Infants' long-term memory for stimulus color.

Two experiments examined the effects of a change in a reinforcing stimulus's color on memory for an operant response in 32 3- to 4-mo old infants. Ss were trained on 2 successive days to produce movement in an overhead mobile containing either all-blue or all-green objects. Subsequent exposure to a novel colored mobile produced a decrement in conditioned responding during cued-recall tests 1 but not 7 days following training. Data confirm that infants store information about a stimulus's color and indicate that this information is forgotten more rapidly than that representing other, more general features of the conditioning experience. Results also support the notion that the perception of stimulus color is a basic and early developing (perhaps innate) human characteristic and provide additional evidence of the importance of this variable for early memory. (19 ref) (PsycINFO Database Record (c) 2010 APA, all rights reserved)     

The relationships between working memory and long-term memory

Recent studies have led to the proposal that working memory operates not as a gateway between sensory input and long-term memory but as a workspace. The core of argument is that access to acquired knowledge and prior learning occurs before information becomes available to working memory. This proposition is a way to accommodate Baddeley's multiple component working memory model and the view that considers that working memory is nothing other than temporary activations of representations and procedures in long-term memory. However, this 'workspace' conception of working memory raises the question of the relationships between the central executive system and long-term memory.     

A role for the Ras signalling pathway in synaptic transmission and long-term memory

Members of the Ras subfamily of small guanine-nucleotide-binding proteins are essential for controlling normal and malignant cell proliferation as well as cell differentiation. The neuronal-specific guanine-nucleotide-exchange factor, Ras-GRF/CDC25Mm, induces Ras signalling in response to Ca2+ influx and activation of G-protein-coupled receptors in vitro, suggesting that it plays a role in neurotransmission and plasticity in vivo. Here we report that mice lacking Ras-GRF are impaired in the process of memory consolidation, as revealed by emotional conditioning tasks that require the function of the amygdala; learning and short-term memory are intact. Electrophysiological measurements in the basolateral amygdala reveal that long-term plasticity is abnormal in mutant mice. In contrast, Ras-GRF mutants do not reveal major deficits in spatial learning tasks such as the Morris water maze, a test that requires hippocampal function. Consistent with apparently normal hippocampal functions, Ras-GRF mutants show normal NMDA (N-methyl-D-aspartate) receptor-dependent long-term potentiation in this structure. These results implicate Ras-GRF signalling via the Ras/MAP kinase pathway in synaptic events leading to formation of long-term memories.     

Adult age differences in short-term memory and subsequent long-term memory for actions.

Short-term memory for actions was investigated for young adult and elderly adult Ss with the Brown-Peterson procedure at retention intervals of 0 and 15 sec. The short-term memory trials were followed by the long-term recall of the prior to-be-remembered actions. The 15-sec retention interval was filled either with no activity or with 1 of 3 different interfering activities. Verbal interference had little effect on short-term memory at either age level. Actions performed in the interval either by the Ss or by the experimenter produced significantly lower recall scores at each age level, with the decrement being more pronounced for the elderly than for the young Ss. The long-term memory results indicated that successful short-term recall enhanced later long-term recall, regardless of age level. (PsycINFO Database Record (c) 2010 APA, all rights reserved)     

Two circuits to convert short-term memory into long-term memory

In this prospective study we tested the hypothesis that atropine administration, which is known to increase heart rate and cardiac output in infants, will result in a faster onset of neuromuscular block with atracurium. Thirty infants scheduled for elective surgery had anaesthesia induced with nitrous oxide and halothane. Fifteen patients were given atropine and 15 patients acted as controls. All the infants were given atracurium 0.5 mg.kg-1, and neuromuscular block was recorded with the Datex 221 neuromuscular transmission monitor. Although atropine caused an increase in heart rate compared to the control group (median 164 [range 151-182] vs 120 [98-160]min-1 P < 0.0001), there was not a statistically significant difference in the onset of neuromuscular block between the two groups. We conclude that onset of neuromuscular block after atracurium is determined mainly by noncirculatory factors and less by the circulation time to the muscle. The effect of atropine on the time course of neuromuscular block might be different with faster acting neuromuscular blockers.     

Adult age differences in long-term memory for performed activities

Participants in two studies conducted by Salthouse (in press) were called 2 to 182 days after participation and asked to describe the activities that they had performed in the previous study. Hierarchical regression analyses were used to examine the prediction of activity recall from age, speed, and retention interval. Overall, age was associated with 20% of the variance in activity recall, and retention interval was associated with 19%, but there was no significant interaction of age and retention interval. When perceptual speed was entered into the regression equation before age, the age-related variance was reduced by 70%. A small, but statistically significant, amount of age-related variance in activity memory remained after controlling for speed and retention interval.     

Simulation of human long-term memory.

