NOTE
CONFABULATION FOLLOWING RUPTURE OF POSTERIOR
COMMUNICATING ARTERY
Gianfranco Dalla Barbal, 2, Marie-Françoise Boissé2, Paolo Bartolomeol, 2 and AnneCathérine Bachoud-Lévi2, 3
(1U.324 INSERM, Centre Paul Broca, Paris, France; 2Department of Neurology, Hôpital
Henri Mondor, Créteil, France; 3Laboratoire de Sciences Cognitives et Psycholinguistique,
Ecole d’Hauts Etudes en Sciences Sociales, Paris, France)

ABSTRACT
In this study we report a patient, MG, who following rupture of left posterior
communicating artery exhibited an amnesic-confabulatory syndrome. Neuropsychological
examination showed severe impairment on episodic memory tasks, which were marred by
florid but plausible and semantically appropriate confabulation. Performance on tasks
involving various kinds of semantic knowledge was normal or only mildly impaired.
Performance on tasks traditionally considered sensitive to frontal dysfunction was severely
impaired with the exception of Cognitive Estimates where MG’s performance was completely
normal. There was no evidence of structural (CT scan) or metabolic (SPECT) damage to
the frontal lobe. It is argued that tasks traditionally considered sensitive to frontal dysfunction
are not specifically implemented by cognitive resources based on frontal structures. MG’s
confabulation is discussed in terms of a possible disruption of cognitive functions involved
in the control of the subjective experience of feeling of remembering.

INTRODUCTION
Confabulation, the unintentional production of actions and verbal statements that are
incongruous to the patient’s history, background and present situation (Dalla Barba, 1993a),
is a symptom that accompanies many neuropsychological disorders.
The quality of confabulation’s content can vary considerably, ranging from minor
distortions of facts and information to really implausible and bizarre reports. According to
its content, a distinction between two different types of confabulation have been proposed
(Bonhoeffer, 1904; Berlyne, 1972; Kopelman, 1987). The first type involves minor
distortion of true autobiographical events or their misplacement in time and place and is
usually produced in response to specific questions, whereas the second consists of the
spontaneous fabrication of fantastic and implausible tales. Following a different perspective,
Dalla Barba (1993a, 1993b) suggested that the confabulation content varies along a gradient
from minor distortion to bizarre and semantically anomalous tales according to the level of
semantic memory impairment.
A number of ideas about mechanisms underlying confabulation emphasise the role of a
frontal executive dysfunction in confabulation (Baddeley and Wilson, 1986; Kopelman, 1987;
Baddeley and Wilson, 1988; Moscovitch, 1989; Delbecq-Derouesne, Beauvois and Shallice,
1990; Johnson, 1991; Moscovitch, 1995; Burgess and Shallice, 1996). The impairment of
executive functions resulting from damage to the frontal lobe would prevent both the active
process of retrieval and the evaluation of its output and thus would be directly responsible
for confabulatory behaviour. However, two patients have been described with a confabulatory
syndrome, limited to the autobiographical component of episodic memory, where there was
Cortex, (1997) 33, 563-570

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Gianfranco Dalla Barba and Others

Fig. 1 – Contrast-enhanced CT brain scan showing an aneurysm of the left posterior communicating
artery and signs of subarachnoidal haemorrage, in the absence of frontal and thalamic lesions.

