A multimodal investigation of matching mechanisms in automatic imitation

In recent years, research on imitation focused on investigating the underlying neural mechanisms; to this aim simple paradigms were developed to experimentally investigate the phenomenon. Following the natural tendency of humans to mimic gestures and postures of their conspecifics, paradigms of automatic imitation are nowadays widely used in the field. The main aim of my dissertation is to investigate how imitation occurs using an automatic imitation paradigm, in particular focusing on the matching processes that are required to map model and performers actions.The dissertation contains six chapters. In chapter 1, I will provide a brief background of the current theoretical accounts of imitation and of the concepts of automatic imitation and compatibility effects. I will particularly focus on the questions concerning automatic imitation that are still to be fully addressed, particularly those related to the distinction of imitative and spatial compatibility. I will also address the neuroimaging and neuropsychological literature on the neural correlates of imitation. In chapter 2, I will present a neuroimaging study I carried out to investigate the imitation components. Throughout all the studies of this thesis, we used a simple automatic imitation paradigm that is suitable to differentiate between the spatial compatibility and the imitative compatibility, due to the anatomical correspondence between model and performer. Results of the first study showed that the parietal opercula are active anytime the anatomical correspondence between model and performer is present. Hence, in chapter 3 I will present a study in which double-pulse TMS was used to investigate the role of the parietal opercula in automatic imitation, and in particular in coding the imitative compatibility. Results showed that when the activity in the parietal opercula is interfered by TMS, the imitative compatibility effect disappears. In the second part of my thesis I have investigated the factors that can interact with and modulate imitative behaviors. Chapter 4 contains an fMRI study in which the role of the model in imitation is investigated. Using a simplified version of the automatic imitation paradigm, I found that the fronto-parietal network, usually associated to imitation, is more active when participants perform actions that are compatible with those performed by a human model than by a non biological model. Moreover, in this study I have also investigated how different emotional contexts can influence the automatic tendency to imitate. The results showed that the activation of the fronto-parietal network is suppressed by emotional context, such as an angry face, that does not promote affiliative tendencies. In chapter 5 I will describe a neuropsychological study on brain damaged patients. Associations and dissociations between automatic imitation and action imitation were investigated, to analyze the differences between the two types of imitation. Moreover, the role of putative body representations in imitation and whether these body representations are needed for imitation has been investigated. Lastly, in chapter 6 I will wrap up the main results of my dissertation and I will argue that I was able to provide evidence that in automatic imitation an anatomical matching operates between the model and the performer, and that this is sustained by the parietal opercula. In addition I clarified the importance of the model, showing that the activity of fronto-parietal regions supporting imitative behaviors is modulated by model identity

Selective imitation impairments differentially interact with language processing

Whether motor and linguistic representations of actions share common neural structures has recently been the focus of an animated debate in cognitive neuroscience. Group studies with brain-damaged patients reported association patterns of praxic and linguistic deficits whereas single case studies documented double dissociations between the correct execution of gestures and their comprehension in verbal contexts. When the relationship between language and imitation was investigated, each ability was analysed as a unique process without distinguishing between possible subprocesses. However, recent cognitive models can be successfully used to account for these inconsistencies in the extant literature. In the present study, in 57 patients with left brain damage, we tested whether a deficit at imitating either meaningful or meaningless gestures differentially impinges on three distinct linguistic abilities (comprehension, naming and repetition). Based on the dual-pathway models, we predicted that praxic and linguistic performance would be associated when meaningful gestures are processed, and would dissociate for meaningless gestures. We used partial correlations to assess the association between patients' scores while accounting for potential confounding effects of aspecific factors such age, education and lesion size. We found that imitation of meaningful gestures significantly correlated with patients' performance on naming and repetition (but not on comprehension). This was not the case for the imitation of meaningless gestures. Moreover, voxel-based lesion-symptom mapping analysis revealed that damage to the angular gyrus specifically affected imitation of meaningless gestures, independent of patients' performance on linguistic tests. Instead, damage to the supramarginal gyrus affected not only imitation of meaningful gestures, but also patients' performance on naming and repetition. Our findings clarify the apparent conflict between associations and dissociations patterns previously observed in neuropsychological studies, and suggest that motor experience and language can interact when the two domains conceptually overla

Methods in cognitive neuroscience

The workshop aims at providing an overview of the different methodologies and techniques commonly used in cognitive neuroscience experiments. The methodologies described will include neuroimaging (e.g., functional MRI and EEG), neurostimulation/neuromodulation techniques (e.g., transcranial magnetic stimulation), and computational modeling for the analysis of behavior.For each methodology I will provide a general introduction of the basic mechanisms with particular focus in clarifying how these techniques can be applied to understand the connection between brain functioning and cognitive processes. In addition, I will present examples of recent studies using these methodologies to show how they can be effectively used to unveil the functioning of cognitive processes and their neural correlates

Anatomical and spatial matching in imitation: Evidence from left and right brain-damaged patients.

