Reward produced memories regulate memory-discrimination learning, extinction, and other forms of discrimination learning.

In memory-discrimination learning, reward-produced memories are differentially rewarded such that they are the only stimuli available to support discriminative responding. Memory-discrimination learning was used in this study as follows: Reward-produced memories that were assumed to regulate instrumental performance in previously reported extinction and discrimination learning investigations were isolated and explicitly differentially reinforced (prior to a shift to extinction) in each of 4 runway investigations with rats. Results obtained here in the explicit discrimination learning stage and in the subsequent extinction stage were consistent with the prediction of the memory view and with prior discrimination learning and extinction findings. The memory interpretation was applied to memory-discrimination learning, to extinction, and to 2 other types of discrimination learning. It appears that a theory must use reward-produced memories to explain all 4 types of discrimination learning. (PsycINFO Database Record (c) 2010 APA, all rights reserved)     

Time between events as a retrieval cue: Recall and the temporal similarity between the storage and retrieval intervals.

Examined the hypothesis that the time elapsing between events may be a potent cue that accompanies the storage and retrieval of memories. If so, it follows that as the retention interval increases, recall may either increase or decrease, depending on whether the retrieval interval is becoming more similar or less similar to the storage interval. Six experiments employing a runway were conducted, using a total of 102 naive male Holtzman rats as Ss. The target memory to be recalled in acquisition was measured in a subsequent extinction phase in all 6 experiments reported; faster extinction indicated poorer recall in acquisition. Consistent with the present hypothesis, it was found that regardless of whether the retention interval in extinction was long (10–20 min) or short (about 30 sec), resistance to extinction was greater when in acquisition the storage and retrieval intervals were alike (both 30 sec or 10–20 min) rather than different. Results rule out 4 alternative explanations to the present hypothesis: a temporal discrimination view, time tagging the memory of nonreward, generalization decrement occasioned by a change in retention interval from acquisition to extinction, and what was called the last-trial hypothesis. (26 ref) (PsycINFO Database Record (c) 2010 APA, all rights reserved)     

Context, time, and memory retrieval in the interference paradigms of Pavlovian learning.

Reviews research and theory on the "interference paradigms" in Pavlovian learning. In these situations (e.g., extinction, counterconditioning, and latent inhibition), a CS is associated with different unconditioned stimulus/stimuli (UCS) or outcomes in different phases of the experiment; retroactive interference, proactive interference, or both are often observed. In all of the paradigms, contextual stimuli influence performance, and when information is available, so does the passage of time. Memories of both phases are retained, and performance may depend on which is retrieved. Despite the similarity of the paradigms, conditioning theories tend to explain them with separate mechanisms. They also do not provide an adequate account of the context's role, fail to predict the effects of time, and overemphasize the role of learning or storage deficits. By accepting 4 propositions about animal memory (i.e., contextual stimuli guide retrieval, time is a context, different memories are differentially dependent on context, and interference occurs at performance output), a memory retrieval framework can provide an integrated account of context, time, and performance in the various paradigms. (PsycINFO Database Record (c) 2010 APA, all rights reserved)     

Effects of ethanol on encoding, consolidation, and expression of extinction following contextual fear conditioning.

Studies of contextual fear conditioning have found that ethanol administered prior to a conditioning session impairs the conditioned freezing response during a test session the next day. The present experiments examined the effects of ethanol on extinction, the loss of conditioned responding that occurs as the animal learns that a previously conditioned context no longer signals shock. Ethanol (1.5 g/kg) administered prior to single (Experiment 1) or multiple (Experiment 2) extinction sessions impaired extinction. Ethanol administered prior to a test session disrupted the expression of freezing after extinction (Experiments 3-5). There was some evidence that ethanol served as an internal stimulus signaling the operation of conditioning or extinction contingencies (Experiments 4-5). In Experiment 6, postsession injections of 1.5 g/kg ethanol had no effect on extinction with brief (3 min) or long (24 min) exposures to the context, but injections of 3 g/kg after long exposures impaired extinction. Together, these results indicate that ethanol affects extinction by acting on multiple learning and performance processes, including attention, memory encoding, and memory expression. (PsycINFO Database Record (c) 2010 APA, all rights reserved)     

Acquisition, retention, and extinction of operant discriminations in rats with nucleus basalis magnocellularis lesions.

