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PubMed1992

Memory for schema-relevant information: a meta-analytic resolution.

The research on memory for schema-relevant information has produced sharply contradictory results. Some studies demonstrate memory selectivity for schema-consistent information, others demonstrate memory selectivity for schema-inconsistent information. Meta-analytic procedures are applied to a sample of 60 independent studies with 165 comparative tests. The overall result shows a slight overall memory advantage for schema-inconsistent information. As the effect sizes are highly heterogeneous, it was hypothesized that schema-based processing is moderated by an array of variables. In large part the direction of the effect is dependent on the memory measure used. Both recognition tests corrected for guessing and recall tests reveal consistently better memory for schema-inconsistent information. But recognition tests uncorrected for guessing consistently uncover better memory for schema-consistent information. In addition, several moderators derived from Wyer & Srull's (1989) Associative Network model of person memory influence the amount of inconsistent information recalled. Processing demands, length of exposure to inconsistent information, delay between presentation of the stimulus and the memory test, proportion of inconsistent items, order of schema-presentation, degree of inconsistency and importance of categories to subjects all had significant impacts on inconsistency resolution. Most of these moderator effects support the Wyer-Srull model; but several of its contentions are called into question. In particular, inconsistency resolution emerges as a more robust consequence than schema-bolstering of longer stimulus exposure and delays between exposure and memory test. The results are compared with a similar meta-analysis, then discussed in relation to the possibilities for stereotype change.

Attention↗

PubMed2002

An fMRI study on the time-limited role of the medial temporal lobe in long-term topographical autobiographic memory.

The time-limited role of the medial temporal lobe (MTL) in human long-term memory is well known. However, there is still no direct neuroimaging evidence to confirm it. In this fMRI study, nine subjects were scanned while asked to recall the places they visited more than seven years ago (remote memories); and the places they visited recently (recent memories). We observed robust and dominant MTL activity peaking in the left parahippocampal gyrus when recent memories were contrasted with remote memories. This result provided direct evidence for the time-limited role of the MTL in long-term topographical autobiographic memory. Further analysis revealed that this MTL activity was not due to the fact that the retrieval of recent memories was accompanied by more details. When detailed recent memories were contrasted with detailed remote memories, there was still MTL activity peaking in the left parahippocampal gyrus. The effects of details in remote memories are also discussed.

Adult↗

PubMed2006

Selective verbal and spatial memory impairment after 5-HT1A and 5-HT2A receptor blockade in healthy volunteers pre-treated with an SSRI.

Serotonergic neurotransmission has been implicated in memory impairment. It is unclear however if memory performance is mediated through general 5-HT availability, through specific 5-HT receptors or both. The aim of the present study was to assess the contribution of 5-HT reuptake inhibition and specific blockade of 5-HT(1A) and 5-HT(2A) receptors to memory impairment. The study was conducted according to a randomized, double-blind, placebo-controlled, four-way cross-over design including 16 healthy volunteers. The treatment consisted of oral administration of escitalopram 20 mg + placebo, escitalopram 20 mg + ketanserin 50 mg, escitalopram 20 mg + pindolol 10 mg and placebo on 4 separate days with a washout period of minimum 7 days. Different memory tasks were performed including verbal memory, spatial working memory and reversal learning. Escitalopram showed an impairing effect on immediate verbal recall which nearly reached statistical significance. No effects of escitalopram were found on other types of memory. In combination with pindolol, immediate verbal recall was significantly impaired. Escitalopram in combination with ketanserin impaired spatial working memory significantly. No effects were found on reversal learning. Selective impairment of immediate verbal recall after a 5-HT(1A) partial agonist and selective impairment of spatial working memory performance after 5-HT(2A) receptor antagonist, both in combination with a selective serotonergic reuptake inhibitor (escitalopram), suggests that 5-HT(1A) and 5-HT(2A) receptors are distinctly involved in verbal and spatial memory.

Administration, Oral↗

PubMed2005

A linear memory algorithm for Baum-Welch training.

