ABSTRACT
A crucial aspect of comparative biomechanical research is the center of mass (CoM) estimation in animal locomotion scenarios. Important applications include the parameter estimation of locomotion models, the discrimination of gaits, or the calculation of mechanical work during locomotion. Several methods exist to approximate the CoM position, e.g. force-plate-based approaches, kinematic approaches, or the reaction board method. However, they all share the drawback of not being suitable for large scale studies, as detailed initial conditions from kinematics are required (force-plates), manual interaction is necessary (kinematic approach), or only static settings can be analyzed (reaction board). For the increasingly popular case of X-ray-based animal locomotion analysis, we present an alternative approach for CoM estimation which overcomes these shortcomings. The main idea is to only use the recorded X-ray images, and to map each pixel to the mass of matter it represents. As a consequence, our approach is surgically noninvasive, independent of animal species and locomotion characteristics, and neither requires prior knowledge nor any kind of user interaction. To assess the quality of our approach, we conducted a comparison to highly accurate reaction board experiments for lapwing and rat cadavers, and achieved an average accuracy of 2.6mm (less than 2% of the animal body length). We additionally verified the practical applicability of the algorithm by comparison to a previously published CoM study which is based on the kinematic method, yielding comparable results.
Subject(s)
Locomotion/physiology , Models, Biological , Tomography, X-Ray Computed/methods , Animals , Birds , RatsABSTRACT
We investigated the influence of Fourier power spectrum (1/f(p)) characteristics on face learning while recording ERPs that are associated with the representation of faces. Two image sets with an altered 1/f(p) characteristics were created. The first set consisted of stimuli with a STEEP SLOPE (1/f(3.5)) and therefore enhanced low spatial frequencies (LSF) and attenuated high spatial frequencies (HSF). The second set consisted of stimuli with a SHALLOW SLOPE (1/f(2)), similar to complex natural scenes and artwork, resulting in enhanced HSF and attenuated LSF. Faces with a SHALLOW SLOPE elicited larger N170 and N250 amplitudes and larger old/new effects for central positivity in comparison to unmodified faces. The opposite effect was observed for faces with a STEEP SLOPE that led to slower reaction times. This result suggests that diminishing the ratio of fine detail (HSF) to coarse structures (LSF) impairs face learning, whereas increasing it facilitates neurocognitive correlates of face learning.
Subject(s)
Evoked Potentials/physiology , Face , Learning/physiology , Recognition, Psychology/physiology , Adolescent , Adult , Data Interpretation, Statistical , Electroencephalography , Female , Fourier Analysis , Humans , Male , Photic Stimulation , Psychomotor Performance/physiology , Reaction Time/physiology , Visual Perception/physiology , Young AdultABSTRACT
The purpose of this project was to continue the development of the Work boxTM following three studies to standardize instructions and determine test-retest reliability. Normative data were collected from 118 non-disabled female subjects between the ages of 20 and 49 years. Means, standard deviations, and ranges of performance for 5-year-age intervals were calculated and reported for assembly time, disassembly time, and total test time. Analysis of the data indicates a minor, though not significant, decline in test performance with increasing age and great variability in completion times overall.