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At least 451 records · Page 25Linked to original sources

PubMed2003

Galanin regulates spatial memory but not visual recognition memory or synaptic plasticity in perirhinal cortex.

It has previously been shown that the neuropeptide galanin plays a role in the age-dependent regulation of hippocampal synaptic plasticity and spatial memory. Here, we further extend these studies by demonstrating that galanin knockout mice also have deficits in an object-in-place spatial memory task. In contrast however, there is no deficit in single item object recognition memory, a memory that depends on perirhinal cortex. Furthermore, in perirhinal cortex slices there are no differences in activity-dependent long-term potentiation or depotentiation, nor in muscarinic receptor-dependent long-term depression between galanin knockout mice and wild-type litter-mates. Therefore, these results suggest that galanin has a differential role in hippocampal-dependent and perirhinal cortex-dependent memory.

Animals↗

PubMed2002

Memory for the position of stationary objects: disentangling foveal bias and memory averaging.

The perceived and remembered position of stationary target objects is subject to a large number of distortions. Objects are localized toward the fovea, and when an additional object (distractor) is presented, a tendency to average target and distractor position was observed. These distortions in visual short-term memory have been referred to as foveal bias and memory averaging, respectively. Because most studies on memory averaging did not monitor eye fixation, foveal bias and memory averaging may have been confounded. That is, observers may have fixated the distractor. To disentangle these factors, target and distractor were presented in the periphery, and fixation was monitored. Memory averaging was not observed. Rather a bias away from the distractor occurred when the distractor was briefly presented during the retention interval, or when it was visible throughout the trial. In contrast, a foveal bias was observed regardless of whether an additional object was present.

Fixation, Ocular↗

PubMed2003

Active reversal of motor memories reveals rules governing memory encoding.

Learning systems must be able to store memories reliably, yet be able to modify them when new learning is required. At the mechanistic level, new learning may either reverse the cellular events mediating the storage of old memories or mask the old memories with additional cellular changes that preserve the old cellular events in a latent form. Behavioral evidence about whether reversal or masking occurs in a particular circuit can constrain the cellular mechanisms used to store memories. Here we examine these constraints for a simple cerebellum-dependent learning task, motor learning in the vestibulo-ocular reflex (VOR). Learning can change the amplitude of the VOR in two opposite directions. Contrary to previous models about memory encoding by the cerebellum, our results indicate that these behavioral changes are implemented by different plasticity mechanisms, which reverse each other with unequal efficacy.

Animals↗

PubMed2003

The nucleus basalis and memory codes: auditory cortical plasticity and the induction of specific, associative behavioral memory.

Receptive field (RF) plasticity develops in the primary auditory cortex (ACx) when a tone conditioned stimulus (CS) becomes associated with an appetitive or aversive unconditioned stimulus (US). This prototypical stimulus-stimulus (S-S) association is accompanied by shifts of frequency tuning of neurons toward or to the frequency of the CS such that the area of best tuning of the CS frequency is increased in the tonotopic representation of the ACx. RF plasticity has all of the major characteristics of behavioral associative memory: it is highly specific, discriminative, rapidly induced, consolidates (becomes stronger and more specific over hours to days) and can be retained indefinitely (tested to two months). Substitution of nucleus basalis (NB) stimulation for a US induces the same associative RF plasticity, and this requires the engagement of muscarinic receptors in the ACx. Pairing a tone with NB stimulation actually induces specific, associative behavioral memory, as indexed by post-training frequency generalization gradients. The degree of acquired behavioral significance of sounds appears to be encoded by the number of neurons that become retuned in the ACx to that acoustic stimulus, the greater the importance, the greater the number of re-tuned cells. This memory code has recently been supported by direct neurobehavioral tests. In toto, these findings support the view that specific, learned auditory memory content is stored in the ACx, and further that this storage of information during learning and the instantiation of the memory code involves the engagement of the nucleus basalis and its release of acetylcholine into target structures, particularly the cerebral cortex.

