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PubMed1977

B memory cells in the thymus: part of the pool of potentially circulating memory cells.

Immunization of mice with sheep red blood cells (SRBC) or Escherichia coli lipopolysaccharide (LPS) induces the appearance of B memory cells in the thymus. In this paper the origin of these B memory cells was investigated. Therefore, mice primed with either SRBC or LPS 6 months previously and nonprimed mice were joined for parabiosis. Four weeks later the parabiotic mice were separated from each other. Another 3 weeks later thymus cells from the primed and nonprimed mice were transferred separately into lethally irradiated mice in order to determine the adoptive PFC response. It was found that the 4-week period of parabiosis could account for the appearance of a distinct population of B memory cells in the thymus of the nonprimed mice. This result suggest that the B memory cells which appear in the thymus belong to the pool of potentially circulating memory cells.

Animals↗

PubMed1984

Receptor 'memory' in Tetrahymena: does it satisfy the general criteria of memory? An experimental study on induction and extinction by retroactive interference in a unicellular organism.

Diiodotyrosine induced receptor 'memory' at a concentration as low as 10(-18) M. Repeated exposure enhanced cellular responsiveness. Treatment with diiodotyrosine for 1 h, 4 times, induced receptor 'memory' more efficiently than a single uninterrupted treatment for 4 h. Immediately after induction, the receptor 'memory' is subject to retroactive interference by foreign hormonal stimuli, and can be extinguished completely by combined hormone treatment. Thus, the phenomenon of retroactive interference also takes effect at the unicellular level. The experimental observations indicate that receptor 'memory', induced in Tetrahymena by hormonal imprinting, has certain common features with the neuronal memory of higher organisms.

Diiodotyrosine↗

PubMed1983

Relationship of germinal centers in lymphoid tissue to immunologic memory. VI. Transfer of B cell memory with lymph node cells fractionated according to their receptors for peanut agglutinin.

We isolated germinal center B cells by exploiting their high affinity for peanut agglutinin (PNA). The PNA+ and PNA- B cells, fractionated by panning on PNA-coated petri dishes, were examined for their ability to transfer memory responses to irradiated recipients at various times after priming. With such fractionated B cells from lymph nodes taken at the peak of germinal center formation, the largest response was obtained in recipients of the PNA+ B cell population. At 4 to 5 wk after priming, and 10 days after challenge with an unrelated antigen, memory responses were approximately equal in recipients of PNA+ or PNA- B cells. At 14 wk after priming, memory responses were found only in recipients of the PNA- B cell population. Memory B cells from the spleen, taken from mice primed in the footpad 8 wk earlier, were also PNA-. Finally, we show that boosting with a TNP-conjugate in the footpad, 6 mo after priming in the same footpad, induced the reappearance of marked memory responsiveness in the PNA+ B cell fraction of the draining node.

Animals↗

PubMed1981

The generation of memory cells. IV. Immunization with antigen-antibody complexes accelerates the development of B-memory cells, the formation of germinal centres and the maturation of antibody affinity in the secondary response.

Hapten (DNP)-specific B-memory cells were induced by priming mice with soluble or alum precipitated DNP-haemocyanin (KLH) plus Bordetella pertussis or CNP-KLH-anti-DNP antibody complexes at equivalence. Cells from mice given complexes gave a substantial adoptive IgG response five days after priming, whereas those from mice given antigen with conventional adjuvant did not give a comparable response until day 14. Soluble antigen induced poor memory, even 14 days after primary immunization. The emergence of transferable B-memory cells correlated closely with the appearance of germinal centres in lymphoid follicles of the spleen. Furthermore, the relative affinity of the adoptive secondary IgG response induced by priming with complexes was already maximal on day 6. In contrast, the response of memory cells from mice given antigen on alum, increased in affinity between 6 and 23 days after priming. These data support the concept (see Klaus, Humphrey, Kunkl & Dongworth, 1980) that trapping of antigen-antibody complexes in lymphoid follicles induces the formation of germinal centres, which in turn give rise to functional B-memory cells. They further suggest that such retained complexes play a role in selective triggering of high-affinity precursor cells.

Animals↗

PubMed1995

The role of amygdala norepinephrine in memory formation: involvement in the memory enhancing effect of peripheral epinephrine.