Effects of bilateral ibotenic acid lesions of nucleus basalis magnocellularis (NBM) and scopolamine treatment on different aspects of learning and memory in an operant discrimination task were assessed. In Experiment 1, NBM lesions impaired acquisition performance. In Experiment 2, scopolamine lowered response rates but did not affect discrimination accuracy in lesioned or control rats. In Experiment 3, although pretrained rats showed transient increases in commission errors, percentage correct responding remained above chance levels after lesion. During extinction in Experiment 4, operant responding diminished more quickly in pretrained NBM-lesioned rats than in controls, but subsequent reacquisition performance was equivalent in both groups. Results suggest the NBM is importantly involved in discrimination learning, but cholinergic activity may be less critical for memory retention than for acquisition. (PsycINFO Database Record (c) 2010 APA, all rights reserved)     

Autobiographical memory: Reports in adolescence.

A prompt word technique was used to investigate the processes of autobiographical memory in 40 adolescents (aged 12–15 yrs) and 40 undergraduates. Three types of prompts were used: object, action, and affect. Prompt type was found to interact with age for both response time and the reported event age of the memories. Results indicate that affect prompts were responded to differentially by college students but not by adolescents. Affective terms were responded to more slowly and with more recent memories by college students. Changes in the nature of conceptual systems, e.g., levels of abstraction, are suggested as a possible explanation for changes in episodic memory performance. (French abstract) (11 ref) (PsycINFO Database Record (c) 2010 APA, all rights reserved)     

Individual differences in arousal and accessibility to information in memory

The authors conducted 9 experiments to test the hypothesis (S. Schwartz, 1975) that arousal influences the accessibility of information stored in memory. They investigated the relationship between arousal levels (as indexed by personality types) and the type of stimuli or cues presented during study or test. They predicted that low-arousal individuals (stable extraverted individuals in Experiments 1-3 and 5-9 and high-impulsive individuals in Experiment 4) would be influenced by semantic stimuli, whereas high-arousal individuals (neurotic introverted individuals in Experiments 1-3 and 5-9 and low-impulsive individuals in Experiment 4) would be influenced by physical (i.e., graphic, phonetic, or both) stimuli. They tested the arousal-accessibility hypothesis by using a variety of tasks including verbal discrimination, false recognition, cued recall, and paired associates. With the exception of the finding that stable extraverted participants performed better than neurotic introverted participants on an incidental associative-matching task (Experiment 3), the results from the verbal discrimination studies (1-5) did not support the hypothesis. In Experiment 6, the authors tested the hypothesis by using a false-recognition task. False alarms varied as a function of phonetic and semantic stimuli, but personality types were not differentially sensitive to the manipulation. The same was true for the cued-recall studies (Experiments 7 and 8); personality types were not differentially sensitive to the semantic and phonetic stimuli. Experiment 9 (paired-associate learning) was a replication of Schwartz's study. The authors found some support for the Schwartz hypothesis: Extraverted participants were adversely affected by semantic similarity. Overall, the findings did not provide much support for the arousal-accessibility hypothesis.     

Systemic or intrahippocampal delivery of histone deacetylase inhibitors facilitates fear extinction.

