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At least 1,711 records · Page 95Linked to original sources
PubMed1982

Amnesia: a disconnection syndrome?

An attempt is made to account for the ability of severely amnesic patients to learn and retain certain tasks but not others. The hypothesis is advanced that the amnesic subject can show learning through facilitation by repetition or of simple S-R relationships not requiring cognitive mediation. Three examinations are reported. The first demonstrates that the amnesic subjects have adequate speed of access to semantic and phonological knowledge and show the same degree of improvement on retesting as controls. The second and third experiments examine different degrees of cognitive mediation in paired-associate learning. Amnesic subjects are differentially impaired relative to controls on "distant" pairs and on those that, by hypothesis, would benefit from cognitive mediation. The results are discussed in terms of a disconnection syndrome. It is suggested that at the functional level, a "cognitive mediational memory system" and a semantic memory system are disconnected in the amnesic patient. Neuropathological evidence suggests that temporal lobe and frontal lobe structures are disconnected by pathways in the fornix-mammillary body route.

Adult↗
PubMed1984

Encoding of spatial relations with amnesia.

Incidental and intentional learning of spatial location was studied in amnesics and normals. It was found that spatial encoding of amnesics improved with instruction whereas the spatial encoding of normal adults did not. The finding suggests that spatial encoding in amnesics may be qualitatively different from that of normal adults.

Adult↗
PubMed1987

Episodic, semantic and procedural memory in a case of amnesia at an early age.

The patient C.C. developed an amnesic syndrome at the age of 10 yr. Like adult amnesics, C.C. demonstrated impaired episodic memory for both verbal and visual materials although immediate memory span was spared. However, striking deficits were also observed on a wide variety of semantic memory tasks, including reading vocabulary and verbal fluency tests, semantic classification and lexical decision tasks and tests of verbal intelligence. On the other hand, C.C. showed normal learning and retention of two procedural tasks. It was argued that this evidence is inconsistent with the view that the amnesic syndrome represents a selective defect of episodic memory that leaves semantic memory relatively unaffected.

Amnesia↗
PubMed1989

Explicit and implicit remembering: when is learning preserved in amnesia?

Amnesic patients can learn and retain a variety of skills. To investigate what distinguishes tasks that are within the learning abilities of amnesic patients from those that are not, we administered two tests to individuals with Korsakoff's syndrome and two control groups. One was a visual reaction time task with an embedded repeating sequence of stimulus positions. Response times of Korsakoff patients indicated that they learned this sequence and retained it normally for a week. The second task was a tactual stylus maze in which all blind alleys were blocked. Korsakoff patients were impaired in learning this maze, as assessed by the time required to trace it. Differences between the two tasks are outlined and the implications of these differences are discussed.

Adult↗
PubMed1989

Extending the limits of complex learning in organic amnesia: computer training in a vocational domain.

This study explored the limits of learning that could be achieved by an amnesic patient in a complex real-world domain. Using a cuing procedure known as the method of vanishing cues, a severely amnesic encephalitic patient was taught over 250 discrete pieces of new information concerning the rules and procedures for performing a task involving data entry into a computer. Subsequently, she was able to use this acquired knowledge to perform the task accurately and efficiently in the workplace. These results suggest that amnesic patients' preserved learning abilities can be extended well beyond what has been reported previously.

Adult↗
PubMed1992

A re-appraisal of a case of persistent global amnesia following right temporal lobectomy: a clinico-pathological study.

We report a reappraisal of patient NT who became severely amnesic after a right temporal lobectomy for intractable epilepsy (DINSDALE et al., Neuropsychologia 1, 287, 1964 [6]). Histological examination, albeit incomplete, indicated that there was no abnormality in the resected temporal lobe. At autopsy a sclerotic lesion of the unoperated left hippocampal formation was found. This case is therefore not an exception to the general rule that a severe and global amnesic state is only observed with bilateral lesions. Her performance on a wide range of memory tests is shown to be indistinguishable from patients with an amnesic syndrome due to Korsakoff's psychosis.

Aged↗
PubMed1994

When implicit learning fails: amnesia and the problem of error elimination.

We propose that one of the major functions of explicit memory is the elimination of learning errors. The hypothesis is explored by means of a stem completion task in which subjects are presented with stems having many potential completions, and in the initial phase are either encouraged to guess, the "errorful" procedure, or are provided with the correct completion, the "errorless" condition. Learning is then tested over a sequence of nine trials. The performance of amnesic subjects who are assumed to have good implicit but bad explicit learning is compared with that of normal elderly subjects, who are assumed to have an intermediate level of explicit learning skill, and young controls who are expected to be high in both implicit and explicit learning capacity. As predicted, errorless learning is beneficial, with the effect being particularly marked for the amnesic group. A detailed analysis of the intrusion errors supports an interpretation of the results in terms of the relative contribution to the three groups of implicit learning, which is assumed to be particularly vulnerable to interference. Implications for the analysis of normal learning, and for the rehabilitation of brain damaged patients are discussed.

Adult↗
PubMed1996

Recency effect in anterograde amnesia: evidence for distinct memory stores underlying enhanced retrieval of terminal items in immediate and delayed recall paradigms.

This study was devised to investigate immediate and delayed recency effects in anterograde amnesic patients. For this purpose, a word-list immediate recall paradigm and a modified version of the procedure devised by Baddeley and Hitch [Attention and Performance, Erlbaum, NJ, 1977] for eliciting the recency effect in delayed recall conditions was administered to a sample of amnesic patients and to a group of age-matched healthy subjects. Amnesics disclosed a fully normal recency effect in the immediate recall paradigm and a deficient recency effect in the delayed recall condition. These data, taken together with experimental evidence from a patient affected by a pure form of phonological short-term memory impairment [35], draw a double neuropsychological dissociation suggesting a differential origin for the two kinds of recency effects: a short-term memory output underlying enhanced recall of terminal items in immediate recall paradigms, and an ordinal retrieval strategy applied to long-term memory stored units at the root of the delayed recency effect.

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