The present study examined the roles of amygdala alpha 1 and beta noradrenergic receptors in memory formation as well as their involvement in the memory enhancing effect of peripheral epinephrine (E). Male Sprague-Dawley rats with cannulae implanted into the amygdala were trained on the one-trial inhibitory avoidance task and tested for retention 24 hrs later. Immediately after training, they received various treatments to alter amygdala noradrenergic functions and/or peripheral adrenergic functions. Separate groups of animals were decapitated 10 min after training for assays of monoamine levels in various brain regions by the HPLC-EC method. Results indicated that, when infused into the amygdala immediately after training, isoproterenol and 8-bromo-cAMP enhanced retention, while propranolol impaired retention. On the other hand, phenylephrine or prazosin failed to produce statistically significant effects. Posttraining intra-amygdala infusion of propranolol, but not prazosin, abolished the memory enhancing effects of norepinephrine (NE) infused into the amygdala or E given subcutaneously to the adrenal demedullated rats. Depletion of amygdala NE by the selective neurotoxin DSP-4 also abolished the memory modulatory effects of E. These findings support that amygdala noradrenergic beta, but not alpha 1, receptors are involved in both central and peripheral memory modulatory processes. However, since the postmortem tissue NE levels in the amygdala and other brain regions did not differ among various groups, the inhibitory avoidance training and peripheral E may only activate a transient functional increase in the amygdala NE activity.

Amygdala↗

PubMedDate not supplied

[Contribution of studies on animal memory to understanding human memory].

Studies of animal memory have contributed to the understanding of human memory from two points of view. Phylogenetic comparison of memory abilities in different animal groups demonstrates that human memory is a heterogeneous combination of various abilities, of different complexities, which appeared during the evolution. On the other hand, the use of animal models promotes better understanding of the physiological mechanisms underlying human memory. These models can be anatomic ones founded on the functional implication of encephalic areas, bioelectric ones founded on the implication of microscopic or macroscopic bioelectric phenomena or chemical ones founded on the molecular activity of the nervous system.

Animals↗

PubMed1999

A single specific amino acid residue in peptide antigens is sufficient to activate memory CTL: potential role of cross-reactive peptides in memory T cell maintenance.

In the present study, we examined the structural requirements of peptide Ags for productive interactions with the TCR of CTL. For this purpose, we used as a model a previously identified immunodominant epitope that represents the target of EBV-specific HLA-A11-restricted CTL responses. By the use of peptides having minimal sequence homology with the wild-type epitope, we demonstrated that it is possible to selectively expand and reactivate memory CTL precursors without triggering the lytic mechanisms of wild-type specific effectors. In fact, stimulation of PBL from EBV-seropositive donors by polyalanine analogues, sharing only the putative TCR contact residue with the natural epitope, exclusively induced clonal expansion and reactivation of EBV-specific memory CTL precursors. Interestingly, these polyalanine peptides failed to trigger the cytotoxic function of CTLs specific for the wild-type viral epitope. This clearly indicates that reactivation of memory CTL precursors and triggering of the cytotoxic function have different requirements. The same phenomenon was observed using as stimulators naturally occurring peptides carrying the appropriate TCR contact residue. These data strongly suggest that cross-reactive peptides may play an important role in the expansion and reactivation of CTL clones from the memory T cell pool, and may be involved in long-term maintenance of T cell memory.

Amino Acid Substitution↗

PubMed1997

Metamemory Assessment and Memory Behavior in a Simulated Memory Professional Task

This study investigated metamemory knowledge related to a professional task and the relationships between metamemory knowledge and memory performance in a simulated professional task, which was a beverage-service job with memory constraints changes. Metamemory knowledge was assessed by interviewing student waiters about hypothetical recall tasks concerning lists of beverages. They then carried out a simulated beverage-service task, including a first paired-associate recall (beverage-customer), then a global recall (order to the bartender), followed by a second paired-associate recall (beverage-customer). Memory constraints were manipulated with table size and perceptive cues. Results revealed that in metamemory knowledge, task-strategy, and strategy were the only variables that were related. Metamemory knowledge produced an effect on all memory performance, whatever the constraints were. The implications of these findings for professional training are discussed in terms of strategy instruction for enhancing professional performance when memory demands change in the work environment. Copyright 1997Academic Press

Journal Article↗

PubMed1997

Dissociation between features and feature relations in infant memory: effects of memory load.

