Biomedical subjects

Simone R Caljouw

Publications and source records attributed to Simone R Caljouw.

4 recordsLinked to original sources

PubMed2005

The impact of task-constraints on the planning and control of interceptive hitting movements.

On the basis of research in self-paced aiming movements, Glover [S. Glover, Separate visual representations in the planning and control of action, Behav. Brain Sci., 27 (2004) 3-24] proposed a dichotomy between visual systems that accommodate planning and on-line control of action. Specifically, the planning-versus-control model posits that the on-line control system solely adjusts the spatial parameters of a movement. We examined whether this proposition is also adequate for interceptive hitting movements that require being at a specific location at the right time. Participants had to hit an approaching ball by first moving the bat away from the interception point (preparatory phase) and subsequently make the hitting movement (strike phase). The ball had to be projected to a landing location that could be near or far. To examine the ability of actors to use online visual information to adapt to unexpected changes in impact requirements, we perturbed the distance of the landing location from near to far during the unfolding of the movement. No adjustments were observed when the perturbation occurred at the onset of the strike phase. When the perturbation occurred at the onset of the preparatory phase the impact velocity increased and, therefore, the ball traveled a larger distance. This was realized by decreasing the duration of the strike phase and increasing the movement amplitude. So, both spatial and temporal characteristics of the hitting movement were adjusted to comply with an online perturbation of target distance. This observation is incongruent with Glover's recent proposition that the online visual system only accommodates spatial parameters.

Adult↗

PubMed2005

Bi-phasic hitting with constraints on impact velocity and temporal precision.

The aim of the experiment was to investigate how bi-phasic hitting movements are organized to comply with both impact and temporal precision constraints. 'Bi-phasic' refers to a sequential movement with a preparatory movement away from the interception location followed by a strike phase. The interception location was fixed, as the motion of the hitting device was constrained to follow a straight path orthogonal to that of the approaching balls. We manipulated the required temporal precision by projecting balls with different constant approach speeds (1, 1.5, and 2m/s). Different impact constraints were imposed by instructing participants first to simply hit the ball and subsequently to hit the ball to a designated target area located either 55 or 105 cm away from the interception location. We determined several kinematic variables and used Principal Component Factor Analysis to classify these variables. The analysis revealed two independent factors: a 'velocity' factor (formed by impact velocity, peak velocity of the preparatory phase, peak velocity of the strike phase, and amplitude of the strike) and a 'timing' factor (formed by onset of the preparatory phase, moment of peak velocity of the preparatory phase, and onset of the strike phase). The 'velocity' factor scaled significantly with the required impact constraint and the 'timing' factor scaled significantly with ball speed.

Acceleration↗

PubMed2004

A dynamical neural network for hitting an approaching object.

Besides making contact with an approaching ball at the proper place and time, hitting requires control of the effector velocity at contact. A dynamical neural network for the planning of hitting movements was derived in order to account for both these requirements. The model in question implements continuous required velocity control by extending the Vector Integration To Endpoint model while providing explicit control of effector velocity at interception. It was shown that the planned movement trajectories generated by the model agreed qualitatively with the kinematics of hitting movements as observed in two recent experiments. Outstanding features of this comparison concerned the timing and amplitude of the empirical backswing movements, which were largely consistent with the predictions from the model. Several theoretical implications as well as the informational basis and possible neural underpinnings of the model were discussed.

Biomechanical Phenomena↗

PubMed2004

Timing of goal-directed hitting: impact requirements change the information-movement coupling.

In hitting, performers are found to adapt to the approach speed of the ball, i.e. they tend to initiate their movement at a shorter time before contact for faster approaching balls. A change in movement time is always accompanied by a change in movement velocity when the movement trajectory is kept constant. Hence, a fast-approaching ball might induce high impact velocity that is in conflict with low impact constraints, such as propelling the ball towards a near goal. In this study we investigated the capacities of participants to perform one-dimensional hitting movements in the frontal plane to balls approaching on a head-on collision course. The temporal precision (i.e. ball approach speed: 1, 1.5, and 2 m/s) and impact requirements (i.e. No-Goal, Near-Goal, and Far-Goal) were manipulated to examine the influence of task constraints on the temporal regulation of a stroke. The results showed that timing and speed were significantly affected by ball approach speed when the hit was not directed to a goal. In contrast, no speed-coupling and a constant time-to-impact strategy were found when impact velocity was constrained (i.e. aiming for a near goal). We were particularly interested in the nature and relation of information sources and timing patterns of movement initiation. Therefore, the relation between the time evolution of three optical sources related to the approach of the ball and the observed patterns of swing onset were evaluated quantitatively. The analyses revealed that a viable explanation for the two observed qualitatively different onset patterns of the swing is a regulation based on the absolute rate of expansion or a co-varying variable. The flexible adaptation of timing to impact constraints may be realized by an adjustment of the critical region of this optical variable.

Adult↗