Separable forms of reality monitoring supported by anterior prefrontal cortex

Abstract

Reality monitoring refers to the process of discriminating between internally and externally generated information. Two different tasks have often been used to assess this ability: (a) memory for perceived versus imagined stimuli; and (b) memory for participant- versus experimenter-performed operations. However, it is not known whether these two reality monitoring tasks share neural substrates. The present study involved use of a within-subjects functional magnetic resonance imaging design to examine common and distinct brain mechanisms associated with the two reality monitoring conditions. The sole difference between the two lay in greater activation in the medial anterior prefrontal cortex when recollecting whether the participant or the experimenter had carried out an operation during prior encoding as compared to recollecting whether an item had been perceived or imagined. This region has previously been linked with attending to mental states. Task differences were also reflected in the nature of functional connectivity relationships between the medial anterior and right lateral prefrontal cortex: There was a stronger correlation in activity between the two regions during recollection of self/experimenter context. This indicates a role for the medial anterior prefrontal cortex in the monitoring of retrieved information relating to internal or external aspects of context. Finally, given the importance of reality monitoring to understanding psychotic symptoms, brain activity was related to measures of proneness to psychosis and schizotypal traits. The observation of significant correlations between reduced medial anterior prefrontal signal and scores on such measures corroborates these theoretical links.

Figure 1

Examples of the cues and stimuli used in the study and test phases. See text for details.

Figure 2

Significantly greater activation during recollection of self/experimenter status than perceived/imagined status, displayed on the participants’ mean normalized structural image. The distribution of activations identified in previous studies of reality monitoring that used the perceived/imagined task is illustrated by the green shading, and the distribution of previous mentalizing activations indicated in red.

Figure 3

Plot of signal in medial anterior prefrontal cortex during presentation of different reality monitoring retrieval instructions, and during recollection of self/experimenter and perceived/imagined context. Error bars represent standard errors of the mean.

Figure 4

Results of the effective connectivity analysis which identified a psychophysiological interaction between medial anterior prefrontal cortex and right lateral prefrontal cortex, displayed on the participants’ mean normalized structural image.

Figure 5

Scatter plot illustrating the significant correlation between reduced activation in medial anterior prefrontal cortex and total score on scales assessing proneness to psychosis and schizotypal traits.