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Tracey J. Shors - One of the best experts on this subject based on the ideXlab platform.
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Trace Conditioning and the Hippocampus: The Importance of Contiguity
The Journal of neuroscience : the official journal of the Society for Neuroscience, 2006Co-Authors: Debra A. Bangasser, David E. Waxler, Jessica Santollo, Tracey J. ShorsAbstract:Trace Conditioning, a form of classical Conditioning in which the presentation of the conditioned stimulus (CS) and the unconditioned stimulus (US) is separated in time by an interstimulus interval, requires an intact hippocampus. In contrast, classical Conditioning procedures in which the CS and US are not separated by an interstimulus interval (i.e., delay Conditioning procedures) typically do not (Solomon et al., 1986). However, why Trace Conditioning is dependent on the hippocampus is unknown. Several theories suggest that it is specifically the discontiguity between the CS and US in Trace Conditioning that critically engages the hippocampus. However, there are other explanations that do not depend on discontiguity. To determine whether the lack of contiguity renders Trace Conditioning hippocampal dependent, we designed a “contiguous Trace Conditioning” (CTC) paradigm in which CS–US contiguity is restored by re-presenting the CS simultaneously with the US. Although rats with excitotoxic lesions of the hippocampus could not learn a standard Trace fear-Conditioning paradigm, lesioned rats trained on CTC showed significant Conditioning, at levels similar to those with sham surgeries. Importantly, lesioned rats trained solely with simultaneous CS–US presentations did not demonstrate Conditioning. Together, these data suggest that rats with hippocampal lesions can form a memory of a Trace CS–US association when contiguity is restored. Therefore, the dependence of traditional Trace paradigms on the hippocampus can be attributed to the absence of temporal contiguity.
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the role of the hippocampus in Trace Conditioning temporal discontinuity or task difficulty
Neurobiology of Learning and Memory, 2001Co-Authors: Anna V Beylin, Chetan C Gandhi, Gwendolyn E Wood, Andrew C Talk, Louis D Matzel, Tracey J. ShorsAbstract:Abstract It is well established that the hippocampal formation is critically involved in the acquisition of Trace memories, a paradigm in which the conditioned (CS) and unconditioned stimuli (US) are separated by a temporal gap (Solomon et al., 1986). The structure is reportedly not critical for the acquisition of delay memories, where the CS and the US overlap in time (Berger & Orr, 1983; Schmaltz & Theios, 1972). Based on these results, it is often stated that the hippocampus is involved in “filling the gap” or otherwise associating the two stimuli in time. However, in addition to the presence of a temporal gap, there are other differences between Trace and delay Conditioning. The most apparent difference is that animals require many more trials to learn the Trace task, and thus it is inherently more difficult than the delay task. Here, we tested whether the hippocampus was critically involved in delay Conditioning, if it was rendered more difficult such that the rate of acquisition was shifted to be analogous to Trace Conditioning. Groups of rats received excitotoxic lesions to the hippocampus, sham lesions or were left intact. Using the same interstimulus intervals (ISI), control animals required more trials to acquire the Trace than the delay task. As predicted, animals with hippocampal lesions were impaired during Trace Conditioning but not delay Conditioning. However, when the delay task was rendered more difficult by extending the ISI (a long delay task), animals with hippocampal lesions were impaired. In addition, once the lesioned animal learned the association between the CS and the US during delay Conditioning, it could learn and perform the Trace CR. Thus, the role of the hippocampus in classical Conditioning is not limited to learning about discontiguous events in time and space; rather the structure can become engaged simply as a function of task difficulty.
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The contribution of adrenal and reproductive hormones to the opposing effects of stress on Trace Conditioning in males versus females.
Behavioral neuroscience, 2001Co-Authors: Gwendolyn E Wood, Anna V Beylin, Tracey J. ShorsAbstract:Exposure to an acute stressful experience facilitates classical Conditioning in male rats but impairs Conditioning in female rats (T. J. Shors, C. Lewczyk, M. Paczynski, P. R. Mathew, & J. Pickett, 1998; G. E. Wood & T. J. Shors, 1998). The authors report that these effects extend to performance on the hippocampal-dependent task of Trace Conditioning. The stress-induced impairment of Conditioning in females was evident immediately, 24 hr and 48 hr after stress, depending on the stage of estrus. Moreover, the effect could be reactivated days later by reexposure to the stressful context. Corticosterone levels correlated with overall performance in males but not in females. Unlike the effect seen in males, adrenalectomy did not prevent the stress-induced effect on Conditioning in females. These data indicate that exposure to the same experience can have opposite effects on learning in males versus females and that these opposing effects are mediated by differing hormonal systems.
