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Biomedical subjects

T Pozzo

Publications and source records attributed to T Pozzo.

34 records · Page 2Linked to original sources
PubMed1996

[Effects of aging on standing up and sitting down. Kinematic analysis].

Standing up from and sitting down to a chair are a challenging task for many elderly persons. The purpose of this study was to analyse the effects of ageing in kinematic features of each phase of motion. The study was performed on 7 young subjects (22.8 +/- 1.5 years) and 5 healthy elderly subjects (73.2 +/- 5.5 years). The kinematics of the movement were analysed by mean of an optical automatic TV processor (Elite system). Eight reflective markers were placed on left side of body. The elderly subjects showed modifications of velocity profiles of trunk and knee during the two phases of movement, an important need for an adjustment of velocity before seat-on and an inability to increase the velocity of trunk displacement in space. We suggested that these differences between young and elderly subjects, well seen during standing to sitting down, were related to deficits in postural control ability.

Adult↗
PubMed1996

[Search of gravity force in the planning of arm pointing movements].

Arm movements in two directions (downward assisted by gravity and upward against gravity) with three different loads (no load 0.5 and 1 kg) were studied in six subjects. Movements of the arm were recorded using an optoelectronic (2 TV, 100 Hz) system which allowed the computer reconstruction of joint motion. Analyses focused upon finger kinematics in the sagittal plane. Subjects showed curved paths for both directions and load conditions. The path's curvature changed significantly only as a function of the direction of the movement. Velocity profiles were unimodal for all conditions. Upward movements showed greater deceleration than acceleration times in contrast to downward movements which presented more symmetrical velocity profiles. The ratio of acceleration time to total movement time changed significantly only as a function of the direction of the movement but not as a function of the load. Results from this study provide indirect evidence that the CNS executes movements by taking advantage of gravity force.

Adult↗
PubMed1995

Head and trunk movements in the frontal plane during complex dynamic equilibrium tasks in humans.

Eight normal human subjects were asked to maintain monopodal equilibrium on a narrow beam (task 1) or bipodal equilibrium on an unstable rocking platform (task 2) for 5 s. Each task was performed under four experimental conditions: (1) in light, (2) in darkness, (3) in light while subject had to hold a full cup of water, and (4) as in 3, but with additional instructions to fix the gaze on the cup. The movements of the trunk and head in the frontal plane were recorded by means of a 50-Hz TV image analyzer that computed the coordinates of small reflective markers glued on the skin of the subjects. On the beam the trunk was inclined on the side of the supporting foot (13 +/- 9 degrees), on the rocking platform the mean trunk orientation during the tests was nearly vertical (2 +/- 7 degrees). Nevertheless, in both tasks the mean head position was the same and close to vertical: 1.5 +/- 4 degrees on the rocking platform and 1.5 +/- 5 degrees on the beam. For both tasks and all experimental conditions the head remained stabilized relative to vertical, despite large translations in the frontal plane. Standard deviations of head orientation from its mean value were 2.8 +/- 2 degrees for task 1 and 2 +/- 1.5 degrees for task 2. The changes of trunk orientation were significantly higher: 6.2 +/- 4.8 degrees and 4.5 +/- 4 degrees, respectively. The differences in angular stability of head and trunk, measured through the standard deviations of angular displacements, were especially pronounced in trials with large trunk movements. It was concluded that head angular stabilization, providing the central nervous system with necessary visual and vestibular references, is essential for effective dynamic postural control in the frontal plane during complex equilibrium tasks.

Adult↗
PubMed1994

[Vestibular rehabilitation of patients suffering of vertigo: literature review and personal experience].

The paper reports the results of a study on the effectiveness of vestibular rehabilitation therapy in patients suffering from vertigo, mostly in those cases in which spontaneous compensation is only slight or not achieved at all. The main aim or rehabilitation training is to foster functional compensation between the two vestibular hemisystems. Fifty patients were divided into two groups: those with labyrinthine vertigo, who underwent therapy which included vestibular habituation training (VHT); those with disequilibrium, who received balance coordination training. The results turned out successfully in 75% of those patients belonging to the first group, whereas patients in the second group showed relevant improvement of subjective symptoms related to imbalance, confirmed by the results of post-urographic assessment. Moreover, the severity of vertigo decreased by about 50% with regard to initial intensity after the first week of treatment and reduced considerably by the end of the second week.

