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NeuroImage
j o u r n a l h o m e p a g e : w w w. e l s e v i e r. c o m / l o c a t e / y n i m g
Delineating self-referential processing from episodic memory retrieval: Common and
dissociable networks
Bastian Sajonz a, Thorsten Kahnt a,b,c, Daniel S. Margulies c, Soyoung Q. Park a,c, André Wittmann a,
Meline Stoy a, Andreas Ströhle a,c, Andreas Heinz a,b,c, Georg Northoff d, Felix Bermpohl a,c,e,⁎
a
Department of Psychiatry and Psychotherapy, Charité-Universitätsmedizin Berlin, Campus Mitte, Berlin, Germany
Bernstein Center for Computational Neuroscience, Berlin, Germany
Berlin School of Mind and Brain, Berlin, Germany
d
Institute of Mental Health Research, University of Ottawa, Ottawa, Canada
e
Berlin Brandenburg Academy of Sciences, Berlin, Germany
b
c
a r t i c l e
i n f o
Article history:
Received 20 October 2009
Revised 14 January 2010
Accepted 25 January 2010
Available online xxxx
Keywords:
Functional magnetic resonance imaging
fMRI
Medial prefrontal cortex
Lateral parietal cortex
Precuneus
Posterior cingulate cortex
a b s t r a c t
Self-referential processing involves a complex set of cognitive functions, posing challenges to delineating its
independent neural correlates. While self-referential processing has been considered functionally
intertwined with episodic memory, the present study explores their overlap and dissociability.
Standard tasks for self-referential processing and episodic memory were combined into a single fMRI
experiment. Contrasting the effects of self-relatedness and retrieval success allowed for the two processes to
be delineated.
Stimuli judged as self-referential specifically activated the posterior cingulate/anterior precuneus, the medial
prefrontal cortex, and an inferior division of the inferior parietal lobule. In contrast, episodic memory
retrieval specifically involved the posterior precuneus, the right anterior prefrontal cortex, and a superior
division of the inferior parietal lobule (extending into superior parietal lobule). Overlapping activations were
found in intermediate zones in the precuneus and the inferior parietal lobule, but not in the prefrontal
cortex.
While our data show common networks for both processes in the medial and lateral parietal cortex, three
functional differentiations were also observed: (1) an anterior–posterior differentiation within the medial
parietal cortex; (2) a medial–anterolateral differentiation within the prefrontal cortex; and, (3) an inferior–
superior differentiation within the lateral parietal cortex for self-referential processing versus episodic
memory retrieval.
© 2010 Elsevier Inc. All rights reserved.
Introduction
Recently, self-referential processing (SRP) has received increasing
interest in neuroimaging studies (Gillihan and Farah, 2005; Legrand
and Ruby, 2009; Northoff and Bermpohl, 2004; Northoff et al., 2006).
The heterogeneous nature of SRP, entailing a complex set of
operations, poses significant challenges in identifying its specific
neural correlates. Consistently, self-referential (relative to control)
tasks induce increases in BOLD signals (hereafter, “activations”) in the
ventral (VMPFC) and dorsal medial prefrontal cortex (DMPFC)
(extending into the anterior cingulate cortex (ACC)) as well as the
medial and lateral parietal cortex (extending into temporal areas).
Because this self-network is activated across different sensory
modalities and cognitive domains (e.g., spatial, facial, emotional,
⁎ Corresponding author. Department of Psychiatry and Psychotherapy, CharitéUniversitätsmedizin Berlin, Campus Mitte, Charitéplatz 1, D-10117 Berlin, Germany.
Fax: +49 30 450517962.
E-mail address: felix.bermpohl@charite.de (F. Bermpohl).
social) (Northoff et al., 2006), it could be assumed that distinct
subregions within this network may correspond to specific processes
involved in SRP. Investigators have recently started to disentangle
these processes. For instance, they have studied SRP in relation to
emotion processing (Moran et al., 2006; Northoff et al., 2009; Phan et
al., 2004), theory of mind (Vogeley et al., 2001), inferential processing
(Legrand and Ruby, 2009), reward processing (de Greck et al., 2008),
realness (Summerfield et al., 2009) and sexual arousal (Heinzel et al.,
2006).
Here we examine SRP in relation to episodic memory retrieval
(EMR). There appears to be a theoretical consensus that SRP generally
involves EMR; according to some authors, SRP and EMR are even
intrinsically related (Conway and Pleydell-Pearce, 2000; Gardiner,
2001; James, 1892). Similar to EMR, SRP depends on the individual's
life history and involves the recollection of past experiences. On the
other hand, EMR seems to implicate reference to the self, as the
retrieved episodic information is unique to an individual and is tied to
a specific personal context (Craik et al., 1999; Ingvar, 1985; Tulving,
1983). Behaviorally, the link between SRP and EMR is reflected in the
1053-8119/$ – see front matter © 2010 Elsevier Inc. All rights reserved.
doi:10.1016/j.neuroimage.2010.01.087
Please cite this article as: Sajonz, B., et al., Delineating self-referential processing from episodic memory retrieval: Common and dissociable
networks, NeuroImage (2010), doi:10.1016/j.neuroimage.2010.01.087
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B. Sajonz et al. / NeuroImage xxx (2010) xxx–xxx
so-called self-reference effect of memory: encoding with reference to
self yields superior memory performance relative to semantic or
other-referential encoding (Rogers et al., 1977; Symons and Johnson,
1997). Further support for this link comes from neuroimaging
investigations: EMR studies report activations in brain regions that
are also identified by SRP tasks, again including the anterior and
medial prefrontal cortex, as well as the medial and lateral parietal
cortex (Donaldson et al., 2001; Fletcher et al., 1996; Henson et al.,
2005; Konishi et al., 2000; McDermott et al., 2000) (for reviews see
Cavanna and Trimble, 2006; Legrand and Ruby, 2009). Because these
brain areas also show high neural activity during so-called rest
conditions (i.e., conditions without externally focused tasks), both
SRP and EMR have been considered components of the brain's defaultmode network (Buckner et al., 2008).
