Gravity matters: Motion perceptions modified by direction and body position.
Motion coherence thresholds are consistently higher at lower velocities. In this study we analysed the influence of the position and direction of moving objects on their perception and thereby the influence of gravity. This paradigm allows a differentiation to be made between coherent and randomly moving objects in an upright and a reclining position with a horizontal or vertical axis of motion. 18 young healthy participants were examined in this coherent threshold paradigm. Motion coherence thresholds were significantly lower when position and motion were congruent with gravity independent of motion velocity (p=0.024). In the other conditions higher motion coherence thresholds (MCT) were found at lower velocities and vice versa (p<0.001). This result confirms previous studies with higher MCT at lower velocity but is in contrast to studies concerning perception of virtual turns and optokinetic nystagmus, in which differences of perception were due to different directions irrespective of body position, i.e. perception took place in an egocentric reference frame. Since the observed differences occurred in an upright position only, perception of coherent motion in this study is defined by an earth-centered reference frame rather than by an ego-centric frame.
Department of Neurology and German Center for Vertigo and Balance Disorders, University of Munich Hospital, Campus Großhadern, Munich, Germany; Department of Neurology, University Hospital Essen, Germany. Electronic address: jens.claassen@uk-essen.de.
Jens
J
Claassen
Department of Neurology and German Center for Vertigo and Balance Disorders, University of Munich Hospital, Campus Großhadern, Munich, Germany.
Stanislavs
S
Bardins
Department of Neurology and German Center for Vertigo and Balance Disorders, University of Munich Hospital, Campus Großhadern, Munich, Germany; Department of Internal Medicine, University of Basel, Basel, Switzerland.
Rainer
R
Spiegel
Department of Neurology and German Center for Vertigo and Balance Disorders, University of Munich Hospital, Campus Großhadern, Munich, Germany.
Michael
M
Strupp
Department of Neurology and German Center for Vertigo and Balance Disorders, University of Munich Hospital, Campus Großhadern, Munich, Germany; Department of Neurology, University of Bern, Bern, Switzerland.
Roger
R
Kalla
D000328:Adult; D005260:Female; D006112:Gravitation; D006801:Humans; D008297:Male; D009039:Motion Perception / Q000502:physiology*; D011187:Posture / Q000502:physiology*; D012684:Sensory Thresholds / Q000502:physiology*; D055815:Young Adult
Body position; Dorsal medial temporal area; Motion coherence; Perception; Vestibular system