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PubMed1999

Effects of histamine H3 receptor agonists and antagonists on cognitive performance and scopolamine-induced amnesia.

In previous research we found that pre-training administration of histamine H3 receptor agonists such as (R)-alpha-methylhistamine and imetit impaired rat performance in object recognition and a passive avoidance response at the same doses at which they inhibited the release of cortical acetylcholine in vivo. Conversely, in the present study we report that the post-training administration of (R)-alpha-methylhistamine and imetit failed to affect rat performance in object recognition and a passive avoidance response, suggesting that H3 receptor influences the acquisition and not the recall processes. We also investigated the effects of two H3 receptor antagonists, thioperamide and clobenpropit, in the same behavioral tasks. Pre-training administration of thioperamide and clobenpropit failed to exhibit any procognitive effects in normal animals but prevented scopolamine-induced amnesia. However, also post-training administration of thioperamide prevented scopolamine-induced amnesia. Hence, the ameliorating effects of scopolamine-induced amnesia by H3 receptor antagonism are not only mediated by relieving the inhibitory action of cortical H3 receptors, but other mechanisms are also involved. Nevertheless, H3 receptor antagonists may have implications for the treatment of degenerative disorders associated with impaired cholinergic function.

Amnesia↗
PubMed1998

Memory, amnesia, and the issue of recovered memory: neurobiological aspects.

The main thesis of this article is that the debate about the credibility of "recovered memories"--reports by adults of recovered memories of childhood sexual abuse and trauma that were allegedly repressed for many years--can be usefully informed by considering the biological and behavioral facts and ideas about how memory works. Accordingly, the first section of this review describes current facts and ideas about the neurobiology and neuropsychology of memory and amnesia, including what parts of the brain are important for memory, distinctions between different memory systems in the brain, and the phenomena of infantile amnesia and source amnesia. The second section takes into account the information about the biological and behavioral bases of memory and addresses two questions about memory that have become a focus of debate in the recovered memory controversy, that is, whether memories for traumatic events change over time, and whether memories can be created for traumatic events that did not actually happen.

Adult↗
PubMed1989

Duration of amnesia associated with midazolam/fentanyl intravenous sedation.

The purpose of this study was to determine the duration of amnesia associated with the intravenous usage of midazolam and fentanyl. The midazolam was administered in three different dosages based on the patient's weight in kilograms. Patients were shown a series of pen-and-ink drawings at various times throughout the procedure and tested the next day for memory of the drawings using both free recall and match-to-sample paradigms. The results indicate that the low-dosage group (0.07 mg/kg) had insufficient amnesia, whereas the medium (0.10 mg/kg) and high (0.13 mg/kg) groups displayed adequate amnesia in the intraoperative period.

Adolescent↗
PubMed1997

Impaired episodic memory retrieval in a case of probable psychogenic amnesia.

A patient with severe, selective retrograde amnesia for personal material diagnosed as probable psychogenic amnesia, was investigated intensively neuropsychologically with cranial computed tomography (CCT), magnetic resonance imaging (MRI), and single photon emission tomography (SPECT). The patient was of average intelligence and memory with no anterograde amnesia. No evidence for structural brain damage was detected in CCT and MRI. SPECT, performed about 3 weeks after the onset of symptoms, demonstrated reduced perfusion in right temporal and frontal areas, that is, in areas which have been suggested as critical for episodic memory retrieval. To study episodic memory retrieval, positron-emission-tomography (PET) blood flow (rCBF) measurements were performed 6 months after the onset of symptoms. During episodic memory retrieval bilateral neuronal activations were observed in the precuneus, the lateral parietal and the right dorsolateral and polar prefrontal cortex. Compared to the results of previous functional imaging studies on episodic memory retrieval, our findings suggest an underlying functional disturbance of brain areas previously demonstrated to be involved in episodic memory retrieval.

Adult↗
PubMed2001

[The recording of cognitive evoked potentials during and after transient global amnesia: report of three cases].

