Taha Esfandiari - Institute of Medical Sciences and Technology, Shahid Beheshti University, Tehran, Iran
Mahzad Khorassani - Institute of Medical Sciences and Technology, Shahid Beheshti University, Tehran, Iran
Mahnaz Olfati - Institute of Medical Sciences and Technology, Shahid Beheshti University, Tehran, Iran
Mohammad Mahdi Mostafavi Zahed - Institute of Medical Sciences and Technology, Shahid Beheshti University, Tehran, Iran

In this study we compared the activity of the brain during covert verb generation (CV) vs. overt verb generation (OV), overt word repetition (OW) vs. OV, and OW vs. finger, foot, and lip movement (FFL) to understand the underlying mechanisms of speaking.Method Our dataset was obtained from the OpenfMRI Database [1]. Its accession number is ds000114 [2]. This dataset included T1-weighted structural images and fMRI images of 10 healthy subjects (6 females and 4 males, mean age: 52.5). Images were acquired during 2 sessions with 2-3 days interval. Data was analyzed using FSL software [3] on 3 levels: session level, subject level, and group level. Paired t-test was used to compare the brain activity between different conditions (corrected p-value<0.05). Results Anatomical regions were derived using SPM Anatomy Toolbox in MATLAB. Comparing CV vs. OV, results showed that Wernicke s area, secondary somatosensory cortex, and ventral parietal cortex are significantly more active during OV (Figure 1). Comparing OV vs. OW, results showed that intraparietal sulcus is significantly more active during OV. Comparing OW vs. FFL, results showed that superior parietal lobule, ventral parietal cortex, and primary auditory cortex are more active during OW.Conclusions Comparing CV vs. OV showed that in the OV condition, Wernicke s area, which is responsible for the comprehension of speech, is more active. This indicates that individuals try to speak more meaningfully when they are speaking out loud and they hear their voice than the time they speak with themselves. Comparing OV vs. OW condition highlights the role of intraparietal sulcus in tracking the number of items stored in memory and choosing one of them. The higher level of activation of ventral parietal cortex in OW condition vs. FFL condition is due to the importance of this region in language processing.