The Confabulation Phenomenon (Vol. I): Classifications, Neuropathology, and Cognitive Mechanisms

Lidia García, clinical neuropsychologist and researcher, explains in this article what the phenomenon of confabulation is, as well as its classification, neuropathology, and cognitive mechanisms.

Introduction

Confabulations are a cognitive phenomenon that appears in various acquired neurological disorders, but also in some psychiatric disorders.

Although today the term confabulation is sometimes used to refer to false bodily or external-world perceptions (non-mnestic confabulations), traditionally it has referred to false products of memory (mnestic confabulations)[1].

This is a complex phenomenon, for which there is still no consensual definition nor solid criteria for classifying the different types that have been described and whose explanatory models remain under debate [1, 2].

This article constitutes the first volume of a series of two publications on the phenomenon of confabulation, in which the phenomenology, neuropathology and the cognitive mechanisms and theoretical models proposed to explain it will be briefly reviewed. The latter point will be addressed in the second volume of this series.

What do we mean by confabulation?: concept and classifications

Since the term first appeared in the works of Kahlbaum [3] and Wernicke [4] toward the second half of the 19th century, there have been multiple definitions and interpretations given to the term confabulation, which has evolved with the debate over its etiology and other cognitive phenomena closely related [2].

In general, three concepts of confabulation have been considered in the literature, depending on the aspects that are primarily considered:

1. The mnemonic, related to memory.
2. The linguistic, in which the central aspect is the character of an incorrect verbal statement or false narrative
3.  The epistemological, in which what is essential is that the patient does not question the unfounded assertion about something, and this is not necessarily linguistic in nature [1].

An operational definition of confabulations proposed recently [5] describes them as false memories resulting from a retrieval problem, of which the patient is not aware and whose belief in the truthfulness of the memory is genuine. From this conception confabulations are characterized by four aspects:

• They constitute false memories in the context of retrieval, which often also contain false details within their own context (they may consist of real memories misplaced in time, or not be based on any reality).
• They are not produced intentionally, since the patient is not aware that they are confabulating and often is not aware of having a memory deficit, which leads to the interpretation that they probably do not result from compensatory mechanisms.
• Patients may act consistently with their confabulations, reflecting a genuine belief in the false memory.
• Confabulations are most evident when an autobiographical retrieval is requested and, under certain assessment conditions, may also appear in semantic memory tasks [1]

Classifications of confabulation

Regarding their classification into different types, there have also been various proposals. A widely accepted classification today is that proposed by Kopelman [6], which distinguishes confabulations according to the way they arise, thus dividing them into spontaneous confabulations and provoked confabulations.

• The spontaneous confabulations are characterized by being infrequent and being related to an amnesic syndrome, superimposed on frontal dysfunction.
• The provoked confabulations are frequently observed in amnesic patients in the context of assessment, when memory tests are administered.

Another popular classification in the literature distinguishes between momentary and fantastic confabulations [1].

• The momentary confabulations are described as brief, transient in character, provoked “invariably” by questions that test memory, and consisting of real memories displaced in their temporal context.
• The fantastic confabulations appear spontaneously, are firm, cover varied and generally grandiose themes, and are highly evident in the patients’ everyday conversation.

Neuropathology of confabulations

There is a great diversity of disorders in which confabulations manifest; disorders both of an acquired nature (for example, ACVA, traumatic DCA, hypoxia with cardiopulmonary arrest, etc.) as well as degenerative (dementia) or even in psychiatric conditions such as schizophrenia and other psychoses. However, the two prototypical disorders where they are observed are Korsakoff’s syndrome and hemorrhage due to rupture of the anterior communicating artery (ACoA) [1].

In the case of the neuropathology of Korsakoff’s syndrome it has been suggested that there are two dysfunctional systems: one composed of lesions of the mammillary bodies and the anterior thalamic nuclei, which receives afferents from the hippocampus through the fornix and which would be related to the severe amnesia characteristic of the disorder; and another dysfunctional system composed of alteration of the dorsomedial thalamic nuclei, which maintains reciprocal connections with medial and orbitofrontal areas of the prefrontal cortex, and receives cortical and subcortical afferents (amygdala and basal forebrain) and would be related to the production of confabulations [1].

In the case of pathology due to ACoA hemorrhage, studies with patients with an amnesic presentation and presence of confabulations have indicated lesions in the basal forebrain, orbitofrontal and medial prefrontal cortex [1].

A recent review [1] concludes that for confabulations to appear the simultaneous lesion of ventromedial and orbitofrontal areas of the prefrontal cortex is necessary, while another review that addresses spontaneous confabulations more specifically [2] indicates that current evidence identifies four areas implicated in this type of confabulations: the orbitomedial frontal cortex and its connections with the amygdala, the cingulate gyrus, the dorsomedial thalamic nucleus and the medial hypothalamus.

Cognitive mechanisms of confabulations

In summary, three cognitive mechanisms have been proposed to explain the phenomenon of confabulation, which basically differ in the degree to which memory impairment is involved:

1. A memory dysfunction as a primary or central factor, as classically considered.
2. A primary dysfunction of executive functions, considered as a necessary and sufficient condition for the appearance of confabulations.

• Dual hypothesis: a combination of memory impairment and executive dysfunction.

Currently, it seems that the explanation toward which the evidence leans is the dual hypothesis [1], such that confabulations would not be the result of a compensatory mechanism due to a primary memory deficit or amnesia, but a consequence of some degree of alteration in memory systems and some degree of dysfunction in executive processes.

However, it remains to be elucidated what the specific contribution of memory deficits is and what that of executive functions is in the production of confabulations and in which types of confabulations.

One point to emphasize here is that the various studies on the subject have used different memory and executive function tests, which assess different executive processes and different memory subsystems, making it practically unfeasible to compare the results of the various studies to draw conclusions.

Bibliography

1. Lorente-Rovira E, Berrios G, McKenna P, Moro-Ipola M y Villagrán-Moreno JM (2011). Confabulaciones I: concepto, clasificación y neuropatología. Actas EspPsiquiatr, 39(4):251-9.
2. Glowinski R,Payman V &Frencham, K. (2008). Confabulation: a spontaneous and fantasticreview.Australian and New ZealandJournal of Psychiatry, 42:932-940.
3. Kahlbaum K (1863). Die Gruppierung der psychischenKrankheitenund die Eintheilung der Seelenstörungen. Danzig: AW Kafemann (Part III, trans. Berrios GE, HistPsychiatry1996; 7:167181.)
4. Wernicke K(1906).Grundriss der Psychiatrie, 2nd edn. Liepzig: Thieme.
5. Gilboa A, Alain C, Stuss DT, Melo B, Miller S, Moscovitch M. (2006). Mechanisms of spontaneousconfabulations: a strategicretrievalaccount. Brain, 129:1399-414.
6. Kopelman MD (1987). Twotypes of confabulation. JNeurolNeurosurgPsychiatry, 50:1482-7.

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El fenómeno de la confabulación (Vol. I): clasificaciones, neuropatología y mecanismos cognitivos