Reviews computer programs that simulate human long-term memory. A model of memory is described that may be constructed from the various programming efforts. Memory may be conceptualized as a large network with labeled links, where the nodes refer to ideas, and the links to the relations between those ideas. A model of this kind appears capable of giving meaningful answers to factual questions. The model may be so specified as to manifest spontaneous activity and local activity variations based upon excitation of associated contents; this explains context effects and other features. Retrieval, in the model, is effected by means of organized retrieval cues and complex information-retrieval strategies, which later permit the model to respond to cues differing from the original stimuli. (4 P. Ref.) (PsycINFO Database Record (c) 2010 APA, all rights reserved)     

Output interference in long-term memory.

Reports 2 experiments, with 70 and 140 undergraduates, concerning the role of output interference on the recall of organized material. Groups of Ss received blocked presentation of a 49-item list consisting of 7 items in each of 7 categories. At recall, the category name served as the retrieval cue. In Exp. I, a 20-sec recall interval was allowed for each category and 10 Ss were assigned to each group. In Exp. II, this interval was increased to 90 sec. and 20 Ss were assigned to each group. Results of both studies indicate that the number of words recalled from a category is dependent on the position of the category in the output sequence. In general, the earlier a category appears in the output sequence, the greater the number of words recalled from that category. (French summary) (PsycINFO Database Record (c) 2010 APA, all rights reserved)     

Enhancing effects of similarity on long-term memory for order.

Four incidental learning experiments examined the effects of stimulus similarity on long-term memory for order. Although most current theories of order retention easily handle, and often predict, a disruption in order retention under conditions of high intralist similarity, the opposite result, an enhancing effect of similarity, presents a significant interpretive puzzle. All 4 of the present experiments demonstrate conditions in which phonological or categorical similarity significantly improves both absolute and relative long-term memory for sequential order. Tentative interpretations of these results are provided, on the basis of list discrimination arguments and the operation of study–phase reminding processes. (PsycINFO Database Record (c) 2010 APA, all rights reserved)     

Recognition in episodic long-term memory in schizophrenia

Recognition memory is one of the few areas of cognition in schizophrenia in which deficit has not been found. Such a finding has important theoretical implications for the understanding of schizophrenia. However, past studies in this area have been experimentally deficient. This paper presents a study of recognition in long-term episodic memory in schizophrenia in which previous findings of no deficit were replicated. The nature of the cognitive deficit in schizophrenia is discussed.     

The retrieval of attention-dependent long-term memory traces

Phenomenon of memory dissociation is proposed as a paradigm for studying the retrieval processes of the long-term memory. The memory-dissociated states of brain are produced by external influence and result in selective reversible disturbances of the retrieval processes without substantial changes in perception and storage of new information. Analysis of dissociated states induced by pharmacological influences has led us to the following conclusions: 1) the reversible failures of the retrieval processes are usual for the attention-dependent form of long-term memory, 2) hippocampus is the key structure in brain mechanisms that realize the engram selection during memory retrieval, 3) the central cholinergic and GABAergic systems regulate the retrieval of information, 4) steady disturbances of retrieval of the long-term attention-dependent memory are accompanied by strongly pronounced changes in hippocampal cells including those at the membrane and genomic levels.     

Task-set switching and long-term memory retrieval.

The authors tested the hypothesis of a close relationship between the intentional component of task-set switching ("advance reconfiguration;" R. D. Rogers & S. Monsell, 1995) and long-term memory (LTM) retrieval. Consistent with this hypothesis, switch costs are reported to be larger when the switched-to task involves high retrieval demands (i.e., retrieval of episodic information) than when it involves low retrieval demands (i.e., retrieval of semantic information). In contrast, switch costs were not affected by a primary-task difficulty manipulation unrelated to intentional retrieval demands (Experiment 2). Also, the retrieval-demand effect on switch costs was eliminated when time for advanced preparation or task cues explicitly specifying the task rules were provided (Experiment 3). Overall, results were consistent with the hypothesis that the intentional switch-cost component reflects the time demands of retrieving appropriate task rules from LTM. (PsycINFO Database Record (c) 2010 APA, all rights reserved)     

Attention and retrieval from long-term memory.

Conducted 9 experiments with 152 female volunteers (mean age 44.4 yrs) to investigate the disrupting effect of a secondary task on retrieval from long-term memory. Exps I–V studied the influence of concurrent card sorting or digit span on free recall or paired-associate learning of word lists. Exp VI explored recall probability using a recognition paradigm in which accuracy and latency could be measured simultaneously. Exp VII explored the latency effect with a semantic memory paradigm, and Exp VIII required Ss to make semantic category judgments while retaining sequences of 6 digits. Exp IX examined the effect of concurrent digital load on the rate of generating items from semantic categories. Overall findings reveal that a demanding concurrent task did not reduce the probability of retrieving an item from semantic or episodic memory. However, concurrent load during learning substantially effected recall performance. A concurrent task during retrieval did not have a clear effect on latency. The contrast between the pattern shown by errors and by that shown by latencies suggests that attempts to estimate the attentional demands of any task should be interpreted with considerable caution when based on a single measure, such as performance errors, performance latency, or a response to a probe RT signal. (38 ref) (PsycINFO Database Record (c) 2010 APA, all rights reserved)     

Implicit, long-term spatial contextual memory.