BACKGROUND: Baum-Welch training is an expectation-maximisation algorithm for training the emission and transition probabilities of hidden Markov models in a fully automated way. It can be employed as long as a training set of annotated sequences is known, and provides a rigorous way to derive parameter values which are guaranteed to be at least locally optimal. For complex hidden Markov models such as pair hidden Markov models and very long training sequences, even the most efficient algorithms for Baum-Welch training are currently too memory-consuming. This has so far effectively prevented the automatic parameter training of hidden Markov models that are currently used for biological sequence analyses. RESULTS: We introduce the first linear space algorithm for Baum-Welch training. For a hidden Markov model with M states, T free transition and E free emission parameters, and an input sequence of length L, our new algorithm requires O(M) memory and O(LMTmax (T + E)) time for one Baum-Welch iteration, where Tmax is the maximum number of states that any state is connected to. The most memory efficient algorithm until now was the checkpointing algorithm with O(log(L)M) memory and O(log(L)LMTmax) time requirement. Our novel algorithm thus renders the memory requirement completely independent of the length of the training sequences. More generally, for an n-hidden Markov model and n input sequences of length L, the memory requirement of O(log(L)L(n-1) M) is reduced to O(L(n-1) M) memory while the running time is changed from O(log(L)Ln MTmax + Ln(T + E)) to O(Ln MTmax (T + E)). An added advantage of our new algorithm is that a reduced time requirement can be traded for an increased memory requirement and vice versa, such that for any c e {1, ..., (T + E)}, a time requirement of Ln MTmax c incurs a memory requirement of L(n-1) M(T + E - c). CONCLUSION: For the large class of hidden Markov models used for example in gene prediction, whose number of states does not scale with the length of the input sequence, our novel algorithm can thus be both faster and more memory-efficient than any of the existing algorithms.

Algorithms↗

PubMed2004

Emotional intensity predicts autobiographical memory experience.

College students generated autobiographical memories from distinct emotional categories that varied in valence (positive vs. negative) and intensity (high vs. low). They then rated various perceptual, cognitive, and emotional properties for each memory. The distribution of these emotional memories favored a vector model over a circumplex model. For memories of all specific emotions, intensity accounted for significantly more variance in autobiographical memory characteristics than did valence or age of the memory. In two additional experiments, we examined multiple memories of emotions of high intensity and positive or negative valence and of positive valence and high or low intensity. Intensity was a more consistent predictor of autobiographical memory properties than was valence or the age of the memory in these experiments as well. The general effects of emotion on autobiographical memory properties are due primarily to intensity differences in emotional experience, not to benefits or detriments associated with a specific valence.

Adult↗

PubMed2000

Internal languages of retrieval: the bilingual encoding of memories for the personal past.

In contrast to most research on bilingual memory that focuses on how words in either lexicon are mapped onto memory for objects and concepts, we focus on memory for events in the personal past. Using a word-cue technique in sessions devoted exclusively to one language, we found that older Hispanic immigrants who had come to the United States as adults internally retrieved autobiographical memories in Spanish for events in the country of origin and in English for events in the U.S. These participants were consistently capable of discerning whether a memory had come to them "in words" or not, reflecting the distinction between purely imagistic or conceptual memories and specifically linguistic memories. Via examination of other phenomenological features of these memories (sense of re-living, sensory detail, emotionality, and rehearsal), we conclude that the linguistic/nonlinguistic distinction is fundamental and independent of these other characteristics. Bilinguals encode and retrieve certain autobiographical memories in one or the other language according to the context of encoding, and these linguistic characteristics are stable properties of those memories over time.

Adult↗

PubMedDate not supplied

[Group memory therapy in neurologic amnesia].

The aim of our approach was to improve the memory of head injured memory impaired people without associated intellectual deterioration. Subjects participated in group each weekday during ten weeks. The aim of strategies was to help the patient of recovery learning strategies. Exercises can be repeated to produce the use of learning strategies in the real life. 19 patients (11 subjects with a traumatic brain injury and 8 subjects with a cerebral vascular accident) completed the treatment are measured before and after the rehabilitation. In a clinic study our memory therapy was more satisfactory on visual memory than verbal memory on a French standardised memory test (the Signoret memory battery). But there is no change in the evaluation of everyday memory measured with the AMQ of Van Der Linden. The comparison of the two sub groups has given to show which pathology will benefit the more the method. These first findings suggested that it was useful to reinforce everyday memory and to include the family members more. It will also be interesting to modify the program for the reeducation of the verbal memory. A control study was necessary to evaluate the validity of our approach.

Adult↗

PubMed1994

A primer on memory in aging and Alzheimer's disease.

Memory is a complex and difficult area for researchers, physicians, and caregivers of the elderly. Webster's Dictionary describes memory as "the power or process of reproducing or recalling what has been learned and retained, esp. through associative mechanisms." As Squire writes: "The concepts of learning and memory are closely related. Learning is the process of acquiring new information, while memory refers to the persistence of learning in a state that can be revealed at a later time." This overview introduces one of the constructs currently being used to describe the memory process. Memory, as with many other functions in aging, may have some correlation with chronologic age as well as with disease and nondisease factors. The methods used to study memory are important in defining "disease free" memory loss, "disease related" memory loss, and in describing the influence of other variables on performance in memory testing.