Four experiments examined the effects of the number of features and feature relations on learning and long-term memory in infants. Three-month-olds learned to activate a mobile composed of either two or three kinds of blocks that differed in color, the figures displayed on them, and the figures' colors. Twenty-four hours later, infants trained with two objects discriminated feature recombinations but those trained with three objects did not. Even infants trained with three objects discriminated novel features, however, indicating that they remembered the individual features but not the relations among them. A subsequent experiment revealed that this dissociation between features and relations was induced by differential accessibility to memory rather than an encoding failure. We conclude that the size of the memory load selectively constrains infants' long-term memory for relational information. These results suggest that in infancy, as in adulthood, features and relations are psychologically distinct and that memory organization parallels the organization of perceptual processing.

Association Learning↗

PubMed2005

Memories that last in old age: motor skill learning and memory preservation.

Using an automated test panel, age-associated declines in learning, remembering and performing a novel visuomotor task were assessed in 497 normal adults ranging from 18 to 95 years old. As predicted, task performance times slowed with increasing age in the cross-sectional portion of the study. However in the subsequent longitudinal study, while motor learning was significantly slower in adults over 62 years old, motor memory was pristinely preserved in normal adults from 18 to 95 years old. When tested 2 years after the first training session and without intervening rehearsal, mean performance times were retained and continued to improve by 10% in young adults and 13% in aged adults, reflecting long lasting preservation of motor memories. While the maximum lifetime of an unpracticed, novel motor memory in humans is not known, the present study suggests that new motor memories can be retained for at least 2 years without rehearsal in normal aged adults. This age-resistant component of motor memory stands in contrast to the well-known decrements in other motor and cognitive processes with human aging.

Adolescent↗

PubMed2001

Neuromodulatory control of interacting medial temporal lobe and neocortex in memory consolidation and working memory.

A model of the interacting medial temporal lobe and neocortical association areas is formulated and applied to memory consolidation and working memory. A simplified connectivity in terms of superassemblies and assemblies of neurons representing types and values, respectively, of object features is underlying the model. Realistic low-dimensional model neurons, developed in particular to take neuronal adaptation into account, are employed. Observed short- and long-term potentiation and depression of plastic synaptic couplings are incorporated. It is shown that memory consolidation by long-term potentiation, based on repeated activations of neocortical patterns, may be guided by neuromodulated dynamics of the medial temporal lobe via short-term couplings acting as pointers. Bifurcations, i.e. transitions between different modes of network dynamics, with respect to developing synaptic couplings are shown to depend on the adaptivity of excitatory neurons in the medial temporal lobe and thus to be under neuromodulatory control. At weak adaptivity, after an initial temporal segmentation of several objects accounting for the capacity of working memory to resolve several items, attention is selectively focused on a single object according to the model. At intermediate adaptivity, reactivations may persist and long-term synaptic couplings gradually develop. At strong adaptivity, the model predicts attention and memory consolidation to be subsequently terminated. The neuromodulatory control of the interacting medial temporal lobe and neocortical system via the adaptivity of excitatory neurons may account for several observations on the influence of neuromodulators on various cognitive processes and brain disorders.

Animals↗

PubMed2001

High levels of estradiol disrupt conditioned place preference learning, stimulus response learning and reference memory but have limited effects on working memory.

The present study investigated the effects of high levels of estradiol in female rats on four different radial arm maze tasks: the hippocampus-dependent spatial working-reference memory task; the prefrontal cortex-hippocampus dependent delayed win-shift task; the striatum-dependent cued win-stay task; and the amygdala-dependent conditioned place preference task. Ovariectomized female rats were injected daily with either 10 microg of estradiol benzoate or sesame oil vehicle approximately 4 h prior to testing. In Experiment 1, treatment with estradiol disrupted learning on the spatial working-reference memory task by increasing the number of reference memory errors to reach criterion. In Experiment 2, treatment with estradiol had no significant effect on the delayed win-shift task. In Experiment 3, treatment with estradiol resulted in impaired performance on a striatum-dependent cued win-stay task. In Experiment 4, treatment with estradiol impaired the acquisition of a conditioned place-preference task. Taken together these findings suggest that high levels of estradiol inhibit reference memory, stimulus response learning, and amygdala-dependent appetitive conditioning while having little effect on working memory.

Amygdala↗

PubMed1993

Working-memory capacity as long-term memory activation: an individual-differences approach.

One explanation of the correlation often observed between working-memory span scores and reading comprehension is that individuals differ in level of activation available for long-term memory units. Two experiments used the fan manipulation to test this idea. In Experiment 1, high- and low-working-memory Ss learned a set of unrelated sentences varying in the number of shared concepts (fan) and then performed speeded recognition for those sentences. Low-working-memory Ss showed a larger increase in recognition time as fan increased. When the slope of the fan effect was partialed out of the relationship between working-memory span and verbal abilities, the relationship was reduced to nonsignificance. In Experiment 2, Ss learned thematically related sentences that varied in fan. Low-span Ss showed the positive fan effect typically found with thematically unrelated sentences, whereas high-span Ss showed a negative fan effect. The results are discussed in terms of a general capacity theory.

