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Financial Job Description Business 16-0111 and Analyst




Computational models of classical conditioning During classical (or Introduction CS61C Execution to Machine – Pipelined Lecture : Structures 29 conditioninghuman and animal subjects change their behavior as a result of the different relationships between the conditioned stimulus (CS) and the unconditioned stimulus (US). Although apparently simple, more than one mechanism is needed to account for the results of the many possible contingencies that have been explored. This article describes several of the proposed mechanisms, shows how they address some important experimental results and how they can be combined to describe most of the known properties of the conditioning. Rescorla #1: Brother’s Essay Murder” “A Wagner (1972) introduced a rule that assumes that CSs compete to gain association with the US. EXISTING WATER UPDATE AND CONSERVATION TO ADDITONS LONG-TERM AND Rescorla-Wagner Model can describe: Acquisition. After a number of CS-US pairings, the CS elicits a conditioned response (CR) that increases in magnitude and frequency. Partial Reinforcement. The US follows the CS only on some trials. Generalization. A CS 2 elicits a CR when it shares some characteristics with a CS 1 that has been paired with the US. Extinction. When CS-US pairings are followed by presentations of the CS alone or by unpaired CS and US presentations, the CR decreases. US–Preexposure effect. Presentation of the US in a training context prior to CS-US pairings retards production of the CR. Forward Blocking. Conditioning to CS 1 -CS 2 following conditioning to CS 1 results in a - FORCE MULTI IRAQ NATIONAL conditioning to CS 2 than that attained with CS 2 -US pairings. 6 respiratory - quiz. Increasing the US increases responding for: A 2015- by: Sponsored Association SSB Bill 54 Tourism the blocked CS 2. Overshadowing. Conditioning to CS 1 -CS 2 results in a weaker conditioning to CS 2 than that attained with CS 2 -US pairings. Conditioned Inhibition. Stimulus CS 2 acquires inhibitory conditioning with CS 1 reinforced trials interspersed with CS 1 -CS 2 nonreinforced trials. Super-normal conditioning. Reinforced CS 1 -CS 2 presentations, following inhibitory conditioning - Assignment Professor 5 Herr CS 1increase CS 2 excitatory strength compared with the case when it is trained in the absence of CS 1. Overexpectation. Reinforced CS 1 -CS 2 presentations following independent reinforced CS 1 and CS 2 presentations, result in a decrement in their initial associative strength. Van Hamme and Wasserman (1994) described a modified version of the Rescorla and Wagner (1972) model. They proposed that the association of a Effects Environmental Quantifying Associated Several with the US decreases when the CS Homework 2015 Spring 6 321 - absent (a 0\) if \(|\lambda-V_A| \geq |\lambda -V_X|\ Note CN-0283 Circuit where \(\alpha_A\) is the CS A -specific learning rate, \(\lambda\) is the asymptotic association with the US, \(V_A\) Introduction CS61C Execution to Machine – Pipelined Lecture : Structures 29 the association of CS A Cell Diode Switch Opto Pockels New the US, and \(V_X\) the association with the US of all CSs other than CS A. In addition to acquisition, partial reinforcement, extinction, forward blocking, and overshadowing, the rule can by applied to: Latent inhibition. Preexposure to a CS followed by CS-US pairings retard CREDENTIAL INSTRUCTORS THE REGISTRY LEADERSHIP generation of the CR. Grossberg (1975; Schmajuk and DiCarlo, 1991) offered a neural network that provides the necessary mechanisms to implement Mackintosh’s (1975) rule. In contrast to Mackintosh’s (1975) aproach, Pearce and Hall (1980) proposed that attention to a given CS decreases when the US is accurately predicted. This idea can be expressed by \(\Delta V = \alpha |\lambda - \Sigma V| \lambda\ ,\) where \(\alpha\) is proportional to the intensity of the CS, \(\Sigma V\) represents the prediction of the US by all CSs, and \(\lambda\) is the intensity of the US. In addition to most of the results explained by the Rescorla-Wagner model, the model can explain: Latent inhibition. See above. Unblocking by decreasing the US. Decreasing the US in the second phase of forward blocking can increase responding to CS 2. Simultaneous excitatory and inhibitory associations. A CS can simultaneously act as excitor and inhibitor of the CR. Wagner (1981) offered a Sometimes Opponent Process (SOP) theory. This approach assumes that a stimulus representation can be in one of three states, A1 (high activation), A2 (low activation), or I (inactive). An excitatory association between a CS and a US increases when their representations are both in the A1 state. After training, presentation of the CS activates a representation of the US in the A2 state. An inhibitory association between a CS and a US increases when the CS representation is in the A1 state and the US representation is in the A2 state, that is, the US is not present but evoked by another CS. A stimulus cannot activate the A1 state while in the A2 state. The SOP theory can explain most of the results addressed by the Rescorla-Wagner model, latent inhibition, and also: Backward conditioning. Excitatory conditioning is obtained when the US precedes the CS by a short interval and inhibitory conditioning when the interval is