Adult↗
PubMed1992

[Vestibular studies: current status, prospects].

Equilibrium is based on gaze stabilization. Clinical examinations currently test, individually the three components involved in equilibrium: vestibular, visual and proprioception. New investigations are being developed to test equilibrium dynamic conditions. After briefly reviewing vestibular physiology, under the authors discuss the various tests of vestibular function and equilibrium.

Eye Movements↗
PubMed1991

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

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.

Adult↗
PubMed1991

Head stabilization during locomotion. Perturbations induced by vestibular disorders.

Head kinematics was studied in 10 normal subjects (NS) and 7 patients (P) with bilateral vestibular deficit while they executed various locomotor tasks. The movement of the body was recorded with a video system which allowed a computer reconstruction of the 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. Two conditions were studied: free walking (W) and hopping (H). The subjects were tested in light and in darkness. In NS, while walking in darkness, mean head position was tilted downward. In contrast, this flexion was not systematic in P. Darkness did not significantly influence the amplitude and velocity of head angular displacement during W, but, during H the amplitude decreased by 37% for NS. During H in darkness, head stabilization decreased for P. These results suggest that head kinematics, during natural locomotor tasks, could be used to evaluate vestibular deficiencies.

Adult↗
PubMed1990

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

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 0.15 m/s to 1.8 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 degrees in the 4 situations. Vertical angular velocities increased from locomotion tasks to the dynamic equilibrium task although the maximum values remained less than 140 degrees/s. Predominant frequencies of translations and rotations in all the tasks were within the range 0.4-3.5 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.

Adult↗
PubMed1989

Head kinematic during various motor tasks in humans.

Head kinematic during various motor tasks was studied in ten subjects. The movement of the body was recorded with a video system (E.L.I.T.E.) which allows a computer reconstruction of three-dimensional motion of selected points on the body. Analysis is focused on head rotation in the horizontal and vertical planes. The results demonstrate that the amplitude and the maximum velocity do not exceed respectively 38 deg/s and 185 deg/s. However the head is intermittently stabilized and the angle of this stabilization is dependent upon the task and related to the direction of gaze. Darkness had no significant effect on head rotational velocity during walking but caused a decrease in velocity during running and hopping. The results suggest that head stabilization (1) is related to an ocular fixation point in the direction of gaze in space and (2) is probably regulated on the basis of a predictive mode of sensory motor control.

Adult↗
PubMed1988

Contribution of eye positioning to control of the upside-down standing posture.

The present study attempts to clarify the relationship between eye and body positioning during an upside-down standing posture on the hands. In this posture the head was observed to be stable and the eyes were anchored to an earth-fixed target. We measured the variations of body sway when subjects displaced their gaze upward or downward from their anchoring position. They did this voluntarily under instruction, and involuntarily by means of base-down or base-up wedge prisms. Results show that the anchoring point chosen by the subjects corresponds to a perceived limit of their body sway. They suggest that vision is also used to convey the desired optimal zone for the center of gravity in cases where fine balance is required.

Eye Movements↗
PubMedDate not supplied

Effect of weightlessness on posture and movement control during a whole body reaching task.

Here are reported preliminary results of the "Synergy" experiment performed aboard the Russian orbital station "MIR" in July 1993 (Altair Mission). The experiment was carried out before, during, and after the space flight of two astronauts (S1 and S2). The duration of the flight was 21 days for S1 and 6 month for S2. The subjects were tested during preflight, inflight and postflight. The astronaut subjects were fixed on the ground by the feet. They were asked to pick up a box in front of them on the ground. Two velocities of movement and two distances of the target to be reached were tested. The movement of several small markers placed on the body was recorded on video tape. Results show that the shape of head and hand trajectories in the sagittal plane remains roughly the same during the flight in spite of the modification of mechanical constraints. Trajectory invariance does not result in joint angular displacement invariance. These data indicate that the planning of the movement takes place in terms of head and hand trajectories rather than joint rotations as it was previously suggested for simple arm reaching movement.

