Imitative Response Tendencies Research Articles

Automatic imitation in youngsters with Gilles de la Tourette syndrome: A behavioral study

ABSTRACT It is widely known that humans have a tendency to imitate each other and that appropriate modulation of automatic imitative behaviors has a crucial function in social interactions. Gilles de la Tourette syndrome (GTS) is a childhood-onset neuropsychiatric disorder characterized by motor and phonic tics. Apart from tics, patients with GTS are often reported to show an abnormal tendency to automatically imitate others’ behaviors (i.e., echophenomena), which may be related to a failure in top-down inhibition of imitative response tendencies. The aim of the current study is to explore the top-down inhibitory mechanisms on automatic imitative behaviors in youngsters with GTS. Error rates and reaction times from 32 participants with GTS and 32 controls were collected in response to an automatic imitation task assessing the influence of observed movements displayed in the first-person perspective on congruent and incongruent motor responses. Results showed that participants with GTS had higher error rates than controls, and their responses were faster than those of controls in incompatible stimuli. Our findings provide novel evidence of a key difference between youngsters with GTS and typically developing participants in the ability to effectively control the production of own motor responses to sensory inputs deriving from observed actions.

Imitation in one's own presence: No specific effect of self-focus on imitation

Previous studies have reported that imitative responses may be modulated by top-down social factors such as self-focus. However, growing evidence suggests that such social factors may actually modulate domain-general processes such as spatially compatible responding, rather than specifically social processes such as imitation. In this study, we aimed to identify the cognitive processes being modulated under conditions of heightened or diminished self-focus. Participants performed a stimulus-response compatibility task which independently measures both spatial and imitative response tendencies, under two conditions: heightened self-focus, where the task was performed in the presence of two mirrors; and diminished self-focus, where the mirrors were covered. While participants were faster to respond to compatible trials than to incompatible trials, both imitatively and spatially, there was no significant modulation of either spatial or imitative compatibility by self-focus; although the magnitude of the modulation of spatial compatibility was numerically similar to the effect of self-focus on imitation found in previous studies. These results provide no evidence for an effect of self-focus on either social-specific, or domain-general, processes.

The Role of the Temporoparietal Junction in Self-Other Distinction.

Being able to discriminate between what originates from ourselves and what originates from others is critical for efficient interactions with our social environment. However, it remains an open question whether self-other distinction is a domain-general mechanism that is involved in various social-cognitive functions or whether specific 'self-other distinction mechanisms' exist for each of these functions. On the neural level, there is evidence that self-other distinction is related to a specific brain region at the border of the superior temporal and inferior parietal cortex, the temporoparietal junction (TPJ). Demonstrating that the TPJ plays a role in social processes that require self-other distinction would support the idea of a domain-general mechanism of self-other distinction. In the present paper, we review evidence coming from clinical observations, neuroimaging experiments and a meta-analysis indicating the involvement of the TPJ in various cognitive operations requiring self-other distinction. At the perceptual level, we discuss the human ability to identify one's own body and to distinguish it from others. At the action level, we review research on the human ability to experience agency and the control of imitative response tendencies. Finally, at the mental-state level, we discuss the ability to attribute mental states to others. Based on this integrative review, we suggest that the TPJ, and in particular its dorsal part, supports a domain general ability to enhance task-relevant representations when self-related and other-related representations are in conflict. Finally, this conception allows us to propose a unifying architecture for the emergence of numerous socio-cognitive abilities.

Tics as a model of over-learned behavior-imitation and inhibition of facial tics.

Tics are the defining feature in Tourette syndrome and can be triggered by watching tics or single voluntary movements. This automatic imitation of movements referred to as "echopraxia" has been ascribed to a failure in top-down inhibition of imitative response tendencies. Alternatively, it could be interpreted in the context of automatic overlearned behavior. To this end, we investigated 18 Tourette patients aged 28.22 years (9.44 standard deviation; 16 male) and 24 healthy controls (mean age 29.21 years [9.1 standard deviation]; 17 male) using an adapted version of an action-interference paradigm. Patients were asked to respond to 2 different auditory tones with either a facial movement that was part of their tic repertoire (tic-like movement), or a facial movement that was not (nontic movement). Simultaneously, behaviorally irrelevant videos of the 2 same facial movements were presented, which were either compatible or incompatible with the movement executed by the patient. Movements in healthy controls were matched to those in the patients. Healthy participants responded faster in compatible than in incompatible trials. Tourette patients showed the same effect for nontic movements. However, their responses were equally fast in incompatible and compatible trials when the movement they were asked to execute was a tic-like movement. Error rates did not differ between the groups. The results suggest that tic-like movements do not occur as a consequence of a failure to inhibit motor output. Instead, tics might be considered highly overlearned behavior that can be triggered without interference by external, incompatible movement stimuli. © 2016 International Parkinson and Movement Disorder Society.

The controlled imitation task: a new paradigm for studying self-other control

In the automatic imitation task (AIT) participants make a cued response during simultaneous exposure to a congruent or incongruent action made by another agent. Participants are slower to make the cued response on incongruent trials, which is thought to reflect conflict between the motor representation activated by the cue and the motor representation activated by the observed action. On incongruent trials, good performance requires the capacity to suppress the imitative action, in favor of producing the cued response. Here, we introduce a new experimental paradigm that complements the AIT, and is therefore a useful task for studying the control of self and other activated representations. In what we term the “Controlled Imitation Task (CIT)”, participants are cued to make an action, but on 50% of trials, within 100 ms of this cue, an on-screen hand makes a congruent or incongruent action. If the onscreen hand moves, the participant must suppress the cued response, and instead imitate the observed action as quickly and accurately as possible. In direct contrast to the AIT, the CIT requires suppression of a self-activated motor representation, and prioritization of an imitative response. In experiment 1, we report a robust pattern of interference effects in the CIT, such that participants are slower to make the imitative response on incongruent compared to congruent trials. In experiment 2, we replicate this effect while including a non-imitative spatial-cue control condition to show that the effect is particularly robust for imitative response tendencies per se. Owing to the essentially opposite control requirements of the CIT versus the AIT (i.e., suppression of self-activated motor representations instead of suppression of other-activated motor representations), we propose that this new task is a potentially informative complementary paradigm to the AIT that can be used in studies of self-other control processes.

