Sensory and cognitive influences on oculomotor and whole-body coordination during standing turns

• Main Author: Robins, Rebecca
• Other Authors: Hollands, Mark ; Bennett, Simon
• Published: Liverpool John Moores University 2015
• Subjects: 617.1; RC1200 Sports Medicine
• Online Access: http://ethos.bl.uk/OrderDetails.do?uin=uk.bl.ethos.697474

It is well-established that turning on the spot or changing the direction of walking involves a stereotyped sequence of eye, head and body segment rotation characterized by an anticipatory gaze strategy driven primarily by eye movements (nystagmus). However, the relationship between eye movements and whole-body coordination during turning has not been fully explored under different environmental and sensory contexts and as a result, the neural mechanisms responsible for this coordination are poorly understood. The first aim of this thesis was to investigate the effects of turn size and speed on eye movements and intersegmental coordination. Results showed systematic relationships between turn speed, amplitude and eye and whole-body coordination characteristics and that the timing of eye, head and axial segment reorientation onset does not accurately represent coordination during the turn. Secondly, we investigated the effects of either removing vision or suppressing eye movements during turns. We found that eye and motor behaviour during vision removal was similar to behaviour during full vision, however suppressing eye movements delayed gait initiation and decreased stepping frequency throughout the turn. Next we examined the influence of neck muscle vibration on turning and found that stimulating neck proprioceptors to evoke the CNS perception of head rotation with respect to the upper body resulted in early turn initiation. Lastly, we looked at the effects of divided attention using a secondary cognitive task during the turn. We found that turn onset was delayed during dual-tasking, but eye and body coordination were unaffected. We conclude that oculomotor nystagmus during turning represents a crucial component of an automatic, subcortically generated motor synergy, the release of which is dependent on cortical and sensory input (i.e. eye and neck proprioception). We propose that turning on-the-spot is organized centrally as part of a whole-body gaze shift rather than a specialized adaptation to conventional locomotion.