A dynamical model for reflex activated head movements in the horizontal plane

Abstract

We present a controls systems model of horizontal-plane head movements during perturbations of the trunk, which for the first time interfaces a model of the human head with neural feedback controllers representing the vestibulocollic (VCR) and the cervicocollic (CCR) reflexes. This model is homeomorphic such that model structure and parameters are drawn directly from anthropomorphic, biomechanical and physiological studies. Using control theory we analyzed the system model in the time and frequency domains, simulating neck movement responses to input perturbations of the trunk. Without reflex control, the head and neck system produced a second-order underdamped response with a 5.2 dB resonant peak at 2.1 Hz. Adding the CCR component to the system dampened the response by approximately 7%. Adding the VCR component dampened head oscillations by 75%. The VCR also improved low-frequency compensation by increasing the gain and phase lag, creating a phase minimum at 0.1 Hz and a phase peak at 1.1 Hz. Combining all three components (mechanics, VCR and CCR) linearly in the head and neck system reduced the amplitude of the resonant peak to 1.1 dB and increased the resonant frequency to 2.9 Hz. The closed loop results closely fit human data, and explain quantitatively the characteristic phase peak often observed.

Optimal Control of Natural Eye-Head Movements Minimizes the Impact of Noise

“…After a control trial (natural condition, 43 target steps), the head moment of inertia was increased by eccentrically placed masses attached to a helmet (weighted condition, 43 target steps). This gave an additional moment of inertia of 0.0335 kg ⅐ m 2 to the normal head moment of inertia, which was assumed to be 0.0148 kg ⅐ m 2 , as in Peng et al (1996). This difference corresponds to a 3.3-fold increase.…”

“…The plant parameters are selected as (Peng et al, 1996), and h ϭ 100 ms (modified from Tanaka et al, 2006). Instead of 0.1 N ⅐ m ⅐ s/rad in Peng et al (1996), b is selected to be 0.3 N ⅐ m ⅐ s/rad, as in Tangorra et al (2003); this fits the observed head velocity profile better.…”

“…Instead of 0.1 N ⅐ m ⅐ s/rad in Peng et al (1996), b is selected to be 0.3 N ⅐ m ⅐ s/rad, as in Tangorra et al (2003); this fits the observed head velocity profile better. In our previous work (Lehnen et al, 2009a), we observed that the subjects found the optimal trajectories very quickly within the first trials under the weighted head moment of inertia condition.…”

Eye, Head, and Body Coordination During Large Gaze Shifts in Rhesus Monkeys: Movement Kinematics and the Influence of Posture

“…Accordingly, the movement of body allowed both the eye and head deviation to remain within comfortable ranges, while facilitating the redirection of gaze toward a target of interest. It is likely that this eye-head-body gaze reorientation strategy possesses the teleological advantage of ensuring when a second object of interest appears in the vicinity of a current target, a subject can more rapidly align its gaze with the new object since a smaller effort will be required to rotate the eyes (as compared with the head) (Peng et al 1996;Zangemeister et al 1981), or-if required-to rotate the head-onbody as compared with body-in-space.…”

Dynamic head-neck stabilization in cervical dystonia

“…Afferent feedback depicted by eFRFs (see Fig. 5B) indicates a magnitude that increases above 1 Hz, which functions to dampen system dynamics at high frequencies (Keshner et al,1995;Peng et al,1996).…”