Abstract
The cholinergic pedunculopontine tegmental nucleus (PPTN) is one of the major ascending arousal systems in the brainstem, and is linked to motor, limbic and sensory systems. We hypothesize that PPTN is related to integrative control of motor behavior, and present a new model of the PPTN's involvement in the control of arousal, attention and reinforcement aspects of motor behavior, with a focus on the control of saccades. We investigated the relationship between the task performance and activity of PPTN neurons during visually-guided saccade tasks and the effects of reward schedule on them. We found that when the reaction time to the fixation point (RTFP) elongated, the animal tended to fail to complete the task. Activities of a group of PPTN neurons at the FP onset were larger in the success trials than in the error trials irrespective of the current eye position. These results suggested that the activity of the PPTN neurons is closely linked to the RTFP and encodes the animal's vigilance level. To investigate the correlation of PPTN neuron activity and its drive by motivation, we changed the volume of reward systematically and compared the reward volume with the RTFP, task performance and the PPTN neuronal activity in the following trial. Increase in the reward volume enhanced the PPTN neuron activity, decreased the RTFP and decreased the error rate in the next trials. [Jpn J Physiol 54 Suppl:S35 (2004)]
