Degree Name

Doctor of Philosophy


University of Wollongong. Dept. of Psychology


The present study was designed to explore the importance of positive shifts in the period of the Bereitschaftspotential or Readiness Potential (RP) observed in normals by Freude and Ullsperger (1989), and to examine possible interactions with various movement initiation strategies. The functional significance of different components in the period of the RP, and their relation to the opposite polarity shifts in the pre-movement period was also of interest.

The three experiments completed in this study also examined the effect of split attention (from the movement to another task) on the polarity shift of the RP, the effect of a perceptual/cognitive task on the latency, amplitude and topography of the RP and some other movement related potentials (e.g. the P2 and the SPP), the functional significance of the opposite shifts in the period of the RP, the relationship between spontaneous slow potentials and the movement related potentials, and the relation of the RP to specifying and loading of the motor programs. Because the design of the experiments provided an appropriate opportunity, some other potentials (such as the stimulus preceding negativity (SPN) and the auditory N100) were also investigated.

Experiment 1 confirmed that positive potentials exist in the period of the RP. Split attention resulted in a significant increase in the relative frequency of positive potentials. This in turn resulted in a decrease in the magnitude and a delayed latency of the averaged RP. Experiment 2 indicated that the positive shifts in the pre-event potential (or pre-movement potential, but since the task did not always require a movement, the term pre­ event potential is preferred) affect the accuracy of performance on a perceptual/cognitive task, with an increase in the frequency and amplitude of positive shifts associated with poorer performance. A higher negativity of this potential in correct performance --compared with incorrect performance --confirmed previous findings on the association of such negativity with better performance on the task. It was also found that a larger RP predicts a larger Reafferent Potential (P2).

Experiment 3 indicated that the positive shifts only developed early in the period of the RP, while the later potential was always negative. The first component of the pre-movement potential did not differ as a function of press/no-press, and had a symmetric distribution with Cz maximum. A different procedure in initiating the movement was suggested to affect the early component of the RP. The preceding shift of the pre-event potential did not affect the second part of the RP. The second component was found to be largest at Cz but lateralized toward the contralateral area. It is suggested that this potential may indicate specifying and loading of the motor program. Neither the efficacy of the performance nor the previous potential shift were significantly related to its amplitude. The P2 is suggested to reflect the processes involved in termination of the movement and every situation which affects the RP could affect the P2. Cognitive concomitants of the task, not its physical requirements, influenced the skilled performance positivity (SPP). The results will be discussed also in relation to the interaction of the task with the stimulus preceding negativity (SPN) , auditory NIOO and the EMG accompanying the task.

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