A Study of Optimal SOAmin for Motor and Language Tasks in Event-related fMRl using Stochastic Design

ABSTRACT

PURPOSE: The minimum stimulus onset asynchronoy(SOAmin) is one of important experimental parameters for an event-related fMRl experiment designed with the stochastic stimulus. In this study, the most efficient SOAmin is explored for the stronger activation in motor and language tasks with the stimulus designed stochastically. MATERIALS AND METHODS: The event-related fMRl during motor and language tasks were obtained in four normal right-handed subjects. EPI-BOLD sequence is used at 1.5 Tesla MR system for the acquisition of event-related fMRl. For each task the subjects are responded for the stimulus' with 2, 3, 4, and 6 seconds SOAmin. The obtained images are processed with SPM99, and the p value is set as 0.05 for the significant activation detection. The Z value and the number of activated pixels are compared for each task. RESULTS: For the motor task, the primary and supplementary motor areas are activated, and for the language task the consistent activated signals are detected in the Broca's. The activated signal is to be stronger for the shorter SOAmin for both motor and language tasks. At primary motor area, the activated signals is the strongest for 3 seconds SOAmin and for the supplementary motor area the result with 2 seconds SOAmin shows the strongest activation. And the result of language task shows the strongest activation at the 2 seconds SOAmin. CONCLUSION: In the event-related fMRl of motor and language tasks with the stochastically designed stimulus, the 2 or 3 seconds SOAmin is efficient for more activated and clustered activation.