Dynamic Premotor-to-Parietal Interactions during Spatial Imagery

Abstract

The neurobiological processes underlying mental imagery are a matter of debate and controversy among neuroscientists, cognitive psychologists, philosophers, and biologists. Recent neuroimaging studies demonstrated that the execution of mental imagery activates large frontoparietal and occipitotemporal networks in the human brain. These previous imaging studies, however, neglected the crucial interplay within and across the widely distributed cortical networks of activated brain regions. Here, we combined time-resolved eventrelated functional magnetic resonance imaging with analyses of interactions between brain regions (functional and effective brain connectivity) to unravel the premotor-parietal dynamics underlying spatial imagery. Participants had to sequentially construct and spatially transform a mental visual object based on either verbal or visual instructions. By concurrently accounting for the full spatiotemporal pattern of brain activity and network connectivity, we functionally segregated an early from a late premotor-parietal imagery network. Moreover, we revealed that the modality-specific information upcoming from sensory brain regions is first sent to the premotor cortex and then to the medial-dorsal parietal cortex, i.e., top-down from the motor to the perceptual pole during spatial imagery. Importantly, we demonstrate that the premotor cortex serves as the central relay station, projecting to parietal cortex at two functionally distinct stages during spatial imagery. Our approach enabled us to disentangle the multicomponential cognitive construct of mental imagery into its different cognitive subelements. We discuss and explicitly assign these mental subprocesses to each of the revealed effective brain connectivity networks and present an integrative neurobiological model of spatial imagery.

Dynamic interactions of the cortical networks during thought suppression

“…2004; Sack et al. 2008). However, the local peaks of our IC23 were located in the Sylvian fissure, outside of the brain parenchyma, and the time course presented an excessive high‐frequency noise level (low LFPR) that is conceivable even after the grand averaging (Fig.…”

“…2002; Sack et al. 2008). A similar argument applies to another low‐LFPR component, IC18, which is Imagery‐related and centered at the BA45 bilaterally.…”

Foreseeing the future: Occurrence probability of imagined future events modulates hippocampal activation

“…Activation in only one region was positively modulated by event probability, i.e., the right superior parietal lobule (BA 7; see Fig. 3e), which is involved in mental imagery and multisensory integration (Calvert and Thesen, 2004;Sack et al, 2008). Imagination of more probable events presumably elicited more multimodal details that converge in superior parietal lobule during event construction.…”

Optimizing ICA in fMRI using information on spatial regularities of the sources

“…We furthermore considered a time-resolved fMRI experiment involving a complex mental imagery task [31]. Since complex tasks normally involve the activation of networks of brain regions with different HRFs, the use of a conventional hypothesis-driven method -assuming a spatially invariant model of the HRF -may not be optimal.…”

“…In the "auditory" condition of the experimental paradigm from Sack et al [31], subjects were asked to build up simple geometrical figures based on a sequence of auditory instructions. They were subsequently presented a target figure and asked, after performing mental rotation, whether the imagined and target figures were identical or mirror symmetric versions of each other.…”