The present study was designed to investigate the effects of a stimulus change inserted in the large component of a mixed fixed-ratio 10 fixed-ratio 100 schedule. In mixed fixed-ratio schedules, a run of responses which approximates the response requirement of the smaller fixed ratio occurs at the beginning of the larger fixed ratio. This run of responses and the pause it precedes is called a prime. In Experiment I, priming acquisition was compared in a mixed schedule in which a change in key-color followed completion of the first 10 responses of the fixed-ratio 100 component and a mixed schedule with no stimulus change. Primes were acquired more rapidly in the mixed schedule with the stimulus change and the number of responses in a priming run was less variable than occurred without the stimulus change. In Experiment II, the effect of the stimulus change on primes was further investigated by removal of the smaller fixed-ratio component or by varying the location of the stimulus change. Primes occurred only when the smaller fixed-ratio component was present. Varying the location of the stimulus change resulted in the transfer of control from the external stimulus to response-produced stimuli. Future investigation of this point of transfer should prove useful in the study of the proprioceptive stimulus control of homogeneous behavior sequences. In Experiments Ill through VI, the variables controlling the length of the post-prime and the post-reinforcement pauses were investigated using the mixed FR x chained FR x FR y schedule. In this series of experiments, FR x was varied with FR y held constant at both high and low values. In addition, FR y was varied with FR x held constant at both high and low values. The results indicate that the post-prime pause is primarily a function of FR y, the number of responses required after the priming run. On the other hand, both post-reinforcement pauses were shown to be a function of FR x, the size of the small fixed ratio. An interaction between FR x and FR y and both the post-reinforcement and the post-prime pauses suggested that pausing in mixed schedules is a closed system. Taken as a whole, these results indicate the importance of mixed chained schedules in the investigation of the priming phenomenon.

Most studies of gustatory coding have been performed in either anesthetized or awake, passively stimulated rats. In this dissertation the influences of behavioral state on gustatory processing in awake rats are described. In the first set of experiments, the effects of non-contingent tastant delivery on the chemical tuning of single neurons were explored. Tastants were delivered non-contingently through intra-oral cannulas to restrained, non water-deprived rats while single unit responses were recorded from the gustatory cortex (GC). As the subjects' behavior progressed from acceptance to rejection of the tastants, the chemical tuning of the neurons changed as well. This suggests that the subjects' behavioral state powerfully influences gustatory processing. In the second set of experiments, rats were trained to lick for fluid reinforcement on an FR5 schedule while single unit activity was recorded from GC. In this case, the chemical tuning was much more stable. Under this paradigm, chemosensory responses were rapid (~ 150 ms) and broadly tuned. In the third study, it was found that ensembles of GC neurons could discriminate between tastants and their concentrations on a single trial basis, and such discrimination was accomplished with a combination of rate and temporal coding. Ensembles of GC neurons also anticipated the identity of the upcoming stimulus when the tastant delivery was predictable. Finally, it was found that ensembles of GC neurons could discriminate between the bitter stimuli nicotine and quinine. Nicotine is both a bitter tastant and a trigeminal stimulant, and when the acetylcholine receptors in the lingual epithelium were blocked with mecamylamine, the ensembles failed to discriminate nicotine from quinine.

Propofol is a widely in use anesthetic drug. Propofol’s abuse liability has been supported by many case reports and a few animal studies. However, propofol’s reinforcing properties have not yet been investigated in-depth. In this study, multiple aspects of propofol’s abuse-related behaviour were investigated using the drug self-administration model in rats. METHODS: Rats were subjected to propofol self-administration under a fixed ratio 1 (FR1) schedule and different aspects of propofol self-administration behaviour including acquisition, maintenance of the behaviour under a higher ratio schedule, extinction and reinstatement were investigated. RESULTS: Rats acquired propofol self-administration under a FR1 schedule. The acquired behaviour was maintained under a FR2 schedule, showed a modest variation over a range of doses, and was extinguished upon substitution of vehicle for propofol, showing no reinstatement using a range of priming doses of propofol. CONCLUSION: Propofol has abuse potential showing modest reinforcing properties under our experimental conditions.

Propofol is a widely in use anesthetic drug. Propofol’s abuse liability has been supported by many case reports and a few animal studies. However, propofol’s reinforcing properties have not yet been investigated in-depth. In this study, multiple aspects of propofol’s abuse-related behaviour were investigated using the drug self-administration model in rats. METHODS: Rats were subjected to propofol self-administration under a fixed ratio 1 (FR1) schedule and different aspects of propofol self-administration behaviour including acquisition, maintenance of the behaviour under a higher ratio schedule, extinction and reinstatement were investigated. RESULTS: Rats acquired propofol self-administration under a FR1 schedule. The acquired behaviour was maintained under a FR2 schedule, showed a modest variation over a range of doses, and was extinguished upon substitution of vehicle for propofol, showing no reinstatement using a range of priming doses of propofol. CONCLUSION: Propofol has abuse potential showing modest reinforcing properties under our experimental conditions.

Adults with autism spectrum disorder (ASD) and intellectual disability (ID) are the majority of population in residential settings. Many clients in residential settings engage in problem behavior that interferes with their daily routine and work requirements. Restricted and repetitive behavior are one of the features of ASD diagnosis, typically in the form of invariable responding and predictable responses. Differential reinforcement has been used to produce and maintain response variability. I evaluated the utility of a fixed ratio 1 (FR1) schedule on variability to increase the diversity of activity selections in the treatment of problem behavior occasioned by the interruption of routines. Chase engaged in problem behaviors in his bathroom routine, no matter by himself or with his housemate. Results demonstrated a reinforcement-based treatment increased both variable and novel selections while decreasing the rate of self injurious behavior.