Despite these commonalities, several lines of evidence indicate that
SRP and EMR can be well distinguished: First, it is phenomenologically
evident that besides retrieval, SRP requires reference to one's own
person, i.e., reference to the person's self-concept (concerning physical
and psychological traits), value system, motives, and internal goals
among others (Zysset et al., 2002). Episodic memory processes, on the
other hand, also concern the retrieval of events that are characterized
by low self-relevance. Second, a series of priming experiments using
trait adjectives as probes showed no impact of self-description (i.e., a
form of SRP) on EMR and vice versa, indicating that one process does
not automatically invoke the other (Kihlstrom and Klein, 1997). Third,
some case studies in patients with retrograde amnesia following
traumatic brain injury report a loss of EMR in combination with
preserved self-description (Klein et al., 1996; Tulving, 1993), suggesting that both processes may, at least partially, be represented
independently. Fourth, functional connectivity analyses of fMRI
(functional magnetic resonance imaging) data suggest functional
separation within the default-mode network, revealing two distinct
subsystems, namely a medial temporal lobe subsystem associated
with EMR and a medial prefrontal subsystem associated with SRP;
both systems seem to converge on the medial and lateral parietal
cortex (Buckner et al., 2008). Finally, functional neuroimaging studies
suggest that functional specialization may exist within the medial
parietal cortex: Cavanna and Trimble (2006) proposed a dissociation
within the precuneus into an anterior region, involved in SRP and a
posterior region, subserving EMR. Fig. 1 illustrates this dissociation
based on studies reviewed by Cavanna and Trimble (2006).
Taken together, there is evidence for both functional overlap and
dissociation between SRP and EMR. Because evidence provided so far
is either indirect or relies on data from different imaging studies, the
exact extent to which SRP and EMR depend on common and distinct
brain regions remains unclear. The aim of the present study is to
address this issue by combining standard tasks for both processes in
one functional MRI (fMRI) experiment. Healthy volunteers were asked
to perform both a self-referential and an episodic memory task in
relation to each of 160 pictorial stimuli taken from the International
Affective Picture System (IAPS) (Lang et al., 2005). The task demand
thus remained the same, whereas self-relatedness and EMR varied
across pictures. This allowed us to avoid confounds introduced by
differences in task-related cues and task demands. For fMRI data
analysis, picture trials were classified based on the participants'
responses in the self-referential and episodic memory tasks, resulting
in a 2 × 2 factorial design with the factors self-relatedness (selfreferential, non-self-referential) and EMR (retrieved, non-retrieved).
This allowed us to identify (1) the effect of SRP (self-referential N nonself-referential stimuli), (2) the effect of EMR (retrieved N nonretrieved stimuli), (3) common activations for SRP and EMR
(conjunction of the two former contrasts), (4) SRP × EMR interaction
effects, (5) activations specific for SRP relative to EMR (self-referential/
non-retrieved N non-self-referential/retrieved), and (6) activations
specific for EMR relative to SRP (retrieved/non-self-referential N nonretrieved/self-referential).
Fig. 1. Illustration of anterior–posterior functional differentiation within the precuneus.
Talairach stereotactic coordinates reported by the studies listed in Cavanna and Trimble
(2006) Table 3 (episodic memory) and Table 4 (self-referential processing) are
depicted in horizontal and vertical bars, respectively.
Based on the studies reported above, we hypothesized that both
processes, SRP and EMR, would recruit a common neural network
including (1) the medial parietal cortex, (2) the anterior and medial
prefrontal cortex, and (3) the lateral parietal cortex. Besides overlapping activations, we also predicted an anterior–posterior gradient
within the medial parietal cortex with SRP stronger activating the
anterior division and EMR stronger activating the posterior division.
Materials and methods
Subjects
Twenty-nine right-handed healthy volunteers (14 men, 15 women,
aged 30–50 years, mean ± standard deviation (SD) = 39 ± 5.5 years,
mean IQ = 118 ± 13.5 measured with the Mehrfachwahl-WortschatzIntelligenztest (MWT-B) (Lehrl, 2005)), gave written informed
consent to participate in the experiment. Exclusion criteria were lefthandedness, current limiting general medical conditions, current
neurological disorder and history of psychiatric axis I or II disorders in
the subjects (assessed with SCID I and II screening) or axis I disorder in
a first-degree relative according to DSM IV. The subjects were remunerated for their time at a rate of €10/h. The study was in compliance
with the Declaration of Helsinki and was approved by the local ethics
committee of the Charité-Universitätsmedizin Berlin.
Experimental design
The experimental paradigm comprised three blocks conducted
over three subsequent days: An encoding procedure, the fMRI
experiment and a post-scanning rating session.
Experimental stimuli
One hundred sixty standardized non-erotic pictures were selected
from the IAPS (Lang et al., 2005) so that the normative valence scores
of the presented pictures (9-point rating scale from 1, very negative
over 5, neutral to 9, very positive) were neutral to positive and the
variance of normative valence and arousal (9-point rating scale) scores
Please cite this article as: Sajonz, B., et al., Delineating self-referential processing from episodic memory retrieval: Common and dissociable
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3
was reduced to a minimum (meanvalence ± SDvalence = 7.0 ± 0.55;
meanarousal ± SDarousal = 5.0 ± 0.49). The selected photographs were
arranged in two picture sets consisting of 80 photographs matched for
valence and arousal according to the IAPS norm (Lang et al., 2005). We
selected IAPS pictures as stimulus material, because they have
produced robust effects in previous SRP tasks (Gusnard et al., 2001;
Northoff et al., 2009; Phan et al., 2004). We chose pictures of neutral to
positive valence because pilot experiments and a prior study (Northoff
et al., 2009) indicated that this type of material would produce a
sufficient number of trials for both levels of self-relatedness, i.e., rated
as ‘self-referential’ or ‘non-self-referential’ by the study participants.