Aged↗

PubMed1975

Memory functions six to nine months after electroconvulsive therapy.

Memory functions after electroconvulsive therapy (ECT) were assessed in 38 former patients who had received bilateral treatment, right unilateral treatment, or hospitalization without ECT six to nine months previously. Results of six different tests of delayed retention and remote memory provided no evidence for persisting memory impairment. Nevertheless, persons who had received bilateral ECT rated their memory as impaired significantly (P less than .05) more often than did persons in the other follow-up groups. Although considerable effort was made to maximize the sensitivity of the memory tests, it is possible that, long after ECT, some impairment of memory remained that was not detected by these tests. Alternatively, it is hypothesized that the impairment of recent and remote memory initially associated with bilateral ECT could cause some persons to become more alert to subsequent memory failures and then to underestimate their memory abilities.

Adult↗

PubMed1996

Cerebral ischemia: are the memory deficits associated with hippocampal cell loss?

The long-standing notion that damage restricted to the hippocampal formation is sufficient to produce a significant global memory deficit derives from clinical data. Specifically, it is based on the observation that transient global ischemia, which leads to partial cell loss within the hippocampal formation but not in other brain areas important for memory, can produce global amnesia in humans. This view is, however, challenged by a number of experimental findings. First, in both monkeys and rats, there is evidence that ischemia disrupts delayed object recognition, a memory process found to be largely intact following selective hippocampal lesions. These findings indicate that damage confined to the hippocampal formation cannot account for all aspects of the ischemia-induced memory impairments. Second, although some groups of hippocampal neurons are the most prone to degeneration following ischemia, a wide array of extra-hippocampal damage has been observed in all species, for which the precise extent and distribution may well be underestimated by conventional histological evaluations of ischemic brains. Partial neuronal degeneration reported in regions such as the rhinal areas, medial dorsal thalamic nucleus, or cingulate cortex may contribute to varying degrees to ischemia-induced memory deficits. Third, experimental studies have failed to generate a general consensus on the correlation between extent of hippocampal cell loss and memory performance. In sum, the experimental studies do not, as yet, support the view that hippocampal damage is solely responsible for ischemia-induced memory deficits. Rather, they suggest that both the intra- and extra-hippocampal damage contribute to the pattern of memory impairments observed following ischemia. Consequently, although animals with global and focal ischemia represent valuable models for neuropathological and therapeutic studies, they may not be so useful in assessing the role of the hippocampal formation and its sub-components in memory processes.

Animals↗

PubMed2004

Actual and perceived memory deficits in individuals with compulsive hoarding.

Memory problems have been hypothesized to underlie compulsive hoarding behavior [Frost and Hartl, 1996: Behav Res Ther 34:341-350]. This study examined memory performance, memory confidence, and memory beliefs in 22 individuals with severe hoarding symptoms and 24 matched normal control subjects. Participants were administered two measures of learning and memory that required strategic planning and organization for successful performance: the Rey-Osterrieth Complex Figure Test (RCFT) and California Verbal Learning Test (CVLT). Self-reports of memory confidence, perceived consequences of forgetting, importance of remembering, and need to keep possessions in sight also were assessed. In comparison to controls, participants with compulsive hoarding recalled less information on delayed recall of the RCFT and CVLT and used less effective organizational strategies on the RCFT but not the CVLT. Hoarders also reported significantly less confidence in their memory, more catastrophic assessments of the consequences of forgetting, and a stronger desire to keep possessions in sight. Results provide initial evidence of learning and memory impairment and poor memory confidence in subjects with compulsive hoarding.

Adult↗

PubMed2005

Hippocampal lesions that abolish spatial maze performance spare object recognition memory at delays of up to 48 hours.

The hippocampus is widely considered to be a critical component of a medial temporal lobe memory system, necessary for normal performance on tests of declarative memory. Object recognition memory is thought to be a classic test of declarative memory function. However, previous tests of the effects of hippocampal lesions on object recognition memory have not always supported this view. One possible reason for this inconsistency is that previously reported effects of hippocampal lesions on object recognition memory tasks may have stemmed not from a deficit in object recognition memory per se, but as a result of spatial and contextual confounds in the task. Thus, in the present study, we used a spontaneous object recognition test in a modified apparatus designed to minimize spatial and contextual factors. A group of rats with complete excitotoxic lesions of the hippocampus and a group of control rats were tested on this modified spontaneous object recognition task with retention delays of up to 48 h. These rats were also tested on a spatial nonmatching-to-place task. Spatial memory performance was abolished following hippocampal lesions, whereas performance on the recognition memory task was intact at all delays tested.

