Objective: There is growing evidence that a mirror system for action observation exists. Neurons in the monkey premotor cortex discharge with performance of goal directed actions and also with observation of another individual performing a similar action. This mirror neuron system for action observation seems to be important for the recognition and understanding of actions. Recently, bimodal neurons, sensitive both for tactile stimulation and for visual stimuli, were found in the parietal cortex. This suggests the idea that there might be a similar mirror neuron system for observing and receiving (or experiencing) tactile stimulation. The neuronal correlates of observing tactile stimulation are mainly unknown. The purpose of this protocol is to determine the pattern of brain activation related to the observation of a tactile stimulated hand. Study Population: We will test our hypothesis by means of a functional MRI (fMRI) experiment in a group of healthy subjects. Design: We hypothesize that observation of touch will rely on the activation of a cortical network that is different form the observation of non-touch and is in part overlapping with cortical structures active during real tactile stimulation (i.e., somatosensory cortex). Further, we hypothesize that the observation of touch enhances activation in the somatosensory cortex during real tactile stimulation. Outcome Measures: Our outcome measure will be an increase in the number of activated voxels in the somatosensory cortex during the touch observation (for both hypothesis). This would give an important hint for a mirror system for observed and received touch. A mirror neuron system for observed touch may become an important tool in rehabilitative treatment for patients with somatosensory impairments.
- INCLUSION CRITERIA: Only healthy right-handed volunteers aged 18 to 75 years who fulfill the inclusion criteria will be included in this protocol. Subjects should be able to sustain attention to the task over 10 minutes. All volunteers should have no history of neurological and psychiatric illness. EXCLUSION CRITERIA: Volunteers with history of severe alcohol or drug abuse, psychiatric illness like severe depression, poor motivational capacity, or severe language disturbances, particularly of receptive nature or with serious cognitive deficits (defined as equivalent to a mini-mental state exam score of 23 or less). Volunteers with severe uncontrolled medical problems (e.g. cardiovascular disease, severe rheumatoid arthritis, active joint deformity of arthritic origin, active cancer or renal disease, any kind of end-stage pulmonary or cardiovascular disease, or a deteriorated condition due to age, uncontrolled epilepsy or others). Volunteers with increased intracranial pressure (as evaluated by clinical examination). Volunteers with unstable cardiac arrhythmia. Volunteers with history of hyperthyroidism or individuals receiving drugs acting primarily on the central nervous system. Volunteers with more than moderate to severe microangiopathy (as assessed by multiple peri-ventricular T2 hyperintensity on the pre-experimental anatomical MRI), polyneuropathy (as assessed by clinical examination), diabetes mellitus (medical record), or ischemic peripheral disease (as assessed by clinical examination). Volunteers who are on medication with the potential to influence nervous system function, who have a history of surgery with metallic implants or a known history of metallic particles in the eye, a cardiac pacemaker, intracardiac lines, neural stimulators, cochlear implants. Volunteers who are pregnant. Volunteers with significant visual loss/deficits. Volunteers with MRI contraindications. Volunteers with impaired sensation or neuropathy of the hand.