Participants responded with a “yes” or “no” button press with the
left or right index finger, respectively. Debriefing after fMRI revealed
that study participants had started to carry out the tasks implicitly
during the period of picture presentation, i.e., prior to presentation of
the question screens. Because the same two tasks were performed in
response to each picture stimulus, implicit task processing during the
picture period should not have affected the comparison between
experimental conditions in our study. The paradigm consisted of four
runs each comprising 40 trials. All 160 pictures (80 old and 80 new)
were presented in a pseudorandomized order. Prior to scanning
participants were familiarized with the paradigm in a training session.
Encoding procedure
For encoding, participants were presented with pictures from one
of the two picture sets in a randomized order. Each of the 80 pictures
was shown for 4 s followed by fixation cross lasting 2.5 s. Participants
were instructed to memorize the pictures for a memory test on the
next day and to indicate in a forced-choice task during the
presentation of each picture whether it depicted an indoor or outdoor
situation to promote elaborate encoding. During the encoding
procedure subjects were unaware of the SRP task on the second day.
Post-scanning rating session
One day after the fMRI experiment subjects rated all 160 pictures
with regard to self-relatedness (“How much does the picture relate to
you?”), emotional valence and arousal on a 9-point scale ranging from 1
(low personal association/valence/arousal) over 5 (medium) to 9
(high). In addition, participants indicated for each picture whether it
spontaneously elicited an autobiographic memory (defined as both
temporally and spatially unique events (Conway and Pleydell-Pearce,
2000)). These trials were not used for data analysis to avoid
interference of autobiographic memory with the episodic memory task.
fMRI experiment
Twenty-four hours (± 4 h) after the encoding session (24 ± 4 h)
subjects performed the following experimental task during fMRI
acquisition (Fig. 2). Each trial started with a picture viewing phase (4
s). Subsequently, two forced choice judgments were obtained from
the participants in a SRP and EMR task for each stimulus. Question
screens were presented in randomized order each lasting for 3 s. After
the two judgments a fixation-cross period (range: 13.65–19.5 s;
mean: 15.99 s) was shown prior to the next trial. The SRP task was
assessed with the question “Does this picture personally relate to
you?” For the EMR task the question “Is this picture familiar to you?”
was presented and it was explained to the participants that this
question referred to the picture set encoded the day before.
Behavioral data analysis
To examine recognition memory performance the pattern of trial
distribution (i.e., number of trials, classified based on SRP and EMR
judgments given in the scanner) was assessed using a 2 × 2 × 2 (old vs.
new picture × familiar vs. non-familiar judged × self vs. non-self
judged) repeated measures ANOVA. Furthermore d′-values were
calculated for every participant.
Paired t-tests were calculated to compare response times of the
SRP task (RTself) and EMR task (RTmem).
The analysis of post-scanning ratings focused on trials with correct
memory decisions (i.e., hits (old pictures judged as familiar) and
Fig. 2. Schematic of the fMRI paradigm: One day prior to MRI-scanning a set of 80 pictures was memorized by the participants (old pictures). During the fMRI paradigm 80 old and 80
new pictures were presented in pseudorandomized order followed by two forced choice tasks in randomized order: A self-task (“Does this picture relate to you?”) and a memory
task (“Is this picture familiar to you?”) requiring a yes/no-button press. Each trial ended with a variable fixation period. Trials were classified based on the participants' responses
resulting in a 2 × 2 × 2 factorial design. fMRI and post-hoc rating data analysis focused on correct memory trials only. Hits (M+ = retrieved): old pictures judged as familiar; correct
rejections (CRs = M− = non-retrieved): new pictures judged as non-familiar; misses: old pictures judged as non-familiar; false alarms (FAs): new pictures judged as familiar.
Self = self-referential (S+); non-self = non-self-referential (S−).
Please cite this article as: Sajonz, B., et al., Delineating self-referential processing from episodic memory retrieval: Common and dissociable
networks, NeuroImage (2010), doi:10.1016/j.neuroimage.2010.01.087
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correct rejections (CRs: new pictures judged as non-familiar)).
Corresponding to fMRI data analysis trials with misses (old pictures
judged as non-familiar) and false alarms (FAs: new pictures judged as
familiar) were excluded resulting in a 2 × 2 factorial design with the
factors SRP (self-referential vs. non-self-referential) and EMR
(hits = retrieved vs. CRs = non-retrieved) (Fig. 2). Two-way repeated
measures ANOVAs were calculated to examine post-scanning ratings
of valence, arousal and self-relatedness.
fMRI data acquisition and preprocessing
T2⁎-weighted echo planar images (EPIs) sensitive to blood oxygen
level dependent (BOLD) contrast were acquired on a 1.5 T Siemens
(Erlangen, Germany) Sonata scanner with a repetition time (TR) of
1950 ms, an echo time (TE) of 40 ms and a flip angel of 90°. Thirty-five
oblique axial slices aligned to the plane connecting the anterior and
posterior commissure were collected with a voxel dimension of
3 × 3 × 3.5 mm3 providing full brain coverage.
fMRI data was analyzed using the Statistical Parametric Mapping
(SPM 5) software (Wellcome Department of Imaging Neurosciences,
London, UK). Preprocessing included slice time correction, realignment to the mean volume, spatial normalization to a standard MNI
template and spatial smoothing using a Gaussian kernel of
FWHM = 8 mm. A 128 s high-pass filter was applied to the time
series in each voxel to remove low-frequency drifts.
referential (S−M+ N S+M−) (p b 0.001, k ≥ 20) were used as seed
regions of interest for a functional connectivity analysis employing the
psychophysiological interaction (PPI) term (Cohen et al., 2005; Cohen
et al., 2008; Friston et al., 1997; Kahnt et al., 2009; Pessoa et al., 2002).
