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PubMed2006

The contribution of familiarity to associative memory in amnesia.

In Experiment 1, using the remember/know paradigm with control participants, we compared the contribution of recollection and familiarity to associative recognition for compound stimuli and for unrelated word pairs. It was demonstrated that familiarity makes a greater contribution to associative recognition of compound stimuli than to associative recognition of unrelated word pairs. In Experiment 2, we examined associative recognition memory in medial temporal lobe amnesics, diencephalic amnesics, and control participants for the stimuli employed in Experiment 1. Whereas associative recognition for compounds and unrelated words was nearly identical in control participants, associative recognition was higher for compounds than for unrelated word pairs in amnesic patients. This pattern was observed in the medial temporal amnesic group as well as in the diencephalic amnesic group. These results suggest that associative recognition in amnesia is enhanced to the extent that performance can be supported by study-induced familiarity for the studied pair.

Aged↗
PubMed2006

Acquired amnesia in childhood: a single case study.

We report the case of C.L., an 8-year-old child who, following the surgical removal of an ependymoma from the left cerebral ventricle at the age of 4 years, developed significant difficulties in retaining day-to-day events and information. A thorough neuropsychological analysis documented in C.L. a severe anterograde amnesic syndrome, characterised by normal short-term memory, but poor performance on episodic long-term memory tests. In particular, C.L. demonstrated virtually no ability to recollect new verbal information several minutes after the presentation. As for semantic memory, C.L. demonstrated general semantic competencies, which, depending on the test, ranged from the level of a 6-year-old girl to a level corresponding to her actual chronological age. Finding a patient who, despite being severely impaired in the ability to recollect new episodic memories, still demonstrates at least partially preserved abilities to acquire new semantic knowledge suggests that neural circuits implicated in the memorisation of autobiographical events and factual information do not overlap completely. This case is examined in the light of growing literature concerned with the dissociation between episodic and semantic memory in childhood amnesia.

Amnesia, Anterograde↗
PubMed2006

Recall and recognition memory in amnesia: patients with hippocampal, medial temporal, temporal lobe or frontal pathology.

The relationship between recall and recognition memory impairments was examined in memory-disordered patients with either hippocampal, medial temporal, more widespread temporal lobe or frontal pathology. The Hirst [Hirst, W., Johnson, M. K., Phelps, E. A., & Volpe, B. T. (1988). More on recognition and recall in amnesics. Journal of Experimental Psychology: Learning, Memory, & Cognition, 14, 758-762] technique for titrating exposure times was used to match recognition memory performance as closely as possible before comparing recall memory scores. Data were available from two different control groups given differing exposure times. Each of the patient groups showed poorer recall memory performance than recognition scores, proportionate to the difference seen in healthy participants. When patients' scores were converted to Z-scores, there was no significant difference between mean Z-recall and Z-recognition scores. When plotted on a scatterplot, the majority of the data-points indicating disproportionately low recall memory scores came from healthy controls or patients with pathology extending into the lateral temporal lobes, rather than from patients with pathology confined to the medial temporal lobes. Patients with atrophy extending into the parahippocampal gyrus (H+) performed worse than patients with atrophy confined to the hippocampi (H-); but, when H- patients were given a shorter exposure time (5s) and compared with H+ at a longer exposure (10s), their performance was virtually identical and did not indicate any disproportionate recall memory impairment in the H- group. Parahippocampal volumes on MRI correlated significantly with both recall and recognition memory. The possibility that findings were confounded by inter-stimulus artefacts was examined and rejected. These findings argue against the view that hippocampal amnesia or memory disorders in general are typically characterised by a disproportionate impairment in recall memory. Disproportionate recall memory impairment has been observed in a number of published cases, and the reason for the varying pattern obtained across hippocampal patients requires further examination.

Adult↗
PubMed2006

Bovine brain phosphatidylserine attenuates scopolamine induced amnesia in mice.

