The amplitude transition function and the manual and oculomotor control systems.

This article discusses the updating of visuospatial information during the preparation and execution of rapid manual and oculomotor movements. Responses in a double-step target tracking situation are investigated. Both the manual and the oculomotor literature concur on the principle of an amplitude transition function (ATF), which specifies the relationship between the amplitude of the first tracking response and the delay between the occurrence of the second target step and the commencement of the first response. However, different principles underlie the ATF across the two systems. The oculomotor ATF is determined by the temporal integration of the input signals such that the amended amplitude is specified in the initial efferent command. The manual ATF reflects the interaction of parallel programmed responses such that the initial response amplitude is amended after the efferent command is released. The accuracy of a corrective response is discussed in terms of efference copy and mass-spring notions. (PsycINFO Database Record (c) 2010 APA, all rights reserved)     

Effects of task variables on the amplitude and phase-locking of auditory gamma band responses in human

The present study was designed to assess the effects of stimulus certainty and motor task-relevance on auditory transient 40-Hz or gamma band responses. To study the effects of these factors in a balanced design, auditory event-related potentials (ERPs) of 9 young adults were recorded in a passive listening, simple reaction task, and choice-reaction task (target tone probability = 0.5) conditions. Amplitude and phase-locking of event-related gamma activity were analyzed separately at the level of single sweeps by applying a method that allows the independent quantification of phase synchronization between consecutive single responses. Major results demonstrated that (1) During auditory stimulus processing discernible gamma oscillation bursts were observed in three time windows of the poststimulus epoch: early (0-120) ms, middle (120-250 ms) and late (250-400 ms). (2) Early gamma response amplitudes were significantly largest for highly expected motor-task stimuli, whereas the phase-locking did not depend on either of the two variables. (3) The phase-locking of late gamma responses, however, was significantly stronger to targets than to nontargets. These results indicate that auditory gamma responses are functionally involved in the processing of task variables such as stimulus certainty and motor-task relevance. It is also demonstrated that single gamma response amplitude and phase-locking have independent functional significance as being affected in a different manner by different task conditions.