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, 8 (11), e01116

The Role of Prefrontal Cortex in a Moral Judgment Task Using Functional Near-Infrared Spectroscopy


The Role of Prefrontal Cortex in a Moral Judgment Task Using Functional Near-Infrared Spectroscopy

Hadis Dashtestani et al. Brain Behav.


Background: Understanding the neural basis of moral judgment (MJ) and human decision-making has been the subject of numerous studies because of their impact on daily life activities and social norms. Here, we aimed to investigate the neural process of MJ using functional near-infrared spectroscopy (fNIRS), a noninvasive, portable, and affordable neuroimaging modality.

Methods: We examined prefrontal cortex (PFC) activation in 33 healthy participants engaging in MJ exercises. We hypothesized that participants presented with personal (emotionally salient) and impersonal (less emotional) dilemmas would exhibit different brain activation observable through fNIRS. We also investigated the effects of utilitarian and nonutilitarian responses to MJ scenarios on PFC activation. Utilitarian responses are those that favor the greatest good while nonutilitarian responses favor moral actions. Mixed effect models were applied to model the cerebral hemodynamic changes that occurred during MJ dilemmas.

Results and conclusions: Our analysis found significant differences in PFC activation during personal versus impersonal dilemmas. Specifically, the left dorsolateral PFC was highly activated during impersonal MJ when a nonutilitarian decision was made. This is consistent with the majority of relevant fMRI studies, and demonstrates the feasibility of using fNIRS, with its portable and motion tolerant capacities, to investigate the neural basis of MJ dilemmas.

Keywords: dorsolateral prefrontal cortex; functional near-infrared spectroscopy; mixed effect model; moral judgment.


Figure 1
Figure 1
The configuration of probes for the fNIRS device. There are four sources and 10 detectors resulting in 16 source/detector (channels) pairs
Figure 2
Figure 2
(a) The MJ paradigm for this study. Each question consisted of three slides: the first two slides described a scenario, the third one included a MJ question in which subject had 30 s to respond, and then a 15 s resting period. The participant answered “Yes” or “No” by pressing “1” or “2” on the keyboard, respectively. “Yes” indicated they were for the action presented. (b) Shows a sample personal scenario, which has a utilitarian response. (c) Shows an impersonal scenario, which also has a utilitarian response. (d) To control for random responses, subjects were asked to press “1” if they saw one word and press “2” if they saw another word. (e) Nonmoral control questions. (d) and € ensured the subject was paying attention and reading the scenarios throughout the task. Accuracy on these slides controlled for random responses and fatigue. (f) Shows an example of the three slides presented to participants in this MJ task
Figure 3
Figure 3
Average HbO changes in approximate prefrontal brain regions for personal and impersonal dilemmas
Figure 4
Figure 4
Changes in mean HbO which have been approximately mapped on different brain regions during (a) personal and (b) impersonal MJ. The captured brain activity during impersonal scenarios was significantly higher than personal dilemmas. The average hemodynamic change in the left DL‐PFC for impersonal dilemmas was especially large

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