Adaptation, Physiological↗
PubMedDate not supplied

Arm end-point trajectories under normal and micro-gravity environments.

The purpose of the present experiment was to study the way in which the CNS represents gravitational force during vertical arm pointing movements. Movements in upward and downward directions were executed by two cosmonauts in normal-gravity and weightlessness. Analyses focused upon finger kinematics in the sagittal plane. In normal-gravity, downward direction movements showed smaller curvatures and greater relative times to peak velocity (AT/MT) when compared with upward direction movements. Data from the weightlessness experiments showed that whilst downward movements decreased their curvature during space flight, curvatures of upward movements changed slightly. Furthermore, AT/MT was modified during the first days in micro-gravity for both directions, recovering, however, to pre-flight values after 18 days in space. Results from the present study, provide evidence that gravitational force is centrally treated constituting an important component of the motor plan for vertical arm movements.

Aerospace Medicine↗
PubMedDate not supplied

Does the centre of mass remain stable during complex human postural equilibrium tasks in weightlessness?

In normal gravity conditions the execution of voluntary movement involves the displacement of body segments as well as the maintenance of a stable reference value for equilibrium control. It has been suggested that centre of mass (CM) projection within the supporting base (BS) is the stabilised reference for voluntary action, and is conserved in weightlessness. The purpose of this study was to determine if the CM is stabilised during whole body reaching movements executed in weightlessness. The reaching task was conducted by two cosmonauts aboard the Russian orbital station MIR, during the Franco-Russian mission ALTAIR, 1993. Movements of reflective markers were recorded using a videocamera, successive images being reconstructed by computer every 40ms. The position of the CM, ankle joint torques and shank and thigh angles were computed for each subject pre- in- and post-flight using a 7-link mathematical model. Results showed that both cosmonauts adopted a backward leaning posture prior to reaching movements. Inflight, the CM was displaced throughout values in the horizontal axis three times those of pre-flight measures. In addition, ankle dorsi flexor torques inflight increased to values double those of pre- and post-flight tests. This study concluded that CM displacements do not remain stable during complex postural equilibrium tasks executed in weightlessness. Furthermore, in the absence of gravity, subjects changed their strategy for producing ankle torque during spaceflight from a forward to a backward leaning posture.

Aerospace Medicine↗
PubMedDate not supplied

[Chronic cholesteatomatous otitis media: the histopathological and clinical aspects].

In recent years the immunologic aspects of the normal and pathological ear have been studied by several authors, with particular attention given to the histopathologic aspects of the epidermis of the tympanic membranes of the outer ear canal and of the middle ear mucosa in normal physiologic as well as in inflammatory conditions. Such studies may help in giving a more precise definition to the pathogenesis and clinical behavior of middle ear cholesteatoma. In this paper we report the results of an immunohistopathologic study carried out using the immunohistochemical technique of monoclonal antibodies on cholesteatoma matrix samples taken during radical mastoidectomy or tympanoplasty. In particular, the presence of T-lymphocytes and Langerhans cells was evaluated using selective monoclonal antibodies and a relationship between the data collected and the clinical expression of the disease in each case was sought. In this study it was not possible to establish a close relationship between clinical behavior and immunohistopathological findings, which appeared rather similar in all the cases. The presence of Langerhans' cells may confirm the hypothesized role they play in phlogistic reactions and bone reabsorption due to the presence of the cholesteatoma in the middle ear. Yet, in order to evaluate their true role correctly, more detailed studies should be carried out on the spatial distribution of T-lymphocytes and Langerhans' cells in the cholesteatoma matrix as well as on their ultrastructural characteristics.

Adult↗