Recent advances in virtual-interface and computer technologies, including helmet-mounted displays (HMDs), three-dimensional auditory displays, haptic displays, head and eye position tracking devices, and computer-generated imaging techniques, have permitted the development of multi-sensory, interactive virtual environments. In spite of the dramatic ability of these environments to represent the perceptual world, they are limited by the problem of time delay---the delay between the input to a system and its corresponding output. For example, in the case of HMDs, time delays are present in the sampling of head position by a tracking device attached to the user's helmet and the appearance of the updated image in the HMD. Such delays cause the image to lag behind the user's head movement, thereby causing the image to be displayed in an incorrect position.
Compared to other drugs of abuse, studies of the effects of nicotine on intracranial self-stimulation (ICSS) are few in number. Since the effect of nicotine on reward is not well established, one goal of the present study was to clarify the characteristics of nicotine-induced changes in brain stimulation reward using a rigorously validated, rate-free and reward-selective procedure. Once established, the second goal was to assess the ability of specific dopamine (sulpiride), serotonin (MDL 26,508), and mixed dopamine/serotonin (MDL 28,133A) antagonists to modify nicotine's effects.