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Continuous Theta Burst Stimulation of the Posterior Medial Frontal Cortex to Experimentally Reduce Ideological Threat Responses

Decades of behavioral science research have documented functional shifts in attitudes and ideological adherence in response to various challenges, but ...

University of California, Los Angeles

The posterior parietal cortex is a fundamental structure for visuo-motor integration and control. Here I discuss recent transcranial magnetic stimulation (TMS) and functional magnetic resonance imaging (fMRI) studies that I interpret as suggesting four concepts. The evolutionary process has enlarged the human posterior parietal cortex while still preserving the internal structure of the posterior parietal cortex of other primates. Visuo-motor control in the posterior parietal cortex may be implemented by coding primarily action goals. The lateralization of visuo-motor functions in the posterior parietal cortex suggests that the left posterior parietal cortex is more concerned with tool use and the right posterior parietal cortex is more concerned with imitation of the actions of others. Finally, visuo-motor inter-hemispheric transfer through parietal callosal fibers occurs at the level of 'motor intention'.

Visuo-motor integration and control in the human posterior parietal cortex: evidence from TMS and fMRI.

The discovery of premotor and parietal cells known as mirror neurons in the macaque brain that fire not only when the animal is in action, but also when it observes others carrying out the same actions provides a plausible neurophysiological mechanism for a variety of important social behaviours, from imitation to empathy. Recent data also show that dysfunction of the mirror neuron system in humans might be a core deficit in autism, a socially isolating condition. Here, we review the neurophysiology of the mirror neuron system and its role in social cognition and discuss the clinical implications of mirror neuron dysfunction.

The mirror neuron system and the consequences of its dysfunction.

Recent research on the neurobiology of imitation has gone beyond the study of its 'core' mechanisms, focus of investigation of the past years.. The current trends can be grouped into four main categories: (1) non 'core' neural mechanisms that are also important for imitation; (2) mechanisms of control, in both imitative learning and inhibition of imitation; (3) the developmental trajectory of neural mechanisms of imitation and their relation with the development of social cognition; (4) neurobiological mechanisms of imitation in non-primates, in particular vocal learning in songbirds, and their relations with similar mechanisms of vocal learning in humans. The existing data suggest that both perceptual and motor aspects of imitation follow organizing principles that originally belonged to the motor system.

Neurobiology of imitation.

Giacomo Rizzolatti, Stanislas Dehaene, and Trevor Robbins were recently awarded the 2014 Grete Lundbeck European Brain Research Prize for their 'pioneering research on higher brain mechanisms underpinning such complex human functions as literacy, numeracy, motivated behavior and social cognition, and for their effort to understand cognitive and behavioral disorders'. Why was their work highlighted? Is there anything that links together these seemingly disparate lines of research? 

The Brain Prize 2014: complex human functions.

Increasing contextual interference (CI) during practice benefits learning, making it a desirable difficulty. For example, interleaved practice (IP) of motor sequences is generally more difficult than repetitive practice (RP) during practice but leads to better learning. Here we investigated whether CI in practice modulated resting-state functional connectivity during consolidation. 26 healthy adults (11 men/15 women, age = 23.3 ± 1.3 years) practiced two sets of three sequences in an IP or RP condition over 2 days, followed by a retention test on Day 5 to evaluate learning. On each practice day, functional magnetic resonance imaging (fMRI) data were acquired during practice and also in a resting state immediately after practice. The resting-state fMRI data were processed using independent component analysis (ICA) followed by functional connectivity analysis, showing that IP on Day 1 led to greater resting connectivity than RP between the left premotor cortex and left dorsolateral prefrontal cortex (DLPFC), bilateral posterior cingulate cortices, and bilateral inferior parietal lobules. Moreover, greater resting connectivity after IP than RP on Day 1, between the left premotor cortex and the hippocampus, amygdala, putamen, and thalamus on the right, and the cerebellum, was associated with better learning following IP. Mediation analysis further showed that the association between enhanced resting premotor-hippocampal connectivity on Day 1 and better retention performance following IP was mediated by greater task-related functional activation during IP on Day 2. Our findings suggest that the benefit of CI to motor learning is likely through enhanced resting premotor connectivity during the early phase of consolidation.

Article	Year
Visuo-motor integration and control in the human posterior parietal cortex: evidence from TMS and fMRI. Neuropsychologia\| PubMed ID: 16759673	2006
The mirror neuron system and the consequences of its dysfunction. Nature reviews. Neuroscience\| PubMed ID: 17115076	2006
Neurobiology of imitation. Current opinion in neurobiology\| PubMed ID: 19896362	2009
The Brain Prize 2014: complex human functions. Trends in neurosciences\| PubMed ID: 25303794	2014
Contextual interference enhances motor learning through increased resting brain connectivity during memory consolidation. NeuroImage\| PubMed ID: 29966717	2018

Marco Iacoboni

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