How do Korsakoff patients learn new concepts?

The relationship between semantic and episodic memory: evidence from a case of severe anterograde amnesia

It is increasingly being recognized that new declarative, consciously accessible information can be learned in anterograde amnesia, but it is not clear whether this learning is supported by episodic or semantic memory. We report a case of a 55-year-old man who experienced severe amnesia after limited damage to the medial temporal lobe following neurosurgical complications. His general cognitive performance and knowledge of new French words and public events that occurred before and after the onset of amnesia were assessed. Performance remained satisfactory on post-morbid vocabulary and public events, with a drop in performance observed for very recent public events only, while knowledge of very recent vocabulary was comparable to that of the control subjects. The implications of these findings for our understanding of the underlying learning mechanisms are discussed. This is the first report of acquisition of consciously accessible postmorbid knowledge of public events in a patient with severe amnesia.

Identifying, Assessing, and Treating Korsakoff Syndrome Patients: Updated Perspectives

ABSTRACT

Objectives consist of updating published reports on the recognition, assessment, and care of patients with Wernicke-Korsakoff syndrome (WKS). Methods included defining relevant terms, describing core clinical phenomena, conducting meaningful reviews for latter-day WKS publications, and selecting instructive case examples. Findings covered epidemiology, precipitants, neuroimaging studies, alternate learning strategies in WKS, adjunctive treatments, and promising research. In conclusion, patients, their family members, clinicians, and public health experts should benefit from this updated knowledge. Countries with substantial alcohol consumption should consider emulating Holland in designating WKS research centers, founding regional clinical facilities, and funding multidisciplinary expert teams.

New Long-Term Encoding in Severely Amnesic Alzheimer's Disease Patients Revealed Through Repeated Exposure to Artistic Items

BACKGROUND

Encoding of new information is considered to be impossible in people with Alzheimer's disease (PWAD) at a moderate to severe stage. However, a few case studies reported new learning under special circumstances, especially with music.

OBJECTIVE

This article aims at clarifying PWAD's learning capacities toward unknown material under more ecological settings, which is repeated exposure without encoding instruction.

METHODS

Twenty-three PWAD (Age: m = 84.6(5.2), 5≤MMSE≤19) underwent presentations of unknown artistic pieces (targets) through 8 daily individual sessions. These sessions were followed by a test session, during which their knowledge of the targets was assessed through a verbal and behavioral scale (the sense of familiarity scale) against a series of unknown items (distractors).

RESULTS

Through this design, we were able to objectify encoding of three types of targets (verses, paintings, and music) against distractors the day after exposure sessions, and 2 months after the last presentation (study 1). Music and paintings were eventually well-encoded by most participants, whereas poems encoding was poorer. When compared to distractors, target items were significantly better recognized. We then compared the recognition of target paintings against two types of painting distractors, either perceptually or semantically related (study 2). The targets were better recognized than all three painting distractors, even when they were very close to the targets.

CONCLUSION

Despite massive anterograde amnesia, our results clearly showed that recognition-based learning without conscious memory of the encoding context is preserved in PWAD at a severe stage, revealed through an increasing sense of familiarity following repeated exposure. These findings could open new perspective both for researchers and clinicians and improve the way we understand and care for PWAD living in healthcare facilities.

Korsakoff's syndrome: a critical review

In this review, we present a survey on Korsakoff's syndrome (KS), a residual syndrome in patients who suffered from a Wernicke encephalopathy (WE) that is predominantly characterized by global amnesia, and in more severe cases also by cognitive and behavioral dysfunction. We describe the history of KS and its definition, its epidemiology, and the lack of consensus criteria for its diagnosis. The cognitive and behavioral symptoms of KS, which include anterograde and retrograde amnesia, executive dysfunction, confabulation, apathy, as well as affective and social-cognitive impairments, are discussed. Moreover, recent insights into the underlying neurocognitive mechanisms of these symptoms are presented. In addition, the evidence so far on the etiology of KS is examined, highlighting the role of thiamine and alcohol and discussing the continuity hypothesis. Furthermore, the neuropathology of KS is reviewed, focusing on abnormalities in the diencephalon, including the mammillary bodies and thalamic nuclei. Pharmacological treatment options and nonpharmacological interventions, such as those based on cognitive rehabilitation, are discussed. Our review shows that thiamine deficiency (TD) is a crucial factor in the etiology of KS. Although alcohol abuse is by far the most important context in which TD occurs, there is no convincing evidence for an essential contribution of ethanol neurotoxicity (EN) to the development of WE or to the progression of WE to KS. Future research on the postmortem histopathological analysis of brain tissues of KS patients is crucial for the advancement of our knowledge of KS, especially for associating its symptoms with lesions in various thalamic nuclei. A necessary requirement for the advancement of studies on KS is the broad acceptance of a comprehensive definition and definite diagnostic criteria. Therefore, in this review, we propose such a definition of KS and draft outlines for prospective diagnostic criteria.

