Decoding Parametric Grip-Force Anticipation from fMRI-Data
Previous functional magnetic resonance imaging (fMRI) studies have shown that activity in premotor and parietal brain-regions covaries with the intensity of upcoming grip-force. However, it remains unclear how information about the intended grip-force intensity is initially represented and subsequently transformed into a motor code before motor-execution. In this fMRI study, we used multivoxel pattern analysis (MVPA) to decode where and when information about grip-force intensities is parametrically coded in the brain. Human participants performed a delayed grip-force task in which one of four cued levels of grip-force intensity had to be maintained in working memory (WM) during a 9-second delay-period preceding motor execution. Using time-resolved MVPA, with a searchlight approach and support vector regression (SVR), we tested which brain regions exhibit multivariate WM codes of anticipated grip-force intensities. During an early delay-period, we observed above-chance decoding in the ventromedial prefrontal cortex (vmPFC). During a late delay-period, we found a network of action-specific brain regions, including the bilateral intraparietal sulcus (IPS), left dorsal premotor cortex (l-PMd) and supplementary motor areas (SMA). Additionally, cross-regression decoding was employed to test for temporal generalization of activation patterns between early and late delay-periods with those during cue presentation and motor execution. Cross-regression decoding indicated temporal generalization to the cue-period in the vmPFC, and to motor-execution in the l-IPS and l-PMd. Together, these findings suggest that the WM representation of grip-force intensities undergoes a transformation where the vmPFC encodes information about the intended grip-force, which is subsequently converted into a motor code in the l-IPS and l-PMd before execution.