Psychophysiological Interaction Analysis

In Newman. SD, et al., (2013) participant’s characteristics including age, gender, education, occupation is described. None of the participants had neurological disorder. Also, participants ‘consent to do experiments on them was gotten and approved by the Indiana University Institutional Review Board. According to Newman. SD, et al., (2013) this study is a combination of three different studies with overlapping stimuli. Each study was composed of three sessions, training, imaging and debriefing sessions. In the training session, all participants were given a Reading Span Test in order to measure their working memory capacity. Meanwhile, they were introduced to sentence comprehension experiment and were asked to complete 16 practice trials to get familiar with

the experimental process. Soon after fMRI scan, they were asked to complete a debriefing questionnaire in order to determine how they carry out a task as well as their perception of difficulty. The single trial used in Newman. SD, et al., (2013) was event-related design in which trial was treated as an event block. The trial itself composed of two phases; a sentence reading phase and a responding to a comprehension probe phase. The required time for each trial was estimated as 16sec. Each experiment was made of four runs. So, in Newman. SD, et al., (2013) the methodology is fully clarified. In Newman. SD, et al., (2013) fMRI was taken by TRIO scanner but before statistical analysis of the images, conventional preprocessing procedures were conducted using SPM8 software. Then, conventional statistical inference was performed on the normalized functional images from each individual by using the general linear model and Gaussian random field theory (Friston et al. 1995). By the use of SPM8, multiple regression analysis was performed for sentence and probe phases. Furthermore, functional connectivity between regions that were influenced by working memory capacity in comprehension process was analyzed.

Psychophysiological interactions analysis (PPI) was performed to examine whether individuals with varying working memory have different activity in brain regions. After that, partial correlation analysis was done on each pair of regions using mean signal intensity. According to Newman. SD, et al., (2013) the limitations of this study are related to default network and the use of a language comprehension task with three processing phases. No particular ethical considerations arose except for five participants who were excluded from this analysis due not having a complete dataset. In Chantel S. Prat & Marcel Adam Just (2013); however, the number of participants who took part in this study were 27 right-handed individuals including 15 male and 12 female. The participants age ranged between 18-25. Let it not remain unsaid that, 7 more participants were tested but they weren’t included in the analysis. According to Chantel S. Prat & Marcel Adam Just (2013) 60sentences were presented to participants under three different working memory conditions to test information

recognition. The three conditions were No Load, Low load, and High Load in each of the above mentioned memory load condition, participants were instructed to read sentences of different length and asked to create a mental picture of the same length they read. In Chantel S. Prat & Marcel Adam Just (2013) behavioral testing and fMRI practice sessions were administered before scanning participants for 1 or 2 days. Then, the Reading Span Test (Daneman and Carpenter 1980), the Nelson-Denny Reading Test (Riverside Publishing Company), and the Edinburgh Handedness Inventory (Oldfield 1971) were administered. Next, they had time to practice the model with sample stimuli inside a mock scanner. The instruments and procedure s which used to analyze collected data in Chantel S. Prat & Marcel Adam Just (2013) were adequately described. No ethical consideration arose in relation to the methodology since their contentment was gotten before the trial.