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stress enhances excitatory Trace eyeblink Conditioning and opposes acquisition of inhibitory Conditioning
Behavioral Neuroscience, 1998Co-Authors: Anna V Beylin, Tracey J. ShorsAbstract:Exposure to a brief, stressful event is reported to facilitate classical eyeblink Conditioning in the male rat (Rattus norvegicus) by use of a delay paradigm in which the conditioned stimulus (CS) and unconditioned stimulus (US) overlap and coterminate. This study examined the effects of stress on Trace Conditioning, a task in which the CS and US were separated by 500 ms. Experiment 1 showed that exposure to brief (1 s), low-intensity (1 mA) tailshocks facilitated acquisition 24 hr later. Experiment 2 showed that stressor exposure did not affect retention or extinction of Trace Conditioning in rats that were stressed after acquisition. Experiment 3 showed that exposure to the same stressor opposed acquisition of inhibitory Conditioning. These results suggest that exposure to a stressful event persistently facilitates acquisition of Trace Conditioning and enhances a bias toward acquiring positive versus negative associations.
Helen J. Cassaday - One of the best experts on this subject based on the ideXlab platform.
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Infusions of scopolamine in dorsal hippocampus reduce anticipatory responding in an appetitive Trace Conditioning procedure.
Brain and behavior, 2018Co-Authors: Marie A. Pezze, Hayley J. Marshall, Helen J. CassadayAbstract:INTRODUCTION Trace Conditioning is impaired by lesions to dorsal hippocampus, as well as by treatment with the muscarinic acetylcholine antagonist scopolamine. However, the role of muscarinic receptors within hippocampus has received little attention. METHODS The present study examined the effects of intra-hippocampal infusion of scopolamine (30 µg/side) in an appetitive (2 vs. 10 s) Trace Conditioning procedure using sucrose pellets as the unconditioned stimulus (US). Locomotor activity (LMA) was examined in a different apparatus. RESULTS Intra-hippocampal scopolamine reduced responding to the 2 s Trace conditioned stimulus (CS). Intra-hippocampal scopolamine similarly depressed responding within the inter-stimulus interval (ISI) at both 2 and 10 s Trace intervals, but there was no such effect in the inter-trial interval. There was also some overall reduction in responding when the US was delivered; significant at the 10 s but not at the 2 s Trace interval. A similar pattern of results to that seen in response to the CS during acquisition was shown drug-free (in the 5 s post-CS) in the extinction tests of conditioned responding. LMA was increased under scopolamine. CONCLUSIONS The results suggest that nonspecific changes in activity or motivation to respond for the US cannot explain the reduction in Trace Conditioning as measured by reduced CS responding and in the ISI. Rather, the findings of the present study point to the importance of associative aspects of the task in determining its sensitivity to the effects of scopolamine, suggesting that muscarinic receptors in the hippocampus are important modulators of short-term working memory.
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Scopolamine Impairs Appetitive But Not Aversive Trace Conditioning: Role of the Medial Prefrontal Cortex
The Journal of neuroscience : the official journal of the Society for Neuroscience, 2017Co-Authors: Marie-astrid Pezze, Hayley J. Marshall, Helen J. CassadayAbstract:The muscarinic acetylcholine (ACh) receptor is an important modulator of medial prefrontal cortex (mPFC) functions, such as the working memory required to bridge a Trace interval in associative leaning. Aversive and appetitive Trace Conditioning procedures were used to examine the effects of scopolamine (0.1 and 0.5 mg/kg i.p.) in male rats. Follow-up experiments tested the effects of microinfusion of 0.15 μg scopolamine (0.075 μg in 0.5 μL/side) in infralimbic (IL) versus prelimbic (PL) regions of rat mPFC, in appetitive Trace and locomotor activity (LMA) procedures. Systemic scopolamine was without effect in an aversive Trace Conditioning procedure but impaired appetitive Conditioning at a 2 s Trace interval. This effect was demonstrated as reduced responding during presentations of the conditioned stimulus (CS) as well as during the inter-stimulus-interval (ISI). There was no such effect on responding during food (unconditioned stimulus, US) responding or in the inter-trial-interval (ITI). In contrast, systemic scopolamine dose-relatedly increased LMA. Trace Conditioning was similarly impaired at the 2 s Trace (shown as reduced responding to the CS and during the ISI, but not during US presentations or in the ITI) after infusion in mPFC, whilst LMA was increased (after infusion in IL only). Thus, results point to the importance of cholinergic modulation in mPFC for Trace Conditioning and show that the observed effects cannot be attributed to reduced activity.
