This multiple case report presents two groups of survivors from aneurysms of the anterior communicating artery (ACoA); amnesic and non-amnesics, to examine the similarities and differences in neuropsychological profiles. All six patients were consecutive admissions to acute inpatient rehabilitation, and exhibited generally intact attention, concentration and intellectual ability. Confabulation and personality changes were observed only among the amnesic ACoA patients. However, difficulties in concept formation and perseverative responding was observed in all subjects. A neurobehavioral hypothesis addressing the underlying mechanism of the main features of the "ACoA syndrome" is presented.
"Just as there remains uncertainty as to how to best classify confabulation, questions remain regarding its neuroanatomical underpinning. Dual-lesion hypotheses suggest that a combination of damage to prefrontal structures and to areas that support memory functions, such as the basal forebrain and medial temporal lobes, is required for confabulation to occur (Damasio et al., 1985 ; DeLuca, 1993 ). However, an extensive review of the literature (Gilboa & Moscovitch, 2002 ) found that lesions to ventromedial aspects of the prefrontal cortex appear to be suffi cient for confabulation; additional damage to memory-related structures was reported in only approximately 50% of the cases. "
"Patients with a history of ACoA disease demonstrate several cognitive impairments, but they are especially impaired on tests of frontal-lobe function (DeLuca 1993; Jorn and Rybarczyk 1995; Diamond et al 1997). DeLuca (1993) suggested that the amnesia resulting from rupture of an ACoA aneurysm is a result of a basal forebrain infarct. The ACoA connects the anterior cerebral arteries and completes the anterior segment of the vascular Circle of Willis. "
[Show abstract][Hide abstract] ABSTRACT: This study compared patterns of frontal-lobe dysfunction in alcoholics with Korsakoff's syndrome (KS: n = 9), non-Korsakoff alcoholics (AL: n = 28), patients with Parkinson's disease (PD: n = 18), and patients with rupture and repair of the anterior communicating artery (ACoA: n = 4) relative to healthy non-neurological control (NC) participants (n = 70). The tests administered were sensitive to functions of dorsolateral prefrontal and orbito-frontal subsystems. Measures included perseverative errors on the Wisconsin Card Sorting Test (WCST-pe), errors on object alternation (OA), errors on Trails B, number of words generated on the Controlled Oral Word Association Test (COWAT), and number of categories completed on the WCST (WCST-cc). KS patients were as impaired as AL participants on orbitofrontal measures and, on dorsolateral prefrontal measures, were impaired relative to AL participants, whose performance did not differ from controls. Patients with PD also were impaired on tests of orbitofrontal and dorsolateral prefrontal functioning but to a lesser extent than the KS patients. Moreover, most of the PD deficits were driven by the impaired performance of patients whose initial symptoms were on the right side of the body. The ACoA patients were significantly impaired on tests of orbitofrontal but not dorsolateral prefrontal functioning relative to the control group. Together, the results confirm different patterns of frontal-system impairments in patient groups having compromised frontal lobe functioning consequent to varying etiologies.
"Confabulation is sometimes found in a sub-group of patients who survived aneurysms of the anterior communicating artery (ACoA; Talland, 1965; Lindqvist and Norlen, 1966; Kapur and Coughlan, 1980; Alexander and Freedman, 1984; Damasio et al., 1985; Vilkki, 1985; Baddeley and Wilson, 1988; Moscovitch, 1989; DeLuca and Cicerone, 1991; DeLuca, 1993; Fischer et al., 1995; Diamond et al., 1997). The 'ACoA syndrome' (Alexander and Freedman, 1984; Damasio et al., 1985; Vilkki, 1985; DeLuca, 1993) includes personality changes, amnesia and confabulations, which may occur independently of each other so that memory deficits may appear in the absence of confabulation (DeLuca, 1993; Diamond et al., 1997). Because the ACoA amnesic syndrome can occur with or without confabulation, the present report focuses on this group of patients to study the specific cognitive and neuroanatomical conditions that produce confabulatory amnesia as compared with amnesia without confabulation. "
[Show abstract][Hide abstract] 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.
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