Imitation is a sensorimotor process whereby the visual information present in the model's movement has to be coupled with the activation of the motor system in the observer. This also implies that greater the similarity between the seen and the produced movement, the easier it will be to execute the movement, a process also known as ideomotor compatibility. Two components can influence the degree of similarity between two movements: the anatomical and the spatial component. The anatomical component is present when the model and imitator move the same body part (e.g., the right hand) while the spatial component is present when the movement of the model and that of the imitator occur at the same spatial position. Imitation can be achieved by relying on both components, but typically the model's and imitator's movements are matched either anatomically or spatially. The aim of this study was to ascertain the contribution of the left and right hemisphere to the imitation accomplished either with anatomical or spatial matching (or with both). Patients with unilateral left and right brain damage performed an ideomotor task and a gesture imitation task. Lesions in the left and right hemispheres gave rise to different performance deficits. Patients with lesions in the left hemisphere showed impaired imitation when anatomical matching was required, and patients with lesions in the right hemisphere showed impaired imitation when spatial matching was required. Lesion analysis further revealed a differential involvement of left and right hemispheric regions, such as the parietal opercula, in supporting imitation in the ideomotor task. Similarly, gesture imitation seemed to rely on different regions in the left and right hemisphere, such as parietal regions in the left hemisphere and premotor, somatosensory and subcortical regions in the right hemisphere

Combined TMS-fMRI Reveals Behavior-Dependent Network Effects of Right Temporoparietal Junction Neurostimulation in an Attentional Belief Updating Task

Updating beliefs after unexpected events is fundamental for an optimal adaptation to the environment. Previous findings suggested a causal involvement of the right temporoparietal junction (rTPJ) in belief updating in an attention task. We combined offline continuous theta-burst stimulation (cTBS) over rTPJ with functional magnetic resonance imaging (fMRI) to investigate local and remote stimulation effects within the attention and salience networks. In a sham-controlled, within-subject crossover design, 25 participants performed an attentional cueing task during fMRI with true or false information about cue predictability. By estimating learning rates from response times, we characterized participants’ belief updating. Model-derived cue predictability entered the fMRI analysis as a parametric regressor to identify the neural correlates of updating. rTPJ-cTBS effects showed high interindividual variability. The expected learning rate reduction with false cue predictability information by cTBS was only observed in participants showing higher updating in false than in true blocks after sham. cTBS modulated the neural signatures of belief updating, both in rTPJ and in nodes of the attention and salience networks. The interindividual variability of the behavioral cTBS effect was related to differential activity and rTPJ connectivity of the right anterior insula. These results demonstrate a crucial interaction between ventral attention and salience networks for belief updating

Resting-state Functional Connectivity of the Right Temporoparietal Junction Relates to Belief Updating and Reorienting during Spatial Attention

Although multiple studies characterized the resting-state functional connectivity (rsFC) of the right temporoparietal junction (rTPJ), little is known about the link between rTPJ rsFC and cognitive functions. Given a putative involvement of rTPJ in both reorienting of attention and the updating of probabilistic beliefs, this study characterized the relationship between rsFC of rTPJ with dorsal and ventral attention systems and these two cognitive processes. Twenty-three healthy young participants performed a modified location-cueing paradigm with true and false prior information about the percentage of cue validity to assess belief updating and attentional reorienting. Resting-state fMRI was recorded before and after the task. Seed-based correlation analysis was employed, and correlations of each behavioral parameter with rsFC before the task, as well as with changes in rsFC after the task, were assessed in an ROI-based approach. Weaker rsFC between rTPJ and right intraparietal sulcus before the task was associated with relatively faster updating of the belief that the cue will be valid after false prior information. Moreover, relatively faster belief updating, as well as faster reorienting, were related to an increase in the interhemispheric rsFC between rTPJ and left TPJ after the task. These findings are in line with task-based connectivity studies on related attentional functions and extend results from stroke patients demonstrating the importance of interhemispheric parietal interactions for behavioral performance. The present results not only highlight the essential role of parietal rsFC for attentional functions but also suggest that cognitive processing during a task changes connectivity patterns in a performance-dependent manner

Lateralization, functional specialization, and dysfunction of attentional networks

The present review covers the latest findings on the lateralization of the dorsal and ventral attention systems, their functional specialization, and their clinical relevance for stroke-induced attentional dysfunction. First, the original assumption of a bilateral dorsal system for top-down attention and a right-lateralized ventral system for stimulus-driven attention is critically reviewed. The evidence for the involvement of the left parietal cortex in attentional functions is discussed and findings on putative pathways linking the dorsal and ventral network are presented. In the second part of the review, we focus on the different attentional subsystems and their lateralization, discussing the differences between spatial, feature- and object-based attention, and motor attention. We also review studies based on predictive coding frameworks of attentional functions. Finally, in the third section, we provide an overview of the consequences of specific disruption within the attention networks after stroke. The role of the interhemispheric (im)balance is discussed, and the results of new promising therapeutic approaches employing brain stimulation techniques such as transcranial magnetic stimulation (TMS) or transcranial direct current stimulation (tDCS) are presented. (C) 2020 Elsevier Ltd. All rights reserved