■已知轻度创伤性脑损伤(mTBI)患者的视觉注意力分配能力受损。在本研究中,我们通过在执行改良的Posner视觉搜索任务时检查mTBI患者的瞳孔反应,研究了这种认知缺陷的可能神经相关性。
■进行了两个实验,其中不提示(实验1)或提示(实验2)目标位置。此外,在实验2中,提示类型(内源性与外源性提示)和提示有效性被视为独立变量。在这两个实验中,通过改变目标和干扰物模式之间的形状相似性来改变搜索效率。判断目标存在或不存在所需的反应时间以及瞳孔扩张指标,特别是瞳孔扩张延迟(PDL)和幅度(PDA),被测量。13例慢性mTBI患者和21岁,sex-,和智商匹配的对照组参与了研究。
■在实验1中,mTBI患者在高效和低效搜索条件下都显示出类似的PDA,而对照参与者在低效搜索条件下的PDA明显大于高效搜索条件.由于认知负荷与PDA呈正相关,我们的研究结果表明,mTBI患者在进行视觉搜索时无法应用更多的脑力,特别是当视觉搜索效率低下时,任务很困难。在实验2中,当目标位置被提示时,无论搜索效率如何,mTBI患者对目标没有明显的瞳孔扩张反应,也不是提示是有效的还是无效的。这些结果与对照参与者形成对比,他们对提示的有效性也很敏感,其中PDA对于提示有效条件比无效条件小,特别是对于有效的搜索条件。
■瞳孔测量提供了mTBI后注意力分配不足的进一步证据。
The ability to allocate visual attention is known to be impaired in patients with mild traumatic brain injury (mTBI). In the present study, we investigated a possible neural correlate of this cognitive deficit by examining the pupil response of patients with mTBI whilst performing a modified Posner visual search task.
Two experiments were conducted in which the target location was either not cued (Experiment 1) or cued (Experiment 2). Additionally, in Experiment 2, the type of cue (endogenous vs exogenous cue) and cue validity were treated as independent variables. In both experiments, search efficiency was varied by changing shape similarity between target and distractor patterns. The reaction time required to judge whether the target was present or absent and pupil dilation metrics, particularly the pupil dilation latency (PDL) and amplitude (PDA), were measured. Thirteen patients with chronic mTBI and 21 age-, sex-, and IQ -matched controls participated in the study.
In Experiment 1, patients with mTBI displayed a similar PDA for both efficient and inefficient search conditions, while control participants had a significantly larger PDA in inefficient search conditions compared to efficient search conditions. As cognitive load is positively correlated with PDA, our findings suggest that mTBI patients were unable to apply more mental effort whilst performing visual search, particularly if the task is difficult when visual search is inefficient. In Experiment 2, when the target location was cued, patients with mTBI displayed no significant pupil dilation response to the target regardless of the efficiency of the search, nor whether the cue was valid or invalid. These results contrasted with control participants, who were additionally sensitive to the validity of the cue in which PDA was smaller for cue-valid conditions than invalid conditions, particularly for efficient search conditions.
Pupillometry provided further evidence of attention allocation deficits following mTBI.