Acetylcholine↗

PubMed1992

Memory improvements and pharmacological treatment: a method to distinguish direct effects on memory from secondary effects due to attention improvement.

Chronic cerebrovascular disturbances of the aged are characterized by a decline of attention. When these patients undergo pharmacological treatment, it is very difficult to distinguish between a direct benefit and/or a secondary effect on memory resulting from attention improvement. In our study we have proposed and evaluated a new method for identifying the different components of therapeutic efficacy on memory and attention in chronic cerebrovascular patients. This method is based on the use of the Randt Memory Test, traditional scores of memory efficiency (Acquisition, Recall, and a combined index), and the RMT three-factor scores derived from a structural model of memory functioning. The three scores have been called Encoding and Organization, Cognitive Efficiency, and Attention Efficiency. Participants were 96 selected chronic cerebrovascular patients treated in a double-blind study for 12 weeks with dihydroergocristine versus placebo. While changes in both acquisition and recall scores were related to the treatment, only changes of the Encoding and Organization factor scores were systematically related to therapy. Changes in Attention Efficiency were positively related to therapy only in proportion to the degree of cerebrovascular impairment.

Attention↗

PubMed2005

From sensory to long-term memory: evidence from auditory memory reactivation studies.

Everyday experience tells us that some types of auditory sensory information are retained for long periods of time. For example, we are able to recognize friends by their voice alone or identify the source of familiar noises even years after we last heard the sounds. It is thus somewhat surprising that the results of most studies of auditory sensory memory show that acoustic details, such as the pitch of a tone, fade from memory in ca. 10-15 s. One should, therefore, ask (1) what types of acoustic information can be retained for a longer term, (2) what circumstances allow or help the formation of durable memory records for acoustic details, and (3) how such memory records can be accessed. The present review discusses the results of experiments that used a model of auditory recognition, the auditory memory reactivation paradigm. Results obtained with this paradigm suggest that the brain stores features of individual sounds embedded within representations of acoustic regularities that have been detected for the sound patterns and sequences in which the sounds appeared. Thus, sounds closely linked with their auditory context are more likely to be remembered. The representations of acoustic regularities are automatically activated by matching sounds, enabling object recognition.

Adolescent↗

PubMed1998

Event-based prospective memory and executive control of working memory.

In 5 experiments, the character of concurrent cognitive processing was manipulated during an event-based prospective memory task. High- and low-load conditions that differed only in the difficulty of the concurrent task were tested in each experiment. In Experiments 1 and 2, attention-demanding tasks from the literature on executive control produced decrements in prospective memory. In Experiment 3, attention was divided by different loads of articulatory suppression that did not ultimately lead to decrements in prospective memory. A high-load manipulation of a visuospatial task requiring performance monitoring resulted in worse prospective memory in Experiment 4, whereas in Experiment 5 a visuospatial task with little monitoring did not. Results are discussed in terms of executive functions, such as planning and monitoring, that appear to be critical to successful event-based prospective memory.

Adult↗

PubMed2003

Memory organization of action events and its relationship to memory performance.

Previous research yielded inconsistent results regarding the memory organization of self-performed actions. The authors propose that task performance changes the very basis of memory organization. Enactment during study and test (Experiment 1) yielded stronger enactive clustering (based on motor-movement similarities), whereas verbal encoding yielded stronger conceptual clustering (based on semantic-episodic similarities). Enactment enhanced memory quantity and memory accuracy. Both measures increased with enactive clustering under self-performance instructions but with conceptual clustering under verbal instructions. Enactment only during study (Experiment 2) or only during testing (Experiment 3) also enhanced enactive clustering. It is proposed that different conditions affect the relative salience of different types of memory organization and their relative contribution to recall.

Female↗

PubMed2005

Personal memories for remote historical events: accuracy and clarity of flashbulb memories related to World War II.