This study verifies the effects of bovine brain phosphatidylserine (PS) on passive avoidance (PA) and contextual fear conditioning (CFC) tests in scopolamine-treated mice. Mice received daily i.p. 50 mg/kg PS or 0.2 M Tris pH 7.4 (TRIS) for 5 days. On day 6, mice received saline (TRIS-SAL and PS-SAL) or 1 mg/kg SCO (TRIS-SCO and PS-SCO) i.p. After 20 min, the animals were submitted to PA (experiment 1) or CFC (experiment 2) training sessions, and tests were performed 24 h later. Latency in entering the dark chamber of the PA apparatus presented by TRIS-SCO (but not PS-SCO) group in the test was significantly higher than those presented by controls. Except for TRIS-SCO, all the groups presented higher latencies in the test compared to the training session. In experiment 2, the TRIS-SCO (but not PS-SCO) group presented significantly lower freezing duration than that presented by the TRIS-SAL group in the test. Animals treated with PS alone presented higher freezing duration than that presented by the TRIS-SAL group. The results demonstrate that PS attenuates SCO-induced amnesia in both PA and CFC tests. In addition, PS per se improves retention in the CFC test.

Amnesia↗
PubMed2005

No morning cortisol response in patients with severe global amnesia.

Activity of the hypothalamus pituitary adrenal (HPA) axis is characterized by a pronounced circadian rhythm. An acute increase in cortisol levels occurs after awakening in the morning with continuously declining levels over the course of the remaining day. The morning cortisol increase probably reflects an activational response of the HPA axis aimed at preparing the body for the day. Some studies found patterns of enhanced or blunted waking cortisol responses observed under chronic stress, burnout, or post traumatic stress disorder. The present study wanted to characterize the morning cortisol response and the circadian cortisol day profile in a sample of six male patients with severe amnesia due to hypoxia, herpes simplex encephalitis or closed head injury. Age and gender matched relatives or friends served as controls. Cortisol was measured from saliva samples collected at home on two consecutive days. The patients were woken up in the morning by their partners or caregivers. The morning cortisol increase typically observed in healthy subjects and also observed in the control group was absent in the amnesic patients. In contrast, a normal circadian day profile was found in the amnesic patients, with a pronounced circadian cortisol decrease. Further studies are needed to understand the neurological or psychological mechanisms leading to a missing morning cortisol response in amnesic patients.

Adult↗
PubMed2005

Drug-induced amnesia impairs implicit relational memory.

Amnesic patients have difficulty consciously recollecting past events, but they perform normally on implicit memory measures that do not require conscious access. Now, an innovative study offers compelling evidence that even implicit memory can be impaired during amnesia, temporarily induced in healthy subjects using a neuropharmacological manipulation (midazolam). Importantly, midazolam impaired implicit, relational memory, whereas non-relational memory was preserved, supporting the characterization of conscious memory in terms of relational encoding.

Amnesia↗
PubMed2002

Memory protective effect of indomethacin against electroconvulsive shock-induced retrograde amnesia in rats.

BACKGROUND: Nonsteroidal antiinflammatory drugs (NSAIDs) have been suggested to retard cognitive decrements in patients with Alzheimer's disease. We postulated that NSAIDs also may protect acute disruption of memory. METHODS: We studied the effect of indomethacin (4 mg/kg/day) administered daily for 19 days on retrograde amnesia induced by two once-daily electroconvulsive shocks in rats. RESULTS: Indomethacin produced statistically significant prolongation of recall latency in a passive avoidance task using a step-down apparatus. CONCLUSIONS: Our study suggests that NSAIDs may prevent memory disruption through other mechanisms apart from attenuating chronic inflammation. In patients receiving electroconvulsive therapy, as in those diagnosed with Alzheimer's disease, antiinflammatory drugs may hold promise in the attenuation of cognitive impairments.

