A study developed at CIMA of the University of Navarra and published in the scientific journal Neuroimage sample the brain areas activated in a sensory perception test. In the presence of certain tactile and auditory stimuli, the most immediate or automatic responses of the person examined produce an activation of the so-called Putamen. This brain nucleus, which regulates muscle tone and associated and automatic movements such as typing, is affected at the onset of Parkinson's disease. Therefore, the results of the study could help in earlier diagnosis. The authors are Dr. Maria A. Pastor, a neurologist at the research center Applied Medicine (CIMA) of the University of Navarra and the University Clinic, together with scientists from the Institute of Neurology of University College London.

Dr. Pastor explains that, if a healthy person receives two stimuli in a row -skin contacts, auditory signals or the switching on of a light-, he or she perceives them as separate signals or as simultaneous, if they are very close together. If the time interval is very large or very small, the subject's perception is clearer and, therefore, his response more certain. Between these two extremes the perceptions are inaccurate. By presenting these stimuli within the scanner, by means of functional magnetic resonance imaging, it is possible to visualize which brain areas are involved in this perception subject .

60 to 40 frames per second

According to the neurologist at CIMA and the University Clinic, Parkinson's patients need a longer interval between two stimuli to be sure that they are separate signals: "For example, a normal movie has about 60 frames per second. If we reduce the frequency of emission, it would be choppy. A Parkinson's patient does not perceive this difference and is able to see the film without flickering in the image at up to 40 frames per second. 

The results now published in Neuroimage reveal that it is the posterior area of the Putamen area of the brain that is linearly related to presentations of greater certainty: very short intervals in which one signal is grade or long intervals in which two signals are noted. "This test will help us to evaluate the onset of Parkinson's disease," concludes María A. Pastor.