One hundred forty-five Danes between 72 and 89 years of age were asked for their memories of their reception of the news of the Danish occupation (April 1940) and liberation (May 1945) and for their most negative and most positive personal memories from World War II. Almost all reported memories for the invasion and liberation. Their answers to factual questions (e.g., the weather) were corroborated against objective records and compared with answers from a younger control group. The older participants were far more accurate than what could be predicted on the basis of results from test-retest studies using short delays. The "permastore" metaphor (Bahrick, 1984) provides a possible interpretation of this discrepancy. Participants with reported ties to the resistance movement had more vivid, detailed, and accurate memories than did participants without such ties. Ratings of surprise and consequentiality were unrelated to the accuracy and clarity of the memories.

Affect↗

PubMed2007

Available but unattended conceptual information in working memory: temporarily active semantic content or persistent memory for prior operations?

In 2 experiments, the authors investigated available but unattended information following working memory task demands. The experimental task presented a memory set containing exemplars from 2 conceptual categories. Following instructions to focus attention on only 1 category, priming of both categories was assessed with category comparisons of exemplar pairs. Priming was greatest for the focused category and for exemplars from the memory set (direct priming). Priming also extended to new exemplars of both categories (indirect priming) and showed little decline over more than 1 min of intervening processes. Finally, changing between category exemplars and features across memory set and comparison phases eliminated the indirect priming. These results support a persistent, operation-specific, procedural account of available but unattended conceptual information in working memory.

Adolescent↗

PubMed2006

Memory self-efficacy predicts memory performance: results from a 6-year follow-up study.

The purpose of this study was to examine the relationship between memory self-efficacy (MSE) and a 6-year follow-up assessment of memory functioning in a sample of Dutch older adults. MSE was assessed by a Dutch abridged version of the Metamemory in Adulthood questionnaire (MIA; R. A. Dixon, D. F. Hultsch, & C. Hertzog, 1988; C. Hertzog, D. F. Hultsch, & R. A. Dixon, 1989; R. W. H. M. Ponds & J. Jolles, 1996). The total MSE score predicted memory performance at 6 years, as measured by the Visual Verbal Learning Task (VVLT; N. Brand & J. Jolles, 1985). A separate analysis of the different MSE subscales indicated that the MIA Change score was the most salient domain-specific MSE predictor of subsequent memory performance after 6 years. An extreme groups analysis of the MIA Change score revealed a pattern of performance for those who perceived that their memory was worsening, performing less well on the 3 trials of the VVLT when these were readministered at the 6-year follow-up.

Age Factors↗

PubMed2002

Impairment of immunological memory in the absence of MHC despite survival of memory T cells.

The mechanisms by which immunological memory is maintained after infection or vaccination are still a matter of debate. Long-term survival of memory T cells does not require major histocompatibility complex (MHC) contact. We show here that compared with memory CD4+ T cells that maintain contact with MHC class II, memory CD4+ T cells deprived of MHC class II contact show distinct functional defects upon antigen re-encounter. Thus, in contrast to their survival, maintenance of the typical quality of memory T cells crucially depends on MHC-derived signals.

Animals↗

PubMed2002

Frontal theta activity in humans increases with memory load in a working memory task.

Recent theoretical work has suggested that brain oscillations in the theta band are involved in active maintenance and recall of working memory representations. To test this theoretical framework we recorded neuromagnetic responses from 10 subjects performing the Sternberg task. Subjects were required to retain a list of 1, 3, 5 or 7 visually presented digits during a 3-s retention period. During the retention period we observed ongoing frontal theta activity in the 7-8.5-Hz band recorded by sensors over frontal brain areas. The activity in the theta band increased parametrically with the number of items retained in working memory. A time-frequency analysis revealed that the task-dependent theta was present during the retention period and during memory scanning. Following the memory task the theta activity was reduced. These results suggest that theta oscillations generated in frontal brain regions play an active role in memory maintenance.

