**8. Proprioceptive imagery**

Proprioceptive processing is part of the haptic system. In particular, proprioceptive imagery involves the ability to generate organic images based on body sensations, such as the

How fMRI Technology Contributes to the Advancement of Research in Mental Imagery: A Review 339

ensure that the acoustic scanner noise did not lead to interferences with the auditory perception and imagery conditions, the primary auditory cortex was not activated (Bunzeck et al., 2005). This pattern of results shows that when imaging environmental sounds the topdown process is initiated mostly by the inferior frontal gyrus and insular regions, and

Still, the fMRI literature on musical imagery, with the exception of Kraemer et al. (2005), showed no activation of the primary auditory cortex, even when enrolling musicians. Given the pattern of activation yielded by musical imagery, an associative network independent of primary sensory-motor and auditory activity is likely representing the cortical elements most intimately linked to music production. In addition, considering that both amateurs and professional musicians did not report any activation in the primary auditory cortex, and that motor areas were not recruited, either, during musical imagery involving mental performances, it is highly probable that these areas become tightly coupled with executed activities during musical training. Finally, given that musical imagery in professional musicians revealed more anterior cerebellar activations, it is possible to conclude that musical imagery involves the recruitment of stored movement programs of sequential finger

The extent to which the primary motor cortex is involved in motor imagery remains unclear. However, recent fMRI studies have highlighted the importance of the supplementary motor area, which seems to be involved in suppressing the activity of the primary motor cortex, and consequently, movements that are not intended to be performed. This would mean that

Regarding olfactory imagery, fMRI results are in line with behavioral findings: if images of smells are cued by verbal labels it is hard to detect the activation of the primary olfactory cortex. On the contrary, if odors are perceptually encoded, it is possible to find activation in the piriform cortex when generating images of smells. However, the activity in the olfactory primary cortex was found to be modulated by the hedonic pattern of stimuli to be imagined, and by expertise in generating or using olfactory images. This means that olfactory imagery may activate olfactory areas under specific conditions, basically when people really evoke

The literature on gustatory, tactile, and proprioceptive imagery is more consistent. All three of these modalities seem to rely on the primary sensory cortices. Nevertheless, given the scarcity of studies carried out on these imagery systems, especially on the proprioceptive

In conclusion, fMRI technique has helped to clarify the neural circuits of mental imagery, but a lot a work needs to be still done. For example, the role of certain cortical areas remains unclear, as does the connectivity among cortices in mental imagery. Research is trying to clarify this issue in respect to the motor imagery modality, but it should also be addressed in respect to the others. It is also important to explore the common cortical networks involved in all imagery modalities to clarify the extent to which mental imagery relies on non-sensory cortices. Indirectly, this information would contribute to improve our understanding of the imagery debate, as having access to the common areas shared by all imagery modalities provides an understanding of the extent to which imagery involves propositional encoding. Currently, only Olivetti Belardinelli et al. (2001, 2004b) have attempted to investigate this issue. Though there has been some difference in terms of anatomical extension, results revealed that the generation of images in all sensory modalities activated the left inferior temporal cortex (including the left fusiform gyrus) and the bilateral inferior parietal lobule.

motor imagery and motor execution do not rely on the same neural network.

manages to activate only secondary auditory areas.

movements (Lotze et al., 2003).

images of smells.

imagery, any conclusion would be premature.

sensations of hungry, thirsty, cold, drunkenness, etc. Very few fMRI studies were devoted to proprioceptive imagery. Olivetti Belardinelli et al. (2004a) did not show any activation of the primary somatosensory cortex during proprioceptive imagery, whereas Olivetti Belardinelli et al. (2009) revealed that high vivid participants activated the right post-central gyrus (BA 2/3) during proprioceptive imagery in comparison with low-vivid participants.
