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Investigations into Vestibular and Non-Vestibular Contributions to Eye Movements that Compensate for Head Rotations during Viewing of Near Targets

Han, Yanning Helen
http://rave.ohiolink.edu/etdc/view?acc_num=case1105646958

Abstract Details

2005, Doctor of Philosophy, Case Western Reserve University, Biomedical Engineering.
The vestibulo-ocular reflex (VOR) guarantees a clear, stable percept of the visual world during locomotion. Other mechanisms, such as visually mediated eye movements, also contribute to the generation of eye movements that compensate for head rotation under a range of viewing conditions. The current research attempted to determine the relative contributions of vestibular and non-vestibular mechanisms, such as smooth pursuit, to the overall response to head rotation (referred to as the enhanced VOR, or EVOR) during viewing of a near target that was either earth-fixed (EFT), head-fixed (HFT), or consisted of the subject’s own face viewed through a close mirror. Ten normal human subjects and two individuals with impairment of vestibular responses were tested during sinusoidal en-bloc head rotations in the frequency range 0.2 – 2.8 Hz in yaw. By applying head perturbations (> 1,000 deg/s/s) during sinusoidal head rotations, it was shown that the early VOR, measured within 70 msec after each onset of head perturbation, was no different, regardless of whether viewing an EFT or HFT, and contributed only ~75% to the overall eye response during EFT. Thus, non-vestibular factors made a substantial contribution and comprised retinal image slip (as demonstrated in experiments using strobe illumination), predictive mechanisms (evident from pseudorandom head rotations), and visual cues of target proximity (indicated by results during mirror viewing), but not vergence angle (which was uncorrelated with responses during monocular viewing). No one mechanism completely accounted for the non-vestibular component which exceeded, for example, the contribution due to smooth-pursuit eye movements, as shown by modeling EVOR responses. Comparison with prior studies indicates that mechanisms for generation of eye rotations during near viewing depend on head stimulus type (rotation or translation), waveform (transient or sinusoidal), and the species being tested.
R. John Leigh (Advisor)
235 p.
Engineering, Biomedical
vestibulo-ocular reflex (VOR); smooth pursuit; retinal image slip; predictive eye movements; vergence.

Recommended Citations

Citations

  • Han, Y. H. (2005). Investigations into Vestibular and Non-Vestibular Contributions to Eye Movements that Compensate for Head Rotations during Viewing of Near Targets [Doctoral dissertation, Case Western Reserve University]. OhioLINK Electronic Theses and Dissertations Center. http://rave.ohiolink.edu/etdc/view?acc_num=case1105646958

    APA Style (7th edition)

  • Han, Yanning. Investigations into Vestibular and Non-Vestibular Contributions to Eye Movements that Compensate for Head Rotations during Viewing of Near Targets. 2005. Case Western Reserve University, Doctoral dissertation. OhioLINK Electronic Theses and Dissertations Center, http://rave.ohiolink.edu/etdc/view?acc_num=case1105646958.

    MLA Style (8th edition)

  • Han, Yanning. "Investigations into Vestibular and Non-Vestibular Contributions to Eye Movements that Compensate for Head Rotations during Viewing of Near Targets." Doctoral dissertation, Case Western Reserve University, 2005. http://rave.ohiolink.edu/etdc/view?acc_num=case1105646958

    Chicago Manual of Style (17th edition)

case1105646958
1,149
© 2005, all rights reserved.
This open access ETD is published by Case Western Reserve University School of Graduate Studies and OhioLINK.