Baselines for Fmri Studies of Language

Newman, Sharlene

Abstract

The use of imaging techniques to observe brain function is a relatively new research area, so variations in methodology (e.g., choice of baseline, and task instructions) may account for discrepancies observed in results between studies. This variation in methodology make it difficult to draw reliable, consistent conclusions across studies. If we are to gain greater insight into brain/behavior relationships, then these methodological inconsistencies should be addressed. The goal of this study is to develop a sound experimental protocol to be used in future studies of language processing, particularly phonological processing. Therefore, the proposed research attempts to 1) determine which baseline procedure produces the most stable activation pattern, 2) determine whether the discrepancies in the results across studies is partially attributed to differences in the baseline procedures employed, 3) determine if the two tasks used to examine phonological processing (phoneme discrimination and phoneme monitoring) activate similar brain areas implying that they require the use of similar aspects of phonological processing, 4) determine if areas with functional specificity are affected by the addition of cognitive processes, and 5) determine whether areas of decreased signal intensity are correlated to areas of increased signal intensity implying that suppression (a decrease in oxygen consumption not inhibition) of some areas may be necessary in order for other areas to be active. Also, the majority of the functional studies previously performed used PET to obtain image data. The current study will use a 4.1T magnetic resonance system to perform imaging. The 4.1T MR system allows for much better signal to noise ratio (SNR) as well as improved spatial and temporal resolution compared to both PET and conventional 1.5T systems. Improvements in resolution and SNR provide the opportunity to obtain a clearer picture of brain activation than possible with other imaging systems thereby, improving the ability to differentiate between activation created during the activation task and the baseline task.