Implications of Stimulation Modality and Control Condition on BOLD Response: An Example From the MOUS Dataset

The choice of control conditions can significantly influence the outcomes of functional MRI (fMRI) studies. Moreover, especially in language experiments, the sensory modality (auditory, visual) of stimuli might have an influence on experimental results. In this study we leverage a repository dataset (Mother of Unification Studies; MOUS), to systematically investigate the influence of control condition and stimulation modality on fMRI results during sentence processing. Here, we explored fMRI data of 187 subjects that underwent sentence comprehension with either auditory or visual task presentation (reading or listening). Sentences were either complex, including a relative clause, or simple, not including a relative clause. Control conditions were randomly scrambled words as constructed out of the latter sentence conditions. While auditory stimulation resulted in strong activation changes in the bilateral auditory cortices, visual stimulation revealed stronger activation changes in the anterior temporal lobe if compared to simple and complex words, but not simple sentences. A direct comparison between the auditory and visual modality revealed stronger involvement of the primary auditory cortices for auditory stimulation and left inferior frontal gyrus for visual stimulation over all four conditions (complex sentences, simple sentences, complex words, simple words). The results of this study suggest that stimulation modality and control condition strongly influence sentence processing fMRI results. Future fMRI studies should bear this in mind for study planning.