For each of the two models, the entire time series over the experiment
was extracted from each subject in the two clusters mentioned above.
Regressors for the antero-superior cluster (SRP-specific model) were
created by multiplying the normalized time series with two condition
vectors that contain ones for six TRs after presentation of each selfreferential (S+/M+ and S+/M−) and non-self-referential (S−/M+
and S−/M−) picture, respectively and zeros otherwise. For the
postero-inferior cluster (EMR-specific model) regressors were created
by multiplying the time series with two condition vectors that contain
ones for six TRs after presentation of each retrieved (S+/M+ and S−/
M+) and non-retrieved (S+/M− and S−/M−) picture, respectively.
After estimation, individual contrast images were computed for
functional connectivity during self-referential N non-self-referential
[(S+M+/S+M−) N (S−M+/S−M−)] and retrieved N non-retrieved
[(S+M+/S−M+) N (S+M−/S−M−)] trials. Individual contrast
images were then entered into second-level one-sample t-tests. To
identify significant functional connectivity, t-maps were thresholded
at p N 0.001 and a cluster extent of k ≥ 20 voxels.
Results
Behavioral data
fMRI data analysis
Preprocessed fMRI data of each subject were then submitted to a
two-level procedure. First, condition and subject effects were
estimated using the general linear model (GLM) approach. The fMRI
data analysis focused on trials with correct responses in the EMR task.
These trials were assigned to experimental conditions based on the
online judgments in the SRP and EMR tasks, resulting in a 2 × 2
factorial design (Fig. 2) with the factors SRP (self-referential = S+
versus/non-self-referential = S−) and EMR (hits = retrieved = M+
versus/CRs = non-retrieved = M−). The picture onsets of the resulting four conditions (S+/M+, S+/M−, S−/M+, S−/M−) were
modeled as regressors of interest. Picture valence as rated by the
subjects in the post-scanning session was included as a parametric
regressor. Regressors of no interest were movement parameters, a run
constant, regressors for left-hand and right-hand button press during
the task period and an error regressor containing error trials in the
memory task (FAs, misses). The regressors were convolved with a
hemodynamic response function (HRF) provided by SPM5. The
regressors were simultaneously regressed against the BOLD signal in
each voxel using the least squares criteria, and contrast images were
computed from the resulting parameter estimates.
For second-level random-effects analysis, the single-subject contrasts
were submitted to one-sample t-tests across the 29 subjects. Statistical
parametric maps were estimated for the contrasts self-referential N nonself-referential [(S+M+/S+M−) N (S−M+/S−M−)], retrieved N nonretrieved [(S+M+/S−M+) N (S+M−/S−M−)], the conjunction of the
two former contrasts testing the conjunction null hypothesis (Friston
et al., 2005), the SRP × EMR interaction [(S+M+ N S−M+) N (S+M− N
S−M−)], self-referential N retrieved (S+M− N S−M+) and retrieved N
self-referential (S−M+ N S+M−). Significant activations were identified at a threshold of p b 0.001 with a cluster extend k ≥20 voxels
(Hayasaka and Nichols, 2004).
In relation to the ongoing debate on a potential anterior–posterior
division of the precuneus (Cavanna and Trimble, 2006) we examined
the context-dependent neural interplay of anterior and posterior
precuneus activations specific for SRP and EMR, respectively. Specifically, an antero-superior precuneus cluster derived from the contrast
self-referential N retrieved (S+M− N S−M+) (p b 0.001, k ≥ 20) and a
postero-inferior cluster derived from the contrast retrieved N self-
Trial distribution and familiarity task performance
Pictures presented during scanning were classified based on the
participants' responses in the SRP and EMR tasks as well as the
Fig. 3. Brain areas activated by the following contrasts: Red: ‘self-referential N non-selfreferential’ [(S+M+/S+M−) N (S−M+/S−M−)]; blue: ‘retrieved N non-retrieved’ [(S+
M+/S−M+) N (S+M−/S−M−)]; uncorrected p b 0.001, cluster size k ≥ 20. Overlapping
areas are shown in violet. L = Left, R = Right, t =t-value. (For interpretation of the
references to colour in this figure legend, the reader is referred to the web version of this
article.)
Please cite this article as: Sajonz, B., et al., Delineating self-referential processing from episodic memory retrieval: Common and dissociable
networks, NeuroImage (2010), doi:10.1016/j.neuroimage.2010.01.087
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B. Sajonz et al. / NeuroImage xxx (2010) xxx–xxx
oldness of the pictures (Fig. 2). Analysis of the resulting number of
trials per condition yielded a main effect for the factors SRP [F
(1,28) = 11.977, p = 0.002] and familiarity [F(1,28) = 13.016,
p = 0.001] with more pictures judged as non-self-referential and
familiar, respectively [mean number of trials ± SD rated as selfreferential: 67 ± 4; non-self-referential: 93 ± 20; familiar: 71 ± 13;
non-familiar: 88 ± 13]. In addition, a strong oldness × familiarity
interaction was found [F(1,28) = 588.182, p b 0.001] with old
pictures predominantly judged as familiar, reflecting the participants' very good performance in the memory task [mean d′ ±
SD = 2.07 ± 0.6]. We observed no main effect of oldness [F(1,28) =
0.051, p = 0.823], no SRP × familiarity interaction [F(1,28) = 0.195,
p = 0.662], and no SRP × oldness interaction [F(1,28) = 1.018,
p = 0.322].
