The lateralized readiness potential and response kinetics in response-timetasks

Previous studies have found that the magnitude of the lateralized readiness potential (LRP) at the time of response initiation is constant across spon taneous variations iri. response time in both cued and uncued, speeded task s. Other studies have found that the LRP is also unaffected by instructed c hanges in peak response force and time to peak force in cued, self-paced ta sks, but that the LRP is sensitive to instructed changes in force gain rate in uncued, self-paced tasks. The present study examined the LRP in an uncu ed, speeded task as a function of response time and several measures of res ponse kinetics. The magnitude of the LRP at the time of electromyographic o nset was constant across spontaneous variations in all measures. The peak o f the contingent negative variation did vary as a function of peak response force and integrated force to peak, but not response time. These findings support the idea that the LRP in speeded tasks is a selective, on-line inde x of the preparation associated with using a particular hand, and is not an index of the elements of motor programming that determine subsequent respo nse kinetics.