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The common perception of Parkinson's disease is of a disorder that leads to problems with movement, tremors, involuntary spasms, and a shuffling gait. However, functional MRI has now confirmed that the disease can also cause widespread abnormalities in the sense of touch and vision for sufferers. An international team from the US and China presented their findings at the Society for Neuroscience meeting in Atlanta on October 17. Research into Parkinson's disease has previously focused mainly on the brain's motor and premotor cortex, sidestepping the somatosensory and the visual cortex because the most prominent symptoms are associated with movement and not the senses. However, neurologist Krish Sathian of Emory University and colleagues discovered through tests of tactile ability, that PD patients also have sensory problems with touch. The researchers recently designed a study using fMRI to investigate this earlier finding and to ascertain whether or not changes in the brain underly these sensory abnormalities. Sathian and colleagues studied six patients with moderately advanced PD and six age-matched healthy control volunteers. They documented the sufferers typical movement problems and ruled out dementia and nerve problems in the PD patients. They then had the PD patients and the volunteers carry out a common test of tactile ability. They asked the participants to use their fingers to distinguish the orientation of ridges and grooves on plastic gratings. While the people were carrying out the test, the researchers conducted an fMRI scan, hoping that it would reveal any significant differences between blood flow and so activation pattern between PD patients and volunteer controls while the subjects carried out the touch task. Such differences would provide insight into the brain basis of their earlier work. The fMRI scans did indeed reveal that the PD patients had much less activation of the somatosensory areas in the brain's cortex than the healthy controls. Surprisingly, however, the team also found similar widespread differences in the visual cortex, even though vision was not involved in the task. "Our finding that the visual cortex is affected in Parkinson's disease, while surprising, makes sense given that our laboratory and many others have shown previously that areas of the brain's visual cortex are intimately involved in the sense of touch," Sathian says, "Although the reasons for this are uncertain, they may involve a process of mental visualization of the tactile stimuli and may also reflect a multisensory capability of the visual cortex." The study has implications for PD sufferers and their treatment. "These problems need to be appreciated in caring for these patients and in designing newer strategies for treatment and rehabilitation," Sathian emphasizes. The study has implications for PD sufferers and their treatment, as the problems with sensation can affect how they obtain information about objects in the environment, and also how they use them. "These problems need to be appreciated in caring for these patients and in designing newer strategies for treatment and rehabilitation," Sathian emphasizes. Related links:
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Sathian and colleagues found PD has wider effects |
