McPeek Robert M
The Smith-Kettlewell Eye Research Institute, 2318 Fillmore Street, San Francisco, CA 94115, USA.
J Neurophysiol. 2008 May;99(5):2694-702. doi: 10.1152/jn.00591.2007. Epub 2008 Mar 26.
Recent evidence indicates that inactivation of the primate superior colliculus (SC) results in an increase in saccade target-selection errors. The pattern of errors suggests that a winner-take-all competition selects the saccade goal and that SC inactivation perturbs this process by biasing the competition against stimuli in the inactivated field. To investigate this idea, the difficulty of target selection was manipulated in a color-oddity search task by varying the number of homogeneous distractors in the search array. Previous studies have shown that target selection is easier when a greater number of homogeneous distractors is present, due to perceptual grouping of the distractors. These results were replicated when testing with the SC intact. Surprisingly, during SC inactivation, this normal trend was reversed: target-selection performance declined significantly with more distractors, resulting in a greater proportion of errant saccades to distractors. Examination of the saccade endpoints indicates that after SC inactivation, many errant saccades were directed to distractors adjacent to the target. This pattern of results suggests that the salience signal used by the SC for target selection is relatively broad in spatial scope. As a result, when the area of the SC representing the target location is inactivated, distractors near the target are at a competitive advantage relative to more distant distractors and, consequently, are selected more often as the saccade goal. This contributes to the trend of worse performance with more distractors due to the greater proximity of distractors to the target.
最近的证据表明，灵长类动物上丘（SC）失活会导致扫视目标选择错误增加。错误模式表明，赢家通吃的竞争选择了扫视目标，并且SC失活通过使竞争偏向于失活区域中的刺激而扰乱了这一过程。为了研究这一观点，在颜色奇异性搜索任务中，通过改变搜索阵列中同质干扰物的数量来操纵目标选择的难度。先前的研究表明，当存在更多同质干扰物时，由于干扰物的知觉分组，目标选择会更容易。在SC完整的情况下进行测试时，这些结果得到了重复。令人惊讶的是，在SC失活期间，这种正常趋势发生了逆转：随着干扰物数量的增加，目标选择性能显著下降，导致更多的错误扫视指向干扰物。对扫视终点的检查表明，在SC失活后，许多错误扫视指向目标附近的干扰物。这种结果模式表明，SC用于目标选择的显著性信号在空间范围内相对较宽。因此当代表目标位置的SC区域失活时，目标附近的干扰物相对于更远的干扰物具有竞争优势，因此更常被选为扫视目标。这导致了随着干扰物数量增加性能变差的趋势，因为干扰物与目标的距离更近。