no frontal pathology and spared executive functions (Dalla Barba, Cipolotti and Denes, 1990;
Dalla Barba, 1993a). In addition the confabulating patient described by Delbecq-Derouesne,
Beauvois and Shallice (Delbecq-Derouesne et al., 1990) had a documented frontal lobe lesion
but performed normally on executive tasks supposed to be sensitive to frontal lesion. These
findings cast doubts both on the hypothetical prominent role of a frontal-executive dysfunction
in confabulation and on the anatomical basis of executive tasks.
ln this study we describe a patient, MG, who developed an amnesic-confabulatory
syndrome following the rupture of an aneurysm of the posterior communicating artery (PCoA).
While several studies report confabulation following the rupture of the anterior communicating
artery (ACoA) (Luria, 1976; Stuss, Alexander, Lieberman et al., 1978; Kapur and Coughlan,
1980; De Luca and Cicerone, 1991), to our knowledge this is the first case report of
confabulation following the rupture of an aneurysm of the PCoA. In addition MG showed a
massive impairment on tasks supposed to be sensitive to frontal dysfunction without showing
any evidence of damage to the frontal lobe or related structures.
CASE REPORT
MG is a 42-year-old right-handed clerk with a high-school education, with no history of
psychiatric or neurologic diseases. On February 2, 1996 he was admitted to the Neurology
department of the Hôpital Henri Mondor for a meningeal syndrome with neck rigidity without
photofobia and nausea. A CT brain scan performed on that day showed a small intra-ventricular
haemorrhage involving both occipital horns. There were no signs of any focal lesion. In
particular, there was no evidence of frontal or thalamic lesion (Figure 1). Also, in this and
subsequent scans there was no evidence of hydrocephalus. A brain arteriography revealed the
presence of an aneurysm of the left posterior communicating artery. On a second CT scan
performed three days later the haemorrhage was no longer observable and there were no signs
of residual focal lesions. On February 9 he was operated in order to clip the aneurysm of the

Confabulation and PCoA aneurysm

565

PCoA. A SPECT HMPAO perfusion scanning 13 did not show any brain hypoperfusion. A
third CT scan performed ten days after the operation was unremarkable.
Since his admission to the hospital MG was never in a confusional state nor has he ever
shown any minimal sign of confusion. Indeed, apart from his verbal confabulation, he behaved
appropriately and was totally independent in his daily life at the hospital. For example, he
never got lost inside the hospital, he frequently went to the coffee shop located on the ground
floor, and would return to his room located on the third floor. He also used to leave the
hospital without permission, but he always came back for lunch and dinner. He is a charming
and kind man who used to talk to other people in the ward, and nobody, apart the authors
of the present paper, ever realised that he was suffering from any neuropsychological
impairment.
Neuropsychological Examination
MG was tested on various occasions between February and March 1996. His collaboration
during testing sessions was excellent. MG’s performance on the WAIS is given in Table I.
He obtained a Verbal IQ of 82 and a Performance IQ of 73 (full scale = 75). On bedside
tests of oral expression, understanding of oral language, reading, writing, neglect, praxis
and calculation, the patient was judged to be norrnal.
A variety of memory tests, including the Wechsler Memory Scale (WMS) (Table II)
was administered to MG. He achieved a MQ of 62. On the recall of the Logical Memory
Passages he produced completely confabulatory takes. On the Paired Associate subtest he
was able to recall only 4 easy and 2 difficult items in three trials and produced 19 intrusions.
On forced-choice recognition tests MG’s performance was also markedly impaired. On these
tests (Warrington, 1984), 50 items were presented one after the other for 3 s each, together
with the orienting task used by Warrington (1984) (the patient had to say whether he found

TABLE I

MG’s Standard Scores on the WA.I.S.
Verbal IQ
Performance IQ
Full scale
Information
Comprehension
Arithmetic
Digit span
Vocabulary
Similarities
Digit symbol
Picture completion
Block design
Pictures arrangement
Objects assembly

82
73
75
11
7
6
5
5
8
5
9
3
3
1

TABLE II

MG’s Scores on the Wechsler Memory Scale

MQ
Personal information
Orientation
Mental control
Logical memory
Digits
Visual reproduction
Paired associate learning

MG

Mean for his age

S.D.

