PubMed · 6405886
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F J Mills, R M Harding. 1983-05-14. Acceleration. I: Long duration acceleration.. https://doi.org/10.1136/bmj.286.6377.1557
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1. Perception of two-dimensional (2-D) whole-body passive motion in the horizontal plane was studied in twelve blindfolded healthy volunteers: pure rotation in place (180 deg), linear motion (4.5 m) and a semicircular trajectory (radius, 1.5 m; angular acceleration, 0.2 rad s-2) were applied in random sequence by means of a remote-controlled robot equipped with a racing-car seat. The seat orientation in the horizontal plane was controlled by the experimenter, independent of the robot trajectory. Thus different degrees of otolith-canal interaction were obtained. The maximal linear acceleration during the semicircular trajectory was 0.1 g; however, the linear acceleration vector was complex as it rotated relative to the subject's head. 2. In the first of two sessions, subjects were instructed to maintain an angular pointer oriented towards a remote (15 m) previously seen target during the passive movements. In the second session they had to make a drawing of the path of the perceived trajectory, after the movement was finished. 3. The results showed that, on average, the movement of the pointer matched the dynamics of the rotatory component of the 2-D motion well. This suggests that, in the range of linear accelerations used in this study, no appreciable influence of otolith input on canal-mediated perception of angular motion occurred. 4. The curvature of the drawn paths was mostly explained by the input to the semicircular canals. Subjects' reconstruction of motion did not account for the directional dynamics of the input to the otoliths occurring during passive motion. 5. This finding proves that reconstructing trajectory in space does not imply a mathematically perfect transformation of the linear and angular motion-related inputs into a Cartesian or polar 2-D representation. Physiological constraints on the interaction between motion direction and change of heading play an important role in motion perception.
The pattern of acceleration was recorded during horizontal saccadic eye movements using a light-weight accelerometer fixed to a scleral contact lens. Horizontal saccades of 15-20 degrees were dominated by either several pulses of acceleration, with a frequency of around 40 Hz. or a single acceleration-deceleration wave followed by lower amplitude polyphasic activity of about 80 Hz. These features are unlikely to be due to slippage or resonance in the contact lens-accelerometer system, as very similar patterns of acceleration were simultaneously recorded with an accelerometer taped over the closed eyelid of the contralateral eye. Analysis of simultaneous surface electromyogram recordings indicated that the multicomponent acceleration profiles were the product, at least in part of the rhythmic and synchronous modulation of eye muscle discharge during saccades.
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