Animals↗

PubMed2005

A check on the memory deficit hypothesis of obsessive-compulsive checking.

A number of recent studies have challenged the hypothesis that patients with obsessive-compulsive disorder (OCD) display global memory deficits. An alleviated form of the memory deficit hypothesis posits that OCD patients share deficits to vividly recall memory episodes. According to the latter view, checking rituals can be understood as counter-productive coping strategies to "enrich" memory episodes in order to make them more distinctive. A source memory task was administered to 27 OCD (17 checkers) and 51 healthy participants. Along with confidence judgments, a remember-know procedure was employed to assess whether OCD patients display problems with conscious/vivid recollection. Patients with or without checking compulsions did not exhibit differences to controls on source memory accuracy and meta-memory. Patients forgot more self-generated items, which, however, was related to comorbid depressive but not OCD symptoms. Findings challenge the ubiquity of memory deficits in OCD. To account for the inconclusive pattern of results in the literature, it is suggested that patients mistrust their memories and adopt checking rituals only when perceived responsibility is inflated.

Adaptation, Psychological↗

PubMed2005

Brain tumour surgery in the vicinity of short-term memory representation--results of neuronavigation using fMRI images.

OBJECTIVE: Functional information concerning the surrounding brain is mandatory for a good clinical outcome in brain tumour surgery. The value of fMRI to detect the motorcortex and Broca's area is widely accepted today. If an appropriate paradigm is used, short-term memory areas can be visualized as well. Obviously this information must be integrated into cranial neuronavigation for an appropriate intra-operative use. We report our first experiences with the direct integration of short-term memory fMRI into cranial neuronavigation. METHOD: From January 2001 to March 2002 14 patients were operated on for intracranial tumours with short-term memory fMRI imaging, using the "two-back-paradigm". Both pre- and postoperatively, the short-term memory of all patients was tested additionally by a standardized test battery including 16 different verbal and visuo-spatial items. RESULTS: In all 14 patients the general level of working memory capacity was preserved after surgery. The visuo-spatial performance was kept unchanged or deteriorated slightly, the alertness slightly worsened as well, but we found an improvement in verbal test items. CONCLUSION: The two-back paradigm is able to visualize verbal memory tasks in fMRI. For visuo-spatial items, a new paradigm has to be designed. In contrast to deep seated brain lesions, focal cortical impairments do not lead to obvious and serious memory deficits. Therefore, the aim of gross total tumour removal has to be balanced against the aim of preservation of short-term memory fields. Nevertheless, the knowledge of the localization of cortical short-term memory fields may combine both aims during navigated brain tumour surgery, thus preserving the patient with a better quality of life.

Adult↗

PubMed1996

Beta-adrenergic dysfunction exacerbates impairment of working memory induced by hippocampal NMDA receptor blockade in rats.

To clarify the interactions between hippocampal glutamatergic and adrenergic systems in the working memory function of rats, the effects of hippocampal NMDA receptor blockade combined with noradrenaline depletion or alpha- and beta-adrenoceptor blockade on this behavior were examined with a three-panel runway task. Intrahippocampal administration of the potent and competitive NMDA receptor antagonist (+/-)-3-(2-carboxypiperazin-4-yl)propyl-1-phosphonic acid (CPP) at a dose of 32 ng/side significantly increased the number of errors (attempts to pass through two incorrect panels of the three panels gates at four choice points) in the working memory task, whereas the 3.2 ng/side dose of CPP did not affect working memory errors. Administration of the noradrenergic neurotoxin N-(2-chloroethyl)-N-ethyl-2 -bromobenzylamine (DSP-4) at 50 mg/kg i.p. produced marked reductions in hippocampal and cortical noradrenaline contents, but it had no effect on working memory errors. Intrahippocampal administration of 3.2 ng/side CPP, the behaviorally ineffective dose in intact rats, significantly increased the number of working memory errors in the noradrenaline-depleted rats. The alpha-adrenoceptor antagonist phentolamine (3.2 mg/kg i.p.) did not affect working memory errors whether administered alone or in combination with intrahippocampal CPP (3.2 ng/side). The beta-adrenoceptor antagonist propranolol (10 mg/kg i.p.) also had no effect on working memory errors. However, propranolol (10 mg/kg) produced a significant increase in working memory errors when administered together with intrahippocampal CPP (3.2 ng/side). These results suggest that hippocampal NMDA/beta-adrenergic interactions are involved in neural processes mediating working memory function of rats.