62
5
3
5
2.5
7
7
4

5.90
4.95
6.71
9.64
10.35
11.48
15.44

0.39
0.27
2.06
4.24
1.96
2.94
4.68

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Gianfranco Dalla Barba and Others
TABLE III

MG’s Performance on “Frontal Lobe” Tasks
MG

Comments

1
45.5

Controls mean = 5, S.D. 1.6
Controls mean = 6.6, S.D. 4
Cut-off score for frontal lesion patients ≥ 50

24
15
4
48

Controls mean = 38.2, S.D. 12
Controls mean = 36.5, S.D. 11
Controls mean = 3.6, S.D. 1.92
Mean of left frontals = 8.9, S.D. 4.3
Controls mean = 78, S.D. 15

66
240
20
14.5

Controls mean = 30, S.D. 10
Controls mean = 75, S.D. 36
Normal values ≥ 35
Controls mean = 4.3, S.D. 2.1

Modified Card Sorting Test1
Categories achieved
Error score
Verbal fluency
3 categories, each 60 s (total retrieved)
FPL2, each 60 s (total retrieved)
Cognitive Estimates3 (error score)
Graphic sequences (total correct)4
Trial Making Test5 (seconds)
A
B
Stroop Test6
Anosognosia Index7

1Nelson, 1976. 2Ramier and Hécaen, 1970. 3Shallice and Evans, 1978. 4Luria, 1966. 5Davies, 1968. 6Stroop, 1935.
7Della Barba et al., 1995.

the item pleasant or unpleasant). He was not told that his memory for the items was tested
using a two-alternative forced choice recognition procedure. Two different forms were used:
in the first stimuli were words, in the second they were faces. He achieved a score of 39
(mean for his age = 45.5, S.D. 3.1) and of 31 (mean for his age = 44.7, S.D. 3.3) on the
words and faces tests respectively.
MG’s level of performance in tasks involving various kinds of semantic knowledge,
including linguistic, visual, arithmetic, historical and geographical, was normal or only mildly
impaired. However, even when he was not able to retrieve the correct information, MG
never confabulated in this kind of task.
MG did not show any direct evidence of structural or functional lesions involving the
frontal lobe or related structures such as the thalamus or the thalamus-prefrontal projections.
However, since a deficit of frontal-executive functions has often been invoked as a prominent
factor in confabulation, MG’s performance was assessed on tasks thought to be sensitive to
frontal lobe lesions. MG’s performance on this set of tasks (Table III) was severely impaired
with the exception of the Cognitive Estimates (Shallice and Evans, 1978) where he scored
well, without producing any extreme response. However, although his performance was
severely impaired on these tasks, from a clinical point of view MG did not show a clear
frontal syndrome. In particular there was no evidence of grasping and snout reflex,
utilization behaviour and changes in mood and self control.
MG was completely unaware of his memory difficulties and he never admitted explicitly
to having memory problems, either spontaneously or when specifically requested by the
examiner.
MG produced most of his confabulations in informal conversation, both in answering
specific questions and spontaneously, mainly referring to autobiographical episodic memory.
Confabulation was always plausible and semantically appropriate so that an hypothetical
observer not familiar with MG’s history, background and present situation could hardly tell
whether MG’s report were confabulatory or not. For example, while he was waiting to
undergo the CT scan, MG told the radiologist that he had accompanied a friend to be admitted
to the neurology department that day. The neurologist who was taking care of MG’s friend
realized that MG also had neurological problems and so decided to refer him to the radiology
department for a CT scan. On that occasion the radiologist did not even suspect that MG
was confabulating.
Confabulation and intrusions were massively present in learning tasks such as Logical
Memory and Paired Associate. For example on the Logical Memory task, the recall of the