Adult↗

PubMed2005

The relation between source memory and episodic memory: comment on siedlecki et Al. (2005).

On the basis of an interesting structural equation analysis, K. L. Siedlecki, T. A. Salthouse, and D. E. Berish argued that "it may not be meaningful to refer to source memory as a construct distinct from episodic memory" (p. 31). This commentary highlights that this same point could also be made on conceptual grounds. To suggest that source and episodic memory are distinct concepts would confound tasks with theoretical constructs. All episodic tasks involve making attributions about the origin of mental experiences (source monitoring). Conversely, source memory tasks are designed to investigate episodic memory. No task is special, but each may be useful, depending on the focus of interest.

Aged↗

PubMed1980

The effects of memory strategy instruction in the short-term motor memory of the mentally retarded.

The present study investigated the effectiveness of teaching mnemonic strategies aimed at overcoming difficulties of mentally retarded students in retaining the motor short-term memory information of a preselected movement. The memory strategy employed was a combination of the "feel" of the movement and the spatial location of the hand relative to the body. The design of the study was a 2 x 2 (Instructional Treatment x Retention Condition) factorial. The instructional treatment factor included teaching the subjects a memory strategy versus no memory-strategy instruction. The retention condition factor included immediate recall and a 15-sec retention interval. There were five trials per subject. The data were interpreted as supporting the effectiveness of the memory-strategy instruction.

Journal Article↗

PubMed2002

Creating memory illusions: expectancy-based processing and the generation of false memories.

The present research investigated the generation of memory illusions. In particular, it attempted to delineate the conditions under which category-based thinking prompts the elicitation of false memories. Noting fundamental differences in the manner in which expected and unexpected person-related information is processed and represented in the mind, it was anticipated that, via gist-based recognition, participants would display a pronounced propensity to generate expectancy-consistent false memories. The results of three experiments supported this prediction. In addition, the research revealed that participants' false memories were accompanied by the subjective experience of knowing (Expt. 2) and that false recognition was exacerbated under conditions of executive dysfunction (Expt. 3). We consider the theoretical implications of these findings for recent treatments of memory illusions and social cognition.

Adult↗

PubMed2004

Determining the effects of memory and action potential duration alternans on cardiac restitution using a constant-memory restitution protocol.

Restitution, the dependence of action potential duration (APD) on diastolic interval, may be causally linked to the vulnerability of cardiac tissue to certain types of arrhythmias. While a number of pacing protocols are commonly used to quantify the restitution relation, one of these, the dynamic protocol, may result in the occurrence of APD alternans. However, the effects of APD alternans, and the concomitant alternation in cardiac memory, on the restitution curve are currently not well understood. Alternans preceding a given action potential may cause that action potential to have a different duration from one preceded by action potentials of identical duration. This interaction of alternans and memory can result in a dynamic restitution curve that is not unique. To address this, we have developed a constant-memory restitution protocol that enables the experimenter or modeller to obtain unique, constant-memory restitution curves at all diastolic intervals. Using this protocol, we obtained unique restitution curves for two ionic models of the cardiac action potential in the absence of alternans at all diastolic intervals. A comparison of the unique constant-memory and non-unique dynamic restitution curves for the two models shows that the presence of alternans can significantly alter the shape of the restitution curve compared to when alternans is absent.

Action Potentials↗

PubMed1995

Scylla and Charybdis. Sexual abuse or 'false memory syndrome'? Therapy-induced 'memories' of sexual abuse.

The increasing importance and frequency of so-called 'false memories' of sexual abuse, which in reality never occurred, occasions a theoretical reflection about therapy-induced 'memories' of sexual abuse. Sexual abuse is first seen to involve a serious loss of psychic structure. As such it has much in common with other, endogenous forms of severe psychic disorders. Drawing upon the (Kleinian) categories of projective identification, projective counter-identification and psychotic personality aspects, together with the Jungian conception of the 'mutual unconsciousness' between therapist and patient, the author presents a psychodynamic hypothesis regarding the origins of 'false memories' or 'recovered memories' of sexual abuse. This is exemplified with two therapy cases involving such memories of abuse.

Adolescent↗