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In the vestibular labyrinth of mammals there are five separate end-organs, the cristae of the three semicircular canals and the maculae of the utricle and saccule. These end-organs normally react to mechanical stimulation, the cristae to rotatory acceleration, and the maculae to linear acceleration and to gravity. By using natural stimuli, however, it is difficult to selectively stimulate single receptors.Since experiments utilizing single organ stimulation are frequently of interest, a variety of techniques have been devised to accomplish this purpose. Ewald! used a pneumatic hammer connected to a small catheter to stimulate single semicircular canals of pigeons. Lorente de N6 2 heated individual semicircular canals of rabbits with a hot needle. Szentagothai" introduced catheters directly into semicircular canals of dogs, and also stimulated the utricular macula with a probe.' Anderson and Cernandt," Fluur," Szentagothai," and others?" have used electrical stimulation for activating single ampullary or otolithic nerves in acute experiments.We have previously devised techniques for implanting stimulating electrodes near single vestibular nerve branches in both short

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Abstract.To elucidate the role of the prefrontal cortex in cognitive control of reaching movements, by multichannel near-infrared spectroscopy we examine changes in oxygenated hemoglobin (oxy-Hb) as an indicator of changes in regional cerebral blood flow in the bilateral dorsolateral (DLPFC), ventrolateral prefrontal cortex (VLPFC), and frontopolar cortex (FPC) during a reaching task with normal visual feedback (a consistent task) and a reaching task with flipped horizontal visual feedback (an inconsistent task). Subjects first perform 12 trials of the consistent task, and then perform six blocks of the inconsistent task, each of which consists of six trials. During the consistent task, oxy-Hb is increased only in the right VLPFC. During the first block of the inconsistent task, increases in oxy-Hb are observed in the bilateral DLPFC and the right VLPFC, whereas the increased oxy-Hb was gradually reduced as the block proceeded, which was accompanied by an improvement in the task performance. Eventually, there were no differences in the degree of change in oxy-Hb between the consistent and inconsistent tasks in the DLPFC and VLPFC. These findings suggest that the DLPFC is engaged in higher order cognitive control, while the right VLPFC is engaged in both higher and lower order cognitive controls. C 2011 Society of Photo-Optical Instrumentation Engineers (SPIE).