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567

correct short story, concerning a cleaning woman with four hungry children who was robbed
while she was on her way home, was replaced by the following tale: “It is a story about a
woman living in a small flat. Somebody rang at her door, she opened it and saw in front of
her a man who had first threatened her and then beaten her and stolen her savings. She
asked her children to go to the kitchen and not to move from there. She then went to the
police where she was asked to usual questions.”
To further examine MG’s confabulation, we submitted him to the Confabulation Battery
(Dalla Barba, 1993a), including questions probing personal, general and linguistic semantic
memory, episodic memory, orientation for space and time and questions to which the
appropriate response would be “I don’t know”, both semantic (e.g. “What did Marilyn
Monroe’s father do?”) and episodic (e.g. “Do you remember what you did on March 13,
1985?”. It was found that confabulations appeared only in response to questions probing
episodic memory and orientation for space and time (see Appendix).
Between three and four weeks after the vascular accident, MG’s clinical picture started
to improve significantly. Confabulations disappeared first, followed by gradual improvement
of the performance on frontal executive tasks. Eventually also memory functions started to
improve. By the end of March MG showed only mild learning deficit and some perseveration.

DISCUSSION
The patient we described had a florid confabulatory syndrome confined to episodic
memory tasks. He was impaired on learning tasks and had relatively well preserved semantic
knowledge. In addition he was severely impaired on a set of tasks supposed to measure
frontally based executive functions, with the exception of Cognitive Estimates where his
performance was normal. However, there was no evidence of structural or functional
damage to the frontal lobe or to brain structures functionally related to the frontal lobe.
Also, from a clinical point of view MG did not show a clear frontal syndrome.
In addition to his impaired memory abilities MG showed a general intellectual impairment as
measured by the WAIS. It could be argued that MG’s general intellectual and memory
impairment, as well as his confabulation, were part of a general confusional state. However,
this was clearly not the case. In fact, not only from a clinical point of view MG was not confused,
but the type of responses he gave in formal testing did not resemble those usually given by
confused patients. Confused patients usually tend to produce bizarre and in some sense
confabulatory-like responses in tasks demanding general intellectual abilities and semantic
knowledge, such those included in the WAIS. This was never the case for MG. For example on
the Vocabulaty subtest of the WAIS, where his performance was very defective, MG produced
plausible definitions of words that were scored poorly because they did not meet the scoring
criteria of the WAIS. On the Similarities subtest he scored quite well and even for the last three
items where he scored zero his responses were plausible. So it seems improbable that MG’s
general intellectual deficit is due to confusion. MG’s general intellectual decline may be the
result of a non-specific effect of the lesion upon the cognitive system, so that even in the absence
of confusion, a variety of cognitive resources were temporarily not accessible. It must be noted,
however, that MG’s general intellectual decline as measured by the WAIS was not confirmed
by clinical impression or by other bedside tests of semantic and general cognitive abilities (see
Neuropsychological Examination).
Confabulation has been associated to lesions involving the ventromedial portion of the
frontal lobes and related structures, including the basal forebrain, septum, fornix, cingulate
gyrus, cingulum, anterior hypothalamus and the head of the caudate nucleus (Kapur and
Coughlan, 1980; Alexander and Freedman, 1984; Wilkki, 1985; Moscovitch, 1989; De Luca
and Cicerone, 1991; Irle, Wowra, Kunert et al., 1992), all brain regions fed by the ACoA.
However damage to other frontal regions has also been linked to confabulation (Stuss et al.,
1978; Baddeley and Wilson, 1986). In view of the fact that all these patients with documented
frontal lesions and confabulations also showed poor performance on tests supposed to measure
frontal executive functions, it has been suggested that impairment of executive functions
may play a special role in confabulation. At least two kinds of observations, however, seem
to be in contrast with the hypothesis of a crucial role of executive dysfunction in

