Adaptive plasticity of head movement propensity

Area of Science:

• Neuroscience
• Ophthalmology
• Biomechanics

Background:

• Individual head movement propensity during gaze shifts varies.
• Understanding factors influencing head movement tendencies is crucial for gaze control research.

Purpose of the Study:

• To investigate if neck mobility reduction (cervical collar) or visual field restriction (aperture spectacles) can modify head movement propensity.
• To quantify changes in customary ocular motor range and eye-only range.

Main Methods:

• Three subjects wore rigid cervical collars for up to 9 days.
• Three subjects wore aperture spectacles restricting the field of view to approximately 20 degrees for up to 9 days.
• Head movement propensity was measured using customary ocular motor range and eye-only range before, during, and after adaptation.

Main Results:

• Cervical collar adaptation significantly increased customary ocular motor range (27.6° to 66.1°) and eye-only range (24.6° to 67.6°), persisting post-removal in some subjects.
• Aperture spectacle adaptation decreased customary ocular motor range (35.1° to 25.4°) and eye-only range (35.1° to 23.0°), with variable effects across subjects.
• Collar adaptation improved eccentric gaze maintenance, suggesting brainstem-level effects, while spectacle adaptation indicated different underlying mechanisms.

Conclusions:

• Neck mobility restriction effectively reduces head movement propensity, potentially through modulation of reflex circuits.
• Visual field restriction has a less pronounced and possibly different effect, possibly involving alternative head control strategies.
• Enduring effects of neck restriction on head movement tendencies may link to clinical observations of dysequilibrium after neck injury.