Online response times
Response times were significantly longer in the SRP task
(meanRTself ± SD = 1197 ± 242 ms) compared to the EMR task
(1106 ± 218 ms; tpaired = −4.96, ptwo-sided b 0.001).
Post-scanning self-relatedness ratings
Self-referential (according to SRP task) and retrieved pictures
received clearly higher post-scanning self-relatedness ratings than
non-self-referential and non-retrieved pictures, respectively [main
effect for SRP: F(1,28) = 234.919, p b 0.001; EMR: F(1,28) = 20.442,
p b 0.001; mean post-scanning self-relatedness rating ± SD for pictures judged as self-referential during fMRI: 5.5 ± 1.3; non-self-
5
referential: 2.7 ± 0.9; retrieved: 3.9 ± 1.0; non-retrieved: 3.6 ± 1.0].
The interaction [SRP × EMR: F(1,28) = 0.159, p = 0.693] was not
significant.
Post-scanning valence ratings
Self-referential and retrieved pictures received higher postscanning valence ratings than non-self-referential and non-retrieved
pictures, respectively [main effect for SRP: F(1,28) = 155.124,
p b 0.001; EMR: F(1,28) = 31.398, p b 0.001; mean valence rating ± SD
for pictures judged as self-referential: 6.8 ± 0.8; non-self-referential:
5.4 ± 0.7; retrieved: 6.1 ± 0.7; non-retrieved: 5.8 ± 0.7]. The interaction [SRP × EMR: F(1,28) = 0.119, p = 0.732] was not significant.
Post-scanning arousal ratings
Post-scanning arousal ratings showed no significant main effects
[SRP: F(1,28) = 0.796, p = 0.38; EMR: F(1,28) = 1.984, p = 0.17] nor
an interaction [SRP × EMR: F(1,28) = 3.038, p = 0.092].
fMRI data
Self-referential N non-self-referential
To assess the main effect of SRP, we contrasted self-referential with
non-self-referential trials [(S+M+/S+M−) N (S−M+/S−M−)]. This
contrast revealed clusters of activation in the medial prefrontal cortex
(DMPFC and VMPFC extending into ACC and lateral prefrontal cortex),
the medial parietal cortex (posterior cingulate cortex (PCC)/retrosplenial cortex and precuneus), the inferior parietal lobule extending
Table 1
Contrasts ‘self-referential N non-self-referential’ and ‘retrieved N non-retrieved’.
Anatomical region
Self-referential N non-self-referential:
(S+M+/S+M−) N (S−M+/S−M−)
LNR DMPFC, VMPFC: medial frontal gyrus, ACC
R subgenual ACC
L DLPFC: superior frontal gyrus, middle frontal gyrus
L DLPFC: middle frontal gyrus, inferior frontal gyrus
L VLPFC: inferior frontal gyrus
R precentral gyrus, postcentral gyrus
LNR precuneus, PCC
L inferior parietal lobule, superior temporal gyrus,
middle temporal gyrus
L inferior temporal gyrus
L middle temporal gyrus
R caudate head and body
Retrieved N non-retrieved:
(S+M+/S−M+) N (S+M−/S−M−)
R aPFC: superior frontal gyrus
L aPFC: superior frontal gyrus, middle frontal gyrus
L DLPFC: middle frontal gyrus
R mid-cingulate cortex
L precentral gyrus, middle frontal gyrus
R precentral gyrus, postcentral gyrus,
R postcentral gyrus, precentral gyrus
R premotor cortex: middle frontal gyrus
R precuneus
L precuneus
R inferior parietal lobule, superior parietal lobule
L inferior parietal lobule, superior parietal lobule
R cerebellum: tuber, uvula, declive
R cerebellum: declive, uvula
L cerebellum: culmen, declive
L caudate head and body
R caudate head and body
L putamen
BA
k
T
Peak (x, y, z)
10, 9, 32, 24, 33
25
8, 9
9
47
4, 3
31, 7, 23, 30
39, 40, 22, 21
2033
28
1351
24
405
290
1237
1020
6.53⁎
4.47
7.58⁎
3.93
5.32⁎
5.88⁎
7.58⁎
5.45⁎
−6
4
−22
− 40
−44
44
−4
− 52
46
8
34
10
32
−16
−60
−58
2
−8
44
38
−14
56
34
26
29
20
44
4.13
3.75
4.41
− 62
− 60
14
−14
−48
16
−30
−6
4
47
22
20
78
36
549
33
47
559
263
267
856
67
193
121
305
302
45
4.41
3.77
3.65
5.46⁎
3.70
7.18⁎
4.00
4.49
6.62⁎
5.13
5.34⁎
6.33⁎
4.70
5.98⁎
4.48
4.86
5.76⁎
5.05
28
−28
−42
6
−34
42
32
36
18
−10
38
−42
34
12
− 22
− 12
12
− 16
58
62
40
−8
10
− 18
−36
2
− 62
− 64
−70
− 60
−68
−80
−54
−2
10
6
0
4
18
36
48
56
62
64
28
32
44
44
−34
−26
−30
20
8
−12
20
21
10
10
46
24
4, 6
4, 3, 6
3, 4
6
7, 31
7, 31
7, 19, 39, 40
40, 7, 39
Maximum t-values and peak voxel coordinates for activation clusters, uncorrected p = 0.001, k ≥ 20; ⁎ activations with asterisked t-values survive FWE-correction at 0.05.
Anatomical regions and BAs sorted in descending order according to their proportion of the cluster. Following Van Hoesen et al. (1993) we regard BA 31 as a transition zone that
belongs to both PCC and precuneus.
BA=Brodmann area, k=cluster size, t = t-value, L = Left, R = Right, ACC = anterior cingulate cortex, aPFC = anterior prefrontal cortex, DLPFC = dorsolateral prefrontal cortex,
DMPFC = dorsomedial prefrontal cortex, PCC = posterior cingulate cortex, VMPFC = ventromedial prefrontal cortex, VLPFC = ventrolateral prefrontal cortex.
