Detection of malingering behavior using functional MRI

Abstract

We used a functional magnetic resonance imaging (fMBI) paradigm to investigate the specific neural response in the presence of feigned memory problem, and to determine if it was distinguishable from normal recall. A forced-choice memory task format was used to examine specific neural activation when feigning memory impairment. The hypothesis tested was that activation of specific neural structures involved in the cognitive control of response manipulation (prefrontal cortex and subcortical structures), selection and adoption of retrieval strategies (prefrontal cortex), and the calculation of the proportion of correct responses (frontal-parietal cortices), would be observed during the process of feigning memory impairment when tested with forced-choice memory tasks. Two fMBI studies were conducted on 5 male volunteers to obtain convergent evidence in hypothesis testing. Study 1 employed a digit memory task of a forced-choice format. During each trial, each number was exposed for 0.75 followed by visual fixation on a cross hair for 2.25 sec. Bach subject was asked to decide if the two stimuli were the same. Upon completion of this, a new number was again presented for 0.75 set followed by a cross hair for 3.25 sec. Study 2 used an autobiographic memory task, also of a forced-choice format. The procedure employed was essentially the same as that utilized in Study 1. However, this time each subject was presented with an autobiographic question followed by an answer to that question which was presented 2.25 seconds later. Bach participant was asked to identify if the answer was correct. Pressing an air pump connected to a bell in the MB console room indicated a yes response. To encourage skillful lying, two other conditions, namely, answering incorrectly and answering randomly, were added. Therefore, there were altogether four experimental conditions: answering correctly, answering incorrectly, answering randomly, and faking memory failure. By subtracting cerebral activity during recall from that obtained during intentional lying, a clear picture about the pattern of brain activation underlying lying was derived. Three blocks were repeated for each of the four conditions. The duration of each block was 46 seconds. Care was taken to ensure that the order of the experimental conditions was balanced among the 12 blocks of scanning. As expected, we observed a large increase in the volume of activation in the prefrontal regions bilaterally that was accompanied by significant activation involving both the fronto-polar prefrontal areas (BA 10) during simulated malingering. Significant activation was also seen bilaterally in the following areas of the brain: angular (BA 39) and supramarginal (BA 40) gyri of the parietal lobe, and the cingulate and caudate locations of subcortical regions. Our findings provide evidence of the existence and involvement of a fronto-parietal-subcortical circuit in feigning a memory problem. Extensive examination of lying and deception detection in both normal and clinical populations using behavioral and functional imaging paradigms will provide further theoretical refinement of these findings.