The relation between monosynaptic spinal reflex amplitudes and some EEG alpha activity parameters

Abstract

Some investigators have found that in normal human subjects the amplitudes of repetitively evoked tendon reflexes decrease as the number of evoked reflexes progresses. The question whether this decrement is a spinal phenomenon or that it can be ascribed to supraspinal influences that are related to the degree of cortical activation was investigated in two experiments designed to test whether a relation exists between the Hoffmann (H) and Achilles tendon (T) reflex amplitudes and EEG alpha activity parameters during a rest condition. The principal results can be summarized as follows: 1. 1. A constant alpha index was accompanied by stable reflex amplitudes. 2. 2. A decreasing alpha index was accompanied by decreasing reflex amplitudes. 3. 3. A positive relation was found between H. and T reflex amplitudes. 4. 4. A positive relation was found beween alpha index and alpha amplitude. 5. 5. No circumscribed relation was found between the alpha wave period on the one side and the alpha index and amplitude on the other side. Apparently these relations are dependent on the state of activation of the subject. 6. 6. The relations between the reflex amplitudes and the alpha parameters showed great interindividual differences. © 1976.