Please cite this article as: Sajonz, B., et al., Delineating self-referential processing from episodic memory retrieval: Common and dissociable
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Fig. 4. Brain areas detected by the conjunction analysis testing the conjunction null hypothesis of the contrasts ‘self-referential N non-self-referential’ [(S+M+/S+M−) N
(S−M+/S−M−)] and ‘retrieved N non-retrieved’ [(S+M+/S−M+) N (S+M−/S−M−)]; uncorrected p b 0.001. Bar graphs illustrate parameter estimates (± standard error of the
mean) of each condition averaged for the 29 subjects in arbitrary units for the peak voxels indicated. L = Left, R = Right, t = t-value.
into superior and middle temporal gyrus and further regions (Fig. 3
and Table 1).
Retrieved N non-retrieved
The contrast ‘retrieved N non-retrieved’ [(S+M+/S−M+) N (S+
M−/S−M−)] identified the main effect of EMR success. Clusters of
activation included among others the bilateral anterior prefrontal
cortex (aPFC), the precuneus and the superior and inferior parietal
lobule (Fig. 3 and Table 1). Fig. 3 illustrates that the main effects of
SRP and successful EMR revealed partly overlapping and partly
dissociable activations in the medial and lateral parietal cortex.
Conjunction analysis
To further explore the overlap between SRP and EMR success, we
conducted a conjunction analysis testing the conjunction null
hypothesis of the contrasts ‘self-referential N non-self-referential’
[(S+M+/S+M−) N (S−M+/S−M−)] and ‘retrieved N non-retrieved’ [(S+M+/S−M+) N (S+M−/S−M−)]. This analysis revealed
activations in the left precuneus and the left inferior parietal lobule
(Fig. 4 and Table 2). Effects observed in right sensorimotor areas were
most likely related to the preparation of the button response given by
the participants during the experiment (left hand responded to both
self-related and familiar pictures; right hand responded to non-selfrelated and non-familiar pictures).
Interaction effect
We found no significant SRP × EMR interaction effect [(S+M+ N
S−M+) N (S+M− N S−M−)].
Self-referential N retrieved
To dissociate SRP from EMR and identify specific effects of SRP, we
contrasted self-referential with retrieved trials (S+M− N S−M+).
Among other regions, this contrast revealed significant activations in
the medial prefrontal cortex (DMPFC/VMPFC extending into ACC and
lateral prefrontal cortex), the medial parietal cortex (PCC, anterior
superior portion of the precuneus) and the inferior division of the
inferior parietal lobule extending into the superior and middle
temporal gyrus (Fig. 5 and Table 3).
The contrast ‘self-referential N retrieved’ (S+M− N S−M+) may
reveal both activation related to SRP and deactivation related to EMR.
To determine the contribution of each of the two processes to the
observed differential effect, each condition was separately compared
to baseline (bar graphs in Fig. 5). This analysis showed that differential
effects were mainly related to increased signal intensities during SRP
rather than decreased signal intensities during EMR. In the MPFC, both
effects seem to contribute to the differential effect observed.
Retrieved N self-referential
To dissociate EMR from SRP and to identify specific effects of EMR,
we contrasted retrieved with self-referential (S−M+ N S+M−) trials.
This contrast revealed activations in the right aPFC, the posterior
inferior portion of the right precuneus, the superior parietal lobule
and the superior division of the inferior parietal lobule (Fig. 5 and
Table 3).
Baseline comparisons showed that these differential effects were
mainly related to increased signal intensities during EMR rather than
decreased signal intensities during SRP (bar graphs in Fig. 5).
Table 2
Conjunction: self-referential N non-self-referential ∩ retrieved N non-retrieved: (S+M+/S+M−) N (S−M+/S−M−) ∩ (S+M+/S−M+) N (S+M−/S−M−).
Anatomical region
BA
k
t
Peak (x, y, z)
R precentral gyrus, postcentral gyrus
L precuneus
L inferior parietal lobule
R caudate head and body
4, 3
7, 31
40, 39
239
151
198
26
5.88⁎
5.08
4.11
4.25
44
−8
−44
14
−16
−66
− 56
16
56
32
50
4
Maximum t-values and peak voxel coordinates for activation clusters, uncorrected p = 0.001, k ≥ 20; ⁎ activations with asterisked t-values survive FWE-correction at 0.05.
Anatomical regions and BAs sorted in descending order according to their proportion of the cluster. BA=Brodmann area, k=cluster size, t = t-value, L = Left, R = Right.
Please cite this article as: Sajonz, B., et al., Delineating self-referential processing from episodic memory retrieval: Common and dissociable
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Fig. 5. Brain areas activated by the following contrasts: Red: ‘self-referential N retrieved’ (S+M− N S−M+); blue: ‘retrieved N self-referential’ (S−M+ N S+M−); uncorrected
p b 0.001, cluster size k ≥ 20. Bar graphs illustrate parameter estimates (± standard error of the mean) of each condition averaged for the 29 subjects in arbitrary units for the
peak voxels indicated. aPFC = anterior prefrontal cortex, DMPFC = dorsomedial prefrontal cortex, MTG = middle temporal gyrus, L = Left, R = Right, t = t-value. (For interpretation
of the references to colour in this figure legend, the reader is referred to the web version of this article.)