Adult↗

PubMed1998

Memory and long-term potentiation (LTP) dissociated: normal spatial memory despite CA1 LTP elimination with Kv1.4 antisense.

Long-term potentiation (LTP) in the hippocampal slice preparation has been proposed as an in vitro model for long-term memory. However, correlation of LTP with memory in living animals has been difficult to demonstrate. Furthermore, in the last few years evidence has accumulated that dissociate the two. Because potassium channels might determine the weight of synapses in networks, we studied the role of Kv1.4, a presynaptic A-type voltage-dependent K+ channel, in both memory and LTP. Reverse transcription-PCR and Western blot analysis with specific antibodies showed that antisense oligodeoxyribonucleotide to Kv1.4 microinjected intraventricularly into rat brains obstructed hippocampal Kv1.4 mRNA, "knocking down" the protein in the hippocampus. This antisense knockdown had no effect on rat spatial maze learning, memory, or exploratory behavior, but eliminated both early- and late-phase LTP and reduced paired-pulse facilitation (a presynaptic effect) in CA1 pyramidal neurons without affecting dentate gyrus LTP. This presynaptic Kv1.4 knockdown together with previous postsynaptic Kv1.1 knockdown demonstrates that CA1 LTP is neither necessary nor sufficient for rat spatial memory.

Animals↗

PubMed1983

Factor analysis of the WAIS and Wechsler Memory Scale: an analysis of the construct validity of the Wechsler Memory Scale.

The WAIS and Wechsler Memory Scale subtest scores of 256 neurologic and nonneurologic subjects were factor analyzed. The results supported the construct validity of the Wechsler Memory Scale as a measure of verbal learning and memory, attention and concentration, and orientation. Construct validity was not demonstrated for the Visual Reproduction subtest as a measure of visual memory. Suggestions are offered for future development and research on measures of visual memory.

Attention↗

PubMed2000

Evaluation of an electronic memory aid in the neuropsychological rehabilitation of prospective memory deficits.

Five subjects with acquired memory impairment were trained to use a new electronic memory aid, the Voice Organizer, to manage prospective memory errors. Performance was assessed on two measures analogous to everyday memory tasks; a Message-Passing task requiring prospective recall after a delay of 9 hours, and a Domestic Task measure which involved the recall of household chores following a delay of 1-6 days. All subjects benefited from the introduction of the aid on the Message-Passing task and all but one improved their prospective recall on the Domestic Task measure. These results suggest that the Voice Organizer may be a useful aid in the neuropsychological rehabilitation of prospective memory impairment.

Adult↗

PubMed1998

Detecting malingered memory deficits with the Recognition Memory Test.

The purpose of the present study was to examine the efficacy of using the Recognition Memory Test (RMT) as a marker for malingered memory deficits. Data from 60 subjects, including 40 patients seen for neuropsychological evaluation and 20 university undergraduates, are reported. The university students were given experimental instructions to malinger. Students were compared to 20 memory-impaired and 20 memory-nonimpaired patients. The students who were instructed to malinger memory impairment performed more poorly than both groups of patients. Discriminant function analyses using the two scores derived from the RMT as predictors of group membership resulted in a 100% initial correct classification rate and a 96.7% correct classification rate on cross-validation.

Adolescent↗

PubMed1990

Temporal memory and content memory for actions: adult age differences in acquisition and retention.

Young adult and elderly adult subjects were tested under incidental memory conditions for recognition memory of content and temporal memory for the order of a series of actions performed in the laboratory. The tests were conducted both shortly after completion of the series and 24 hours later, with different sets of actions tested on each occasion. Recognition memory of content showed no forgetting for the young subjects, but significant forgetting for the elderly subjects. Memory for temporal information was substantially greater for the young subjects than for the elderly subjects. Both age groups showed substantial forgetting of temporal information over the 24-hour retention interval.

Adolescent↗