Brain potentials related to voluntary sustained effort.
The task of the present study was the investigation of the brain potentials while performing a complex motor task, including voluntary sustained contraction (thumb opposition to the index finger). The fast press of a transducer was sustained for periods of 1.5, 5 or 10 seconds, followed by fast release. Potentials related to the start of the contraction were registered (Bereitschaftspotential, N2, etc.) with considerable interindividual variability. The end of the contraction was preceded, too, by a slow potential, similar to Bereitschaftspotential, with prevailing positivity over frontal areas and negativity over postcentral areas; N2 at the release was well expressed, regardless of the polarity of the preceding slow potential. During the sustained contraction a steady positivity was registered. The presence of potentials related to the start as well as to the end of the voluntary effort suggests the existence of two separate commands. The positivity sustained throughout the contraction, strongly expressed frontally and decreasing postcentrally, implies a decisive role for central processes including the organization and preprogramming of the motor task, but not direct reflection of feedback kinaesthetic afferentation.
D000200:Action Potentials; D001921:Brain / Q000502:physiology*; D004569:Electroencephalography; D004576:Electromyography; D006801:Humans; D009119:Muscle Contraction; D005082:Physical Exertion; D013997:Time Factors