Beyond consciousness of external reality: a "who" system for consciousness of action and self-consciousness

Combinations of DMARDs are currently used to treat rheumatoid arthritis by almost all rheumatologists. This article reviews the published data on the triple combination of methotrexate, sulfasalazine, and hydroxychloroquine, discusses caveats for clinical use, compares efficacy of different combinations, and speculates on future combination therapies.     

Asymptotically fast polynomial matrix algorithms for multivariable systems

We present the asymtotically fastest known algorithms for some basic problems on univariate polynomial matrices: rank; nullspace; determinant; generic inverse reduced form (Giorgi et al. 2003, Storjohann 2003 Storjohann, A. 2003. “High-order lifting and integrality certification”. In J. Symb. Comp. Edited by: Giusti, M and Pardo, LM. Vol. 36, 613–648. Nice, France, 3, , USA Special issue International Symposium on Symbolic and Algebraic Computation (ISSAC’2002). Guest editors: [Google Scholar], Jeannerod and Villard 2005 Jeannerod, C-P and Villard, G. 2005. Essentially optimal computation of the inverse of generic polynomial matrices. J. Comp., 21: 72–86.  [Google Scholar], Storjohann and Villard 2005 Storjohann, A and Villard, G. July 2005. “Computing the rank and a small nullspace basis of a polynomial matrix”. In Proc. International Symposium on Symbolic and Algebraic Computation, 309–316. Beijing, China: ACM Press.  [Google Scholar]). We show that they essentially can be reduced to two computer algebra techniques, minimal basis computations and matrix fraction expansion/reconstruction, and to polynomial matrix multiplication. Such reductions eventually imply that all these problems can be solved in about the same amount of time as polynomial matrix multiplication. The algorithms are deterministic, or randomized with certified output in a Las Vegas fashion.     

Spatial localization with paralyzed eye muscles

Four subjects suffering from a unilateral peripheral paralysis of the 3rd or the 6th nerves have been studied in spatial localization tasks, with their normal eye occluded. When peripheral targets were presented in the hemifield corresponding to the paralysis, the saccadic eye movements (recorded from the normal occluded eye) were of an exaggerated amplitude. 'Staircase' oculomotor patterns, closely similar to those occurring in 'open-loop' visual stimulation, could also be observed. Our patients also presented the classical hypermetric misreaching when attempting to point by hand at visual targets in an otherwise dark room. This effect (past-pointing) was likely to be due to a monitoring of the exaggerated oculomotor signal: in one subject past-pointing disappeared when reaching at the targets on the basis of the sole retinal cues. Finally, the classically described illusory visual effects of ocular paralysis were limited to a feeling of instability during self-motion.     

Is visual experience necessary for the maturation of vestibular control of eye movement

The vestibular system contributes to the stabilisation of visual images on the retina by means of vestibulo-ocular compensatory reactions. The development of vestibular control of eye movements has been studied in twelve week old kittens, reared in total darkness, which have been compared with a control group of kittens reared in normal conditions. Post-rotatory nystagmus, nystagmus during sinusoidal oscillations, visual suppression of vestibular nystagmus by fixation, have been used as indicators of the functional state of the vestibulo-ocular control system. The results show that most of the essential features of this control are present in dark-reared kittens. However differences have been noted which possibly concern precise regulation of compensatory movements and head-eye coordination. The frequency of vestibular nystagmus is much smaller in dark-reared animals and the initial deviation of post rotatory nystagmus in the direction of the change of movement is absent in dark-reared kittens. Habituation also seems to operate differently in the two groups of kittens. Visual suppression of vestibular nystagmus is present.     

Constrained and unconstrained movements involve different control strategies

This experiment was carried out to test whether or not the rules governing the execution of compliant and unconstrained movements are different (a compliant motion is defined as a motion constrained by external contact). To answer this question we examined the characteristics of visually directed movements performed with either the index fingertip (unconstrained) or a hand-held cursor (compliant). For each of these categories of movements, two experimental conditions were investigated: no instruction about hand path, and instruction to move the fingertip along a straight-line path. The results of the experiment were as follows: 1) The spatiotemporal characteristics of the compliant and unconstrained movements were fundamentally different when the subjects were not required to follow a specific hand path. 2) The instruction to perform straight movements modified the characteristics of the unconstrained movements, but not those of the compliant movements. 3) The target eccentricity influenced selectively the curvature of the "unconstrained-no path instruction" movements. Taken together, these results suggest that compliant and unconstrained movements involve different control strategies. Our data support the hypothesis that unconstrained motions are, unlike compliant motions, not programmed to follow a straight-line path in the task space. These observations provide a theoretical reference frame within which some apparently contradictory results reported in the movement generation literature may be explained.     

Limited conscious monitoring of motor performance in normal subjects

Normal subjects traced sagittal lines on a graphic tablet using a stylus held in their right hand. The hand was hidden by a mirror in which they saw the lines projected from a computer screen. In normal trials, the line seen in the mirror exactly corresponded to the traced line. In perturbed trials, a bias was introduced by the computer, so that the line appeared to deviate in one direction (right or left) by a variable angle (2, 5, 7 or 10 degrees). Subjects consistently displaced their hand in the opposite direction for producing a visually sagittal line. After each trial, they were asked in which direction they thought their hand had moved. In perturbed trials, they grossly underestimated the hand deviation. In addition, a post-hoc analysis revealed that one group of subjects misperceived the direction of their hand movement in the direction opposite to the perturbation (Group 1, including 9 Ss), whereas the other group gave responses in the correct direction (Group 2, including 4 Ss). In a second session using the same experimental paradigm, a motor response was asked for: subjects had to indicate the perceived direction of their hand during each trial by drawing a line with their eyes closed. Again, responses indicated a poor conscious monitoring of motor performance. These results suggest that normal subjects are not aware of signals generated by their own movements.     

Constraints on human arm movement trajectories.

Analyzed the 3-dimensional arm movement trajectories of 5 right-handed undergraduates under the following conditions: pointing to a target with the index finger vs grasping a target-sized disk, grasping a fragile object vs a soft resilient object, and grasping a disk either to throw into a large box or place into a tight fitting well. Results show that the main factor in the shape of arm trajectories was the point where peak velocity was reached as a function of total movement duration. When task demands required greater precision, the main deceleration phase of the trajectory increased. Results support a view of movement production as relatively specific to the past experience of the performer and the constraints of the task. (French abstract) (PsycINFO Database Record (c) 2010 APA, all rights reserved)