ABSTRACT

Pattern separation and pattern completion are generally studied in humans using mnemonic discrimination tasks such as the Mnemonic Similarity Task (MST) where participants identify similar lures and repeated items from a series of images. Failures to correctly discriminate lures are thought to reflect a failure of pattern separation and a propensity toward pattern completion. Recent research has challenged this perspective, suggesting that poor encoding rather than pattern completion accounts for the occurrence of false alarm responses to similar lures. In two experiments, participants completed a continuous recognition task version of the MST while eye movement (Experiments 1 and 2) and fMRI data (Experiment 2) were collected. In Experiment 1, we replicated the result that fixation counts at study predicted accuracy on lure trials (consistent with poor encoding predicting mnemonic discrimination performance), but this effect was not observed in our fMRI task. In both experiments, we found that target-lure similarity was a strong predictor of accuracy on lure trials. Further, we found that fMRI activation changes in the hippocampus were significantly correlated with the number of fixations at study for correct but not incorrect mnemonic discrimination judgments when controlling for target-lure similarity. Our findings indicate that while eye movements during encoding predict subsequent hippocampal activation changes for correct mnemonic discriminations, the predictive power of eye movements for activation changes for incorrect mnemonic discrimination trials was modest at best.

摘要

模式分离和模式完成通常使用助记符辨别任务在人类中进行研究，例如助记符相似性任务 (MST)，参与者从一系列图像中识别相似的诱饵和重复项。未能正确区分诱饵被认为反映了模式分离的失败和模式完成的倾向。最近的研究对这一观点提出了挑战，表明编码不良而不是模式完成导致了对类似诱饵的错误警报反应的发生。在两个实验中，参与者完成了 MST 的连续识别任务版本，同时收集了眼球运动（实验 1 和 2）和 fMRI 数据（实验 2）。在实验一中，我们在研究中复制了注视计数的结果预测诱饵试验的准确性（与预测记忆辨别性能的编码不佳一致），但在我们的 fMRI 任务中没有观察到这种效果。在这两个实验中，我们发现目标-诱饵相似性是诱饵试验准确性的有力预测指标。此外，我们发现海马体中的 fMRI 激活变化与研究中的注视次数显着相关，以便在控制目标-诱饵相似性时做出正确而非错误的记忆辨别判断。我们的研究结果表明，虽然编码过程中的眼球运动可以预测随后的海马体激活变化以进行正确的助记符辨别，但眼球运动对不正确的助记符辨别试验的激活变化的预测能力充其量是适度的。