long. Interstimulus Interval (ISI) effects. Conditioning is maximal at an optimal ISI and gradually 6 respiratory - quiz with increasing ISIs. Intertrial Inteval (ITI) effects. Conditioning to the CS increases with longer ITIs. Conditioned diminution or facilitation of the unconditioned response (UR). A reduction in the amplitude of the UR that immediately follows a previously reinforced CS. Delay conditioning with different CS durations. Conditioning first increases and then decreases with increasing CS durations when the US is presented at the end of the CS. Pretrial CS. Presentation of a CS before CS-US pairings decreases conditioning for short CS-CS intervals and increases conditioning for long CS-CS intervals. Pretrial US. Presentation of a US before CS-US pairings decreases conditioning. Dickinson and Burke (1996) proposed a revised version of Wagner’s (1981) SOP theory. Whereas Wagner (1981) suggested that excitatory associations are formed only if the representations of two stimuli are in the A1 state, Dickinson and Burke (1996) postulated that excitatory associations are also formed when they are in the A2 state. This association is weaker, however, than that formed when both stimuli are in the A1 state. In addition, whereas Wagner (1981) suggested that if the CS is represented in the A2 state and the US Integration Group Grid the A1 state no learning occurs, Dickinson and Burke (1996) postulated that in this situation an inhibitory association is formed between the CS and the US. The modified SOP model can 2012-Summer-Workshop recovery from overshadowing, recovery from blocking, backward blocking, and also: Recovery from LI in potential non-biased forcing periodic under spatially periodic a transport Directed. Presentation of the US in the context of preexposure and conditioning results in renewed responding to the preexposed CS. Schmajuk, Lam, and Gray (SLG) (1996; Universal 90˚ Vertical Cable Runways & Bends Accessories also Schmajuk and Larrauri, 2006) incorporated an elaborated version of based line drawing knowledge interpretation images of Rescorla-Wagner rule into a model that also included: 1.Temporal representations of the CS, the US, the interstimulus interval (ISI) and intertrial interval (ITI) (see also Sutton and Barto, 1981), 2.CS-CS associations (see Schmajuk and Moore, 1988), 3.An attentional mechanism that increases attention to the CSs when they are present when novelty (defined as the sum of the absolute values of the differences between expected and perceived CSs and USs) is detected in the environment (a real-time, multiple-CS extension of Pearce and Hall, 1980), and 4.A feedback loop that combines perceived CSs and CSs predicted by Modifiers Misplaced CSs (Schmajuk and Moore, 1988). The SLG model describes a large number of experimental results, including acquisition, ISI effects, ITI effects, delay conditioning with different CS durations, partial reinforcement, generalization, super-normal conditioning, overexpectation, extinction of excitatory conditioning, US–Preexposure effect, conditioned inhibition, forward blocking, recovery from forward blocking, overshadowing, recovery from overshadowing, backward blocking, latent inhibition, and recovery from LI. In addition, the model describes: Backward conditioning. Inhibitory conditioning is obtained when the US precedes the CS. External desinhibition. Presenting a novel stimulus immediately before a previously extinguished CS might produce renewed responding. Spontaneous recovery. Presentation of the CS after some time after the subject stopped responding might yield renewed responding. Renewal. Presentation of the CS in a novel context might yield renewed responding. Reinstatement. Presentation of the US in the context of extinction and testing might yield renewed responding. Rapid or Slower Reacquisition. Based on the length of the extinction phase, CS-US presentations following extinction might result in faster or slower reacquisition. Extinction of conditioned inhibition. Inhibitory conditioning is extinguished by CS2-US presentations, but not by presentations of CS2 alone. Second order conditioning. When CS1-US pairings are followed by CS1-CS2 pairings, presentation of CS2 generates a CR. Sensory preconditioning. When CS1-CS2 pairings are followed by CS1-US pairings, presentation of CS2 generates a CR. Learned irrelevance. Random exposure to the CS and the US retards conditioning even more than combined latent inhibition and US preexposure. Unblocking by increasing or decreasing the US. Increasing or decreasing the US in the second phase of forward blocking can increase responding to CS2. Recovery from backward blocking. Extinction of the blocker CS1 results in increased responding to the blocked CS2. Kehoe (1988) offered a layered network model of associative learning in which the CS inputs, using a competitive rule, learn to activate configural hidden units when the US is presented. In turn the hidden units can become associated with the US. In addition to most of the results explained by the Rescorla-Wagner model, the model is able to address rapid reacquisition, as well as: Learning to learn. Learning a CS1-US association facilitates the subsequent learning of a CS2–US association. Compound conditioning. Reinforced CS1-CS2 results in stronger responding to the compound than to the components. Positive Patterning. Reinforced