Several recent studies have shown that chromatin, the DNA-protein complex that packages genomic DNA, has an important function in learning and memory. Dynamic chromatin modification via histone deacetylase (HDAC) inhibitors and histone acetyltransferases may enhance hippocampal synaptic plasticity and hippocampus-dependent memory. Little is known about the effects of HDAC inhibitors on extinction, a learning process through which the ability of a previously conditioned stimulus, such as a conditioning context, to evoke a conditioned response is diminished. The authors demonstrate that administration of the HDAC inhibitors sodium butyrate (NaB) systemically or trichostatin A (TSA) intrahippocampally prior to a brief (3-min) contextual extinction session causes context-evoked fear to decrease to levels observed with a long (24-min) extinction session. These results suggest that HDAC inhibitors may enhance learning during extinction and are consistent with other studies demonstrating a role for the hippocampus in contextual extinction. Molecular and behavioral mechanisms through which this enhanced extinction effect may occur are discussed. (PsycINFO Database Record (c) 2010 APA, all rights reserved)     

Olfaction and the "data" memory system in rats.

Conducted studies to characterize the memory system involved in successive olfactory discrimination learning in rats. Two odors emanated from different arms of a radical maze; 1 of the arms contained a water reward. After training on 4 to 5 pairs of odors Ss learned to discriminate the members of a new pair in 5–20 trials. Experiments in which either member of the pair was compared with a novel cue indicated that the Ss learn both positive and negative odors, rather than ignoring the negative cue. The memories for the odors were apparently persistent, and no evidence for retroactive interference from subsequent training was obtained. Animals trained on 3 component odors with 2 in common did not recognize the elements that were unshared when these were presented by themselves. Even when 1 of the 2 shared components was combined with the differentiating component into a cue the new cue was treated as a novel odor. Inclusion of a previously learned simple odor in a complex odor did affect the learning of that odor. Findings, combined with those of previous studies in which lesions were used, suggest that learning that a series of odor discriminations involves a version of the "data" memory system described by cognitive psychologists. (PsycINFO Database Record (c) 2010 APA, all rights reserved)     

Reality monitoring.

People remember information from 2 basic sources: external (perceptual processes) and internal (processes such as reasoning, imagination, and thought). Of particular interest are the processes people use in deciding whether information initially had an external or an internal source, i.e., "reality monitoring." A working model of reality monitoring is proposed to account for both discrimination and confusion between memories for thoughts and memories for perceptions. Examples of questions the model addresses are: What types of information are more likely to be represented in memories of external events than in memories of internal events?; What assumptions do individuals have about their memory for their thoughts compared to their memory for their perceptions?; and How accurate are these assumptions? Research that demonstrates the usefulness of the model is summarized. (100 ref) (PsycINFO Database Record (c) 2010 APA, all rights reserved)     

Why there are complementary learning systems in the hippocampus and neocortex: Insights from the successes and failures of connectionist models of learning and memory.

Damage to the hippocampal system disrupts recent memory but leaves remote memory intact. The account presented here suggests that memories are first stored via synaptic changes in the hippocampal system, that these changes support reinstatement of recent memories in the neocortex, that neocortical synapses change a little on each reinstatement, and that remote memory is based on accumulated neocortical changes. Models that learn via changes to connections help explain this organization. These models discover the structure in ensembles of items if learning of each item is gradual and interleaved with learning about other items. This suggests that the neocortex learns slowly to discover the structure in ensembles of experiences. The hippocampal system permits rapid learning of new items without disrupting this structure, and reinstatement of new memories interleaves them with others to integrate them into structured neocortical memory systems. (PsycINFO Database Record (c) 2010 APA, all rights reserved)     

Associations between autobiographical memories and concepts.

Three experiments investigated associations between autobiographical memories and different types of concepts. Two types of concepts, goal-derived categories and taxonomic categories, were used to prime memory retrieval to related category exemplar cues. In all 3 experiments, only goal-derived categories were found to reliably speed memory retrieval. Weak associations between speed of memory retrieval and both the specificity and the personal importance of the memory were found; memories that were high in these qualities were retrieved more quickly than memories low in these qualities, and this was independent of the type of cue used to prompt retrieval. These findings demonstrate that goal-derived categories are closely associated in long-term memory with records of specific experiences. It is proposed that this close association is mediated by the role of goal-derived concepts in event knowledge. (PsycINFO Database Record (c) 2010 APA, all rights reserved)     

Autobiographical memory across personalities in dissociative identity disorder: A case report.

