The purpose of this study was to investigate the regions of brain activation during deception or truth-telling by functional MRI using BOLD contrast and a novel question technique and compare the results with standard polygraph examination.
METHOD AND MATERIALS
The experiments were performed on 6 normal volunteers using a 1.5T MRI. Three different types of physiological responses were measured using the polygraph, eg., the rate and depth of respiration; blood pressure; and galvanic skin conductance. All the polygraph signals were digitally recorded (Lafayette Instruments). FMRI experiment used a box-car type block design. The order of the fMRI and polygraph procedure was randomized. Subjects' responses were measured using a response box. Axial anatomical images were acquired parallel to the AC-PC line covering the entire brain. FMRI images were acquired with EPI in the same plane. MR parameters: matrix=128*128; FoV=22 cm; st=5mm; TR=4s; TE=54 ms; & NEX=1. A relevant situation was created prior to the fMRI scanning and polygraph testing. Of the six subjects, three were asked to tell the truth, that they were not involved in the relevant situation, and three were asked to deliberately lie. The subjects were presented with 5 separate blocks of control (irrelevant) and relevant questions alternating with rest period blocks. During each block (24 sec long), 6 volumes of EPI images were acquired, yielding a total of 120 EPI volumes. The data was then analyzed using SPM software.
The results show areas of frontal lobe (medial, inferior and superior frontal gyrus) [BA 9, 10, 47], temporal lobe [BA 37], and limbic lobe (anterior cingulate) to be significantly active (p<0.001) during the deception process. During truth telling, no significant activation regions were seen in the brain. However, at lower threshold levels (p=0.05) smaller areas of activation were seen in the temporal lobe and medial frontal gyrus.
These results suggest that there may be unique area(s) in the brain involved in deception or truth-telling process that can be measured using fMRI. The polygraph results correlated well with both the lying and truth telling subjects.