Neural correlates of action perception

When observing others we usually do not require a verbal explanation to understand what they are doing and, in many cases, why they are doing it. Specific brain regions are involved in the processing of observed actions and some of them belong to the motor system, which is mainly involved in the planning and production of movements. Intensive research of these regions suggests, that the same neurons are active during action observation and execution. It has been proposed that these neurons, so called mirror neurons, allow the simulation of observed actions in a person’s motor system. This simulation may help to understand the actions of others. This theory of motor simulation is an intriguing way to explain certain aspects of action perception, as learning by observation, but many questions remain, some of which have been addressed in this thesis

The role of the theory of mind network in action observation - an rTMS study

Understanding the actions of other people is a crucial skill to function in a social environment. When observing actions, one can understand implied goals and mental-states. The mirror neuron system (MNS) plays an important role in action understanding by internal simulation of the observed movements. This simulation process may be sufficient to decipher thoughts and intentions incorporated in an action. However, a more abstract mentalizing network may be necessary to efficiently process these inner states. In a recent fMRI study, we demonstrated that nodes of the theory-of-mind network (ToM) are activated when participants observe hesitations conveyed in hand movements. However, activation of a brain region does not the imply its necessity to perform the given task. Therefore, we designed a repetitive TMS study using the same experimental paradigm. On three experimental days, participants received 15 minutes of 1-Hz inhibitory rTMS stimulation, either on a MNS node (PF in the inferior parietal lobe), a ToM node (temporo-parietal junction (TPJ)), or a control region (vertex). After the stimulation, the participants performed three tasks: judging the size of a chosen object based on hand aperture, judging the level of hesitation and a control task. The first hypothesis was that a virtual lesion of PF would impair the performance in the hand aperture and hesitation task because they require the analysis of movement nuances. The second hypothesis was that a virtual lesion of the TPJ would influence the performance on the hesitation task only, because it requires inference about a mental state (confidence of choice). As predicted, we observed increased response latencies on the hand aperture task following the PF stimulation and increased response latencies on the hesitation task following both PF and TPJ stimulation. These results suggest that the TPJ is necessary to efficiently decipher mental states encoded in hand actions

Esophageal dysfunction in different stages of Parkinson's disease

BACKGROUND: Dysphagia is a clinically relevant symptom in patients with Parkinson's disease (PD) leading to pronounced reduction in quality of life and other severe complications. Parkinson's disease-related dysphagia may affect the oral and pharyngeal, as well as the esophageal phase of swallowing. METHODS: To examine the nature and extend of esophageal dysphagia in different stages of PD and their relation to oropharyngeal dysfunction, we examined 65 PD patients (mean age 66.3±9.7 years, mean disease duration 7.9±5.8 years, mean Hoehn & Yahr [H&Y] stage 2.89±0.91) and divided into three groups (early [H&Y I+II; n=21], intermediate [H&Y III; n=25], and advanced stadium [H&Y IV+V; n=19]), using esophageal high-resolution manometry (HRM) to detect esophageal motor disorders. Oropharyngeal impairment was assessed using fiberoptic endoscopic evaluation of swallowing. KEY RESULTS: Major esophageal motor disorders were detected in nearly one third of the PD patients. Minor impairment of the esophageal body was present in 95% of participants and throughout all disease stages with pathological findings especially in peristalsis and intrabolus pressure (IBP). The IBP was found to significantly increase in the advanced stadium. Although dysfunction of the upper and lower esophageal sphincters was observed in individual patients, alterations in these esophageal segments revealed no statistical significance compared with normative data. No clear association was found between the occurrence of oropharyngeal dysphagia and esophageal impairment. CONCLUSIONS & INFERENCES: Esophageal body impairment in PD is a frequent phenomenon during all disease stages, which possibly reflects α-synucleinopathy in the enteric nervous system

Assessment of the capability to target cerebellar sub-regions with high-definition transcranial direct current stimulation High-Definition transcranial Direct Current Stimulation:High-Definition transcranial Direct current stimulation (HD-tDCS) over the cerebellum

The increasing interest in the application of tDCS over different cerebral regions has induced increasing efforts into the optimization of specific electrodes montages to selectively target the desired volumes. In order to increase the stimulation focusing, High-Definition (HD) tDCS electrodes have been proposed and their efficacy was firstly assessed by computational methods. In this paper, we optimized the deployment of HD-TDCS bipolar electrodes montages designed to target three different neural clusters in the cerebellum. The assessment of the electric field generated by and the focusing capability of the montages was evaluated through computational techniques on an anatomical high-definition head model. Results show the possibility to reach even deep target in the cerebellum with an electric field able to induce neuromodulation, while in parallel limiting its field distribution spread.</p