Did I turn off the gas? Reality monitoring of everyday actions

Abstract

Failing to remember whether we performed, or merely imagined performing, an everyday action can occasionally be inconvenient, but in some circumstances it can have potentially dangerous consequences. In this fMRI study, we investigated the brain activity patterns, and objective and subjective behavioral measures, associated with recollecting such everyday actions. We used an ecologically valid "reality-monitoring" paradigm in which participants performed, or imagined performing, specified actions with real objects drawn from one of two boxes. Lateral brain areas, including prefrontal cortex, were active when participants recollected both the actions that had been associated with objects and the locations from which they had been drawn, consistent with a general role in source recollection. By contrast, medial prefrontal and motor regions made more specific contributions, with supplementary motor cortex activity being associated with recollection decisions about actions but not locations, and medial prefrontal cortex exhibiting greater activity when remembering performed rather than imagined actions. These results support a theoretical interpretation of reality monitoring that entails the fine-grained discrimination between multiple forms of internally and externally generated information.

Fig. 1

Schematic design of the study and test phases. In the study phase, real everyday objects were taken out of either the left or the right box and presented to the participant, who was asked to perform a specified action with the object or to imagine performing that action with the object. In the scanned test phase, photographs of the studied objects were presented, and participants were cued to recollect whether each object had been associated with a performed or imagined action (action recollection) or whether it had been taken out of the left or the right box (location recollection). In the perceptual baseline condition, participants had to press one of two buttons, according to the number on the screen

Fig. 2

Brain regions activated during both action and location recollection, relative to the nonmemory baseline condition, displayed at an uncorrected threshold of p < .001. Considerable overlap between the two kinds of recollection is seen in regions that include lateral prefrontal, parietal, fusiform, and occipital cortices, all significant at the corrected thresholds (see the text for details)

Fig. 3

Brain regions active during the action memory task at the threshold of p < .05, corrected for voxels within regions of interest. (a) Action recollection was associated with significantly greater activity than was location recollection in left ventrolateral PFC (left panel) and in supplementary motor area (right panel). (b) Location recollection resulted in greater medial parietal activity, including the precuneus, as compared with recollection of actions. (c) Medial prefrontal cortex was the only area of the brain to show significantly greater activity specifically during action recollection of performed rather than imagined actions

Fig. 4

Time course analysis of activity during the action recollection and location recollection tasks in (a) anterior medial prefrontal cortex (amPFC), indicating greater activity specifically during reality-monitoring judgments about performed rather than imagined actions, and (b) precuneus, indicating greater activity specifically during location recollection judgments about performed rather than imagined actions

Fig. 5

Scatterplots illustrating correlations between anterior medial prefrontal cortex (amPFC) activity during action recollection and postscan memory characteristics questionnaire ratings, identifying an association with ratings of retrieved internal detail (see the text for details; auc = area under curve)