**7. Gustatory imagery**

336 Neuroimaging for Clinicians – Combining Research and Practice

superior pre-central sulcus and intra-parietal sulcus areas, predominantly on the left, was

However, the fMRI approach based on "effective connectivity" between network components, defined as the influence of one neural system over another, clarified the issue of the primary motor cortex activation during motor imagery. In particular, Solodikin et al. (2004) demonstrated the connectivity between the supplementary motor area and the primary motor cortex during motor imagery. By using structural equation modelling to estimate the effective connectivity networks underlying motor execution, visual mental imagery, and kinesthetic mental imagery with specified regions of interests, Solodikin et al., (2004) showed that the inputs from the supplementary motor area and lateral–dorsal premotor cortex to the primary motor cortex had a suppressing effect during motor imagery. These results suggest a physiological mechanism encompassing the prevention of overt movements. Using Dynamic Causal Modeling, Kasess et al. (2008) confirmed that the activity of the primary motor cortex was heavily suppressed by the supplementary motor area during motor imagery, namely imagine pressing buttons on a small panel, first with the index finger, then the middle finger, and again with the index finger, as rapidly as possible. Then, by using the Granger Causality Mapping method, Chen et al. (2009) found forward and backward connectivity between the supplementary motor area and the contra-lateral primary motor cortex during both the left- and right-hand motor imagery (finger tapping sequences cued by pictures). Gao et al. (2011) extended these results revealing the influence of the brain asymmetry of right-handedness on effective connectivity networks: left dorsal pre-motor cortex, inferior parietal lobule, and superior parietal lobule were identified as

Olfactory mental images can be defined as short-term memory representations of olfactory events that give rise to the experience of smelling with the "mind's nose" (Rinck et al., 2009). However, experimental evidence about the existence of olfactory imagery is controversial given that it is not clear whether an olfactory mental image is semantically or perceptually mediated, or whether it reflects the influence of explicit knowledge of olfactory principles rather than a specific mode of operation of odour imagery (Elmes, 1998; Herz, 2000). Using fMRI, Levy et al. (1999), and Henkin & Levy (2002) found a substantial overlap in the areas activated by real and imagined stimuli (ripe banana and peppermint), although all activations were reduced in the imagery condition. However, given the lack of anatomical details, it is not possible to draw reliable conclusions from these two studies. Later, Olivetti Belardinelli et al. (2004a) found activation in the left insula, but not in the primary olfactory area, when the olfactory imagery condition was contrasted with the abstract condition. The lack of activity in the primary olfactory cortex was also observed when high-vivid participants were contrasted with low-vivid participants (Olivetti Belardinelli et al., 2009). In Olivetti et. al.'s studies, the olfactory-specific modality activations likely were not found because of the difficulty in generating vivid images of smells, especially when they are verbally cued (Herz, 2000). This is confirmed by Zelano et al. (2009), who found that remembering nameable odorants was reflected in sustained activity in prefrontal language areas, and remembering unnameable odorants was reflected in sustained activity in primary olfactory cortex. In other words, only smells dissociated from their verbal label were eligible

associated with the accuracy of the imagery task performance.

causal sources in both motor imagery and motor execution.

**6. Olfactory imagery** 

to activate the primary olfactory cortex.

Gustatory imagery refers to the ability to generate mental images of tastes. Although gustatory imagery is involved in food craving, or the "irresistible urge to consume" (Tiggemenn & Kemps, 2005), which in turn may have implications for clinical and nonclinical population, relatively little experimental research has been devoted to this imagery system. It is also uncertain whether proper gustatory mental imagery can be evoked, and to what extent images of tastes activate the primary gustatory cortex. In an fMRI study, Kobayashi et al. (2004) instructed their participants to perceive (water stimuli) and imagine several tastes (grapefruit, candy, pudding, coffee, lemon, banana, beer, sugar). Images were verbally cued by written words, by spoken language, and by using pictures. In general, results revealed that gustatory imagery can activate the primary gustatory cortex (anterior insula/frontal operuculm), especially the left side, sharing common parts of neural substrates with gustatory perception. Authors also clarified that the middle and superior frontal gyri were not activated by gustatory perception, but they participated in the generation of gustatory images, plausibly mediating the top-down control of retrieving gustatory information from the storage of long-term memories. The activation of the anterior insula and the middle frontal gyri during gustatory imagery (the spicy taste, the tart taste, etc) were confirmed also by Olivetti Belardinelli et al. (2004a) relative to an abstract condition, and by Olivetti Belardinelli et al. (2009) according to the level of vividness of participants. Finally, Kikuki et al. (2005) revealed that when participants concentrated on pickled plums (umeboshi), a traditional Japanese food with a strong and sour taste, activations were observed weakly in the right insula, but more strongly in the bilateral opercula, the bilateral orbitofrontal cortices, and the left Broca's area.
