Neural Correlates Of Feigning Long-term Memory Impairment

ObjectiveAttempts to feign memory impairment are especially common in forensic evaluations. Extensive research conducted to date with the aim of revealing the neural correlates and neural mechanisms of feigning memory impairment has found that feigning working memory impairment possess a fronto-parietal-subcortical circuit which was very much the same independent of stimuli types, genders, and mother tongues, has a high consistency and generality. In addition, neuroimaging studies about the neural mechanism of memory have shown that functions of different memory are accompanied with overlapping activating brain regions, besides its specificity. So whether feigning different type of memory impairment shares a same neural circuit or distinct from each other? On account of this question, our primary objective was to investigate the neural correlates of feigning long-term memory impairment, and make compare with feigning working memory impairment, to explore the general pattern of neural correlates of feigning memory impairment.MethodsA word forced-choice pattern was adopted in this study, combined with a functional magnetic resonance imaging (fMRI) test. A total of 12 healthy university students (6 men, 6 women) took part in this study(right-handed,digital span≥7), all of them went through feigning long-term memory impairment(experiment 1) and working memory impairment conditions (experiment 2), and were asked to make truth response, lie response and random response during scanning. The behavioural data (ie.reaction time) and imaging data were recorded while scanning, besides the strategies used for random response and lie response recorded after scanning.ResultsExperiment 11.Behavioural data: The reaction time (RT) of lie response was significant prolonged than truth response and random response(P <0.01); while the random response was much shorter than truth response and lie response(P <0.05). The accuracy of lie response and random response was significant lower than truth respons(eP <0.01), no significance was found between lie response and random response(P >0.05).2.Imaging data: Significant activation was found in the right angular gyrus and supramarginal gyrus, the left inferior parietal lobule, anterior cingulate cortex, inferior occipital gyrus and inferior orbital frontal cortex, as well as the bilateral cerebellum for truth response. The group analysis for lie minus true revealed significant activation in the left frontal cortex; while no significant was found for random minus true. The group analysis of truth minus random and lie minus random revealed no areas of significant activation. When contrasting the random response versus lie response conditions, significant activation was observed in the bilateral medial cingulate cortex, no regions were more active when contrasting truth response versus random response conditions.Experiment 21.Behavioural data: The reaction time (RT) of lie response was significant prolonged than truth response and random response(P <0.01); while no significance was found between the truth response and random response (P >0.05). The accuracy of lie response and random response was significant lower than truth respons(eP <0.01), while significance was found when compared lie response with random response(P <0.05).2.Imaging data: Activations of the right supplementary motor area, superior frontal gyrus, inferior temporal gyrus and hippocampus, the left cerebellum,medial prefrontal cortex and inferior occipital gyrus, and the bilateral inferior parietal lobule were observed while subjects were making truth responses. Significant activation was found in the right anterior cingulate cortex, the left precuneus, superior frontal gyrus and cerebellum, and the bilateral fusiform for faked responses, relative to truth; while two clusters in the left postcentral gyrus and the right precentral gyrus in which activity was greater in random than truth conditons. Compared to lie response, there was no significant for truth response, while the right superior frontal gyrus, the left inferior parietal lobule and the postcentral gyrus were significant activated when answer randomly. Conclusion:1. Feigning long-term memory impairment mainly activated the left prefrontal cortex, including the left superior frontal gyrus and the medial prefrontal cortex; feigning working memory impairment possess a fronto-parietal-subcortical circuit.2. Feigning long-term memory and working memory impairment has different neural correlates, but we also found the overlapping brain regions. Our results suggest that the left superior frontal gyrus may act as the basic neural mechanism for feigning memory impairment.3. Random response may conducts as a master strategy for faking, related to complicate cognitive control processes.