Percentage of overlapping between each of the 66 pairs of muscles.

<p>Percentage of overlapping between each of the 66 pairs of muscles.</p

Inter-position comparison of co-activation and covariation measures (obtained from the right hemisphere) between pairs of muscles belonging to three different districts (hand, forearm, arm).

<p>Inter-position comparison of co-activation and covariation measures (obtained from the right hemisphere) between pairs of muscles belonging to three different districts (hand, forearm, arm).</p

Inter-hemispheric comparison of co-activation and covariation measures (obtained with hand in prone position) between pairs of muscles belonging to three different districts (hand, forearm, arm).

<p>Inter-hemispheric comparison of co-activation and covariation measures (obtained with hand in prone position) between pairs of muscles belonging to three different districts (hand, forearm, arm).</p

Experimental setting and electrode positioning for simultaneous MEP recordings from the examined muscles.

<p>Experimental setting and electrode positioning for simultaneous MEP recordings from the examined muscles.</p

TMS-MRI integration: number of co-activated muscles for each scalp position in a paradigmatic subject.

<p>TMS-MRI integration: number of co-activated muscles for each scalp position in a paradigmatic subject.</p

Results of Experiment 1.

<p>Mean percent changes of log-transformed MEP amplitude from hand muscles (FDI and ADM) versus the control condition Basal (the 100% reference line). The condition “Neutral” (N) was similar to Basal. Sniffing unimodal olfactory (O), bimodal olfacto-gustative (OG), and natural odorants as <i>coffee</i> and <i>mortadella</i> increased MEPs' size. Such facilitation of corticospinal output disappeared when sniffing odorants with a trigeminal component (OT and OTG, grey area). Notably, no cognitive tasks except sniffing are required to subjects. Statistics are in the text.</p

Results of Experiment 3.

<p>Mean percentual changes of MEP amplitude versus “<i>Basal</i>” in the FDI muscle, which was prime mover for the observed grasping action, and in the ADM muscle which has no functional role in grasping. Only the congruency between the odour of <i>bombolone</i> with the observation of grasping a <i>bombolone,</i> but not other food or non-food objects, produced a significant increase of MEP size, which selectively took place in the prime mover. No changes are observed in the ADM muscle. Statistics are in the text.</p

Results of Experiment 2 (only food objects).

<p>Graphical representations of the main significant interactions: a) an higher MEP increase occurred in FDI than in ADM when the subjects observed a grasping movement; b) similarly, an higher MEP increase occurred in FDI than in ADM when the subjects smelled a food; c) even if “smelling” produces a lower MEP increase with, than without, concomitant grasping observation, a significant further facilitation (27% in the original µV scale) was found.</p

Results of Experiment 2 (Food vs Soap).

<p>Graphical representations of the main significant interactions: a) an higher MEP increase occurred when the subjects observed a grasping movement toward a food object than toward a non-food object; b) an higher MEP increase occurred when the subjects smelled a food object than a non-food object</p

Experimental designs.

<p>Panel a): The two hand muscle from which motor evoked potentials (MEPs) were recorded. Panel b): Experiment 2. Here, the four food or non-food objects were separately presented. Within each of these main conditions, subjects were asked to observe the grasping (with or without the corresponding odour) or to simply smell the object without observing food or soap. “Salame” is the Italian name of salami, “Mortadella” represents the English term “balony”, and “Bombolone” is the Italian word to define something like a custard filled donut. Panel c): Experiment 3. Here, the four objects were simultaneously presented. The subjects smelled a single odorant (i.e.,<i>bombolone</i>), while observing the experimenter reaching and grasping three edible objects (one of which was <i>bombolone</i>) or a non-edible object of a similar shape (soap).</p