ten normal subjects while they executed various locomotor tasks The movement of the body was recorded with a video system which allowed a computer reconstruction of motion of joint articulations and other selected points on the body in three dimensions Analyses focus on head translation along the vertical axis and rotation in the sagittal plane This was done by recording the displacement of a line approximating the plane of horizontal semi-circular canals (the Frankfort plane: F-P) Four conditions were studied: free walking (W) walking in place (WIP) running in place (R) and hopping (H) In the 4 experimental conditions, amplitude and velocity of head translation along the vertical axis ranged from 1 cm to 25 cm and 015 m/s to 18 m/s In spite of the disparities in the tasks regarding the magnitude of dynamic components, we found a significant stabilization of the F-P around the earth horizontal Maximum amplitude of F-P rotation did not exceed 20° in the 4 situations Vertical angular velocities increased from locomotion tasks to the dynamic equilibrium task although the maximum values remained less than 140°/s Predominant frequencies of translations and rotations in all the tasks were within the range 04–35 Hz and harmonics were present up to 6–8 Hz During walking in darkness, mean head position is tilted downward, with the F-P always below the earth horizontal Darkness did not significantly influence the amplitude and velocity of head angular displacement during W, WIP and R, but during H the amplitude decreased by 37% Residual head angular displacement is found to compensate for head translation during the 4 conditions Our study emphasizes the importance of head stabilization as part of the postural control system and described as a basis for inertial guidance

Head stabilization during various locomotor tasks in humans. II : Patients with bilateral peripheral vestibular deficits

Abstract: This experiment, which extends a previous investigation (Pozzo et al. 1990), was undertaken to examine how head position is controlled during natural locomotor tasks in both normal subjects (N) and patients with bilateral vestibular deficits (V). 10 normals and 7 patients were asked to perform 4 locomotor tasks: free walking (W), walking in place (WIP), running in place (R) and hopping (H). Head and body movements were recorded with a video system which allowed a computed 3 dimensional reconstruction of selected points in the sagittal plane. In order to determine the respective contribution of visual and vestibular cues in the control of head angular position, the 2 groups of subjects were tested in the light and in darkness. In darkness, the amplitude and velocity of head rotation decreased for N subjects; these parameters increased for V subjects, especially during R and H. In darkness, compared to the light condition, the mean position of a line placed on the Frankfort plane (about 20-30 degrees below the horizontal semi-circular canal plane) was tilted downward in all conditions of movement, except during H, for N subjects. In contrast, this flexion of the head was not systematic in V subjects: the Frankfort plane could be located above or below earth horizontal. In V subjects, head rotation was not found to be compensatory for head translation and the power spectrum analysis shows that head angular displacements in the sagittal plane contain mainly low frequencies (about 0.3-0.8 Hz). The respective contribution of visual and vestibular cues in the control of the orientation and the stabilization of the head in space is discussed.

Encoding of human action in Broca's area.

Abstract: Broca's area has been considered, for over a century, as the brain centre responsible for speech production. Modern neuroimaging and neuropsychological evidence have suggested a wider functional role is played by this area. In addition to the evidence that it is involved in syntactical analysis, mathematical calculation and music processing, it has recently been shown that Broca's area may play some role in language comprehension and, more generally, in understanding actions of other individuals. As shown by functional magnetic resonance imaging, Broca's area is one of the cortical areas activated by hand/mouth action observation and it has been proposed that it may form a crucial node of a human mirror-neuron system. If, on the one hand, neuroimaging studies use a correlational approach which cannot offer a final proof for such claims, available neuropsychological data fail to offer a conclusive demonstration for two main reasons: (i) they use tasks taxing both language and action systems; and (ii) they rarely consider the possibility that Broca's aphasics may also be affected by some form of apraxia. We administered a novel action comprehension test--with almost no linguistic requirements--on selected frontal aphasic patients lacking apraxic symptoms. Patients, as well as matched controls, were shown short movies of human actions or of physical events. Their task consisted of ordering, in a temporal sequence, four pictures taken from each movie and randomly presented on the computer screen. Patient's performance showed a specific dissociation in their ability to re-order pictures of human actions (impaired) with respect to physical events (spared). Our study provides a demonstration that frontal aphasics, not affected by apraxia, are specifically impaired in their capability to correctly encode observed human actions.

Evidence for composite cost functions in arm movement planning: an inverse optimal control approach.

Abstract: An important issue in motor control is understanding the basic principles underlying the accomplishment of natural movements. According to optimal control theory, the problem can be stated in these terms: what cost function do we optimize to coordinate the many more degrees of freedom than necessary to fulfill a specific motor goal? This question has not received a final answer yet, since what is optimized partly depends on the requirements of the task. Many cost functions were proposed in the past, and most of them were found to be in agreement with experimental data. Therefore, the actual principles on which the brain relies to achieve a certain motor behavior are still unclear. Existing results might suggest that movements are not the results of the minimization of single but rather of composite cost functions. In order to better clarify this last point, we consider an innovative experimental paradigm characterized by arm reaching with target redundancy. Within this framework, we make use of an inverse optimal control technique to automatically infer the (combination of) optimality criteria that best fit the experimental data. Results show that the subjects exhibited a consistent behavior during each experimental condition, even though the target point was not prescribed in advance. Inverse and direct optimal control together reveal that the average arm trajectories were best replicated when optimizing the combination of two cost functions, nominally a mix between the absolute work of torques and the integrated squared joint acceleration. Our results thus support the cost combination hypothesis and demonstrate that the recorded movements were closely linked to the combination of two complementary functions related to mechanical energy expenditure and joint-level smoothness.

疟原虫var基因转换速率变化导致抗原变异[英]／Paul H, Robert P, Christodoulou Z, et al//Proc Natl Acad Sci U S A

Abstract: 抗原变异可使得多种致病微生物易于逃避宿主免疫应答。表达在感染红细胞表面的恶性疟原虫红细胞表面蛋白1（PfPMP1）与感染红细胞、内皮细胞、树突状细胞以及胎盘的单个或多个受体作用，在黏附及免疫逃避中起关键的作用。每个单倍体基因组var基因家族编码约60种成员，通过启动转录不同的var基因变异体为抗原变异提供了分子基础。

Principles of Neural Science

Abstract: I have developed "tennis elbow" from lugging this book around the past four weeks, but it is worth the pain, the effort, and the aspirin. It is also worth the (relatively speaking) bargain price. Including appendixes, this book contains 894 pages of text. The entire panorama of the neural sciences is surveyed and examined, and it is comprehensive in its scope, from genomes to social behaviors. The editors explicitly state that the book is designed as "an introductory text for students of biology, behavior, and medicine," but it is hard to imagine any audience, interested in any fragment of neuroscience at any level of sophistication, that would not enjoy this book. The editors have done a masterful job of weaving together the biologic, the behavioral, and the clinical sciences into a single tapestry in which everyone from the molecular biologist to the practicing psychiatrist can find and appreciate his or

Beta-band oscillations--signalling the status quo?

Abstract: In this review, we consider the potential functional role of beta-band oscillations, which at present is not yet well understood. We discuss evidence from recent studies on top-down mechanisms involved in cognitive processing, on the motor system and on the pathophysiology of movement disorders that suggest a unifying hypothesis: beta-band activity seems related to the maintenance of the current sensorimotor or cognitive state. We hypothesize that beta oscillations and/or coupling in the beta-band are expressed more strongly if the maintenance of the status quo is intended or predicted, than if a change is expected. Moreover, we suggest that pathological enhancement of beta-band activity is likely to result in an abnormal persistence of the status quo and a deterioration of flexible behavioural and cognitive control.