Component processes of memory in alcoholism: pattern of compromise and neural substrates

Initially, alcohol-related memory deficits were considered only through the prism of Korsakoff's syndrome (KS). It is now clear, however, that chronic alcohol consumption results in memory disorders in alcoholics without ostensible neurologic complications, such as Wernicke's encephalopathy and KS. Most of the principal memory components are affected, including working memory, episodic memory, semantic memory, perceptual memory, and procedural memory. The extent of those cognitive impairments depends on several factors, such as age, gender, nutritional status, and psychiatric comorbidity. While memory disorders, especially episodic memory deficits, are largely definitive in patients with KS, recovery of memory abilities has been described with abstinence in uncomplicated alcoholics. Neuropsychologic impairments, and especially memory disorders, must be evaluated at alcohol treatment entry because they could impede patients from benefiting fully from cognitive and behavioral treatment approaches for alcohol dependence. Screening of memory deficits could also enable clinicians to detect, among alcoholics without ostensible neurologic complications, those at risk of developing permanent and debilitating amnesia that features KS.

Dynamics of the cognitive procedural learning in alcoholics with Korsakoff's syndrome

BACKGROUND

While procedures acquired before the development of amnesia are likely to be preserved in alcoholic patients with Korsakoff's syndrome, the ability of Korsakoff patients (KS) to learn new cognitive procedures is called in question. According to the Adaptive Control of Thoughts model, learning a new cognitive procedure requires highly controlled processes in the initial cognitive phase, which may be difficult for KS with episodic and working memory deficits. The goals of the present study were to examine the learning dynamics of KS compared with uncomplicated alcoholic patients (AL) and control subjects (CS) and to determine the contribution of episodic and working memory abilities in cognitive procedural learning performance.

METHODS

Fourteen KS, 15 AL, and 15 CS were submitted to 40 trials (4 daily learning sessions) of the Tower of Toronto task (disk-transfer task similar to the tower of Hanoi task) as well as episodic and working memory tasks.

RESULTS

The 10 KS who were able to perform the cognitive procedural learning task obtained lower results than both CS and AL. The cognitive phase was longer in the Korsakoff's syndrome group than in the other 2 groups but did not differ between the 3 groups any more when episodic memory abilities were controlled.

CONCLUSIONS

Our results indicate that KS have impaired cognitive procedural learning abilities compared with both AL and CS. Episodic memory deficits observed in KS result in a delayed transition from the cognitive learning phase to more advanced learning phases and, as a consequence, in an absence of automation of the procedure within 40 trials.

Anterograde episodic memory in Korsakoff syndrome

A profound anterograde memory deficit for information, regardless of the nature of the material, is the hallmark of Korsakoff syndrome, an amnesic condition resulting from severe thiamine (vitamin B1) deficiency. Since the late nineteenth century when the Russian physician, S. S. Korsakoff, initially described this syndrome associated with "polyneuropathy," the observed global amnesia has been a primary focus of neuroscience and neuropsychology. In this review we highlight the historical studies that examined anterograde episodic memory processes in KS, present a timeline and evidence supporting the myriad theories proffered to account for this memory dysfunction, and summarize what is known about the neuroanatomical correlates and neural systems presumed affected in KS. Rigorous study of KS amnesia and associated memory disorders of other etiologies provide evidence for distinct mnemonic component processes and neural networks imperative for normal declarative and nondeclarative memory abilities and for mnemonic processes spared in KS, from whence emerged the appreciation that memory is not a unitary function. Debate continues regarding the qualitative and quantitative differences between KS and other amnesias and what brain regions and neural pathways are necessary and sufficient to produce KS amnesia.

The advantage of errorless learning for the acquisition of new concepts' labels in alcoholics

BACKGROUND

Previous findings revealed that the acquisition of new semantic concepts' labels was impaired in uncomplicated alcoholic patients. The use of errorless learning may therefore allow them to improve learning performance. However, the flexibility of the new knowledge and the memory processes involved in errorless learning remain unclear.

METHOD

New concepts' labels acquisition was examined in 15 alcoholic patients and 15 control participants in an errorless learning condition compared with 19 alcoholic patients and 19 control subjects in a trial-and-error learning condition. The flexibility of the new information was evaluated using different photographs from those used in the learning sessions but representing the same concepts. All of the participants carried out an additional explicit memory task and an implicit memory task was also performed by subjects in the errorless learning condition.

RESULTS

The alcoholic group in the errorless condition differed significantly from the alcoholic group in the trial-and-error condition but did not differ from the two control groups. There was no significant difference between results in the learning test and the flexibility task. Finally, in the alcoholic group, the naming score in the learning test was correlated with the explicit memory score but not with the implicit memory score.

CONCLUSIONS

Using errorless learning, alcoholics improved their abilities to learn new concepts' labels. Moreover, new knowledge acquired with errorless learning was flexible. The errorless learning advantage may rely on explicit rather than implicit memory processes in these alcohol-dependent patients presenting only mild to moderate deficits of explicit memory capacities.