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Head-trunk coordination during linear anterior-posterior translations
1Sensory Motor Performance Program, Rehabilitation Institute of Chicago and Department of Physical Medicine and Rehabilitation, Feinberg School of Medicine, Northwestern University, Chicago, Illinois 60611, USA. eak@northwestern.edu
Journal of Neurophysiology
|April 11, 2003
Summary
This study shows the vestibular system primarily dampens head movements, with trunk feedback crucial for initial head-trunk coordination. Diminished vestibular input highlights the importance of system mechanics and segmental receptors for postural reactions.
Area of Science:
- Neuroscience
- Biomechanics
- Human Movement Science
Background:
- Head-trunk coordination is vital for maintaining balance and executing tasks.
- The relative contributions of vestibular and somatosensory (trunk) inputs to this coordination are not fully understood.
Purpose of the Study:
- To evaluate the distinct roles of vestibular and trunk inputs in head-trunk coordination during translations.
- To compare coordination strategies in healthy individuals versus those with diminished vestibular function.
Main Methods:
- Twelve healthy adults and 6 adults with labyrinthine deficiency (LD) underwent controlled anterior-posterior translations.
- Head and trunk kinematics were recorded using motion analysis and accelerometry.
- Electromyography (EMG) of neck and paraspinal muscles was measured under fixed and free trunk conditions.
Main Results:
- Healthy subjects showed different initial head acceleration patterns with fixed versus free trunks; LD subjects did not.
- Peak head accelerations were higher in LD subjects and when the trunk was fixed.
- Neural compensation patterns observed in healthy subjects were absent in LD subjects.
Conclusions:
- Head-trunk coordination initially relies heavily on mechanical factors and trunk proprioception.
- The vestibular system appears to modulate later responses and monitor head position, rather than initiating postural reactions.
- Somatosensory feedback from segmental receptors plays a primary role in postural control of the head-trunk system.