Brain Stimul
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Empathic responses to facial cues are a main social competency. Both appraisal processes (facial emotion detection) and self-perceived empathy (empathic responsiveness) in response to emotional faces are thought to be related to empathic behavior, although no systematic analysis has been performed to assess their relationship. ⋯ The ability to monitor emotional cues and the behavioral empathic responsiveness to emotional situations was shown to be partially compromised in the case of frontal activity disruption, highlighting the main role of the sensorimotor system for empathic social skills.
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Neuromodulatory techniques, such as transcranial magnetic stimulation (TMS) and transcranial direct current stimulation (tDCS), have been increasingly studied as possible treatments for many neurological and psychiatric disorders. tDCS is capable of inducing changes in regional cerebral blood flow in both cortical and subcortical structures, as shown by positron emission tomography studies, and might conceivably affect hypothalamic and autonomic nervous system functions. However, it remains unknown whether acute changes in autonomic or hypothalamic functions may be triggered by conventional tDCS protocols. ⋯ The changes in hand temperature and cortisol levels, having occurred in both the sham and experimental groups, probably reflect a non-specific stress response to a new procedure. There were no significant changes in autonomic functions, ventilation rate or core body temperature that can be attributed to conventional tDCS applied to healthy volunteers.
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Comparative Study
Differences in the experience of active and sham transcranial direct current stimulation.
A limited number of studies have shown that modulation of cortical excitability using transcranial direct current stimulation (tDCS) is safe and tolerable. Few have directly evaluated whether sham and active stimulation are indistinguishable. ⋯ TDCS is a safe well-tolerated technique with no evidence of risk for serious adverse effects. Sensory side effects are common, but the severity is typically low. Because sensory side effects are more frequent and more severe in active compared with sham tDCS, the current method of sham stimulation may not be an adequate control condition for some studies.
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Transcranial direct current stimulation (tDCS) is able to modify cortical excitability and activity in humans. ⋯ Cathodal tDCS of the primary sensory cortex significantly reduced the sensitivity to Aδ-fiber-mediated cold sensation, C-fiber-mediated warm sensation was reduced only compared with baseline, whereas Aß-fiber-mediated somatosensory inputs were less affected. Our results correspond with our previous observations of primary motor cortex tDCS effects on QST parameters.
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Repetitive transcranial magnetic stimulation (rTMS) of motor and prefrontal cortex has been shown to modulate pain perception. Even though evidence suggests an involvement of cerebellar structures in pain processing, the effect of rTMS over the cerebellum on pain perception has not yet been investigated. ⋯ Our findings suggest that changes in sensory perception after rTMS over the cerebellum are largely due to stimulation effects on peripheral structures and support recent reports of analgesic effects of neck rMS. They advocate the critical review of the proposed analgesic effects of rTMS and encourage the future use of proper control conditions in rTMS research.