Learning and memory of novel spatial configurations aids behaviors such as visual search through an implicit process called contextual cuing (M. M. Chun & Y. Jiang, 1998). The present study provides rigorous tests of the implicit nature of contextual cuing. Experiment 1 used a recognition test that closely matched the learning task, confirming that memory traces of predictive spatial context were not accessible to conscious retrieval. Experiment 2 gave explicit instructions to encode visual context during learning, but learning was not improved and conscious memory remained undetectable. Experiment 3 illustrates that memory traces for spatial context may persist for at least 1 week, suggesting a long-term component of contextual cuing. These experiments indicate that the learning and memory of spatial context in the contextual cuing task are indeed implicit. The results have implications for understanding the neural substrate of spatial contextual learning, which may depend on an intact medial temporal lobe system that includes the hippocampus (M. M. Chun & E. A. Phelps, 1999). (PsycINFO Database Record (c) 2010 APA, all rights reserved)     

Evolution and resolution of long-term cardiac memory

BACKGROUND: Cardiac memory (CM) refers to T-wave changes induced by ventricular pacing or arrhythmia that accumulate in magnitude and duration with repeated episodes of abnormal activation. We report herein the kinetics of long-term CM and its association with the ventricular action potential. METHODS AND RESULTS: Dogs were paced from the ventricles at rates of 110 to 120 bpm for approximately 3 weeks. CM characterized by gradual sinus rhythm T vector rotation toward the paced QRS vector evolved in all dogs regardless of pacing site (left ventricular [LV] anterior apex or base, posterior LV, or right ventricular free wall). Cardiac hemodynamics and myocardial flow (microsphere studies) were unaltered by the pacing. Recovery time for the memory T wave to return to control increased with duration of the previous pacing. The protein synthesis inhibitor cycloheximide markedly (P<.05) and reproducibly attenuated evolution of CM. When pacing was performed from the atrium, CM did not occur. Standard microelectrode techniques were used to study action potential from the LV free wall of control and CM dogs. CM was associated with increased action potential duration in epicardial and endocardial but not midmyocardial cells, significantly altering the transmyocardial gradient for repolarization. CONCLUSIONS: CM is a dynamic process for which the final T vector is predicted by the paced QRS vector and which is associated with significant changes in epicardial and endocardial but not midmyocardial cell action potential duration, such that the transmural gradient of repolarization is altered. It is unaccompanied by evidence of altered hemodynamics or flow, requires a change in pathway of activation, and appears to require new protein synthesis.     

Conceptual distinctiveness supports detailed visual long-term memory for real-world objects.

Humans have a massive capacity to store detailed information in visual long-term memory. The present studies explored the fidelity of these visual long-term memory representations and examined how conceptual and perceptual features of object categories support this capacity. Observers viewed 2,800 object images with a different number of exemplars presented from each category. At test, observers indicated which of 2 exemplars they had previously studied. Memory performance was high and remained quite high (82% accuracy) with 16 exemplars from a category in memory, demonstrating a large memory capacity for object exemplars. However, memory performance decreased as more exemplars were held in memory, implying systematic categorical interference. Object categories with conceptually distinctive exemplars showed less interference in memory as the number of exemplars increased. Interference in memory was not predicted by the perceptual distinctiveness of exemplars from an object category, though these perceptual measures predicted visual search rates for an object target among exemplars. These data provide evidence that observers' capacity to remember visual information in long-term memory depends more on conceptual structure than perceptual distinctiveness. (PsycINFO Database Record (c) 2010 APA, all rights reserved)     

The amygdala's role in long-term declarative memory for gist and detail.

In humans, the emotional nature of stimuli appears to have a complex influence on long-term declarative memory for those stimuli: Whereas emotion enhances memory for gist, it may suppress memory for detail. On the basis of prior studies, the authors hypothesized that the amygdala helps mediate the above 2 effects. Long-term memory for gist and for visual detail of aversive and neutral scenes was assessed in 20 subjects with unilateral amygdala damage and 1 rare subject with bilateral amygdala damage. Comparisons with 2 control groups (15 brain-damaged and 47 healthy) provided evidence that bilateral, but not unilateral, damage to the amygdala results in poorer memory for gist but superior memory for visual details. The pattern of findings provides preliminary support for the idea that the amygdala may help filter the encoding of relevant information from stimuli that signal threat or danger. (PsycINFO Database Record (c) 2010 APA, all rights reserved)     

Organization of public events in long-term memory.

A model of "historical memory" is proposed. This model identifies three primary levels of organization (the news event, the public narrative, the historical period) and allows public events to be associated with personal information. Three experiments were conducted to evaluate this model: a verbal protocol study, a response time study, and a free-association study. In accordance with the model, these studies demonstrated that (a) associations between same-narrative events tend to be stronger than other interevent associations, (b) political events are more likely to be related to accessible historical periods than are nonpolitical events, and (c) public events are often stored with accessible personal information. These studies also indicated that (d) political events are more likely than nonpolitical events to be embedded in public narratives and (e) nonpolitical events are more likely than political events to be associated with personal information. (PsycINFO Database Record (c) 2010 APA, all rights reserved)