Adrenergic alpha-Antagonists↗

PubMed1995

Physostigmine, but not 3,4-diaminopyridine, improves radial maze performance in memory-impaired rats.

The results of some studies suggest that 3,4-diaminopyridine (3,4-DAP), a drug that enhances the release of acetylcholine, may improve memory. The present study examined the ability of 3,4-DAP to reverse the memory impairment produced by scopolamine and the ability of 3,4-DAP and physostigmine to reverse the memory impairment produced by quinolinic acid lesions of the nucleus basalis magnocellularis (nbm) in rats. Mnemonic functioning was assessed with the use of a partially baited eight-arm radial maze. Entries into arms that were never baited were defined as reference memory errors; entries into baited arms from which the food already had been eaten were defined as working memory errors. In Experiment 1, 0.1 mg/kg scopolamine produced a significant increase in working and reference memory errors. Various doses of 3,4-DAP had no significant ameliorative effect on the mnemonic deficit. In Experiment 2, cholinergic function was impaired using a unilateral intra-nbm injection of quinolinic acid (120 nmol in 1.0 microliter). These lesions reduced the levels of the cholinergic marker, choline acetyltransferase, in the cortex by more than 40%. Results showed that the nbm lesion animals were significantly more impaired on the working than reference memory component of the task. Physostigmine (0.01, 0.05, 0.10, 0.20, 0.50 mg/kg) dose-dependently decreased the number of working but not reference memory errors. 3,4-DAP (10(-8), 10(-6), 10(-4), 10(-2), 10(0) mg/kg) had no reliable effect. It was concluded that physostigmine, but not 3,4-DAP, ameliorates memory impairments following decreases in cholinergic function.

4-Aminopyridine↗

PubMed1990

The consequences of reduced memory span for the comprehension of semantic versus syntactic information.

Aphasic patients with restricted memory spans were assessed on their comprehension of syntactically simple sentences varying in numbers of content words and on their comprehension of sentences matched in content words but varying in syntactic complexity. Three different presentation modes were used: unlimited visual presentation, limited visual presentation, and auditory presentation. The difference between performance in the unlimited and limited modes was used as a measure of the extent to which memory decrements caused comprehension failure. These difference scores were related to memory span in order to assess whether the memory involved in sentence processing overlaps that assessed by a memory span task. For the sentences varying in number of content words, performance was worse for the limited presentation modes than the unlimited mode, and the difference between unlimited and limited presentation modes was highly related to memory span. For the sentences varying in syntactic complexity, there was no clear reduction in performance for limited presentation modes, and the difference scores did not relate to memory span. The results support the view that the processing of sentences with many content words draws on the short-term memory capacity assessed by memory span, while the processing of syntactic complexity does not.

Aged↗

PubMed2005

Schizophrenic patients are impaired in memory reinstatement underlying mismatch negativity system.

OBJECTIVE: We modified the paradigm used in the report of Cowan et al. [J Exp Psychol Learn Mem Cogn 19 (1993) 909] to investigate how the silent intervals influence the memory trace underlying mismatch negativity (MMN) generation in schizophrenic patients. METHODS: Experiment 1 was designed to explore how long an inter-train interval would be needed for the memory to become dormant. Experiment 2 was designed to elucidate how many standard stimuli would be needed to reinstate the memory. RESULTS: In Experiment 1, schizophrenic patients showed a significant reduction in MMN amplitude after the longer inter-train intervals compared to the shorter ones, although little difference was observed in controls. Specifically, the memory trace underlying the MMN system in the schizophrenic patients easily became dormant after the extended silent intervals. In Experiment 2, we could not conclude that schizophrenic patients needed more reminders than did controls in order to reinstate the memory once the memory trace became dormant. The patients might be little impaired with respect to forming the memory trace. CONCLUSIONS: In schizophrenic patients, the memory trace in MMN generation might easily become out of context after silent intervals. Patients could not effectively reinstate the memory that was put out of context by the extended silent interval. SIGNIFICANCE: This article provides some suggestions in terms of patients' difficulty encoding episodes and retrieving them within distinct contexts in preconscious processes.

Acoustic Stimulation↗