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The dopamine D1 receptor agonist SKF81297 has dose-related effects on locomotor activity but is without effect in a CER Trace Conditioning procedure conducted with two versus four trials
Learning and motivation, 2016Co-Authors: Marie A. Pezze, Hayley J. Marshall, Helen J. CassadayAbstract:In an appetitively motivated procedure, we have previously reported that systemic treatment with the dopamine (DA) D1 receptor agonist SKF81297 (0.4 and 0.8 mg/kg) depressed acquisition at a 2s inter-stimulus-interval (ISI), suitable to detect Trace Conditioning impairment. However since DA is involved in reinforcement processes, the generality of effects across appetitively- and aversively-motivated Trace Conditioning procedures cannot be assumed. The present study tested the effects of SKF81297 (0.4 and 0.8 mg/kg) in an established conditioned emotional response (CER) procedure. Trace-dependent Conditioning was clearly shown in two experiments: while Conditioning was relatively strong at a 3-s ISI, it was attenuated at a 30-s ISI. This was shown after two (Experiment 1) or four (Experiment 2) Conditioning trials conducted in - as far as possible - the same CER procedure. Contrary to prediction, in neither experiment was there any indication that Trace Conditioning was attenuated by treatment with 0.4 or 0.8 mg/kg SKF81297. In the same rats, locomotor activity was significantly enhanced at the 0.8 mg/kg dose of SKF81297. These results suggest that procedural details of the Trace Conditioning variant in use are an important determinant of the profile of dopaminergic modulation.
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Dopaminergic modulation of appetitive Trace Conditioning: the role of D1 receptors in medial prefrontal cortex
Psychopharmacology, 2015Co-Authors: Marie-astrid Pezze, Hayley J. Marshall, Helen J. CassadayAbstract:Rationale Trace Conditioning may provide a behavioural model suitable to examine the maintenance of ‘on line’ information and its underlying neural substrates.
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Ro 04-6790-induced cognitive enhancement: No effect in Trace Conditioning and novel object recognition procedures in adult male Wistar rats
Pharmacology biochemistry and behavior, 2014Co-Authors: Karen E. Thur, Andrew J.d. Nelson, Helen J. CassadayAbstract:The evidence for cognitively enhancing effects of 5-hydroxytryptamine6 (5-HT6) receptor antagonists such as Ro 04-6790 is inconsistent and seems to depend on the behavioral test variant in use. Trace Conditioning holds promise as a behavioral assay for hippocampus-dependent working memory function. Accordingly, Experiment 1 assessed the effect of Ro 04-6790 (5 and 10 mg/kg i.p.) on associating a noise conditioned stimulus paired with foot shock (unconditioned stimulus) at a 3 or 30 s Trace interval in adult male Wistar rats. Contextual Conditioning was measured as suppression to the contextual cues provided by the experimental chambers and as suppression to a temporally extended light background stimulus which provided an experimental context. Experiment 2 assessed the effect of Ro 04-6790 (5 and 10 mg/kg i.p.) on recognition memory as tested by the exploration of novel relative to familiar objects in an open arena. In Experiment 1, Ro 04-6790 (5 and 10 mg/kg) was without effect on Trace and contextual Conditioning. In Experiment 2, there was no indication of the expected improvement under Ro 04-6790 at the same doses previously found to enhance recognition memory as measured in tests of novel object exploration. Thus, there was no evidence that treatment with the 5-HT6 receptor antagonist Ro 04-6790 acted as a cognitive enhancer in either Trace Conditioning or object recognition procedures. We cannot exclude the possibility that the experimental procedures used in the present study would have been sensitive to the cognitive enhancing effects of Ro 04-6790 in a different dose range, behavioral test variant, or in a different strain of rat. Nonetheless the drug treatment was not ineffective in that object exploration was reduced under 10 mg/kg Ro 04-6790.
