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The level of activity in this reticular formation reflects an individual’s general state of arousal. Artificial over-stimulation of the entire area does not result in limb-flailing or the exaggeration of particular gestures; instead, it causes a stiffened tetany in all the muscles of the body simultaneously. Everything locks rigidly into place and cannot be moved until stimulation recedes. Conversely, blocking stimulation from reaching the whole area results in a general loss of muscle tone throughout the body, as in our anaesthetized patient. That is, activity in this area as a whole does not command our muscles to produce any particular gesture or assume any particular posture. Rather, general activity here provides the conditions of general muscle tone, sensory awareness, and mental alertness which will support and color whatever postures and gestures are made. The reticular formation cannot issue the command “raise right arm,” but it does help to establish the trembling tension, the calm readiness, or the sluggishness which will characterize how I raise my arm in response to a situation. To direct these general levels of arousal into particular movements requires the next level of the “old” brain, the basal ganglia—the highest level of sensory and motor organization of the gamma motor system.
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