Brice, H. 1 & Frost, R. 1, 2, 3
1 The Hebrew University of Jerusalem
2 The Basque Center on Brain and Language
3 Haskins Laboratories
In this study we aimed to examine the neurobiological underpinning of processing regularities in the visual modality for linguistic vs. non-linguistic stimuli. Participants were scanned using fMRI while processing streams of abstract shapes vs. printed syllables. The stimuli were presented either in structured sequences, composed of repeating triplets of stimuli, or in a random order.
For both shapes and printed syllables greater activation was found for structured over random streams in the anterior cingulate gyri, the bilateral parahippocampal gyri, and the bilateral cuneus. This activation reflects domain-general computations of regularities. However, for the printed syllables, we found increased activation for structured over random sequences also in the left insula and the bilateral middle occipital and parahippocampal gyri, spreading into the fusiform gyri. This suggests that processing structure of linguistic stimuli calls on a wider network than processing regularities in non-linguistic stimuli such as abstract visual shapes, reflecting patterns of domain-specificity in SL.
Additionally, the left inferior frontal gyrus (IFG) revealed greater activation for random linguistic stimuli over structured linguistic sequences. Since activation in the left IFG is associated with effortful linguistic processing, this suggests that regularities in the sequence were picked up, resulting in reduced effort in processing predictable stimuli.
Our findings provide evidence for joint domain-general and domain-specific computations while processing regularities. We interpret these differences in the processing of linguistic and non-linguistic structure as a reflection of the importance of existing representations on the computation of statistical regularities. In a nutshell, our findings demonstrate that in addition to the domain-general mechanisms, the networks recruited for processing a given input such as print are also recruited for processing statistical regularities in that input.