Chapter

Mechanisms of confabulation

Armin Schnider

in The Confabulating Mind

Published on behalf of Oxford University Press

Published in print February 2008 | ISBN: 9780199206759
Published online February 2013 | e-ISBN: 9780191754487 | DOI: http://dx.doi.org/10.1093/med/9780199206759.003.0007
Mechanisms of confabulation

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Over more than a century, many hypotheses have been proposed to explain confabulations. Most models covered all types of confabulation, assuming that all confabulations represented a common disorder. Most models were derived from clinical, some from neuropsychological observations, but only few sought controlled evidence. None brought forward an experimental procedure specific for the proposed hypothesis. Consequently, none of the hypotheses indicated a way to explore the physiology of the cognitive mechanisms whose supposed failure should explain confabulation.

The status of the proposed mechanisms can be summarized as follows: ♦ A tendency to fill gaps in memory, be it under the influence of increased suggestibility or not, is not a generally valid mechanism of confabulation, although – on the basis of clinical observation – it appears to be the best explanation in some patients. ♦ Motivation to see things better than they are and particular personality patterns have been suggested as factors contributing to the generation of all forms of confabulation, mnestic and non-mnestic. Controlled evidence is scarce. The hypothesis fails to explain why distorted memories come up in the first place and are then accepted as veridical. ♦ Executive failures have been found in many confabulating patients, but no association of specific executive failures with specific forms of confabulations has been demonstrated. Provoked confabulations may even be associated with relatively preserved executive functions. Behaviourally spontaneous confabulations are independent of the severity of executive dysfunction. ♦ Diverse hypotheses on the recollection of memories and the monitoring of this process have been put forward. Most applied to both correct and false memory retrieval. None was specific for any type of confabulation and none of these models provided solid evidence for answering the central question: How – by what physiological mechanism – does the brain monitor the outflow from memory, which is obviously defective in confabulation? And what specific monitoring deficits would explain the different types of confabulation? ♦ The idea that confabulators’ consciousness is determined by a past, present and future displaced in time, has been deduced from case observations but lacks experimental evidence.

With regards the different forms of confabulation, the following conclusions can be drawn: ♦ Provoked confabulations (intrusions) appear to be a normal response to a faulty memory. They reflect a subject's attempt to retrieve as much information as possible from memory and are the price to pay for maximum item recollection. ♦ Momentary confabulations cannot be attributed to one specific mechanism. Executive dysfunction, motivational factors, a poorly guided search in memory, a false sense of time and other disturbances might contribute to different degrees and characteristics of momentary confabulations. Diverse authors favoured an interpretation in terms of impaired ‘monitoring’, but failed to indicate a way to explore the physiologic basis of monitoring. It may be that the ‘one and only’ mechanism of momentary confabulation will never be found: In view of the different situations that may evoke momentary confabulations (questionnaires, discussions), the different domains of memory that may be concerned (episodic, semantic memory), the varying associated features (disorientation present or not), the varying clinical course (appearing or disappearing over time), and the varying degree of conviction held in the confabulations, it appears likely that momentary confabulations, in fact, represent the common expression of many different disorders of memory and cognition. These different disorders probably have different mechanisms, which vary according to lesion location and associated cognitive failures. ♦ Fantastic confabulations have never been specifically explored. Their common occurrence in the context of a confusional state (delirium), severe dementia, or psychosis suggests that they reflect a high degree of formal thought disorder with detachment from reality. However, studies are lacking. ♦ Behaviourally spontaneous confabulations have not been the target of any of the above models. The next chapter will – hopefully – demonstrate that the focused exploration of this type of confabulation constitutes a worthwhile endeavour. As seen in this chapter, the specificity of the syndrome has allowed us to exclude gap-filling and executive dysfunction as relevant mechanisms. The idea of faulty temporal consciousness seems to have been derived primarily from the observation of such patients.

The next chapter will specifically deal with behaviourally spontaneous confabulation. We will see that this form of confabulation – but not other forms – is associated with a particular failure to distinguish between memories that pertain to ongoing reality and memories that do not – a disorder of temporality in consciousness. We drew this conclusion from experimental exploration comparing behaviourally spontaneous confabulators and non-confabulating amnesics. Subsequent studies using similar experimental designs in healthy subjects suggested that this failure is probably based on the defect of a pre-conscious orbitofrontal ‘monitoring’ process, which normally intervenes in the early phase of a memory's ‘re-construction’.

Chapter.  11603 words.  Illustrated.

Subjects: Psychiatry

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