It is often assumed that decision making involves neural competition, accumulation of evidence “scores” over time, and commitment to a particular alternative once its scores reach a critical decision threshold first. So far, however, neither the first-to-threshold rule nor the nature of competition (feedforward or feedback inhibition) has been revealed by experiments. Here, we presented two simultaneously flashed targets that reversed their intensity difference during each presentation and instructed human subjects to make a saccade toward the brightest target. All subjects preferentially chose the target that was brightest during the first stimulus phase. Unless this first phase lasted only 40 ms, this primacy effect persisted even if the second, reversed-intensity phase lasted longer. This effect did not result from premature commitment to the initially dominant target, because a strong target imbalance in the opposite direction later drove nearly all responses toward that location. Moreover, there was a nonmonotonic relation between target imbalance and primacy: increasing the target imbalance beyond 40 cd/m2 caused an attenuation of primacy. These are the hallmarks of hysteresis, predicted by models in which target representations compete through strong feedback. Reaction times were independent of the choice probability. This dissociation suggests that target selection and movement initiation are distinct phenomena.
展开▼
机译：通常认为决策过程涉及神经竞争，随着时间的推移积累证据“分数”，以及一旦其分数首先达到关键决策阈值，便要做出特定选择。但是，到目前为止，实验还没有揭示出第一个到第一个规则，也没有揭示竞争的性质（前馈或反馈抑制）。在这里，我们展示了两个同时闪光的目标，它们在每次演示过程中都反转了它们的强度差，并指示人类对象朝最明亮的目标扫视。所有受试者都优先选择在第一个刺激阶段最亮的目标。除非该第一阶段仅持续40毫秒，否则即使第二反向强度阶段持续更长的时间，这种首要效应也将持续。这种效果不是由于过早地承诺了最初的主导目标而导致的，因为相反方向上强烈的目标失衡随后导致几乎所有响应都朝该位置移动。此外，目标不平衡与首要性之间存在非单调关系：将目标不平衡增加到40 cd / m 2 会导致首要性减弱。这些是磁滞的标志，由模型预测，其中目标表示通过强大的反馈进行竞争。反应时间与选择概率无关。这种分离表明目标选择和运动开始是不同的现象。
展开▼