It is of interest to record event-related potentials in the course of transient global amnesia (TGA) because the hippocampus and diencephalon, generally considered to be the sites of the dysfunction responsible for the amnesic episodes are also considered as two possible generators of the P300 wave. However, the only four cases reported so far in the literature showed an intact auditive P300 in three cases and an intact auditive P300 with reduction of visual P300 in one case. Here are reported four new cases. The P300 wave was readily identifiable in all four cases, without any amplitude reduction, thus suggesting that the condition did not entail inactivation or functional depression of P300 generators. Concerning P300 latency, in one case it was delayed but became normal after the ictus. In the second case, the latency, although within normal limits, shortened after the ictus. In the third and the fourth cases, the latency, initially within normal limits, remained unchanged. These apparently disparate results should be analysed in the light of the results of isotope measurement of cerebral blood flow during the amnesia, which are also inconsistent but most frequently indicate bilateral temporal or thalamic flow reduction. It remains to be determined in the future whether the stability or change in the P300 will make it possible to predict the brain region involved in transient global amnesia, which could perhaps vary from one patient to another.

Acoustic Stimulation↗
PubMed1995

Isolated retrograde amnesia for autobiographical material associated with acute left temporal lobe encephalitis.

Retrograde amnesia for autobiographical material in the absence of anterograde amnesia or other memory disturbances was found in a patient with acute viral encephalitis. Memory loss showed a temporal gradient, but new learning was spared. Both brain perfusion imaging with 99mTc-HMPAO SPECT, and EEG localized the lesion in the left temporal lobe while CT and MRI were normal. This observation supports the anatomical differentiation between the different memory functions. The uncommon combination of isolated retrograde amnesia without other neuropsychological findings may raise the doubt of psychogenic aetiology, which in this case was refuted.

Adult↗
PubMed1995

Normal perceptual priming of orthographically illegal nonwords in amnesia.

This study examined priming in perceptual identification of orthographically illegal nonwords in control subjects and patients with global amnesia. Subjects studied a list of orthographically illegal nonwords and then performed a perceptual identification task in which half of the stimuli were from the prior study list and half were new (unstudied) stimuli. Priming was reflected in enhanced identification accuracy of studied compared to unstudied nonwords. Amnesic patients showed significant and normal priming despite impaired recognition memory performance. Because the experimental stimuli were dissimilar to real words in terms of orthography and phonology, it is unlikely that this priming effect was mediated by activation of pre-existing representations of orthographically or phonologically similar words, morphemes, or syllables. These results demonstrate that intact perceptual priming in amnesia is not limited to stimuli that are premorbidly represented in long-term knowledge, nor to novel stimuli that conform to the rules that characterize familiar items. Further, because the experimental stimuli comprised novel letter assemblies, the results suggest that amnesic patients can show normal priming for new perceptual associations. These findings demonstrate that processes spared in amnesia can support the creation and subsequent retrieval of novel stimulus representations.

Adult↗
PubMed2004

Retrograde amnesia in patients with rupture and surgical repair of anterior communicating artery aneurysms.

The retrograde amnesia of patients with memory loss related to rupture and surgical repair of anterior communicating artery (ACoA) aneurysms is compared with the retrograde amnesia of temporal amnesic patients and nonamnesic control participants. Two tests which focus on popular culture but which differ according to extent of news exposure and the cognitive processes necessary for task performance were used to measure retrograde memory. ACoA patients demonstrated more significant retrograde memory problems than did nonamnesic controls; however, the severity and pattern of their memory loss was less severe than that seen in association with temporal amnesia. Different factors influenced the remote memory loss of respective groups: ACoA patients' problems were related to impaired lexical retrieval whereas temporal amnesic patients had problems secondary to both retrieval and storage deficits.

Amnesia, Retrograde↗
PubMed1998

Acquired oral reading vocabulary following the onset of amnesia in childhood.