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confabulation. In fact, on the one hand it has been shown that confabulating patients with
frontal lesion may perform normally on tasks supposed to be sensitive to executive dysfunction
(Delbecq-Derouesne et al., 1990). On the other hand, confabulation can occur in patients
without frontal lobe pathology and with normal performance on tests that are sensitive to
frontal damage (Dalla Barba et al., 1990; Dalla Barba, 1993a). The present case casts
additional doubts on the association between confabulation and frontal pathology.
Moscovitch (1989, 1995) distinguishes between two components of retrieval. One,
associative retrieval, is relatively automatic and independent from frontal functions. The other,
strategic retrieval, is self-initiated, goal-directed, effortful and intelligent. Within strategic
retrieval processes, two further components are hypothesized. The first involves organising
a memory search that uses whatever knowledge is available, whether semantic or episodic.
Once knowledge is recovered, a second strategic process is involved in monitoring the output
of the memory search and checking whether it is consistent with other information in semantic
and episodic memory. Similar proposals have been advanced in the literature on normal
(e.g.: Mandler, 1980; Tulving, 1983) and pathological memory (e.g.: Baddeley and Wilson,
1986; Delbecq-Derouesne et al., 1990; Johnson, 1991). According to Moscovitch (1995) the
disruption of the monitoring subcomponent of strategic retrieval would be responsible for
confabulation. However, there are some difficulties in considering MG’s confabulation as
the result of a monitoring deficit. lf this were the case confabulation would have appeared
every time the strategic component of retrieval was involved, i.e. both in episodic and semantic
memory tasks. In fact, MG confabulated only in episodic memory tasks, whereas in semantic
tasks he either was correct or he responded “I don’t know”. It could be argued that MG
confabulated only on episodic memory tasks because semantic tasks required retrieval that
was more associative than strategic. However, apart from the risk of falling in the circularity
of considering as strategic retrieval demanding only those tasks where confabulations are
observed, there is no good reason to think that a task like the WAIS Vocabulary subtest,
where MG did not confabulate, demands less strategic retrieval than the WMS Logical
Memory subtest, where he did confabulate.
A further difficulty in considering MG’s confabulation the result of a deficit of the strategic
component of retrieval comes from his performance on tests considered sensitive to frontal
dysfunction. The only one of these tests where MG showed a completely normal performance
was that of Cognitive Estimates. This test requires that the subject answer questions which
do not have a readily available correct answer (e.g. “How many camels are there in
Holland?”), and the subject, in order to provide a plausible answer, is constrained to make
a judgment involving the activation, coordination and control of several kinds of semantic
information. Thus, strategic retrieval is expected to be prominently involved in the production
of a plausible answer in this test, even more so than in other tests considered sensitive to
frontal dysfunction.
However, MG’s performance on frontal executive tests is interesting in itself because it
confirms that performance on tasks supposed to measure executive functions can be
dramatically impaired in the absence of frontal pathology. It is well known, for example,
that patients with Alzheimer’s disease, which involves predominantly posterior brain
pathology, are very defective on these kind of tasks (see Spinnler, 1991, for a review). As
is the case for any cognitive domain, it is almost impossible to devise tasks which are pure,
in the sense that they measure only the cognitive domain for which they were devised.
Accordingly, executive tasks can be failed in the absence of a specific, isolated disruption
to executive processes. However, it is possible that, whatever its origin, the impairment on
executive tasks shares some common underlying mechanism with confabulation. In particular,
it is possible that the disruption of the same cognitive resources are responsible both for
poor performance on executive tasks and for confabulation in episodic memory tasks. This
kind of deficit could occur as a consequence of a frontal lesion or, as in MG, following a
brain damage that spares the frontal lobe and in the absence of a confusional state.

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569

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Gianfranco Dalla Barba, M.D., Ph.D., U.324 I.N.S.E.R.M., Centre Paul Broca, 2ter rue d’Alésia, 75014 Paris, France.
e-mail: internet: dallabarba@broca.inserm.fr.

(Received 21 June 1996; accepted 25 November 1996)

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APPENDIX
Examples of Confabulatory Responses to the Confabulation Battery (Dalla Barba, 1993a)
Q. What did you do yesterday?
A. I worked, as usual.
Q. Who did you meet this morning?
A. The Professor... I don’t remember his name... with his pupils and nurses.
Q. How did you spend last Christmas?
A. I worked, I did nothing special.
Q. What did you do for your last birthday?
A. I had lunch with my parents... nothing special.
Q. Do you remember the last time you went to see a doctor?
A. It was when I lost my head… I found my-self in the emergency room of the Salpêtrière.