多身份追踪（Multiple identity tracking, MIT）范式由Oksama和 Hyona(Oksama & Hyönä, 2008)提出，MIT范式用于研究对象位置信息、身份信息在多身份追踪任务中的作用。身份信息对追踪成绩影响的研究发现，身份信息不一致时的加工与位置追踪存在权衡现象，当身份信息加工的负荷高时，追踪成绩降低；当身份信息加工负荷低时，则会提高追踪成绩。Oksama和Hyona认为，在MIT任务加工中存在一个情节缓冲器对身份信息和位置信息进行绑定，绑定信息可以在目标之间切换提供追踪识别需要的信息。因此，身份信息的早期加工会影响其与位置信息的绑定(Oksama & Hyönä, 2008)。也有研究者认为这种身份信息和位置追踪的权衡现象，说明身份信息加工与位置追踪占用同一有限的资源(Horowitz et al., 2007; Howard & Holcombe, 2008)。也有研究者认为，身份信息对追踪的影响是因为目标身份特征与非目标身份特征之间的差异程度带来的(Horowitz et al., 2007; Howe & Holcombe, 2012; Liu et al., 2012)对身份特征的注意被混淆引起的。对多目标位置追踪的神经科学研究(P. Howe et al., 2009; Jovicich et al., 2001)发现额叶眼动区（Frontal Eye Field， FEF）、前顶内沟(Anterior Intraparietal Sulcus, AIPS)、后顶内沟(Posterior Intraparietal Sulcus, PIPS)、顶上小叶（Superior Parietal Lobule, SPL) 和运动复合区（Middle Temporal Complex, MT+）在追踪位置时的重要作用。关于身份追踪与位置及其绑定的认知神经机制尚无确定性结论，还有待进一步的研究。基于上述研究现状，本研究拟采用功能磁共振成像(fMRI)技术和多身份追踪范式，探讨MIT任务中身份与位置信息的信息保持与追踪的认知机制与脑功能成像机制。研究方案包括研究一和研究二两部分：（1）研究一包括2个行为实验和1个fMRI实验。实验一考察MIT任务中，对象运动过程中身份信息交换对目标位置上身份信息识别的影响。实验一研究结果发现：目标身份发生改变时追踪成绩显著下降；非目标身份交换和不交换条件没有显著的差异。该结果表明目标身份交换可能因为身份-位置捆绑被破坏，进而显著降低了追踪成绩；也可能因为基于身份特征的注意被混淆，进而显著降低了追踪成绩。实验一也表明可能存在抑制非目标身份交换以维持对目标的有效追踪；（2）实验二，考察了4个目标时，身份交换和探测时位置或身份的改变对追踪成绩的影响。研究发现身份交换显著降低任务追踪成绩；探测时位置或身份的改变也显著降低追踪成绩。（3）实验三探讨在MIT任务的追踪过程中交换身份信息对MIT任务表现的影响。结果显示，目标身份交换与不交换对比时，在FEF，PIPS有显著的激活。说明在目标身份交换任务中，被试在目标身份信息交换时主动加强了对目标的注意（FEF和PIPS）和目标的识别（主要是纹外皮层等区域）脑区的激活，并且FEF对纹外皮层有调控作用；目标身份交换与非目标身份交换对比时，在扣带前回（Anterior Cingulate Cortex，ACC）和PIPS有显著激活，说明在目标身份交换时，有主动增强的对目标的注意，和对非目标的注意的抑制；在非目标身份交换与不交换对比中，发现在额下回-眶部（Orbital part of Inferior Frontal Gyrus, IFG-Orb)、ACC等额叶区域的激活。说明了IFG-Orb和ACC可能在非目标身份交换任务中对注意的控制作用。研究二采用行为实验和功能核磁共振成像技术进一步考察多身份追踪任务中身份信息的保持和位置信息追踪的神经机制。（1）实验一通过改变追踪对象的圆形光栅刺激的身份差异程度，考察目标与非目标身份差异对多身份追踪任务的影响。研究发现身份差异对追踪有显著的影响，身份一致条件的追踪成绩显著低于身份完全不一致条件。在实验一的身份追踪任务中，身份信息仅为横、竖两种光栅。该结果表明在多身份追踪任务中，目标和非目标身份信息的差异对身份追踪有显著影响，而不是身份信息加工负荷的作用。（2）实验二通过对操纵目标与非目标的身份一致性以及主动追踪与被动观察，考察身份的一致性和对被试追踪任务要求探讨目标与非目标身份差异的脑功能成像机制。研究结果发现，当目标与非目标身份不一致时，主动追踪任务与被动观察任务在腹侧注意网络（Ventral Attention Functional Network, VAN）区域存在显著的差异，可能是在被动观察任务中有bottom-up的注意引起的；在被动观察任务中，目标间身份不一致和身份一致时在视觉腹侧通路（Ventral Visual Pathway)存在显著差异，该区域可能参与了字母身份识别，说明在被动观察任务中，当身份不一致时，也存在对身份信息自动加工。

The Multiple Identity Tracking (MIT) task was reported by Oksama and Hyona, which was used for studying not only the tracking of locations, but also tracking of identity. It has been reported that the identity tracking might have a trade-off with location tracking. The more complicate identity is, the less efficient tracking is. It is also suggested by Oksama and Hyona that, an Episodic Buffer for ‘what’ and ‘where’ bindings will provide target’s location for attention shift among targets. Therefore, the identity analysis will influence identity-location binding, and then impair tracking performance. Researchers also suggested a limited-resource theory, which suggested that identity tracking and location tracking share a a limited resource. Furthermore, the effect of visual distinctiveness might lead to the confusion of identity-based attention, which might contribute to track a distractor rather than a target. Studies have found that the Frontal Eye Field (FEF), Anterior Intraparietal Sulcus (AIPS), Posterior Intraparietal Sulcus (PIPS), Superior Parietal Lobule (SPL) and Middle Temporal Complex (MT+）played an important role in location tracking. However, the cognitive and neural mechanism of identity tracking and its’ influence on location tracking is still unclear. Then the present research will try to study the cognitive and neural mechanism of identity tracking based on Multiple Identity Tracking task.The present research was divided into two sections: (1) the first experiment concludes two behavioral experiment and one fMRI experiment. In the first experiment, the influence of identity-switch was studied during moving. The experiment have found that the switch of target identity impact tracking performance, while the switch of distractor identity did not influence tracking performance. This experiment indicated that refreshing identity-location binding will significantly lower tracking performance. Also, the experiment showed an inhibition to distractor. (2) The second experiment further investigate the effect of probe questions will have on tracking performance. The study found that the switch of identity significantly lower tracking performance as same as the first experiment. And the probe questions also significantly influence tracking performance. (3) the third experiment of the first section is conducted on fMRI. It aimed at brain activation for refreshing identity and location. The experiment showed that, compared to No-switch condition, the target-switch condition have higher activation in Frontal Eye Field (FEF), and Intraparietal Sulcus (IPS). The activation of these regions showed the enhancement of voluntary attention to targets. In addition, the compare of distractor-switch condition with No-switch condition showed higher activation in Orbital part of Inferior Frontal Gyrus (IFG-Orb) and Anterior Cingulate Gyrus (ACC). This result showed the IFG-Orb and ACC is involved in inhibition of attention to distractors.The second section uses MRI to further investigate the neural mechanism of distinctiveness have on tracking task. (1) the first experiment of the second section investigated the influence of identity distinctiveness between targets and distractor. And the result showed that the distinctiveness affect tracking performance, but not the identities in present task. The tracking performance is significantly lower when identity of targets and distractors’ is same. (2) the second experiment of the second section conducted four conditions: MIT-Tracking, MIT-Passive, MOT-Tracking, and MOT-Passive. In MIT task, the identity of objects are all unique. While in MOT task, the identity of objects are identical. The result showed that during a MIT task, tracking and passive viewing have significant difference in Triangle part of Inferior Frontal Gyrus (IFG-Tri) and Temporal Parietal Junction (TPJ), which indicated the stimulus-driven attention to objects in MIT-Passive condition. Meanwhile, it showed the difference between MIT task and MOT task when passive viewing is significant in Inferior Temporal Gyrus, Fusiform, Lingual, Angular, Middle Occipital Gyrus, and Inferior Parietal Lobule. The difference showed analysis of identities in MIT-Passive condition.