Browsing by Subject "Extinction"
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Item Affective responses in cocaine-experienced rats reveal cue-induced drug craving and cocaine reward magnitude(2011-08) Maier, Esther Yvonne; Duvauchelle, Christine L.; Schallert, Timothy; Gonzales, Rueben A.; Gore, Andrea C.; Monfils, Marie H.The development and persistence of cocaine dependence are greatly influenced by emotional affect and cocaine associative learning. Cocaine is known to enhance nucleus accumbens (NAcc) dopamine, serve as a positive reinforcer and produce negative effects, such as anxiety that may influence cocaine intake behavior. In the first study, I investigated the effects of the anxiolytic, diazepam on NAcc dopamine levels and cocaine self-administration behavior. These are two factors associated with cocaine rewarding effects. Diazepam has no effect on NAcc dopamine, but affects cocaine self-administration. This supports the notion that decreasing the anxiogenic effects of cocaine increases the rewarding value in a dopamine independent manner. Therefore, increasing the aversive effects of cocaine might be a novel approach to fight cocaine dependence. In the second study, I studied cocaine-induced associative learning and changes in affect during cocaine conditioning and extinction. 50-kHz ultrasonic vocalizations (USVs) in rats are thought to reflect positive affect and occur upon appetitive stimuli and with cocaine delivery. First, I explored whether USVs might be elicited in anticipation of impending drug delivery. Shortly into conditioning, rats elicited USVs when placed in the cocaine-associated environment. USVs progressively increased, indicating a growing learned association between cocaine intake and cocaine-associated cues. This suggests that USVs may be a useful model for investigating cocaine craving and serve as a pharmacological target for interventions aimed to reduce cocaine craving and relapse. I then examined the effects of short-term deprivation of cocaine and cocaine cues on cocaine-conditioned USVs, which were both exaggerated after abstinence. The results may have clinical implications, in that intermittently avoiding cues or context may enhance drug cue salience and increase the probability of relapse. Motivational aspects of cocaine were assessed comparing commonly measured lever response rate and locomotion with cocaine-induced USVs during cocaine administration and extinction. In agreement with prevailing findings, lever responding for cocaine and cocaine-induced locomotor activity increased across conditioning sessions. However, the number of USVs evoked in response to cocaine infusion decreased with cocaine experience. These findings suggest growing tolerance to the rewarding properties of cocaine. These studies underscore the value of USV assessment during drug dependence studies.Item Assessing Visuospatial Neglect in Children with Brain Injury(2014-05-28) Wahlberg, Andrea ChristineVisuospatial neglect (VSN), the failure to report, respond, or orient to novel or meaningful visual stimuli presented in a specific location, is a frequently occurring outcome following stroke. VSN can negatively impact the functions of daily life and is an important predictor for long term outcomes. The phenomenon is frequently studied in adult populations; however, the nature and incidence of VSN following childhood stroke is virtually unknown. Current research investigating the neuroanatomical correlates of VSN and hypothesized models of dysfunction all assume a fully mature brain and thus lack a developmental perspective. Similarly, current neuropsychological measures used to assess VSN are almost exclusively developed and normed with adult populations. While some individual adult tests have been modified for use with children, no standardized battery to assess VSN in young children currently exists. The present study investigated the reliability and validity of a five-task neuropsychological testing battery, the Pediatric Visuospatial Neglect Battery, developed at the Children?s Hospital of Philadelphia (CHOP) to assess VSN in young children ages 2-6 following stroke. Although there were some exceptions, the reliability estimates of task scores obtained from the present sample were generally low. With regard to criterion-related validity, sensitivity to detect brain injury was generally poor while specificity was high. Some of the low reliability and validity estimates were due to measurement problems of the calculated variables. These variables can be reexamined and likely improved in future studies. In other instances, modifications to the tasks are recommended. Specific recommendations for improving the five existing tasks are provided as well as suggestions for additional tasks that could potentially be added to the battery in future administrations. Although somewhat disappointing, low initial reliability and validity estimates are part and parcel to test development. This study represents an important first step in developing a standardized battery to detect VSN in children. With refinement and additional testing, the Pediatric Visuospatial Neglect Battery may soon become an excellent instrument for investigating the VSN phenomenon in children.Item Behavioral mechanisms underlying the extinction of cocaine self-administration(Texas A&M University, 2006-04-12) Valles, Rodrigo, Jr.The aim of the present series of experiments was to outline the influence of different doses of cocaine during training, training schedule, training length and abstinence duration to modulate subsequent extinction and reinstatement patterns. Abram Amsel??s general theory of persistence were used to both design and explain various aspects of these models. For Experiment 1, rats self-administered cocaine (0.25, 0.50 or 1.00 mg/kg) intravenously and were then tested in an extinction preparation using saline infusions (5 days) and then only the stimulus light as the reinforcer (3 days). Experiment 2 examined schedules by magnitude interactions by training rats on two fixed-ratio (FR) schedules (FR-1 or FR-10 using either 0.25 or 1.00 mg/kg cocaine). Animals were tested in an extinction protocol (10 days; no stimulus light) and subsequently tested for reinstatement (1 day) that utilized presentations of the stimulus light. Experiment 3 addressed the effects of training length (15 or 30 days of training using either 0.25 or 1.00 mg/kg cocaine) using the same protocol