John F. Disterhoft - One of the best experts on this subject based on the ideXlab platform.
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the effects of aging in delay and Trace human eyeblink Conditioning
Psychology and Aging, 2010Co-Authors: Dominic T Cheng, John F. Disterhoft, Monica L Faulkner, John E DesmondAbstract:Normal aging has been shown to impact performance during human eyeblink classical Conditioning, with older adults showing lower Conditioning levels than younger adults. Previous findings showed younger adults can acquire both delay and Trace Conditioning concurrently, but it is not known whether older adults can learn under the same conditions. Present results indicated older adults did not produce a significantly greater number of conditioned responses during acquisition, but their ability to time eyeblink responses prior to the unconditioned stimulus was preserved. The decline in eyeblink Conditioning that typically accompanies aging has been extended to concurrent presentations of delay and Trace Conditioning trials.
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Where is the Trace in Trace Conditioning
Trends in Neurosciences, 2008Co-Authors: Diana S. Woodruff-pak, John F. DisterhoftAbstract:Intensive mapping of the essential cerebellar brain circuits for Pavlovian eyeblink Conditioning appeared relatively complete by 2000, but new data indicate the need for additional differentiation of cerebellar regions and mechanisms coding delay and Trace Conditioning. This is especially important, as Trace Conditioning is an experimentally tractable model of declarative learning. The temporal gap in Trace eyeblink Conditioning may be bridged by forebrain regions through pontine–cerebellar nuclear connections that can bypass cerebellar cortex, whereas a cerebellar cortical long-term-depression-like process appears to be required to support normal delay Conditioning. Experiments focusing on the role of cerebellar cortex and deep nuclei in delay versus Trace Conditioning add perspective on brain substrates of these seemingly similar paradigms, which differ only by a brief stimulus-free time gap between conditioned and unconditioned stimuli. This temporal gap appears to impose forebrain dependencies and differentially engage different cerebellar circuitry during acquisition of conditioned responses.
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activity profiles of single neurons in caudal anterior cingulate cortex during Trace eyeblink Conditioning in the rabbit
Journal of Neurophysiology, 2003Co-Authors: Aldis P Weible, Craig Weiss, John F. DisterhoftAbstract:Acquisition of Trace eyeblink Conditioning involves the association of a conditioned stimulus (CS) with an unconditioned stimulus (US) separated by a stimulus-free Trace interval. This form of Conditioning is dependent upon the hippocampus and the caudal anterior cingulate cortex (AC), in addition to brain stem and cerebellar circuitry. Hippocampal involvement in Trace eyeblink Conditioning has been studied extensively, but the involvement of caudal AC is less well understood. In the present study, we compared neuronal responses from rabbits given either paired (Trace Conditioning) or unpaired (pseudoConditioning) presentations of the CS and US. Presentation of the CS elicited significant increases in neuronal activity at the onset of both Trace Conditioning and pseudoConditioning. A robust CS-elicited neuronal response persisted throughout the first 2 days of Trace Conditioning, declining gradually across subsequent training sessions. In contrast, the magnitude of the CS-elicited excitatory response during pseudoConditioning began to decline within the first 10 trials. Neurons exhibiting excitatory responses to the CS during Trace Conditioning also exhibited excitatory responses to the US that were significantly greater in magnitude than US-elicited responses during pseudoConditioning. CS-elicited decreases in neuronal activity became more robust over the course of Trace Conditioning compared to pseudoConditioning. Reductions in activity during the CS interval consistently preceded excitation in both training groups, suggesting that the CS-elicited decreases in neuronal activity may serve to increase the signal-to-noise ratio of the excitatory response to the tone. Taken together, these data suggest that the caudal AC is involved early in Trace eyeblink Conditioning and that maintenance of the CS-elicited excitatory response may serve to signal the salience of the tone.