Functional connectivity analyses (PPI)
SRP and EMR produced partly dissociable (Fig. 5) activations in the
precuneus. If regional dissociation reflects functional dissociation,
functional connectivity should differ between precuneus portions
specifically associated with SRP and EMR. We performed a PPI analysis
using the precuneus clusters identified in the contrasts ‘selfreferential N retrieved’ (hereafter self cluster) and ‘retrieved N selfreferential’ (hereafter memory cluster) as seed regions. Activity in the
self cluster correlated with activations in the medial premotor cortex
(BA 6), left dorsal ACC (BA 33), fusiform gyrus (BA 37), and superior
parietal lobule (BA 7) during self-referential N non-self-referential
stimulus processing (Fig. 6 and Table 4). In contrast, activity in the
memory cluster was associated with the responsiveness in a distinct
region in the left dorsal anterior paracingulate cortex (BA 32, 6)
during successful EMR (Fig. 6 and Table 4).
Discussion
The present data suggest common and dissociable networks for
SRP and EMR. Three main findings concern (1) the medial parietal
cortex (PCC, precuneus), (2) the prefrontal cortex, and (3) the lateral
parietal cortex (Fig. 7). More specifically, self-referential stimuli
specifically activate the PCC/anterior precuneus, the ventral and dorsal
medial prefrontal cortex (extending into the ACC), and an inferior
division of the inferior parietal lobule extending into the superior and
middle temporal gyrus. In contrast, EMR success specifically involves
the posterior precuneus, the aPFC, and a superior division of the
inferior parietal lobule extending into the intraparietal sulcus and the
superior parietal lobule. Overlapping activations can be found in
intermediate zones in the precuneus and the inferior parietal lobule,
but not in the prefrontal cortex.
Please cite this article as: Sajonz, B., et al., Delineating self-referential processing from episodic memory retrieval: Common and dissociable
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Table 3
Contrasts ‘self-referential N retrieved’ and ‘retrieved N self-referential’.
Anatomical region
Self-referential N retrieved: (S+/M−) N (S−/M+)
L N R DMPFC, VMPFC: medial frontal gyrus, ACC,
superior frontal gyrus
bilateral subgenual ACC
L DLPFC: middle frontal gyrus
L VLPFC: inferior frontal gyrus, middle frontal gyrus
R VLPFC: inferior frontal gyrus
R VLPFC extending into DLPFC: inferior frontal gyrus
R VLPFC: inferior frontal gyrus
L FEF, premotor cortex: superior frontal gyrus
L PCC
LNR anterior superior precuneus
L inferior division of inferior parietal lobule,
superior temporal gyrus, middle temporal gyrus
R inferior division of inferior parietal lobule,
superior temporal gyrus
L middle temporal gyrus, inferior temporal gyrus
R parahippocampal gyrus, fusiform gyrus
L substantia nigra, red nucleus
Retrieved N self-referential (S−/M+) N (S+/M−)
R aPFC: superior frontal gyrus
L precentral gyrus, middle frontal gyrus
R premotor cortex: middle frontal gyrus
R posterior inferior precuneus
R superior parietal lobule, superior division of
inferior parietal lobule
R inferior parietal lobule
R superior division inferior parietal lobule
bilateral lingual gyrus, cuneus
L middle occipital gyrus, inferior occipital gyrus
R cuneus, middle occipital gyrus
R cerebellum: declive
BA
k
t
10, 32, 9, 24, 33
2275
7.01⁎
−2
56
18
55
117
230
29
31
21
574
25
199
448
4.57
5.22
4.86
3.78
4.15
4.27
5.97⁎
4.28
4.91
5.56⁎
2
−28
− 48
44
54
58
−16
−6
−4
−58
10
28
30
32
26
32
42
− 54
−60
−68
−12
36
−16
−16
12
0
48
18
36
18
39, 22
46
3.97
48
−62
24
21, 20
37, 36
48
38
24
4.32
3.76
3.84
−60
34
−8
−10
−42
−20
−22
−12
−12
10
6, 4
6
31
7,19, 39
29
21
31
46
75
4.35
3.85
4.27
4.38
4.42
26
−24
36
20
38
60
− 18
2
−62
−68
−2
56
64
28
50
29
31
288
81
71
44
4.06
3.90
4.72
4.74
4.87
4.53
36
48
−4
− 44
18
10
−50
− 50
−92
− 88
−102
−82
40
52
−6
−4
4
−26
25
9
47
47
45, 46
47, 45
8, 6
23, 30
7, 31
39, 22, 40, 21
40
40
17, 18
19, 18
18
Peak (x, y, z)
Maximum t-values and peak voxel coordinates for activation clusters, uncorrected p = 0.001, k ≥ 20; ⁎ activations with asterisked t-values survive FWE-correction at 0.05.
Anatomical regions and BAs sorted in descending order according to their proportion of the cluster.
BA=Brodmann area, k=cluster size, t = t-value, L = Left, R = Right, ACC = anterior cingulate cortex, aPFC = anterior prefrontal cortex, DLPFC = dorsolateral prefrontal cortex,
DMPFC = dorsomedial prefrontal cortex, FEF = frontal eye field, PCC = posterior cingulate cortex, VLPFC = ventrolateral prefrontal cortex, VMPFC = ventromedial prefrontal cortex.
Extending earlier work on SRP and EMR, the present fMRI study
combines standard tasks for both domains in one experiment. This
approach permits reference to one study population, matching of task
demands between conditions, and fMRI data processing in one and the
same analysis (guaranteeing identical preprocessing steps, templates,
statistical tests, and thresholds). As a result, this allows a more direct
and detailed identification of common and dissociable activations for
both processes. Most notably, besides the conventional comparisons
(‘self-referential versus non-self-referential’, retrieval success contrast), our study design allows the contrast ‘self-referential/nonretrieved versus non-self-referential/successfully retrieved’. Thus
subtracting the effects of EMR from SRP (and vice versa), we are able
to delineate the neural correlates of SRP from EMR (and vice versa).
