Proper stabilization of the head is essential for humans to carry out many of the essential activities of daily living. Throughout most of the activities in which we engage the head is held in a stereotyped position with respect to gravity. This helps to maintain the orientation of the head's special sensory receptors in space and regulates the attitude of the head on the trunk as part of overall postural control. Vestibulocollic reflexes (VCRs), which utilize information from sensors of the vestibular labyrinth to generate neck muscle activity to stabilize the head are a critical part of the head stabilization system. They interact with cervicocollic reflexes (CCRs), voluntary and reaction time movements and head-neck biomechanics in controlling head position. To resolve controversies regarding the importance of each of these four mechanisms, our primary goal involves characterizing the 4 mechanisms and determining how they contribute to head stabilization. A second goal is to determine the dynamic and kinematic properties of voluntary head tracking movements. If successful, the proposed resolution of head stabilization and tracking into their component mechanisms will have broad application to many areas of motor control that await similar analysis. To achieve these goals we will pursue three series of experiments in both human and monkey subjects: Exp. 1 will examine the dynamic properties of the open loop VCR and CCR to determine their transfer functions and will characterize the inertial and viscoelastic properties of human and monkey head-neck mechanical plant. Exp. 2 will perform a similar analysis of the closed loop VCR, where the head is free to move in response to body rotation. Exp. 3 will analyze the dynamic and kinematic properties of voluntary head tracking using electromyographic and fluoroscopic recording to obtain data to test our detailed biomechanical models of the head-neck system. Experimental results will be interpreted using two models. The first is a dynamic model which starts with well tested vestibuloocular reflex models and adds biomechanical properties and multiple rotation axes that characterize the head movement system. It will incorporate elements corresponding to known physiology of labyrinthine receptors and reflex pathways and will attempt to show how position, velocity and acceleration information, embedded in firing patterns of regular and irregular peripheral afferents, drives neck muscles to maintain stability of the head in space. The second is a detailed biomechanical model of the human head-neck system that quantifies the actions of all joints, muscles and passive mechanics and allows prediction of appropriate patterns of muscle activity to stabilize the head in the face of angular and linear perturbations.

Agency
National Institute of Health (NIH)
Institute
National Institute of Neurological Disorders and Stroke (NINDS)
Type
Research Project (R01)
Project #
5R01NS022490-13
Application #
2668969
Study Section
Special Emphasis Panel (ZRG4-GRM (01))
Program Officer
Broman, Sarah H
Project Start
1985-09-01
Project End
2000-02-29
Budget Start
1998-03-01
Budget End
1999-02-28
Support Year
13
Fiscal Year
1998
Total Cost
Indirect Cost
Name
Northwestern University at Chicago
Department
Physiology
Type
Schools of Dentistry
DUNS #
005436803
City
Chicago
State
IL
Country
United States
Zip Code
60611
Statler, K D; Keshner, E A (2003) Effects of inertial load and cervical-spine orientation on a head-tracking task in the alert cat. Exp Brain Res 148:202-10
Chen, K J; Keshner, E A; Peterson, B W et al. (2002) Modeling head tracking of visual targets. J Vestib Res 12:25-33
Keshner, E A (2000) Modulating active stiffness affects head stabilizing strategies in young and elderly adults during trunk rotations in the vertical plane. Gait Posture 11:11-Jan
Keshner, E A; Hain, T C; Chen, K J (1999) Predicting control mechanisms for human head stabilization by altering the passive mechanics. J Vestib Res 9:423-34
Peng, G C; Hain, T C; Peterson, B W (1999) Predicting vestibular, proprioceptive, and biomechanical control strategies in normal and pathological head movements. IEEE Trans Biomed Eng 46:1269-80
Perlmutter, S I; Iwamoto, Y; Baker, J F et al. (1999) Spatial alignment of rotational and static tilt responses of vestibulospinal neurons in the cat. J Neurophysiol 82:855-62
Perlmutter, S I; Iwamoto, Y; Barke, L F et al. (1998) Relation between axon morphology in C1 spinal cord and spatial properties of medial vestibulospinal tract neurons in the cat. J Neurophysiol 79:285-303
Perlmutter, S I; Iwamoto, Y; Baker, J F et al. (1998) Interdependence of spatial properties and projection patterns of medial vestibulospinal tract neurons in the cat. J Neurophysiol 79:270-84
Keshner, E A; Statler, K D; Delp, S L (1997) Kinematics of the freely moving head and neck in the alert cat. Exp Brain Res 115:257-66
Graf, W; Keshner, E; Richmond, F J et al. (1997) How to construct and move a cat's neck. J Vestib Res 7:219-37

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