Amnesia, Retrograde↗
PubMed2003

D-Serine alleviates retrograde amnesia of a visual discrimination task in rats with a lesion of the perirhinal cortex.

D-Serine has been suggested to be a potent endogenous glycine-site agonist on the N-methyl-D-aspartate receptor, thereby having a potential role in the process of learning and memory. In rats, perirhinal cortex (PC) constitutes a particularly important structure for mnemonic processing, and damage to this area induces both anterograde and retrograde amnesia. In the present work, we show that intraperitoneal administration of 1000 mg/kg D-serine immediately after bilateral lesion of PC produced complete restoration of retrograde memory in rats, measured by a visual brightness discrimination task, while a higher dose (3000 mg/kg) did not show any reliable effect. Uptake of the drug into the brain was confirmed using high performance liquid chromatography (HPLC).

Amnesia, Retrograde↗
PubMedDate not supplied

Dissociative detachment and memory impairment: reversible amnesia or encoding failure?

The authors propose that clinicians endeavor to differentiate between reversible and irreversible memory failures in patients with dissociative symptoms who report "memory gaps" and "lost time." The classic dissociative disorders, such as dissociative amnesia and dissociative identity disorder, entail reversible memory failures associated with encoding experience in altered states. The authors propose another realm of memory failures associated with severe dissociative detachment that may preclude the level of encoding of ongoing experience needed to support durable autobiographical memories. They describe how dissociative detachment may be intertwined with neurobiological factors that impair memory, and they spell out the significance of distinguishing reversible and irreversible memory impairment for diagnosis, patient education, psychotherapy, and research.

Amnesia↗
PubMed1998

Transient retrograde amnesia associated with impaired naming of living categories.

A ease of pure retrograde amnesia following mild head injury is reported. The patient, who also showed a deficit in verbal fluency and a living/non-living dissociation in naming during the amnesic period, recovered progressively in about ten days post-trauma. Both a psychogenic and an organic origin could be taken into account. A mechanism (no matter if psychogenic or organic) can be hypothesized, which produces a functional inhibition also involving performances that are unlikely to be affected by psychological factors.

Adult↗
PubMedDate not supplied

A case of amnesia at an early age.

A dissociation between short- and long-term memory (LTM) and between the episodic and the semantic component of LTM is reported in a young girl who became amnesic at the age of 6 after an episode of acute encephalopathy resulting in bilateral frontal, insular, thalamic, ponto-mesencephalic, hippocampal and temporal lesions, as documented by MRI. The girl became amnesic a few months after starting school. A follow-up investigation showed that she was able to learn to read, write and acquire number facts and procedures and to improve her semantic knowledge. Our results show that the features of adult amnesia can also be found in children and that new semantic knowledge can be acquired in spite of an anterograde memory deficit. This dissociation does not agree with theories viewing long-term declarative memory as a unitary process mediated by the hippocampal system, but supports recent hypotheses that the acquisition of semantic knowledge is independent from episodic memory processes, and takes place through spared cortical regions subjacent to the hippocampi (Vargha-Khadem et al., 1997).

Amnesia↗
PubMedDate not supplied

The impact of disrupted cortico-cortico connectivity: a long-term follow-up of a case of focal retrograde amnesia.

We report a long-term follow-up study of case JM, who demonstrated a focal retrograde amnesia (FRA) as a consequence of cerebral vasculitis. The present study showed that, several years post-onset, JM experienced considerable impairment in episodic retrograde memory, with normal anterograde autobiographical memory. Further investigations demonstrated that she showed no evidence of accelerated forgetting, unlike some other cases of FRA. Knowledge of people, pre- and post-illness, was also normal. Her ability to recall details of famous public events was good (though weaker for pre-illness events). JM's pattern of impairment is discussed in the context of other recent cases of FRA and developments in models of normal memory function.

Acute Disease↗
PubMed1993

Dense retrograde amnesia, intact learning capability and abnormal forgetting rate: a consolidation deficit?

