engleski

Analysis of soldiers' cognitive performance during Stroop test: An fMRI study

Magnetic resonance imaging (MRI) is an important tool in modern medicine, and functional magnetic resonance imaging (fMRI) is widely used for brain mapping and understanding cognitive behaviour in humans. As part of a larger study, 13 male candidates for Croatian military Special Forces (mean age ± std= 25.77 ± 3.27) were undertaken through a complex paradigm in the MRI scanner (Siemens Prisma 3T, 64-channel head coil) in order to find correlation between their brain activity and resilience to stress. The key structure for emotional response, and subsequently in resilience to stress, is amygdala. Beside amygdala, other structures, such as orbitofrontal cortex, medial prefrontal cortex, parietal cortex, etc. are involved in processing, control and inhibition of emotional (stress) response. One of the tasks in the paradigm was the colour- word matching Stroop test which measures inhibition, attention, and processing speed. Stroop test had a controlled block-design and included three blocks with no tasks and three blocks with tasks, where each block lasted for 30 seconds. Correlation between the blood- oxygen-level-dependent (BOLD) fMRI signal in the amygdala and reaction time of the Stroop test task was analysed. Image processing was done using the FMRIB Software Library, while the correlation was computed using Matlab R2016a. Mean levels of BOLD signal in amygdala are higher in blocks with tasks than in blocks with no tasks. Differences in mean values of BOLD signal from two consecutive blocks were correlated with participants' reaction time. The reaction time highly correlates with differences in mean values of the first two blocks of the test with the incorrect answers removed from the analysis (5.51 % incorrect answers). The correlation is higher when comparing right amygdala (0.90) with reaction time, than when comparing left amygdala (0.62). The results indicate that participants who have higher differences in mean values of signal in amygdala experienced greater stress and took longer to respond to the test, which can be useful for resilience prediction. Also, higher levels of BOLD signal are found in left amygdala than in right, which is, based on previous studies, a characteristic of resilient people.

fMRI ; cognitive performance ; soldiers ; Stroop test ; amygdala

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