as in Experiment 2. Experiment 4 examined the modulation potential of two abstinence lengths (15 or 30 days using either 0.25 or 0.50 mg/kg cocaine) using the same conditions as Experiment 2. Experiment 1 indicated the greatest resistance to extinction using the lowest training dose (0.25 mg/kg). The removal of saline caused an apparent extinction burst indicative of reward seeking. Experiment 2 showed that animals trained under partial reinforcement schedules persisted more during extinction. Furthermore, rats trained using 1.00 were more resistant than those trained with 0.25 mg/kg. Reinstatement of drug seeking was more pronounced in rats trained using an FR-10 schedule. Experiment 3 indicated greater resistance to extinction in rats trained for 15 versus 30 days. Rats trained on 0.50 mg/kg for 30 days showed less cue-induced reinstatement than those trained for 15 days. Experiment 4 showed increased resistance to extinction when rats were trained on 0.25 mg/kg and forced to abstain for 30 versus 15 days. Directionally opposite effects were apparent in groups trained with 0.50 mg/kg. Reinstatement data indicated greater responsivity to cues by animals abstaining for 30 versus 15 days.Item An evaluation of resurgence of appropriate communicative responses in children with developmental disabilities(2011-08) Hoffman, Katherine J.; Falcomata, Terry S.; Ringdahl, JoelThe purpose of the current study was to evaluate the conditions under which resurgence of appropriate communicative responses (mands) would occur with children with developmental disabilities. The experimental preparation consisted of a sequence of conditions that included (a) the reinforcement of one mand (i.e., microswitch activation or card exchange) on a FR 1 schedule, (b) an extinction condition in which the mand was no longer reinforced, (c) the reinforcement of a second mand (i.e., microswitch activation or card exchange) on a FR 1 schedule, and (d) a test for resurgence of the first mand which consisted of placing the second mand on extinction. The results demonstrated resurgence of mands during 2 out of 3 tests for resurgence for one participant. Resurgence of mands was demonstrated during all three tests for resurgence with the second participant.Item How to achieve Extinction without killing yourself : the process of writing a screenplay(2010-08) Zisman, Noah Ira; Kelban, Stuart; Garrison, Andrew“How to Achieve Extinction Without Killing Yourself: The Process of Writing a Screenplay” examines the creative procedure of writing the sci-fi feature Extinction. It explores the step-by-step process of idea genesis through to the third draft.Item Multiple memory systems and extinction(Texas A&M University, 2005-08-29) Gabriele, AmandaSeveral lines of evidence suggest that initial acquisition of learned behavior involves multiple memory systems. In particular, lesions of the hippocampus impair the acquisition of cognitive or relational memory, but do not impair the acquisition of stimulus-response habits. Extinction behavior also involves new learning, and therefore it is possible that multiple forms of memory may also underlie extinction. We examined this hypothesis by training rats in a task in which extinction behavior could putatively be acquired by either a cognitive or habit memory system. Adult male Long-Evans rats were initially trained to run in a straight alley maze for food reward. Following training they were placed into one of two extinction conditions. In one condition rats were allowed to run to an empty goal box (i.e. response extinction). In a second condition rats were placed into an empty goal box without making a running response (i.e. latent or non-response extinction). Prior to each daily session of extinction training, rats received intra-hippocampal infusions of either the local anesthetic bupivacaine (0.75% solution/0.5 ul), or saline. Rats receiving saline infusions displayed extinction behavior in both the response and non-response conditions. In contrast, rats receiving intra-hippocampal infusions ofbupivacaine extinguished normally in the response condition, but did not display nonresponse extinction. This latent extinction effect was enhanced by decreasing the amount of time between the last extinction trial and the probe trial. Additionally, administering extinction training and probe trials in different contexts did not appear to prevent latent extinction, however large variability may be masking this effect. The new context administered during extinction prevented latent extinction in some animals, but not others. These findings suggest that, similar to initial acquisition, the learning that occurs during extinction also involves multiple memory systems. Specifically, the hippocampus may selectively mediate extinction under conditions in which new stimulus-response learning is prevented.Item The interaction of stimulus compounds in extinction(Texas Tech University, 1977-12) Duch, VictorNOT AVAILABLEItem The seasonality of aerosol properties in Big Bend National Park(Texas A&M University, 2007-04-25) Allen, Christopher LeeTwo-week sampling periods during the spring, summer, and fall of 2003, and the winter of 2004 were conducted utilizing a tandem differential mobility analyzer (TDMA) and, during the spring and summer, an aerodynamic particle sizer (APS), to characterize the seasonal variability of the Big Bend regions aerosol optical properties. Mass extinction efficiencies and relative humidity scattering enhancement factors were calculated for both externally and internally mixed aerosol populations for all size distributions collected, in an effort to possibly improve upon the default EPA mass extinction efficiencies used for all Class 1 areas across the United States. The mass extinction efficiencies calculated differed to some extent form the default values employed by the EPA. Sulfate, nitrate, and light absorbing carbon (LAC) exhibited a strong dependence on assumed mixing state, while, additionally, sulfate was also dependent on the assumed dominant aerosol. Seasonal variability was seen with all particle types, excluding LAC, with sulfate mass extinction efficiencies displaying the greatest variability with season. Calculated back trajectories indicated that air masses originating from the southeast had elevated mass extinction efficiencies, while, conversely, air masses originating from the southwest and northwest had the smallest mass extinction efficiencies.