A core feature of dissociative identity disorder (DID) is the amnesia that exists between personalities. This study investigated autobiographical memory in a patient, HS, prior to and after her diagnosis with DID. This diagnosis was associated with increased recall of traumatic memories that were reported by a child personality. The child personality was able to recognize only half of the memories reported by the host personality. HS's responses were dissimilar to responses of control and nonexperiment participants. These findings suggest that DID is associated with alterations in autobiographical memory and that memories differ across personalities. Results are discussed in terms of memory and pseudomemory development in DID. (PsycINFO Database Record (c) 2010 APA, all rights reserved)     

Differential effects of nicotinic acetylcholine receptor stimulation on negative occasion setting.

We have previously shown that nicotine enhances learning in a negative occasion setting task in which rats are trained to distinguish between two different trial types. During reinforced trials, a target stimulus (a tone) is presented and immediately followed by food reward. On nonreinforced trials, a feature stimulus (a light) is presented prior to the tone and indicates the absence of reward following presentation of the tone. The goal of the present study was to identify the behavioral mechanism through which nicotine affects this form of learning, and to determine which subtype(s) of nicotinic acetylcholine receptors mediate the effects of nicotine. Consistent with our prior findings, nicotine administration enhanced the ability of rats to discriminate between the two trial types. Nicotine enhanced the magnitude of the discrimination by decreasing responding to the tone on nonreinforced trials. Nicotine-treated rats also learned the discrimination in fewer sessions than control rats. A significant new finding was that nicotine also increased the orienting response to the light, suggesting that nicotine may enhance learning the serial feature negative discrimination by increasing attention to the visual feature. In addition, we found that RJR-2403, a selective α4β2 nicotinic receptor agonist, also enhanced discrimination. However, RJR-2403 did not affect responding on nonreinforced trials, nor did RJR-2403 affect orienting to the light. Together these data indicate that nicotine may enhance discrimination by enhancing tone-reward associability through α4β2 nicotinic receptors and by enhancing attention to the light through non-α4β2 receptor subtypes. (PsycINFO Database Record (c) 2010 APA, all rights reserved)     

Development of verbatim and gist memory for numbers.

Two theories of developmental and functional relationships between verbatim and gist memories of numbers were compared: (1) the integration hypothesis, which assumes that gist memories are constructive inferences from verbatim memories; and (2) the parallel retrieval hypothesis, which assumes that gist memories are stored in parallel with the encoding of verbatim information. In Exp 1, being able to remember verbatim numbers did not help children remember either the global gist (most or least) or the pairwise gist (more or less) of those numbers, manipulations that improved verbatim memory did not improve gist memory, and the relative accuracy of the 2 types of memory reversed with age. In Exp 2, additional evidence favoring the parallel retrieval model was provided by an instructional manipulation that enhanced preschoolers' gist memories but impaired their verbatim memories. (PsycINFO Database Record (c) 2010 APA, all rights reserved)     

Discrimination learning during the first year: Stimulus and positional cues.

In four studies, 3-, 6-, and 9-month-old human infants were tested in a discrimination learning task in which visual fixation to a particular stimulus or lateral position was reinforced with an auditory stimulus. In Experiment 1, all age groups exhibited acquisition, extinction, and reinstatement of fixation to the reinforced target or position. Experiment 2 revealed that 3-month-olds retained the positional discrimination but not the stimulus discrimination after a 5-min delay between acquisition and extinction; older infants retained both types of discriminations. In Experiments 3 and 4 we investigated a possible developmental shift in the dominance of positional versus stimulus cues by training infants on displays in which stimulus and position were confounded and then by dissociating the cues on test trials. Results from both experiments indicated positional cue dominance for young infants and stimulus cue dominance for older infants. The findings are discussed in terms of differences in the attentional demands elicited by proprioceptive versus exteroceptive cues. (PsycINFO Database Record (c) 2010 APA, all rights reserved)     

Analysis of the content of configural representations: The role of associatively evoked and trace memories.

