Controlling automatic imitative tendencies: Interactions between mirror neuron and cognitive control systems

Abstract

Humans have an automatic tendency to imitate others. Although several regions commonly observed in social tasks have been shown to be involved in imitation control, there is little work exploring how these regions interact with one another. We used fMRI and dynamic causal modeling to identify imitation-specific control mechanisms and examine functional interactions between regions. Participants performed a pre-specified action (lifting their index or middle finger) in response to videos depicting the same two actions (biological cues) or dots moving with similar trajectories (non-biological cues). On congruent trials, the stimulus and response were similar (e.g. index finger response to index finger or left side dot stimulus), while on incongruent trials the stimulus and response were dissimilar (e.g. index finger response to middle finger or right side dot stimulus). Reaction times were slower on incongruent compared to congruent trials for both biological and non-biological stimuli, replicating previous findings that suggest the automatic imitative or spatially compatible (congruent) response must be controlled on incongruent trials. Neural correlates of the congruency effects were different depending on the cue type. The medial prefrontal cortex, anterior cingulate, inferior frontal gyrus pars opercularis (IFGpo) and the left anterior insula were involved specifically in controlling imitation. In addition, the IFGpo was also more active for biological compared to non-biological stimuli, suggesting the region represents the frontal node of the human mirror neuron system (MNS). Effective connectivity analysis exploring the interactions between these regions, suggests a role for the mPFC and ACC in imitative conflict detection and the anterior insula in conflict resolution processes, which may occur through interactions with the frontal node of the MNS. We suggest an extension of the previous models of imitation control involving interactions between imitation-specific and general cognitive control mechanisms.

Visual Perception of Incomplete Human-Like Body Postures: A Near-Infrared Spectroscopy Study

“…Thus, the posterior part of the inferior frontal gyrus seems to be activated when participants attended to the biological characters (humanlike appearance) of the pseudo-postures, but might be normally under inhibitory control. One of the most promising brain regions, which pertain to the inhibitory control of motoric embodiment, is the prefrontal cortex, i.e., the anterior part of inferior frontal gyrus [10] [16] and/or anterior insula [19]. This prefrontal control network could suppress the MNS activity in response to the degree of the configural similarity between observed objects and human body postures stored as conceptual knowledge.…”

“…On the other hand, in the occipital region, we found significant main effects of the ease of picture-naming in channels 13, 15, 20, 21, and 24 (F(1, 13) = 6.00, p < 0.05; F(1, 13) = 6.37, p < 0.05; F(1, 13) = 5.99, p < 0.05; F(1, 13) = 4.87, p < 0.05; F(1, 13) = 9.63, p < 0.01, respectively), and significant interactions between the picture-naming condition and period in channels 13,15,16,20,22,23, and 24 (F(10, 130) = 2.09, p < 0.05; F(10, 130) = 2.25, p < 0.05; F(10, 130) = 2.34, p < 0.05; F(10, 130) = 2.00, p < 0.05; F(10, 130) = 2.07, p < 0.05; F(10, 130) = 3.00, p < 0.01; F(10, 130) = 3.46, p < 0.01, respectively). Post-hoc comparisons using Shaffer's modified Bonferroni correction revealed that these interactions were due to the large responses under the easy condition as compared to those under the difficult condition during the period from target-presentation to confidence-judgment (p < 0.05).…”

“…We presumed that the channels 13,15,16,20,21,22,23, and 24 roughly cover the occipital lobe. The results in the novel contour shape condition showed that the occipital visual cortex is activated during the observation of easy-to-name shapes.…”

“…The activities in human MNS are modulated by the degree of intervention from other brain regions that have some higher-order cognitive functions, such as the cognitive control that inhibits unwanted behavior [15] [16]. For example, Cross et al [16] investigated the interactions between the cognitive control and mirror neuron systems by using an "imitation-inhibition task" in which participants have to execute their index or middle finger movement, respectively, in response to the observed congruent (i.e., the same) or incongruent (i.e., the different) finger movement of a video-taped hand. In the incongruent trials, the stimulus and response were dissimilar.…”

“…This conflict yielded more activation in the prefrontal neural network, specifically in the anterior insula associated with cognitive control system. Cross et al [16] suggested that anterior insula suppresses the automatic activity in MNS in response to the observed incongruent actions.…”