Following a thoracic trauma, which caused brain hypoxia, a 24-year-old man presented with a dense retrograde amnesia for events, persons and environments that spanned his whole life before injury. Knowledge acquired at school or through the media were equally lost, with the exception of arithmetical skills and some geographical knowledge. No deficit was apparent in language, object recognition, motor skills and intellectual tests. Anterograde memory was marked by very efficient learning capacity, an almost perfect retention of information at delay interval of 4 hours and pathologically rapid forgetting at longer delays. Informal observations agreed with test performance in showing that he could relearn facts of the past and easily acquire new information, but tended to lose these memories if the information was not frequently rehearsed. PET showed a hypometabolism of the posterior temporal lobes. Though some points remain obscure, we propose that a consolidation deficit hypothesis provides the most sensible interpretation of this peculiar pattern of memory deficit.

Adult↗
PubMed1993

Recency judgements in Wernicke-Korsakoff and post-encephalitic amnesia: influences of proactive interference and retention interval.

This study further examines the performance of diencephalic and temporal lobe amnesics on the recency judgement task (Parkin, Leng and Hunkin, 1990). The two patient groups were represented by patients with Wernicke-Korsakoff syndrome (WKS) and post-Herpes simplex encephalitis (HSE). Experiment 1 demonstrated that poorer recency judgements by WKS patients were not due to a general proactive interference effect, but from an inability to remember which items had been designated targets on a given trial. Experiment 2 demonstrated that the superior performance of the HSE group was not attributable to a putative faster forgetting rate. In addition, the study found no relationship between recency judgements and degree of frontal lobe impairment. It is concluded that diencephalic damage has a particular effect on the ability to make recency judgements and that this represents a fundamental difference between diencephalic and temporal lobe amnesia. Theoretical interpretations of this difference are discussed.

Alcohol Amnestic Disorder↗
PubMed1981

Hidden memory: a rapid method for the study of amnesia using perceptual learning.

Performance on finding hidden figures in a set of picture-puzzles is shown to separate out autobiographical memory and perceptual learning in a group of male neurosurgical patients. Two traumatic amnesics had normal perceptual learning without ability to recognize which pictures they had seen before. The method may be used in the study of transient amnesias of very short duration.

Adolescent↗
PubMed1986

[Evaluation of the amnesia caused by restricted thalamic infarcts--6 cases].

The amnesic syndrome is analysed in 6 infarctions restricted to the thalamic area. Bilateral lesions were linked to more definite deficits; the anterograde forgetting was unequivocal at the initial stage and affected both verbal and visual memory. In unilateral lesions, deficits were far more discrete and there was no evidence enough for assuming a strict hemispheric specialisation, left for verbal memory, and right for visual memory. These cases and others from the literature suggested that amnesia is more important and pure in infarctions of the anterior part of the thalamus.

Adult↗
PubMed1987

Semantic amnesia with preservation of autobiographic memory. A case report.

A 44-year-old woman showed, following an episode of encephalitis, an impoverished knowledge of the meaning and attributes of words and their referents, in spite of intact command of grammatical-syntactic rules and preserved perceptual abilities. There was also a complete loss of the stock of notions she had acquired over her life and constituting the cultural background of a person, in contrast with normal memory for autobiographic events. The case is interpreted as an instance of semantic amnesia. MRI showed damage confined to the antero-medial part of the left temporal lobe.

Adult↗
PubMed1988

Selective "semantic amnesia" after closed-head injury. A case report.

An 18-year-old girl with a left parietal lesion caused by a closed-head injury exhibited a peculiar memory impairment. The patient showed selective "semantic amnesia" (severe loss of the stock of notions acquired prior to the disease), while autobiographic memory and spatial learning ability were preserved. The semantic/episodic distinction is discussed in the light of the patient's performance on neuropsychological tasks.

Adolescent↗