Inhibition of imitative behaviour and social cognition.

There is converging evidence that the observation of an action activates a corresponding motor representation in the observer through a 'mirror-matching' mechanism. However, research on such 'shared representations' of perception and action has widely neglected the question of how we can distinguish our own motor intentions from externally triggered motor representations. By investigating the inhibition of imitative response tendencies, as an index for the control of shared representations, we can show that self-other distinction plays a fundamental role in the control of shared representations. Furthermore, we demonstrate that overlapping brain activations can be found in the anterior fronto-median cortex (aFMC) and the temporo-parietal junction (TPJ) area for the control of shared representations and complex social-cognitive tasks, such as mental state attribution. In a functional magnetic resonance imaging experiment, we functionally dissociate the roles of TPJ and aFMC during the control of shared representations. Finally, we propose a hypothesis stating that the control of shared representations might be the missing link between functions of the mirror system and mental state attribution.

Diffuse axonal injury due to traumatic brain injury alters inhibition of imitative response tendencies

It is well known that traumatic brain injury particularly affects the frontal lobes. Consequently, patients often suffer from executive dysfunction and behavioral disturbances. Accordingly, our study aimed at investigating patients after traumatic brain injury with two tasks involving different functional processes and structural networks supported by the frontal lobes. Two paradigms were applied: the Stroop color-word task and a task in which subjects had to inhibit imitative response tendencies. We selected a patient group solely with diffuse axonal injury, as this type of injury is homogenous and is correlated with cognitive dysfunction more than focal contusions. To evaluate long-term effects most relevant for rehabilitation, we selected a patient group whose brain injuries dated back several years. Our results show that patients with diffuse axonal injury inhibited imitative responses more successfully than control subjects, whereas executive processes examined with the Stroop task were unaltered. Interestingly, impairments were tightly correlated both with the length of the post-traumatic amnesia predicting outcome in traumatic brain injury and with behavioral disturbances. Impairments in the imitation-inhibition task may indicate alterations in an anterior frontomedian neural network even years after traumatic brain injury.

Imitative response tendencies following observation of intransitive actions.

Clear and unequivocal evidence shows that observation of object affordances or transitive actions facilitates the activation of a compatible response. By contrast, the evidence showing response facilitation following observation of intransitive actions is less conclusive because automatic imitation and spatial compatibility have been confounded. Three experiments tested whether observation of a finger movement (i.e., an intransitive action) in a choice reaction-time task facilitates the corresponding finger movement response because of imitation, a common spatial code, or some combination of both factors. The priming effects of a spatial and an imitative stimulus were tested in combination (Experiment 1), in opposition (Experiment 2), and independently (Experiment 3). Contrary to previous findings, the evidence revealed significant contributions from both automatic imitation and spatial compatibility, but the priming effects from an automatic tendency to imitate declined significantly across a block of trials whereas the effects of spatial compatibility remained constant or increased slightly. These differential effects suggest that priming associated with automatic imitation is mediated by a different regime than priming associated with spatial compatibility.

The inhibition of imitative and overlearned responses: a functional double dissociation

Neuropsychological research has established that the inhibition of dominant response tendencies is a function of the prefrontal cortex. These inhibitory mechanisms are tested using tasks like the Stroop task, in which the prepotency of the dominant response is based on a learned relationship of stimulus and response. However, it has also been reported that patients with prefrontal lesions may have problems inhibiting imitative responses. The question arises of whether the inhibition of overlearned and imitative responses entails the same or different functional mechanisms and cortical networks. In a recent neuropsychological study with prefrontal patients we found first evidence for such a dissociation. The present fMRI study further investigated this question by directly comparing brain activity in the inhibition of overlearned and imitative response tendencies. It emerges that response inhibition in the two tasks involves different neural networks. While the inhibition of overlearned responses requires a fronto-parietal network involved in interference control and task management, the inhibition of imitative responses involves cortical areas that are required to distinguish between self-generated and externally triggered motor representations. The only frontal brain area that showed an overlap was located in the right inferior frontal gyrus and is probably related to the generation of the stop signal.

The Inhibition of Imitative Response Tendencies

Recent neurocognitive studies show that perception and execution of actions are intimately linked. The mere observation of an action seems to evoke a tendency to execute that action. Since such imitative response tendencies are not adaptive in many everyday situations imitative response tendencies usually have to be inhibited. These inhibitory processes have never been investigated using brain imaging techniques. Former work on response inhibition and interference control has focused on paradigms such as the Stroop task or the go/no-go task. We have carried out an event-related functional magnetic resonance imaging study in order to investigate the cortical mechanisms underlying the inhibition of imitative responses. The experiment employs a simple response task in which subjects were instructed to execute predefined finger movements (tapping or lifting of the index finger) in response to an observed congruent or incongruent finger movement (tapping or lifting). A comparison of brain activation in incongruent and congruent trials revealed strong activation in the dorsolateral prefrontal cortex (middle frontal gyrus) and activation in the right frontopolar cortex and the right anterior parietal cortex, as well as in the precuneus. These results support the assumption of prefrontal involvement in response inhibition and extend this assumption to a “new” class of prepotent responses, namely, to imitative actions.