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. 2005 Mar;3(3):e79.
doi: 10.1371/journal.pbio.0030079. Epub 2005 Feb 22.

Grasping the Intentions of Others With One's Own Mirror Neuron System

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Free PMC article

Grasping the Intentions of Others With One's Own Mirror Neuron System

Marco Iacoboni et al. PLoS Biol. .
Free PMC article

Abstract

Understanding the intentions of others while watching their actions is a fundamental building block of social behavior. The neural and functional mechanisms underlying this ability are still poorly understood. To investigate these mechanisms we used functional magnetic resonance imaging. Twenty-three subjects watched three kinds of stimuli: grasping hand actions without a context, context only (scenes containing objects), and grasping hand actions performed in two different contexts. In the latter condition the context suggested the intention associated with the grasping action (either drinking or cleaning). Actions embedded in contexts, compared with the other two conditions, yielded a significant signal increase in the posterior part of the inferior frontal gyrus and the adjacent sector of the ventral premotor cortex where hand actions are represented. Thus, premotor mirror neuron areas-areas active during the execution and the observation of an action-previously thought to be involved only in action recognition are actually also involved in understanding the intentions of others. To ascribe an intention is to infer a forthcoming new goal, and this is an operation that the motor system does automatically.

Figures

Figure 1
Figure 1. Six Images Taken from the Context, Action, and Intention Clips
The images are organized in three columns and two rows. Each column corresponds to one of the experimental conditions. From left to right: Context, Action, and Intention. In the Context condition there were two types of clips, a “before tea” context (upper row) and an “after tea” context (lower row). In the Action condition two types of grips were displayed an equal number of times, a whole-hand prehension (upper row) and a precision grip (lower row). In the Intention condition there were two types of contexts surrounding a grasping action. The “before tea” context suggested the intention of drinking (upper row), and the “after tea” context suggested the intention of cleaning (lower row). Whole-hand prehension (displayed in the upper row of the Intention column) and precision grip (displayed in the lower row of the Intention column) were presented an equal number of times in the “drinking” Intention clip and the “cleaning” Intention clip.
Figure 2
Figure 2. Areas of Increased Signal for the Three Experimental Conditions
Threshold of Z = 2.3 at voxel level and a cluster level corrected for the whole brain at p < 0.05.
Figure 3
Figure 3. Signal Increases for Intention minus Action and Intention minus Context
Threshold of Z = 2.3 at voxel level and a cluster level corrected for the whole brain at p < 0.05. The black arrow indicates the only area showing signal increase in both comparisons. The area is located in the dorsal sector of pars opercularis, where mirror activity has been repeatedly observed [10,11,12,13,14,15,16,17,18,19,20,27]. See Tables S1 and S2 for coordinates of local maxima.
Figure 4
Figure 4. Time Series of the Inferior Frontal Area Showing Increased Signal in the Comparisons Intention minus Action and Intention minus Context
The drinking Intention condition yielded a much stronger response than the cleaning Intention condition (p < 0.003), whereas no reliable difference was observed between the drinking and cleaning Context conditions (p > 0.19). The time series represents the average activity for all subjects in all voxels reaching statistical threshold in the right inferior frontal cortex.
Figure 5
Figure 5. Significant Signal Changes in Subjects Receiving Explicit Instructions Compared to Subjects Receiving Implicit Instructions in the Three Tasks Versus Rest
Threshold of Z = 2.3 at voxel level and a cluster level corrected for the whole brain at p < 0.05. The two black arrows indicate two foci of activity in dorsal premotor cortex that are located deep in the sulci and thus not easily visible on the three-dimensional surface rendering. See Tables S3–S5 for coordinates of local maxima.

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