Neural correlates of true memory, false memory, and deception

Abstract

We used functional magnetic resonance imaging (fMRI) to determine whether neural activity can differentiate between true memory, false memory, and deception. Subjects heard a series of semantically related words and were later asked to make a recognition judgment of old words, semantically related nonstudied words (lures for false recognition), and unrelated new words. They were also asked to make a deceptive response to half of the old and unrelated new words. There were 3 main findings. First, consistent with the notion that executive function supports deception, 2 types of deception (pretending to know and pretending not to know) recruited prefrontal activity. Second, consistent with the sensory reactivation hypothesis, the difference between true recognition and false recognition was found in the left temporoparietal regions probably engaged in the encoding of auditorily presented words. Third, the left prefrontal cortex was activated during pretending to know relative to correct rejection and false recognition, whereas the right anterior hippocampus was activated during false recognition relative to correct rejection and pretending to know. These findings indicate that fMRI can detect the difference in brain activity between deception and false memory despite the fact that subjects respond with "I know" to novel events in both processes.

Figure 1.

Depiction of 1 of the 2 task sessions (see Materials and Methods for details). The study-test phase was conducted twice with different stimulus sets. After participants heard the word lists of semantic associates in the study phase, they were asked to perform the recognition memory task (test phase) consisting of 4 “Truth” and 4 “Lie” blocks with fMRI scanning. In the “Truth” blocks, they were asked to respond honestly to “True targets” (old words from the study phase), “False targets” (nonstudied words that were semantically related to old words), and “New targets” (new words that were not semantically related to old words). In the “Lie” blocks, they were asked to dishonestly respond to “True targets” and “New targets.” In the “Truth blocks,” true recognition (TR) was defined as an “old” response to a “True target,” false recognition (FR) as an “old” response to a “False target,” and correct rejection (CR) as a “new” response to a “New target.” In the “Lie” blocks, lying to “True targets” (LT; i.e., pretending not to know) and lying to “New targets” (LN; i.e., pretending to know) were defined as deceptive responses to each target.

Figure 2.

Regions showing greater activation during lying (LT and LN) relative to truth telling (TR and CR). The signal changes of the following 7 activated regions in the frontal lobe are depicted (error bars represent SEM). (a) Right medial prefrontal cortex [12, 57, −6], (b) right superior frontal gyrus [24, 15, 60], (c) right middle frontal gyrus [42, 6, 51], (d) right superior frontal gyrus [24, −3, 57], (e) left inferior frontal gyrus [−45, 48, −15], (f) left supplementary motor area [−12, 21, 57], (g) left middle frontal gyrus [−27, 3, 60]. TR, true recognition; CR, correct rejection; LT, lying to “True targets” (pretending not to know); LN, lying to “New targets” (pretending to know).

Figure 3.

Statistical parametric map of regions showing greater activation during TR than during CR and FR, displayed on a surface-rendered standard brain. The signal changes of the following 3 activated regions are depicted (error bars represent SEM). (a) Left supramarginal gyrus [−51, −54, 36], (b) left superior temporal sulcus/middle temporal gyrus [−48, −9, −15], (c) left middle temporal gyrus [−60, −18, −12]. TR, true recognition; CR, correct rejection; FR, false recognition.

Figure 4.

The signal change of increased brain activity in (a) the left middle frontal gyrus [−42, 18, 39] during LN in comparison to during CR and FR, and (b) the right hippocampus [36, −9, −15] during FR in comparison to during CR and LN. Error bars represent standard error. The activation is superimposed onto MRIs of MNI templates. CR, correct rejection; FR, false recognition; LN, lying to “New targets” (pretending to know).