Effector-dependent neural representations of perceptual decisions independent of motor actions and sensory modalities.

Neuroscientific research has shown that perceptual decision-making occurs in brain regions that are associated with the required motor response. Recent functional magnetic resonance imaging (fMRI) studies that dissociated decisions from coinciding processes, such as the motor response, partly challenge this, indicating that perceptual decisions are represented in an abstract or sensory-specific manner that might vary across sensory modalities. However, comparisons across sensory modalities have been difficult since most task designs differ not only in modality but also in effectors, motor response, and level of abstraction. Here, we describe an fMRI experiment where participants compared frequencies of two sequentially presented visual flicker stimuli in a delayed match-to-comparison task, which controlled for motor responses and stimulus sequence. A whole-brain searchlight support vector machine analysis of multi voxel patterns was used to identify brain regions containing information on perceptual decisions. Furthermore, a conjunction analysis with data from an analogue vibrotactile study was conducted for a comparison between visual and tactile decision-making processes. Both analyses revealed above-chance decoding accuracies in the left dorsal premotor cortex (PMd) as well as in the left intraparietal sulcus (IPS). While previous primate and human imaging research have implicated these regions in transforming sensory information into action, our findings indicate that the IPS processes abstract decision signals while the PMd represents an effector-dependent, but motor response independent encoding of perceptual decisions that is similar across sensory domains.