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hippocampal encoding of non spatial Trace Conditioning
Hippocampus, 1999Co-Authors: Matthew D Mcechron, John F. DisterhoftAbstract:Trace eyeblink classical Conditioning is a non-spatial learning paradigm that requires an intact hippocampus. This task is hippocampus-dependent because the auditory tone conditioned stimulus (CS) is temporally separated from the corneal airpuff unconditioned stimulus (US) by a 500-ms Trace interval. Our laboratory has performed a series of neurophysiological experiments that have examined the activity of pyramidal cells in the CA1 area of the hippocampus during Trace eyeblink Conditioning. We have found that the non-spatial stimuli involved in this paradigm are encoded in the hippocampus in a logical order that is necessary for their association and the subsequent expression of behavioral learning. Although there were many profiles of single neurons responding to the CS-US trial during training, the majority of the neurons showed an increase in activity to the airpuff-US. Prior to learning, it appears that hippocampal cells and ensembles of cells were preferentially attending to the stimulus with immediate behavioral importance, the US. Hippocampal cells then began to respond to the associated neutral stimulus, the CS. Shortly thereafter, animals began to show increases in the behavioral expression of CRs. In some experiments, hippocampal neurons from aged animals exhibited impairments in the encoding of CS and US information. These aged animals were not able to associate these stimuli and acquire Trace eyeblink CRs. Our findings along with the findings of other spatial learning studies, suggest that the hippocampus is involved in encoding information about discontiguous sets of stimuli, either spatial or nonspatial, especially early in the learning process. Hippocampus 1999;9:385–396. © 1999 Wiley-Liss, Inc.
Anna V Beylin - One of the best experts on this subject based on the ideXlab platform.
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the role of the hippocampus in Trace Conditioning temporal discontinuity or task difficulty
Neurobiology of Learning and Memory, 2001Co-Authors: Anna V Beylin, Chetan C Gandhi, Gwendolyn E Wood, Andrew C Talk, Louis D Matzel, Tracey J. ShorsAbstract:Abstract It is well established that the hippocampal formation is critically involved in the acquisition of Trace memories, a paradigm in which the conditioned (CS) and unconditioned stimuli (US) are separated by a temporal gap (Solomon et al., 1986). The structure is reportedly not critical for the acquisition of delay memories, where the CS and the US overlap in time (Berger & Orr, 1983; Schmaltz & Theios, 1972). Based on these results, it is often stated that the hippocampus is involved in “filling the gap” or otherwise associating the two stimuli in time. However, in addition to the presence of a temporal gap, there are other differences between Trace and delay Conditioning. The most apparent difference is that animals require many more trials to learn the Trace task, and thus it is inherently more difficult than the delay task. Here, we tested whether the hippocampus was critically involved in delay Conditioning, if it was rendered more difficult such that the rate of acquisition was shifted to be analogous to Trace Conditioning. Groups of rats received excitotoxic lesions to the hippocampus, sham lesions or were left intact. Using the same interstimulus intervals (ISI), control animals required more trials to acquire the Trace than the delay task. As predicted, animals with hippocampal lesions were impaired during Trace Conditioning but not delay Conditioning. However, when the delay task was rendered more difficult by extending the ISI (a long delay task), animals with hippocampal lesions were impaired. In addition, once the lesioned animal learned the association between the CS and the US during delay Conditioning, it could learn and perform the Trace CR. Thus, the role of the hippocampus in classical Conditioning is not limited to learning about discontiguous events in time and space; rather the structure can become engaged simply as a function of task difficulty.
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The contribution of adrenal and reproductive hormones to the opposing effects of stress on Trace Conditioning in males versus females.
Behavioral neuroscience, 2001Co-Authors: Gwendolyn E Wood, Anna V Beylin, Tracey J. ShorsAbstract:Exposure to an acute stressful experience facilitates classical Conditioning in male rats but impairs Conditioning in female rats (T. J. Shors, C. Lewczyk, M. Paczynski, P. R. Mathew, & J. Pickett, 1998; G. E. Wood & T. J. Shors, 1998). The authors report that these effects extend to performance on the hippocampal-dependent task of Trace Conditioning. The stress-induced impairment of Conditioning in females was evident immediately, 24 hr and 48 hr after stress, depending on the stage of estrus. Moreover, the effect could be reactivated days later by reexposure to the stressful context. Corticosterone levels correlated with overall performance in males but not in females. Unlike the effect seen in males, adrenalectomy did not prevent the stress-induced effect on Conditioning in females. These data indicate that exposure to the same experience can have opposite effects on learning in males versus females and that these opposing effects are mediated by differing hormonal systems.
