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- All Subjects: Motivation
- Creators: Sanabria, Federico
Description
The present study examined how systemic low doses of nicotine affect the microstructure of food-reinforced behavior in rats. Rats were given an acute saline or nicotine treatment (0.1-0.6 mg/kg, resting at least 48 h between injections), and a chronic saline or nicotine treatment (0.3 mg/kg for 10 consecutive days). Immediately after treatment, rats were required to press a lever to obtain food, whose availability was unpredictable, but programmed at a constant rate (on average every 80 s). Acute nicotine dose-dependently suppressed behavior prior to the delivery of the first reinforcer, but enhanced food-reinforced behavior afterwards. This effect was primarily observed in the time it took rats to initiate food-seeking behavior, and not in the food-seeking behavior itself. A pre-feeding control procedure suggests that these effects cannot be explained only by changes in appetite. Over the course of chronic nicotine exposure, tolerance developed to the suppressive, but not to the enhancing effects of nicotine on food-seeking behavior. These results suggest that ostensive sensitization effects of nicotine on behavior may instead reflect a tolerance for its suppressive effects on behavior.
ContributorsRomero, Korinna Estela (Author) / Sanabria, Federico (Thesis director) / Gipson-Reichardt, Cassandra (Committee member) / Bevins, Rick (Committee member) / Department of Psychology (Contributor) / School of Life Sciences (Contributor) / Barrett, The Honors College (Contributor)
Created2017-05
Description
The capacity to track time in the seconds-to-minutes range, or interval timing, appears to be at least partially dependent on intact hippocampal (HPC) function. The current dissertation sought to dissociate timed responses, non-timed responses, and motivational aspects of behavior in order to propose a role of the HPC in specific timing sub-processes. In Chapter 2, effects of dorsal HPC (dHPC) lesions on temporal responding in a switch-timing task revealed a critical role of dHPC in the acquisition of interval timing criteria. Following dHPC lesions, the start time of responding was systemically shortened, in a manner that was enhanced and sustained when encoding a novel long interval, consistent with a memory-based account of dHPC function in timed responding. Chapter 3 investigated effects of chronic stress, which has been shown to reliably induce HPC dendritic retraction, on interval timing, utilizing response-initiated schedules of reinforcement, which facilitate deconvolution of timing and motivation. This revealed task-dependent effects on interval timing and motivation, where stress induced transient effects on motivation in a prospective timing task, but transient effects on the variability of timed responding in a retrospective timing task, consistent with an effect on memory function in interval timing. Chapter 4 sought to bring timed responding, motivation, and non-timed behaviors under stronger procedural control, through the implementation of a response-initiated timing-with-opportunity-cost task, in which a cost is imposed on temporal food-seeking by the presence of a concurrent source of probabilistic reinforcement. This arrangement garnered strong schedule control of behavior, and revealed individual-subject differences in the effects of reward devaluation, such that it affected motivation in some rats, but temporal responding in others. Using this methodology, Chapter 5 investigated initial temporal entrainment of behavior under pharmacological deactivation of dHPC and revealed its critical involvement in updating memory to new temporal contingencies. Together, data from this dissertation contrast with prior conclusions that the HPC is not involved in learning temporal criteria, and instead suggest that its function is indeed critical to encoding temporal intervals in memory.
ContributorsGupta, Tanya A. (Author) / Sanabria, Federico (Thesis advisor) / Conrad, Cheryl (Committee member) / Olive, Foster (Committee member) / McClure, Samuel (Committee member) / Arizona State University (Publisher)
Created2022
Description
The rate at which an operant is produced has often functioned as a fundamental measure of the efficacy of a reinforcer. Previous research has shown that operant behavior is typically organized into bouts implying that rate of responding is a composite of bout-initiation rate, within-bout response rate, and mean bout length. However, it is still unclear whether this organization of behavioral responses into bouts is a product of the motivational processes or a property that arises from the location of an organism in space. To test this proximity hypothesis, two-response sequences were intermittently reinforced: either pressing one lever twice (manipulandum proximal to response termination) or pressing each of two levers, located on either side of an operant chamber, once (manipulandum distal to response termination). In Experiment 1, rats were first trained to lever press for food on a VI schedule before being exposed to the alternation paradigm. Experiment 1 consisted of three phases. In Phase 1, food-deprived rats learned the alternation paradigm under a tandem variable time (VT) 150-s fixed-ratio (FR) 1 schedule of reinforcement. Phase 2 and 3 increased the FR requirement from 1 to 3 or 5 and removed food deprivation, respectively, to examine their effect on response-rate components. In Experiment 2, rats switched between trials consisting of pressing a single lever repeatedly or alternating between two levers for reward. Following stable behavior, lever pressing was extinguished in both trial types to the effect of extinction on response-rate components. Overall, behavioral bouts persisted under the alternation paradigm suggesting that they reflect motivational states and not just location. Additionally, bout-initiation rate decreased with increased response effort and decreased deprivation. Taken together, these results provide support for the use of response-bout analysis to evaluate the value of a reinforcer and its sensitivity to pharmacological manipulations.
ContributorsGildea, Matthew (Author) / Sanabria, Federico (Thesis advisor) / Gewirtz, Jonathan (Committee member) / Verpeut, Jessica (Committee member) / Arizona State University (Publisher)
Created2024
Description
Timing performance is sensitive to fluctuations in time and motivation, thus interval timing and motivation are either inseparable or conflated processes. A behavioral systems model (e.g., Timberlake, 2000) of timing performance (Chapter 1) suggests that timing performance in externally-initiated (EI) procedures conflates behavioral modes differentially sensitive to motivation, but that response-initiated (RI) procedures potentially dissociate these behavioral modes. That is, timing performance in RI procedures is expected to not conflate these behavioral modes. According to the discriminative RI hypothesis, as initiating-responses become progressively discriminable from target responses, initiating-responses increasingly dissociate interval timing and motivation. Rats were trained in timing procedures in which a switch from a Short to a Long interval indexes timing performance (a latency-to-switch, LTS), and were then challenged with pre-feeding and extinction probes. In experiments 1 (Chapter 2) and 2 (Chapter 3), discriminability of initiating-responses was varied as a function of time, location, and form for rats trained in a switch-timing procedure. In experiment 3 (Chapter 4), the generalizability of the discriminative RI hypothesis was evaluated in rats trained in a temporal bisection procedure. In experiment 3, but not 1 and 2, RI enhanced temporal control of LTSs relative to EI. In experiments 1 and 2, the robustness of LTS medians to pre-feeding but not extinction increased with the discriminability of initiating-responses from target responses. In experiment 3, the mean LTS was robust to pre-feeding in EI and RI. In all three experiments, pre-feeding increased LTS variability in EI and RI. These results provide moderate support for the discriminative RI hypothesis, indicating that initiating-responses selectively and partially dissociate interval timing and motivation processes. Implications for the study of cognition and motivation processes are discussed (Chapter 5).
ContributorsDaniels, Carter W (Author) / Sanabria, Federico (Thesis advisor) / McClure, Samuel M. (Committee member) / Wynne, Clive D.L. (Committee member) / Olive, Michael F. (Committee member) / Arizona State University (Publisher)
Created2018