Decoding Parametric Grip‐Force Anticipation From fMRI Data

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Abstract
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‐s delay‐period preceding motor execution. Using time‐resolved MVPA with a searchlight approach and support vector regression, we tested which brain regions exhibit multivariate WM codes of anticipated grip‐force intensities. During the early delay period, we observed above‐chance decoding in the ventromedial prefrontal cortex (vmPFC). During the 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. 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.
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