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stress enhances excitatory Trace eyeblink Conditioning and opposes acquisition of inhibitory Conditioning
Behavioral Neuroscience, 1998Co-Authors: Anna V Beylin, Tracey J. ShorsAbstract:Exposure to a brief, stressful event is reported to facilitate classical eyeblink Conditioning in the male rat (Rattus norvegicus) by use of a delay paradigm in which the conditioned stimulus (CS) and unconditioned stimulus (US) overlap and coterminate. This study examined the effects of stress on Trace Conditioning, a task in which the CS and US were separated by 500 ms. Experiment 1 showed that exposure to brief (1 s), low-intensity (1 mA) tailshocks facilitated acquisition 24 hr later. Experiment 2 showed that stressor exposure did not affect retention or extinction of Trace Conditioning in rats that were stressed after acquisition. Experiment 3 showed that exposure to the same stressor opposed acquisition of inhibitory Conditioning. These results suggest that exposure to a stressful event persistently facilitates acquisition of Trace Conditioning and enhances a bias toward acquiring positive versus negative associations.
William B Levy - One of the best experts on this subject based on the ideXlab platform.
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The formation of neural codes in the hippocampus: Trace Conditioning as a prototypical paradigm for studying the random recoding hypothesis
Biological cybernetics, 2005Co-Authors: William B Levy, A. Sanyal, P. Rodriguez, D. W. SullivanAbstract:The Trace version of classical Conditioning is used as a prototypical hippocampal-dependent task to study the recoding sequence prediction theory of hippocampal function. This theory conjectures that the hippocampus is a random recoder of sequences and that, once formed, the neuronal codes are suitable for prediction. As such, a Trace Conditioning paradigm, which requires a timely prediction, seems by far the simplest of the behaviorally-relevant paradigms for studying hippocampal recoding. Parameters that affect the formation of these random codes include the temporal aspects of the behavioral/cognitive paradigm and certain basic characteristics of hippocampal region CA3 anatomy and physiology such as connectivity and activity. Here we describe some of the dynamics of code formation and describe how biological and paradigmatic parameters affect the neural codes that are formed. In addition to a backward cascade of coding neurons, we point out, for the first time, a higher-order dynamic growing out of the backward cascade—a particular forward and backward stabilization of codes as training progresses. We also observe that there is a performance compromise involved in the setting of activity levels due to the existence of three behavioral failure modes. Each of these behavioral failure modes exists in the computational model and, presumably, natural selection produced the compromise performance observed by psychologists. Thus, examining the parametric sensitivities of the codes and their dynamic formation gives insight into the constraints on natural computation and into the computational compromises ensuing from these constraints.
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Activity affects Trace Conditioning performance in a minimal hippocampal model
Neurocomputing, 2004Co-Authors: David W. Sullivan, William B LevyAbstract:Using a minimal hippocampal model, previous studies simulating Trace Conditioning have reproduced the empirically observed learnable Trace interval and reproduced the number of training trials required for learning. However, these earlier studies did not address the effects of parameterization on performance. Here, we demonstrate a robust effect of average activity on Trace Conditioning performance.
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A model of hippocampal activity in Trace Conditioning: where's the Trace?
Behavioral neuroscience, 2001Co-Authors: Paul Rodriguez, William B LevyAbstract:The hippocampus is generally thought to play a modulating role in the timing of conditioned responses in classical Trace Conditioning. One hypothesis is that the hippocampus stores a memory Trace of the conditioned stimulus (CS) during the stimulus-free period. Cellular recordings, however, do not show any obvious CS storage. This article examines this issue by using a biologically plausible model of the CA3 region of the hippocampus. Simulations of the model reproduce both behavioral and physiological experimental data. On the basis of neural codes that develop in the model, the authors hypothesize that the hippocampus functions as a time-indexed encoding device for the CS and not as a CS storage buffer. Specifically, the CS initiates a sequence of neural activity during the Trace interval that only indirectly represents the CS. The model yields 2 predictions: Some cells will increase in activity only during the Trace interval, and some unconditioned stimulus (US)-coding cells will shift in time and fire before US onset.
