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P.L. Giever, D.A. Suzuki, P. Kang, R.D. Yee; Quantifying Volitional Recruitment of the Head in Eye-Head Coordinated Saccades; an Improved Methodology for Ranking Subjects According to Head Movement Propensity . Invest. Ophthalmol. Vis. Sci. 2003;44(13):1975.
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© ARVO (1962-2015); The Authors (2016-present)
Purpose: The idiosyncratic diversity in head movement contributions for a given amplitude of gaze shift is well-documented in the literature. This diversity impacts the scientific and clinical community by attenuating the ability to discern specific levels of motor dysfunction in movements involving the head and eyes. Methods: To further understand the relationship between cognitive/attentional processes and eye-head coordination, subjects were tested with an Optotrak video system (NDI) sensitive to infrared LEDs placed on a headband for head movement monitoring. Eye position was monitored with a phase-angle type CNC search coil system and Skalar eye coils. Results: In the no-instruction paradigm (task 1), subjects were asked to look at an eccentric target presented at 30 or 40 degrees to the right or left of a central fixation point, for visually-guided or anti-gaze trials. In task 2 (head movement instruction) subjects were instructed to direct their heads toward or away from the eccentric target randomly presented at the same eccentricities as the no-instruction paradigm. Thus, tasks differed only in the instruction the subjects received. Notable findings include a large individual diversity between reactions to the different paradigms. The majority of subjects (10/18) used no head movements for task 1, lacking the instruction to move the head. However, 5 subjects moved the head a moderate amount, while 3 subjects showed no change in eye-head contribution (p < 0.66) for the two tasks. These latter 3 subjects exhibited a propensity to move their heads and were identified as headmovers. These findings were consistent across 70-100% of the 45 trials for each task. When the subjects were instructed to move their heads, all elicited gaze shifts with a significant head movement contribution. Conclusions: The results indicate that our method provides an easier alternative to more difficult classification schemes (e.g., Fuller 1992) used to identify headmovers from non-headmovers. This would be of value in studying sensori-motor deficits in patient populations. Supported by: RPB & NIH EY09082 grants.
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