Spatial imagery is more associated with unfamiliar than familiar haptic shape perception: Activation and connectivity analyses

We have proposed that haptic activation of the visually shape-selective lateral occipital complex (LOC) reflects a model of multisensory object representation in which the role of visual imagery is modulated by object familiarity (Lacey et al., 2009). Supporting this, a visual object imagery task produced more correlations of activation magnitude and more similar patterns of effective connectivity with haptic perception of familiar (fHS) than unfamiliar (uHS) shapes (Deshpande et al., 2010; Lacey et al., 2010). Here, we hypothesize that visual spatial imagery (spIMG) would evoke activation and effective connectivity patterns more related to uHS than fHS. Participants ( n = 12 ) performed spIMG, uHS and fHS tasks in two fMRI sessions. Conjunction analyses showed numerous parietal cortical foci common to both uHS and spIMG. Conjunction foci for fHS and spIMG involved multiple subcortical regions but also included some parietal foci. Activation magnitudes were correlated between spIMG and both fHs and uHS, with parietal foci featuring in each. The 2D correlation between the spIMG and uHS effective connectivity networks was significant and positive, including paths between the intraparietal sulcus (IPS) and bilateral LOC, as predicted by our model, and between IPS and primary somatosensory cortex. By contrast, the spIMG and fHS networks were non-significantly correlated. Thus, although the activation analyses suggested involvement of spatial imagery in haptic shape perception regardless of object familiarity, the effective connectivity analyses were consistent with our proposed model, supporting a stronger relation between spatial imagery and haptic perception of unfamiliar compared to familiar shapes.