Cruse Damian, Fattizzo Marco, Owen Adrian M, Fernández-Espejo Davinia
School of Psychology, University of Birmingham, Birmingham, B15 2TT, England.
Department of Neurorehabilitation, University Hospital of Ghent, Ghent, 9000, Belgium.
BMC Neurol. 2017 Jan 24;17(1):14. doi: 10.1186/s12883-017-0798-1.
Evidence of reliable smooth visual pursuit is crucial for both diagnosis and prognosis in prolonged disorders of consciousness (PDOC). However, a mirror is more likely than an object to elicit evidence of smooth pursuit. Our objective was to identify the physiological and/or cognitive mechanism underlying the mirror benefit.
We recorded eye-movements while healthy participants simultaneously completed a visual pursuit task and a cognitively demanding two-back task. We manipulated the stimulus to be pursued (two levels: mirror, ball) and the simultaneous cognitive load (pursuit only, pursuit plus two-back task) within subjects.
Pursuit of the reflected-own-face in the mirror was associated with briefer fixations that occurred less uniformly across the horizontal plane relative to object pursuit. Secondary task performance did not differ between pursuit stimuli. The secondary task also did not affect eye movement measures, nor did it interact with pursuit stimulus.
Reflected-own-face pursuit is no less cognitively demanding than object pursuit, but it naturally elicits smoother eye movements (i.e. briefer pauses to fixate). A mirror therefore provides greater sensitivity to detect smooth visual pursuit in PDOC because the naturally smoother eye movements may be identified more confidently by the assessor.
在长期意识障碍（PDOC）中，可靠的平稳视觉追踪证据对于诊断和预后都至关重要。然而，相较于物体，镜子更有可能引出平稳追踪的证据。我们的目的是确定镜子优势背后的生理和/或认知机制。
我们记录了健康参与者在同时完成视觉追踪任务和一项需要认知能力的双任务时的眼动情况。我们在受试者内部对要追踪的刺激（两个水平：镜子、球）和同时存在的认知负荷（仅追踪、追踪加双任务）进行了操控。
与追踪物体相比，追踪镜子中自己的反射脸时，注视时间更短，且在水平面上的分布也更不均匀。在不同的追踪刺激下，次要任务的表现没有差异。次要任务也没有影响眼动测量结果，也未与追踪刺激产生相互作用。
追踪镜子中自己的反射脸在认知需求上并不低于追踪物体，但它自然会引出更平稳的眼动（即注视停顿时间更短）。因此，镜子在检测PDOC中的平稳视觉追踪方面具有更高的敏感性，因为评估者可以更有把握地识别出自然更平稳的眼动。
