F tacheodispersion.

F tacheodispersion is defined as the distribution of the conduction velocities of individual or small groups of nerve fibres estimated from significant numbers of consecutively recorded F waves. The ulnar and peroneal nerves in 18 healthy subjects were studied using this method and histograms of motor fibre conduction velocities for the control nerves were created. F tacheodispersion was applied in nine patients with neuropathies and radiculopathies selected on the basis that at least one nerve was 'normal' as measured by conventional techniques (M response, F wave minimum latency to height). In the patient group it was demonstrated that a significant proportion of motor nerve fibres had F tacheodispersion conduction velocities below normal limits despite normal conventional findings. It is concluded that F tacheodispersion should be considered in routine neurophysiological investigation when conventional methods had failed to reveal a suspected nerve lesion.     

Tony Cragg versus F.X. Messerschmidt

Ohne Zusammenfassung     

B. F. Skinner and the cognitive revolution.

The behaviorism that cognitive scientists attack is a caricature, drawn primarily from the more polemical writings of J. B. Watson and B. F. Skinner. In this brief commentary, I discuss the fact that these writings, and especially Skinner's, offered the neocognitivists such a polar difference from their own position, that it was easier to ignore the distinction between behaviorism and neobehaviorism than to recognize it. I point out that there are factors in Skinner's intellectual history that may account for the emergence of his more radical behaviorism out of what was essentially his own theoretical, neobehavioristic approach to the study of conditioning and learning.     

F waves and motor unit size.

M responses and twitch contractions were evoked in single motor units (MUs) of the first dorsal interosseus muscle by intramuscular microstimulation of motor axons. Two-hundred nine MUs were studied in 21 subjects. Thirty-five MUs (17%) showed F waves in addition to M responses. Twitch force was used to provide an indirect measure of MU size; additionally, twitch contraction time was measured. There was no select group of MUs generating F waves with regard to the above contraction parameters. However, four of five MUs with very high twitch forces, above 70 mN, generated F waves. We conclude that MUs of all sizes produce F waves with similar probability. Only few MUs with very strong twitch forces, i.e., very large MUs, may be more subject to F-wave production and may be involved in the generation of the so-called repeater F waves.