Sektion Funktionelle Sehforschung, Univ.-Augenklinik Freiburg, Killianstr. 5, 79106 Freiburg, Germany.
Sektion Funktionelle Sehforschung, Univ.-Augenklinik Freiburg, Killianstr. 5, 79106 Freiburg, Germany.
Clin Neurophysiol. 2010 Sep;121(9):1464-1472. doi: 10.1016/j.clinph.2010.03.030.
An objective assessment of sensory and sensuo-cognitive function, based on physiological signals rather than on the behavioral response of a patient, is often advisable, albeit challenging. Evoked potentials are frequently used as an objective measure, but usually fail to detect defects beyond primary sensory areas, including those of psychogenic origin. Here we assess whether the event-related P300 component may be used to measure "cognitive" visual acuity.
A visual oddball paradigm was used to elicit P300 responses in subjects with normal or artificially blurred vision. Probe stimuli consisted of infrequently presented gratings with spatial frequencies in the range of 2.2-16.2 cycles per degree, which could be either target or non-target stimuli depending on their orientation. Frequent stimuli were homogeneously grey fields.
Without blur, rare stimuli of all spatial frequencies produced reliable P300 responses. Blur abolished the P300 to fine gratings consistently in 10 of 11 subjects. The drop in P300 amplitude was steep, rather than gradual, between visible and invisible gratings.
The P300 is sensitive to identify the resolution threshold and thus may serve as a tool for estimating acuity in cases of visual impairments.
The study presents a tool for the objective assessment of acuity in cases of higher-level visual impairments. The concept can most likely be extended to other sensory modalities.
基于生理信号而非患者的行为反应进行感官和感觉认知功能的客观评估通常是明智的，尽管具有挑战性。诱发电位常被用作客观测量指标，但通常无法检测到初级感觉区域以外的缺陷，包括精神源性缺陷。在这里，我们评估事件相关 P300 成分是否可用于测量“认知”视力。
使用视觉Oddball 范式在具有正常或人为模糊视力的受试者中诱发 P300 反应。探测刺激由空间频率在 2.2-16.2 周/度范围内的偶尔呈现的光栅组成，根据其方向，它们可以是目标或非目标刺激。常见刺激是均匀的灰色场。
在没有模糊的情况下，所有空间频率的稀有刺激都产生了可靠的 P300 反应。在 11 名受试者中的 10 名中，模糊一致地消除了精细光栅的 P300。P300 振幅在可见和不可见光栅之间的下降是陡峭的，而不是渐进的。
P300 能够识别分辨率阈值，因此可用于估计视力障碍情况下的视力。
该研究提出了一种用于在高级视觉障碍情况下进行视力客观评估的工具。该概念很可能扩展到其他感觉模式。
