Mechanisms of spontaneous confabulations: a strategic retrieval account

Abstract

The 'temporality' hypothesis of confabulation posits that confabulations are true memories displaced in time, while the 'strategic retrieval' hypothesis suggests a general retrieval failure of which temporal confusion is a common symptom. Four confabulating patients with rupture of an anterior communicating artery (ACoA) aneurysm, eight non-confabulating ACoA controls and 16 normal controls participated in three experiments designed to test the two hypotheses. In Experiment 1, participants were tested on two continuous recognition tasks, one requiring temporal context distinctions, previously shown to be sensitive to confabulation and another that only requires content distinctions. Both manipulations were sensitive to confabulation, but not specific to it. Temporal context and content confusions (TCCs and CCs) can be explained as failures to make fine-grained distinctions within memory. In Experiment 2, free recall of semantic narratives that require strategic retrieval but are independent of temporal context was used to induce confabulations associated with remote memory, acquired before the onset of amnesia. Confabulators produced significantly more errors. Thus, when retrieval demands are equated, confabulations can be induced in the absence of temporal confusions. Only confabulators conflated semantic content from different remote semantic narratives and introduced idiosyncratic content, suggesting that qualitatively different mechanisms are responsible for distortions due to normal memory failure and for confabulation. Lesion analyses revealed that damage to ventromedial prefrontal cortex is sufficient for temporal context errors to occur, but additional orbitofrontal damage is crucial for spontaneous confabulation. In Experiment 3, we tested whether failure in memory monitoring is crucial for confabulation. Recognition of details from semantic and autobiographical narratives was used to minimize the initiation and search components of strategic retrieval. Only confabulators made more false alarms on both tasks, endorsed even highly implausible lures related to autobiographical events and were indiscriminately confident about their choices. These findings support a strategic retrieval account of confabulation of which monitoring is a critical component. Post-retrieval monitoring has at least two components: one is early, rapid and pre-conscious and the other is conscious and elaborate. Failure of at least the former is necessary and sufficient for confabulation. Other deficits, including TCC and CC, may be required for spontaneous confabulations to arise. The confluence of different sub-components of strategic retrieval would determine the content of confabulation and exacerbate its occurrence.

Confabulation: What is associated with its rise and fall? A study in brain injury

“…Moreover, Gilboa et al (2006) obtained a similar pattern of results on a task in which participants were asked to make difficult, visuo-perceptual discriminations, instead of temporal context judgements. Gilboa et al (2006) concluded that, whilst TCC errors might be sensitive to confabulation, they were not specific to this condition.…”

“…On the other hand, Gilboa and Moscovitch (2002); (Gilboa et al, 2006); McVittie (McVittie, McKinlay, Della Sala, & MacPherson, 2014) have argued that there is overlap between these categories of confabulation or, at least, not a clear boundary between them (very florid confabulations can be, at least partially, 'provoked').…”

“…Moreover, more recent neuroimaging and evoked potential investigations have particularly pinpointed damage within the ventro-medial and/or orbito-frontal brain regions (Schnider, 2003;Gilboa et al, 2006;Toosy et al, 2008;Turner, Cipolotti, Yousry, & Shallice, 2008;Gilboa & Verfaellie, 2010;Nahum, Bouzerda-Wahlen, Guggisberg, Ptak, & Schnider, 2012;Hebscher, Barkan-Abramski, Goldsmith, Aharon-Peretz, & Gilboa, 2015;Schnider et al, 2013;Manuel, David, Bikson, & Schnider, 2014).…”

“…These include: (i) theories of context memory confusion or a deficit in 'reality monitoring' (Schnider, 2003(Schnider, , 2008; (ii) the theory that temporal consciousness is intact, but malfunctioning (Dalla Barba, 1993;Dalla Barba, Cappelletti, Signorini, & Denes, 1997;La Corte, Serra, Attali, Boisse, & Dalla Barba, 2010);(iii) theories which emphasise deficits in strategic retrieval, trace specification, and verification/editing processes (Burgess & Shallice, 1996;Schacter, Norman, & Koutstaal, 1998;Gilboa et al, 2006); and (iv) motivational accounts of confabulation (Conway & Tacchi, 1996;Fotopoulou, Conway, Griffiths, Birchall, & Tyrer, 2007, Fotopoulou, Conway, Solms, Tyrer, & Kopelman, 2008. Finally, (v) interactionist/multifactorial accounts combine elements of several of these theories (Johnson, O'Connor, & Cantor, 1997;Kopelman, Ng, & Van Den Brouke, 1997).…”

“…7 Gilboa et al (2006) used the TCC to explore these findings. They compared a group of confabulating patients who had suffered anterior communicating artery aneurysm (ACoA), nonconfabulating patients with similar underlying pathology, amnesic patients with medial temporal lobe (MTL) lesions, and healthy controls.…”