While the neuropsychological literature includes few cases of child-onset amnesia, 2 previous case studies suggest that these patients may be able to learn new information of a semantic or academic nature. The previous studies were, in large part, based on neuropsychological testing performed during adulthood and a retrospective review of academic achievement test scores during childhood. We present patient A.C., who acquired severe anterograde amnesia at age 10 years but demonstrated average levels of performance on tests of reading, spelling and arithmetic upon examination at age 19 years. Episodic and semantic memory test scores were severely impaired, but near normal performances were found on tests of implicit and procedural memory. In a prospective study, A.C. learned to read new irregular and pseudowords and retained this learning over a 1-month period, similar to the performance of age-matched controls. This demonstration of postmorbid, acquired oral reading vocabulary supports a previous conclusion that oral reading can progress in childhood following the onset of severe anterograde amnesia. The data also suggest that this new learning probably reflects nondeclarative memory processes rather than preservation of semantic memory, as was proposed in an earlier case study.

Amnesia↗
PubMedDate not supplied

Studies of the interaction between behavioral stereotypes and the effects of activation of presynaptic dopamine receptors during extinction and amnesia in mice.

The involvement of presynaptic dopamine receptors in the retention of a conditioned passive avoidance reflex through extinction and amnesia was studied in C57BL/6J mice selected in a 20-day aggressive conflict test for aggressive and submissive behavioral stereotypes. These experiments showed that in aggressive mice, activation of presynaptic receptors with the agonist (+)3-(3-hydroxyphenyl)-N-n-propylpiperidine [(+)3PPP] at a dose of 2 mg/kg degraded learning, significantly decreased the retention time of the acquired conditioned habit in extinction, and increased the effect of an amnesia-inducing treatment. Mice showing submissive behavior in daily confrontations with aggressors responded to administration of (+)3PPP with long-lasting reproduction of the conditioned passive avoidance reaction during extinction and showed no changes in the development of amnesia. These data on the relationship between the effects of activating presynaptic dopamine receptors in reproduction of the memory trace in conditions of trace disruption on the one hand and behavioral status on the other are assessed from the point of view of different basal levels of dopaminergic system operation in aggressive and submissive mice.

Aggression↗
PubMed2003

The effects of novelty and behavioral stereotype on the development of amnesia in mice.

The aim of the present study was to analyze the significance of the interaction between the basic behavioral strategy, the extinction of the novelty of information, and the efficacy of amnesia-inducing influences. Using a combination of training to passive avoidance with holding the animal in the unsafe sector of the apparatus, comparative analysis was performed of the reproduction of a memory trace in aggressive and submissive mice of line C57BL/6J with and without six sessions of familiarization with the apparatus. These experiments showed that preliminary habituation prevented the development of amnesia in submissive but not aggressive individuals. The cause of these differences in the effects of preexposure on the development of amnesia involves the selectivity of the process of extinction of information novelty characteristic for the behavioral stereotype.

Aggression↗
PubMed1990

Detection of simulated hypnotic amnesia.

Highly hypnotizable nonsimulators and high- and low-hypnotizable simulators of hypnosis were administered a hypnotic amnesia suggestion and tested for recall and recognition of a previously learned word list. Simulators exhibited higher levels of recall and recognition amnesia than nonsimulators. Most important, simulators recognized "forgotten" words at lower levels than expected by chance significantly more often than did nonsimulators. Implications for the detection of simulated amnesia in clinical samples are discussed.

Adolescent↗
PubMed1985

Volitional experiences associated with breaching posthypnotic amnesia.

Highly responsive hypnotic subjects classified as having control over remembering (voluntaries) or not having control over remembering (involuntaries) during posthypnotic amnesia were compared during posthypnotic recall. Subjects rerated their voluntariness after the experiment. Two contextual conditions were employed (2 X 2 design): a lie detector condition meant to create pressure to breach amnesia and a relax control condition. In contrast to earlier findings, the recall data showed that both voluntary and involuntary subjects breached under the lie detector condition compared with their counterparts in the relax condition; however, the degree of breaching was not great in any condition. The results are discussed as they relate to studies attempting to breach posthypnotic amnesia and characteristics of the voluntary-involuntary dimension.

Amnesia↗
PubMed1992

The use of indirect memory tests to assess malingered amnesia: a study of metamemory.

