Effect Of Spatial Reference On Self-motion Heading Discrimination

Self-motion perception is a basic but very important brain cognitive function,which is the premise of human and animals to ensure their own safety and survival.Visual and vestibular sense is two very important sources of self-motion perception,originated from retina in eyes and vestibular labyrinth in head.Usually,in order to obtain optimal heading discrimination ability,the directions of eye,head and body are consistent with our heading(forward direction).Deviation of eye\head position can make offset of spatial reference frames which anchored on them,leading to systematic errors of perception.In order to obtain accurate perception,the brain will integrate motion information of eye\head to compensate the offset of reference frames.For the final reference frames after compensation,previous studies showed:At the neurological level,the conclusion from limited explored brain areas were visual self-motion perception belonged to eye-centred,vestibular self-motion perception was flexible,vestibular-visual self-motion perception was still unclear,which possibly belonged to either a common reference frame or a intermediate reference frame.At the psychophysics level,experiments were fragmentary to have a final conclusion.In addition,whether the fixation point existing in the former study design was a spatial reference in itself also remains unknown.Through psychological experiment,we made participants do time version of heading discrimination task under visual,vestibular and vestibular-visual three kinds of sensory stimulus,analysed the effects of four different spatial reference factors(fixation point,three kinds of head,eye position),and summed up eventual spatial reference frames of visual,vestibular and vestibular-visual self-motin perception respectively.We found that the existence of fixation point indeed had function as spatial reference point,which improved the sensitivity of self-motion perception,especially in visual conditions,but had no significant effect on accuracy.Visual heading discrimination was affected by deviation of eye position,but not affected by deviation of head,so it belonged to eye-centred spatial reference frame.Vestibular heading discrimination was affected by both eye and head position,so it belonged to head-and eye-centered spatial reference frame.The result of vestibular-visual heading discrimination was between the visual only and vestibular only condition,so it belonged to a intermediate reference frame.In addition,we put forward a model in which reaction time curve was affected by accuracy and sensitivity:accuracy changed the symmetry of axes and sensitivity affected the baseline.Through this study,we quantified the effect of fixation point on self-motion perception at the behavioral level,and pointed out the visual,vestibular and their combination self-motion perception belonged to what spatial reference frame respectively.These findings provides important behavioral data to accurately understand spatial reference mechanism of self-motion perception,and will contribute to figure out neurology mechanism of self-motion perception.