The neural correlates of conceptual and perceptual false recognition

Abstract

False recognition, broadly defined as a claim to remember something that was not encountered previously, can arise for multiple reasons. For instance, a distinction can be made between conceptual false recognition (i.e., false alarms resulting from semantic or associative similarities between studied and tested items) and perceptual false recognition (i.e., false alarms resulting from physical similarities between studied and tested items). Although false recognition has been associated with frontal cortex activity, it is unclear whether this frontal activity can be modulated by the precise relationship between studied and falsely remembered items. We used event-related fMRI to examine the neural basis of conceptual compared with perceptual false recognition. Results revealed preferential activity in multiple frontal cortex regions during conceptual false recognition, which likely reflected increased semantic processing during conceptual (but not perceptual) memory errors. These results extend recent reports that different types of false recognition can rely on dissociable neural substrates, and they indicate that the frontal activity that is often observed during false compared with true recognition can be modulated by the relationship between studied and tested items.

Figure 1.

Schematic of the experimental procedure. During the study task, participants viewed word triplets that were either conceptually or perceptually related. Participants were instructed to decide how similar the words in each triplet were to each other while also remembering the words for the subsequent recognition test. During the recognition test, participants viewed five types of words: old conceptual words, old perceptual words, conceptual lures, perceptual lures, and unrelated new words. They gave a “remember,” “know,” or “new” response to each tested word. The condition in which words were tested was counterbalanced across participants by changing the word triplets shown during the study task (e.g., yell could be tested as a perceptual lure [shown here]; as a conceptual lure after studying shout, cry, squeal; as an old perceptual word after studying fell, bell, yell; as an old conceptual word after studying shout, yell, squeal; or as an unrelated new word after studying only unrelated triplets).

Figure 2.

Neural activity associated with conceptual false compared with conceptual true recognition but not with perceptual false compared with perceptual true recognition (“remember”/conceptual lure > “remember”/old conceptual excluding activity in “remember”/perceptual lure > “remember”/old perceptual). In the center, activity identified by this analysis is projected onto the left lateral surface of a three-dimensional template brain. On each side, activity is projected onto coronal slices of the group mean anatomic image, and each of the nine clusters of frontal activity identified by this analysis is demarcated by a circle. In the bottom panel, event-related activity (4–8 sec after stimulus onset) extracted from these active clusters is shown. (a, inferior frontal gyrus; b, medial/superior frontal gyri; c, medial frontal gyrus; d, inferior frontal gyrus; e, middle frontal gyrus; f, middle frontal gyrus; g, middle frontal gyrus; h, inferior frontal gyrus; i, middle frontal gyrus)

Figure 3.

Interaction analysis identifying regions that show a greater difference in activity between conceptual false and true recognition than between perceptual false and true recognition ([“remember”/conceptual lure > “remember”/old conceptual] > [“remember”/perceptual lure > “remember”/old perceptual]). On the right, activity is projected onto a coronal slice of the mean anatomic image, and on the left, the event-related activity (4–8 sec after stimulus onset) extracted from the active cluster within the left inferior frontal cortex (BA 45/47) is shown.