Acoustically presented semantic decision-making tasks provide a robust depiction of the temporo-parietal speech areas

Abstract

Functional MRI (fMRI) is routinely used to depict language areas, for example in the preoperative diagnostic work-up of patients with a brain tumour. The objective of this study was to test whether semantic decision making can activate the temporo-parietal language areas better than phonological generation stimuli. Five fMRI language stimuli were tested in 20 healthy volunteers: (i) word generation to a given letter (WG); (ii) verb generation to a given noun (VG); (iii) generation of groups of words (GW); (iv) detection of a semantic violation in sentences (SV); and (v) detection of pseudowords (PW). The stimuli were presented both visually and acoustically. We used a block design and evaluated the data with SPM5 with predefined regions of interest in the frontal and temporo-parietal language areas. A lateralisation index (LI) was also calculated. We found that WG and VG achieved the best results in frontal language areas; VG, SV and PW presented acoustically achieved the best results in the temporo-parietal language areas; and that LI was most reliably calculated in the frontal language areas. An acoustically presented semantic decision making stimulus should be implemented in the preoperative diagnostic work-up to robustly depict the temporo-parietal language areas. The stimulus is easy to understand and perform, and it achieves robust results.