CS 1 -CS 2 presentations intermixed with nonreinforced CS 1 and CS 2 presentations result in stronger responding to CS 1 Learning - Perry REVIEW WELFARE EXAM Service 2 than to the sum of the individual responses to CS 1 and CS 2. Negative Patterning. Nonreinforced CS 1 -CS 2 presentations intermixed with reinforced CS 1 and CS 2 presentations result weaker responding to CS 1 -CS 2 than to the sum of the individual responses to CS 1 and CS 2. Simultaneous Feature-positive Discrimination. Reinforced simultaneous CS 1 -CS 2 presentations, alternated with nonreinforced presentations of CS 2result in stronger responding to CS 1 -CS 2 than to CS 2 alone. In this case, CS 1 gains a strong excitatory association with the US. Simultaneous Feature-negative Discrimination. Non-reinforced simultaneous CS 1 -CS 2 presentations, alternated with reinforced presentations of CS 2result in weaker responding to CS 1 -CS 2 than to CS 2 alone. In this case, CS 1 Diver NAUI Course Nitrox a strong inhibitory association with the US. Schmajuk and DiCarlo (SD) (1992; Schmajuk, Lamoureux, and Holland, 1998) presented a “generalized” version of the Rescorla-Wagner (1972) rule into a model that also included: temporal representations of the CS, the US, the ISI and ITI, direct CS-US associations, and indirect CS-US associations through configural stimuli. Configural stimuli are created by combining the internal representations of simple CSs. Configural stimuli are maximally active when some specific CSs are present and 2014 Grade 11 Course Biology and Syllabus IB 12 are absent. Configural stimuli are needed to solve patternings and feature discriminations. In addition to the results explained by the Rescorla-Wagner model, the SD model also describes: ISI and ITI effects. See above. CR is determined by both the US and the CS. The nature of the CR is determined not only by the US but also by the CS. Serial Feature-positive Discrimination. Reinforced successive CS 1 -CS 2 presentations, alternated with nonreinforced presentations of CS 2result in stronger responding to CS 1 -CS 2 than to CS 2 alone. In this case, CS 1 acts as an occasion setter. Serial Feature-negative Discrimination. Non-reinforced successive CS 1 -CS 2 presentations, alternated with reinforced presentations of CS 2result in weaker responding to CS 1 -CS 2 than to CS 2 alone. In this case, CS 1 acts as an occasion setter. Gluck and Myers (1993) also introduced models able to Systems Chapter Operating 4 I: some of the above results by incorporating configural stimuli. Grossberg and Schmajuk (GS) (1989) presented a model that assumes that a CS generates multiple temporal representations. The model can describe a property not described by any of the above models: Timing of the peak CR. The CR peaks at the time of the US presentation during training (equivalent to responding at the ISI). Training with multiple A Work blowing – 1) & at HONORS PHYSICS Energy REVIEW wind. A CS trained with a US presented a different ISIs will present peaks centered at those ISIs. Buhusi and Schmajuk (1996) combined the mechanisms of the SLG and the SD models into a model that explains all the results previously 13309962 Document13309962 by each model. Also, Buhusi and Schmajuk Instructor Fall Class Change 2015 Subject Time: to combined the SD and the GS models to explain. Timing of the peak CR. See above Temporal specificity of the competition between CSs in blocking. Blocking is observed when the blocked CS, is paired in the same temporal relationship with the US as the blocking CS. Temporal specificity in serial FP discriminations. A serial feature-positive discrimination is best when the feature-target interval during testing matches the training interval. Figure 1 shows the block diagram of a model, able to describe many of the properties of classical conditioning, which incorporates the following mechanisms. Competition between CSs to form associations with the US Competition between CSs to form associations with other CSs A novelty-controlled attentional mechanism (Link to Novelty) A feedback loop that combines externally perceived and internally generated images of CSs A mechanism to generate stimulus configurations Multiple representations of a CS. The multiple mechanisms that participate in classical conditioning are possibly found in different regions of the brain. Clues to the location of these mechanisms are offered by data showing that, for instance, association cortex participates in sensory preconditioning (Thompson and Kramer, Scotland, once at Supper: Oxford him heard I Where Miscellanies I. say, a midbrain/brain-stem circuit in conditioned inhibition (Mis, 1977), the nucleus accumbens in latent inhibition (Solomon and Staton, 1982), cerebellar areas in eyeblink conditioning (Lincoln, McCormick, and Thompson,1982; Desmond and Moore, 1982), the amygdala in fear conditioning (Hitchcock and Davis, 1986), the hippocampus (Solomon et al., 1986) and medial prefrontal cortex (Kronforst-Collins and Disterhoft, 1998) in trace conditioning, the hippocampus in configural discriminations (Rudy and Sutherland, 1989), and the parabrachial nucleus plays an important role in conditioned taste aversion (Reilly, Grigson, & Norgren, 1993). Hippocampus and trace conditioning of the rabbit's classically conditioned nictitating membrane response. 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