Many techniques have been suggested for identifying criminal suspects who are simulating amnesia for the events surrounding a crime. The present research focuses on indirect memory tests as a potential means of discriminating between those who genuinely suffer from amnesia and those who are simulating. Subjects studied a list of words and subsequently performed either a word completion or a fragment completion task. Under normal indirect test instructions, typical priming effects were observed. When subjects were motivated to simulate amnesia for the list, target completion rates were consistently, and sometimes reliably, below baseline completion rates. This finding is contrary to the performance of genuine amnesics, whose performance on indirect tests typically mirrors that of normal subjects. Indirect tests may prove useful in discriminating genuine and simulating amnesics.

Adult↗
PubMed1982

Comparisons between forms of amnesia: some deficits are unique to Korsakoff's syndrome.

Certain features of abnormal memory, which have figured prominently in theoretical treatments of the amnesic syndrome, were assessed in patients with Korsakoff's syndrome, in Case N.A., and in patients receiving electroconvulsive therapy. Patients with Korsakoff's syndrome differed from the other patients by (a) failing to exhibit release from proactive interference, and (b) being disproportionately impaired in the ability to make judgments about the temporal order of recent events. These deficits appear to be related to frontal lobe damage and are superimposed on a more basic memory disorder. Theories of amnesia should be founded on the basic memory disorder and not on deficits such as these, which have no obligatory relationship to amnesia. Dissociations between aspects of memory, revealed by the study of amnesia, can also shed light on the organization of memory in the brain.

Alcohol Amnestic Disorder↗
PubMed1998

Recollection and familiarity deficits in amnesia: convergence of remember-know, process dissociation, and receiver operating characteristic data.

Previous studies using the process dissociation and the remember-know procedures led to conflicting conclusions regarding the effects of anterograde amnesia on recollection and familiarity. We argue that these apparent contradictions arose because different models were used to interpret the results and because differences in false-alarm rates between groups biased the estimates provided by those models. A reanalysis of those studies with a dual-process signal-detection model that incorporates response bias revealed that amnesia led to a pronounced reduction in recollection and smaller but consistent reduction in familiarity. To test the assumptions of the model and to further assess recognition deficits in amnesics, we examined receiver operating characteristics (ROCs) in amnesics and controls. The ROCs of the controls were curved and asymmetrical, whereas those of the amnesics were curved and symmetrical. The results supported the predictions of the model and indicated that amnesia was associated with deficits in both recollection and familiarity.

Aged↗
PubMed2000

Acquisition and transfer of new verbal information in amnesia: retrieval and neuroanatomical constraints.

Four experiments examined new associative learning in amnesia by contrasting the performance of 2 amnesic participants-1 (C.C.) with basal forebrain damage and the other (R.H.) with medial temporal lobe damage--and 3 controls. Both amnesic individuals were severely impaired on explicit memory measures but showed intact perceptual priming. On the new associations measures, only C.C., not R.H., exhibited learning by producing correct targets (HIJACKER) in the absence of perceptual cues for them (e.g., STAFF shot ???). When the perceptual cue (e.g., MEDICINE cured _I_C_P) was provided, both C.C. and R.H. showed learning. Transfer to information containing conceptually related targets (e.g., TERRORIST or BELCH) was reliably observed only in C.C. This finding was replicated with further reduction in perceptual overlap across original (LIGHTNING torched JUNGLE) and transfer (LIGHTNING burned WILDERNESS) sentences. Together, these findings delineate the role of experimental conditions, severity of amnesia, and different neuroanatomical structures in mediating new verbal learning in amnesia.

Adult↗
PubMed2006

Opioid receptors regulate retrieval of infant fear memories: effects of naloxone on infantile amnesia.

The authors examined the role of the endogenous opioid system in infantile amnesia for contextual fear conditioning. Rats that were 18 days of age received an aversive footshock in a novel context. Rats displayed conditioned fear when tested 1 min after training but not 24 hr after training. Systemic injection of the opioid receptor antagonist naloxone prior to test, but not immediately after training, alleviated infantile amnesia. Naloxone also alleviated infantile amnesia when injected prior to test 7 days after training. These effects of naloxone were due to actions on central rather than peripheral opioid receptors and were not due to any tendency of the drug to produce fear or freezing. These results show that central opioid receptors regulate retrieval of fear memories in infant rats.

Amnesia↗