Matching Items (3)
Filtering by
- Genre: Academic theses
- Creators: Homa, Donald
- Creators: Castillo-Chavez, Carlos
Description
Dopamine (DA) is a neurotransmitter involved in attention, goal oriented behavior, movement, reward learning, and short term and working memory. For the past four decades, mathematical and computational modeling approaches have been useful in DA research, and although every modeling approach has limitations, a model is an efficient way to generate and explore hypotheses. This work develops a model of DA dynamics in a representative, single DA neuron by integrating previous experimental, theoretical and computational research. The model consists of three compartments: the cytosol, the vesicles, and the extracellular space and forms the basis of a new mathematical paradigm for examining the dynamics of DA synthesis, storage, release and reuptake. The model can be driven by action potentials generated by any model of excitable membrane potential or even from experimentally induced depolarization voltage recordings. Here the model is forced by a previously published model of the excitable membrane of a mesencephalic DA neuron in order to study the biochemical processes involved in extracellular DA production. After demonstrating that the model exhibits realistic dynamics resembling those observed experimentally, the model is used to examine the functional changes in presynaptic mechanisms due to application of cocaine. Sensitivity analysis and numerical studies that focus on various possible mechanisms for the inhibition of DAT by cocaine provide insight for the complex interactions involved in DA dynamics. In particular, comparing numerical results for a mixed inhibition mechanism to those for competitive, non-competitive and uncompetitive inhibition mechanisms reveals many behavioral similarities for these different types of inhibition that depend on inhibition parameters and levels of cocaine. Placing experimental results within this context of mixed inhibition provides a possible explanation for the conflicting views of uptake inhibition mechanisms found in experimental neuroscience literature.
ContributorsTello-Bravo, David (Author) / Crook, Sharon M (Thesis advisor) / Greenwood, Priscilla E (Thesis advisor) / Baer, Steven M. (Committee member) / Castaneda, Edward (Committee member) / Castillo-Chavez, Carlos (Committee member) / Arizona State University (Publisher)
Created2012
Description
In this study, the oppositional processes theory was proposed to suggest that reliance on semantic and episodic memory systems hinder originality during idea generation for divergent thinking tasks that are generally used to assess creative potential. In order to investigate the proposed oppositional processes theory, three experiments that manipulated the memory accessibility in participants during the alternative uses tasks were conducted. Experiment 1 directly instructed participants to either generate usages based on memory or not from memory; Experiment 2 provided participants with object cues that were either very common or very rare in daily life (i.e., bottle vs. canteen); Experiment 3 replicated the same manipulation from Experiment 2 with much longer generation time (10 minutes in Experiment 2 vs. 30 minutes in Experiment 3). The oppositional processes theory predicted that participants who had less access to direct and unaltered usages (i.e., told to not use memory, were given rare cues, or were outputting items later in the generation period) during the task would be more creative. Results generally supported the predictions in Experiments 1 and 2 where participants from conditions which limited their access to memory generated more novel usages that were considered more creative by independent coders. Such effects were less prominent in Experiment 3 with extended generation time but the trends remained the same.
ContributorsXu, Dongchen (Author) / Brewer, Gene (Thesis advisor) / Glenberg, Arthur (Committee member) / Homa, Donald (Committee member) / Goldinger, Stephen (Committee member) / Arizona State University (Publisher)
Created2017
Description
It has been suggested that directed forgetting (DF) in the item-method paradigm results from selective rehearsal of R items and passive decay of F items. However, recent evidence suggested that the passive decay explanation is insufficient. The current experiments examined two theories of DF that assume an active forgetting process: (1) attentional inhibition and (2) tagging and selective search (TSS). Across three experiments, the central tenets of these theories were evaluated. Experiment 1 included encoding manipulations in an attempt to distinguish between these competing theories, but the results were inconclusive. Experiments 2 and 3 examined the theories separately. The results from Experiment 2 supported a representation suppression account of attentional inhibition, while the evidence from Experiment 3 suggested that TSS was not a viable mechanism for DF. Overall, the results provide additional evidence that forgetting is due to an active process, and suggest this process may act to suppress the representations of F items.
ContributorsHansen, Whitney Anne (Author) / Goldinger, Stephen D. (Thesis advisor) / Azuma, Tamiko (Committee member) / Brewer, Gene (Committee member) / Homa, Donald (Committee member) / Arizona State University (Publisher)
Created2011