Two experiments examined the content of configural learning in rats. In Experiment 1, after simple pre-exposure to two hybrid contexts (AB and CD), rats acquired a configural discrimination involving two of the contexts (A and C) and two auditory stimuli (X and Y; AX→food, AY→no food, CX→no food, and CY→food). When rats were then placed in context B, they were more likely to respond to X than Y, and when they were placed in context D the reverse was the case. Experiment 2 demonstrated that rats can acquire a configural discrimination involving the presence of context (A) and its memory trace (a; AX→food, AY→no food, aX→no food, and aY→food). These results show that associatively provoked memories (Experiment 1) and memory traces (Experiment 2) can participate in configural discriminations. (PsycINFO Database Record (c) 2010 APA, all rights reserved)     

Intrapair imagery effects in verbal discrimination and incidental associative learning.

Administered 4 study-test trials to 80 17-38 yr. Old students on a verbal discrimination learning (vdl) task where the items varied in imagery (i) value. Ss were then tested for incidental associative learning. The 32-pair mixed list consisted of 8 pairs of high-i and 8 pairs of low-i nouns, and 16 pairs in which 1 item was high-i and the other low-i. For 1/2 of the latter pairs the high-i word was correct. Significantly more errors occurred during vdl with homogeneous low-i pairs than with the other 3 pair types, which did not differ reliably from each other. Incidental associative learning was highest for homogeneous high-i pairs, and stimulus i was more effective than response i when the stimuli had been wrong but not when they had been right during prior vdl. The latter condition was characterized particularly by sharply depressed performance on high-i-low-i pairs. The vdl results are discussed in terms of imagery and frequency hypotheses, and the associative memory data in terms of the effects of the experimental conditions on the amount of attention devoted to 1 or both members during vdl. (french summary) (PsycINFO Database Record (c) 2010 APA, all rights reserved)     

Differential effects of induced mood on retrieval of pleasant and unpleasant events from episodic memory.

Examined the effect of depressed mood on the accessibility of memories of past real-life experiences of a pleasant or unpleasant nature. By means of a mood induction procedure, 30 students (mean age 19.2 yrs) were made happy on one occasion and depressed on another. The 2 mood states differed significantly on self-report, speech-rate, and recall-latency measures. Stimulus words to which Ss had to associate past pleasant or unpleasant experiences were presented in each mood condition, and latency of retrieval was measured. Time to retrieve pleasant memories, relative to time to retrieve unpleasant memories, was significantly longer when Ss were depressed than when they were happy, suggesting a differential effect of mood on the accessibility of these 2 types of memory. Results are considered in relation to state-dependent learning and activation of memories, and their implications for models and treatment of depression are discussed. It is suggested that cognitive models of depression need to be extended to include a reciprocal relation between thought content and depressed mood. (24 ref) (PsycINFO Database Record (c) 2010 APA, all rights reserved)     

Proactive interference and temporal context encoding after diazepam intake

Two experiments were designed to test whether the memory impairment induced by benzodiazepines (BZDs) is due to impaired memory for temporal context. In both experiments, subjects were administered either diazepam (15 mg oral) or placebo, and a standard BZD impairment on prose recall as well as a decreased subjective arousal was found. Key tasks to explore temporal context memory were an A-B A-C proactive interference paradigm and a list discrimination task. Initial learning of both groups on these tasks was broadly matched. In experiment 1, diazepam did not increase susceptibility to proactive interference using semantically related words. However, in experiment 2, using unrelated word pairs, diazepam markedly increased the number of prior list intrusions. Furthermore, after diazepam intake, subjects were clearly impaired in learning unrelated word pairs. Subjects after diazepam intake were not impaired in the list discrimination task. We conclude that (1) diazepam impairs the forming of new associations, whether this is the formation of links between two or more targets or between targets and context, (2) a temporal context encoding deficit cannot account for a broader diazepam-induced memory impairment.