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Confabulations (Vol. II): theoretical models

Confabulations can be defined as false memories due to a retrieval problem, where the patient is unaware that he/she is confabulating and has the belief that the memory is true[1].

In a previous post, the classification, neuropathology and underlying cognitive mechanisms that contribute to the appearance of confabulations were briefly explained. In this second part, the major neuropsychological models proposed to explain confabulations will be outlined.

Theoretical models of confabulation

Early models that were proposed to account for confabulations considered themas a compensatory mechanism resulting from the need to fill gaps in memory. However, this theory is considered outdated nowadays as current motivational models suggest that emotional processes may account for the content of confabulations [1].

Neuropsychological explanations have postulated two large groups of theoretical models: temporality theories and retrieval theories [1].

1.1. Temporality theories

Temporality theories understand confabulation as the result of a disturbed sense of chronology or temporal confusion; thus, confabulating patients can remember the content of events but not their order of occurrence. This explanation stems from the observation that, in many cases, confabulations can be traced back to real memories which are misplaced in time.

There are different versions of this account:

1.1.1. Temporality theory and reality and source monitoring frameworkslimitations

As pointed out by several authors [1, 3], the main limitation of temporality hypothesesis that the temporal context is not specific to confabulation, since confusions in the temporal dimension have been observed both in confabulating and in non-confabulating amnesics. Additionally, the empirical evidence supporting the temporality theory comes from studies on confabulation occurring in theepisodic domain and therefore this theory can neither account for fantastic nor semantic confabulations [1].

Likewise, studies documenting the source monitoring framework have concluded that source monitoring deficits are neither specific to confabulations (SM errors can occur in non-confabulating patients) nor can they predict them [1]. Moreover, discrepancies have been found regardingthe anatomical structures involved insource monitoring (the dorsolateral prefrontal cortex) and confabulations (the medial orbitofrontal cortexand the ventromedial prefrontal cortex).

1.2. Retrieval theories

Retrieval theories relate to the reconstructive nature of memory. These accounts view confabulation as the result of a specific deficit in retrieval processes rather than disturbances in the processes of encoding, consolidation, or storage [1].

The most robust evidence in favor of this hypothesis is that it affects both retrograde and anterograde memory; however, since retrieval is not a unitary process, it is necessary to specify which component of retrieval fails, thus leading to confabulations [1].

There are two models within this group:

Associative retrieval—a relatively automatic process—is engaged when a proximal cue automatically interacts with information stored in memory to recover the memory that is being soughtorprovides the material for subsequent searches. The cue directly activatesboth the medial temporal lobe and posterior neocortex.

Strategic retrieval processes are applied when the retrieval cue is inadequate.These retrieval processes are mediated by different regions of the prefrontal cortex and include:

Thus, errors in cue-dependent retrieval may give rise to confabulation, but they are not a necessary condition for confabulation to arise. The initiation of a search processis often faulty in confabulators although different failures in other sub-processes could also lead to different types of confabulation; thus, this model can account for the production of both spontaneous and provoked confabulation.

Three components are identified in their strategic retrieval model:

  1. Description processes, which specify the type of trace that would satisfy the demands of the retrieval task.
  2. Memory-editing processes, which are continuously implicated in checking that the various outputs of memory search fit with each other and with the overall tasks requirements.
  3. Mediator processes are general strategic and problem-solving procedures, which are used to monitor the adequacy and plausibility of retrieved memories, but are not memory-specific processes.

According to this model, deficits in description, memory-editing and mediator processes will give rise to different types of confabulation.

1.2.1. Retrieval theories limitations

Based on these models, performance in recall tasks is expected to be worse than in recognition tasks; also expected are deficits in executive processes such as search initiation, monitoring the appropriateness of responses, and inhibiting inappropriate responses [1].

However, neuropsychological correlates of confabulation are not consistent across studies, so that, even whilethe evidence seems to suggest that both memory and executive deficits are associated with the phenomenon of confabulation, it has not yet been sufficiently clarified which specific memory and executive processes are responsible forconfabulation [1, 4].

Bibliographical references

  1. Lorente-Rovira E, McKenna P, Berrios G, Villagrán-Moreno JM,Moro-IpolaM (2011). Confabulaciones II: modelos explicativos. Actas EspPsiquiatr, 39(6):384-92.
  2. Glowinski R,Payman V &Frencham, K. (2008). Confabulation: a spontaneous and fantasticreview.Australian and New Zealand Journal of Psychiatry, 42:932-940.
  3. Metcalf K, Langdon R, Coltheart M. (2007). Models of confabulation: a critical review and a new framework. CognNeuropsychol, 24(1):23-47.
  4. Lorente-Rovira E, McKenna PJ, Berrios GE, Moro M, Villagrán JM (2011). Confabulaciones (I): Concepto, clasificación y neuropatología. Actas EspPsiquiatr, 39:251-9.

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