Biomedical subjects

Paola Cesari

Publications and source records attributed to Paola Cesari.

6 recordsLinked to original sources

PubMed2006

Body-goal variability mapping in an aiming task.

Given the number of joints and muscles in the human body, there are typically an infinite number of ways to perform the same action, a feature of directed movements known as equifinality (Bernstein, The coordination and regulation of movements, Oxford, Pergamon, 1967). Here we present a new type of performance analysis based on the idea of a body-goal variability mapping. We show how this mapping arises naturally from the idea of a goal function that theoretically defines a task and, in the presence of equifinality, determines the set of all possible task solution strategies, the goal equivalent manifold (GEM). The approach also yields estimates of the sensitivity of goal-level errors to body-level perturbations, and we derive a general formula expressing the relationship between the two. We apply these ideas to the analysis of redundant kinematic data from subjects performing an aiming task carried out with and without a laser pointer. It is shown that in order to characterize performance one must consider two factors in addition to the body variability: first, the degree of alignment between body variability and the GEM; and second, the sensitivity parameters that control the degree to which goal-relevant body variability is amplified at the target. Both of these factors can be computed using the estimated body-goal mapping. We show that the performance for three conditions involving two different nominal postures and two different sensory conditions (laser/no laser) can be classified by examining the clustering of data in an orientation- sensitivity parameter plane associated with the map.

Adult↗

PubMed2005

Motor facilitation of the human cortico-spinal system during observation of bio-mechanically impossible movements.

Neurophysiological and neuroimaging studies in the human and the monkey brain indicate that links between action observation and execution are much tighter than previously believed. Indeed, the mere observation of movements performed by other individuals brings about a clear increase in activity in specific fronto-parietal neural networks (mirror system). Here, we report a series of four single-pulse transcranial magnetic stimulation studies of the motor system, which show that observation of index and little finger movements brings about a facilitation of potentials recorded from muscles that would be involved in the actual execution of the observed action. Remarkably, however, a clear representational selectivity was found also during observation of bio-mechanically impossible index or little finger movements. Thus, in movement observation tasks, the human cortico-spinal system reacts similarly to the vision of bio-mechanically possible and impossible movements but it is able to detect which muscle would be involved in the actual execution of the observed movement. Importantly, this system may be more related to coding body part movements than precisely simulating their execution.

Adult↗

PubMed2003

Carbohydrate and amino acid metabolism in Tuber borchii mycelium during glucose utilization: a (13)C NMR study.

The metabolism of [1-13C]glucose in the vegetative mycelium of the ectomycorrhizal ascomycete Tuber borchii was studied in order to characterize the biochemical pathways for the assimilation of glucose and amino acid biosynthesis. The pathways were characterized using nuclear magnetic resonance spectroscopy in conjunction with [1-13C]glucose labeling. The enzymes of mannitol cycle and ammonium assimilation were also evaluated. The majority of the 13C label was incorporated into mannitol and this polyol was formed via a direct route from absorbed glucose. Amino acid biosynthesis was also an important sink of assimilated carbon and 13C was mainly incorporated into alanine and glutamate. From this intramolecular 13C enrichment, it is concluded that pyruvate, arising from [1-13C]glucose catabolism, was used by alanine aminotransferase, pyruvate dehydrogenase and pyruvate carboxylase before entering the Krebs cycle. The transfer of 13C-labeled mycelium on [12C]glucose showed that mannitol, alanine, and glutamate carbon were used to synthesize glutamine and arginine that likely play a storage role.

Amino Acids↗

PubMed2003

Sema3A and neuropilin-1 expression and distribution in rat white adipose tissue.

Semaphorins are cell surface and/or soluble signals that exert an inhibitory control on axon guidance. Sema3A, the vertebrate-secreted semaphorin, binds to neuropilin-1, which together with plexins constitutes the functional receptor. To verify whether Sema3A is produced by white adipocytes and, in that case, to detect its targets in white adipose tissue, we studied the cell production and tissue distribution of Sema3A and neuropilin-1 in rat retroperitoneal and epididymal adipose depots. Sema3A and neuropilin-1 were detected in these depots by Western blotting. The immunohistochemical results showed that Sema3A is produced in, and possibly secreted by, smooth muscle cells of arteries and white adipocytes. Accordingly, neuropilin-1 was found on perivascular and parenchymal nerves. Such a pattern of distribution is in line with a role for secreted Sema3A in the growth and plasticity of white adipose tissue nerves. Indeed, after fasting, when white adipocytes are believed to be overstimulated by noradrenaline and rearrangement of the parenchymal nerve supply may occur, adipocytic expression of Sema3A is reduced. Finally, the presence of neuropilin-1 in some white adipocytes raises the interesting possibility that Sema3A also exerts an autocrine-paracrine role on these cells.

Adipocytes↗

PubMed2002

Scaling the components of prehension.

The experiment reported examined: (a) the role of the geometrical body scaled informational invariant for the transition of human grip configurations; (b) whether the same invariant can be scaled considering also the force applied during the grasp phase; and (c) how the temporal duration of the grasp and displacement phases of prehension are scaled to the object properties of size and mass. Adult subjects performed a series of trials in reaching, grasping, and displacing spheres that varied in size and mass. The grip transitions were described by the body scaled relation: [formula: see text] where L(s) and M(s) are, respectively, the diameter and the mass of the spheres grasped and L(h) and M(h) are the length and the mass of the hand. The impulse during the grasp phase was linearly related with the mass of the spheres within each density. The temporal durations of the grasp and displacement components were scaled coherently to the object properties. These findings provide support to the hypothesis that the grasp and displacement components of prehension are organized coherently within a single action.

Adult↗

PubMedDate not supplied

An invariant guiding stair descent by young and old adults.

In this study the author compared the perception-action capability of young and old adults (respectively, mean age 22 and 62 years old) when descending stairs and examined the relevant task constraints that guide the action. It was found that old adults selected and descended stairs that were significantly lower than young adults and showed less hip joint flexibility. However, the performance parameter, defined as the ratio between the height of the stair and the distance taken by the stepping foot to the top edge of the stair, was invariant for both groups. Thus, despite different ability levels, young and old adults are constrained by the same perception-action invariant for guiding the act of stair descent.

Adult↗