Focal Dystonia of the Hand, And What the Brain Has To Do With It :: Biology Essays Research Papers

Focal Dystonia of the Hand, And What the Brain Has To Do With It The body is complicated, and often the origins of a condition are all but obvious. Focal dystonia of the hand is one disorder whose underlying cause has been found in the more recent past. Although it can be genetic (1), the form of focal dystonia of the hand I look at here is caused by environmental factors (2). Focal dystonia of the hand is a condition characterized by a loss in motor control of one or more fingers. A single muscle or group of muscles is involved: muscles in the hand and forearm tense and tighten, with the result of making the hand (or part of it) curl (2). Musicians who have intensively practiced their instruments over a number of years are a group most affected by this condition. The reason is that focal dystonia can be caused by the repetitive movement of the fingers over a significant period of time. The condition was long known as "occupational hand cramp." (3). It can easily be misdiagnosed as simple overuse or stress of the hand (1). Although it may not be obvious at first sight of the symptoms, the level at which the problem is caused is not the hand, but the brain. Researchers at the University of Konstanz report "overlap or smearing of the homuncular organization of the representation of the digits in the primary somatosensory cortex" (3). Given that functions such as motor control cross over from the right side of the body to be represented in the left hemisphere, they found that the distance between the representations of individual fingers was smaller in the somatosensory cortex side corresponding to the hand that had undergone continued repetitious training (the left hand in case of violin players for example). What does all this mean in terms of the brain? Looking at the central nervous system as an input-output system, in very simple terms we can observe that a specific input is presented over and over again - in this case the stimulation of the fingers that play the violin - and as a result the organization within the box changes. More specifically, there is a one-to-one correspondence between input and internal representations of this input: all fingers are individually represented on the somatosensory cortex. But somehow, as these regions of representation begin to smear or overlap, the one-to-one correspondence is blurred.