The interplay of cue modality and response latency in brain areas supporting crossmodal motor preparation: an event-related fMRI study

Crossmodal (auditory, visual) motor facilitation can be defined as a cue in one sensory modality eliciting speeded responses to targets in a different sensory modality. We used event-related functional magnetic resonance imaging (fMRI) to isolate brain activity underlying crossmodal motor preparation. Our predictions were that interactions between input modality and processes underlying response selection would be indexed by distinct spatiotemporal brain dynamics. A crossmodal response selection task was designed in which a central, nonspatial cue indicated the response rule (compatible or incompatible) to a lateralized target. Cues and targets appeared in auditory and visual modalities and were separated by a lengthy delay period in which cue-related brain activity could be dissociated. We found faster reaction times to auditory compared with visual cues. Next, we correlated brain activity with behavioural performance using multivariate spatiotemporal partial least squares. We identified a distinct, significant brain-behaviour pattern in which faster reaction times to auditory cues were correlated with higher blood oxygenation level-dependent percent signal change in medial visual, frontoparietal (inferior parietal lobule, superior frontal gyrus and premotor cortex) and subcortical (thalamus and cerebellum) areas. For visual cues, quicker responses were linked to greater activity in the same frontoparietal and subcortical but not medial visual areas. Our results show that both modality-dependent and modality-independent brain areas with different brain-behaviour relationships are implicated in crossmodal motor preparation.