The finding of shared activations confirms our hypothesis of
commonalities between SRP and EMR which was proposed based on
theoretical considerations (Conway and Pleydell-Pearce, 2000; Gardiner, 2001; James, 1892), behavioral experiments (self reference effect;
Rogers et al., 1977; Symons and Johnson, 1997), functional connectivity
MRI (Buckner et al., 2008), and review of functional neuroimaging
studies investigating each domain separately (Cavanna and Trimble,
2006; Gillihan and Farah, 2005; Legrand and Ruby, 2009; Northoff and
Bermpohl, 2004; Northoff et al., 2006). The identified areas in the medial
parietal cortex (precuneus) and inferior parietal lobule are anatomically
and functionally connected and are both considered components of the
default-mode network (Buckner et al., 2008).
Medial parietal cortex
Extending previous work, our study suggests a functional
segregation within the PCC/precuneus for SRP and EMR, respectively:
SRP induces significantly larger activations relative to EMR in the PCC
and anterior (and superior) precuneus, whereas EMR is associated
with significantly larger activations relative to SRP in the posterior
(and inferior) precuneus. Further support for such functional
dissociation comes from our functional connectivity analysis using
precuneal portions specific for SRP and EMR, respectively, as seed
regions: Activity in the SRP-related seed in the PCC/anterior
precuneus correlates with the medial premotor cortex (BA 6), dorsal
ACC (BA 33), fusiform gyrus (BA 37), and superior parietal lobule (BA
7) during SRP. In contrast, activity in the EMR-related seed in the
posterior precuneus is associated with the responsiveness in a
distinct region in the dorsal anterior paracingulate cortex (BA 32, 6)
during EMR. The observed dissociation within the PCC/precuneus
confirms the hypothesis derived from functional neuroimaging
studies investigating SRP and EMR in separate experiments (Fig. 1
and Cavanna and Trimble, 2006).
Recently, anterior–posterior differentiation within the PCC/precuneus has also been suggested based on studies not related to SRP:
First, cytoarchitectonic maps demonstrate a distinction between PCC
and precuneus as well as subdivisions within the precuneus
(Economo and Koskinas, 1925; Scheperjans et al., 2008). Second,
tract tracing studies in the macaque (Kobayashi and Amaral, 2007;
Leichnetz, 2001) show that these cytoarchitectonic differences reflect
differences in anatomical connectivity. While the PCC has strong
reciprocal connections with the medial temporal lobe, the medial and
lateral prefrontal cortex, the superior parietal cortex (BA 7), and the
precuneus, the precuneus has strong reciprocal connections with
occipital and parietal areas linked to visual processing and frontal
areas associated with motor planning. Third, based on resting state
studies and functional connectivity results, it has been suggested that
Please cite this article as: Sajonz, B., et al., Delineating self-referential processing from episodic memory retrieval: Common and dissociable
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9
(Lou et al., 2004), and autobiographical memory (Burianova and
Grady, 2007). Our findings may help to qualify the function of the PCC/
anterior precuneus in these tasks.
Medial and anterior prefrontal cortex
Fig. 6. Brain areas detected by two connectivity analyses (psychophysiological
interaction, PPI): Red: activity in the contrast ‘self-referential N non-self-referential’
[(S+M+/S+M−) N (S−M+/S−M−)] correlated with the SRP-specific seed cluster in
the anterior precuneus (peak − 4 − 60 36); blue: activity in the contrast ‘retrieved N
non-retrieved’ [(S+M+/S−M+) N (S+M−/S−M−)] correlated with the EMR-specific
seed cluster in the posterior precuneus (peak 20 − 62 28); uncorrected p b 0.001,
cluster size k ≥ 20. L = left, t = t-value. (For interpretation of the references to colour in
this figure legend, the reader is referred to the web version of this article.)
the posterior precuneus is not part of the default-mode network,
whereas the PCC is (Buckner et al., 2008). Fourth, neuroimaging
studies show that different aspects of EMR are represented in distinct
regions within the PCC/precuneus: The posterior precuneus is
associated with EMR success in general (independent of imageable
characteristics (Schmidt et al., 2002) or contextual detail (Henson et
al., 1999; Yonelinas et al., 2005)) and, in particular, with mnemonic
visual information processing (Cavanna and Trimble, 2006), which is
consistent with the co-activation of visual areas during EMR success in
our study. In contrast, the PCC/anterior precuneus is linked to specific
aspects of EMR, including memory-related imagery (Fletcher et al.,
1995), recollection of contextual details (Henson et al., 1999;
Yonelinas et al., 2005), retrieval of previous self-referential judgments
Our data also reveal a functional segregation between the medial
and anterior prefrontal cortex: SRP induces significantly larger
activations in the medial prefrontal cortex relative to EMR, whereas
EMR is associated with significantly larger activations in the lateral
aPFC relative the SRP. These findings are consistent with earlier
neuroimaging studies examining both processes in separate paradigms: The VMPFC has been linked to emotional and representational
aspects and the DMPFC to cognitive and evaluational aspects of selfreferential stimulus processing (Amodio and Frith, 2006; Northoff and
Bermpohl, 2004; Zysset et al., 2002), whereas the bilateral aPFC has
been associated with EMR success (McDermott et al., 2000), control
processes related to EMR (King et al., 2005), and retrieval mode
(Velanova et al., 2003). Combining both processes in one experiment, our data extend these earlier studies: First, both conjunction
analysis and overlay of main contrasts for SRP and EMR suggest
that there is no functional overlap between the prefrontal clusters
engaged in SRP and EMR, respectively. Second, specification of BOLD
effects (baseline comparisons, Fig. 5) indicates that involvement of
EMR does not enhance (but rather attenuates) SRP-related signals
in the medial prefrontal cortex; and involvement of SRP does not
enhance (but rather attenuates) EMR-related signals in the aPFC.
Consequently, we find no interaction between SRP and EMR in the
prefrontal cortex.
The observed functional dissociation is consistent with data from
functional connectivity MRI studies suggesting that the medial
prefrontal cortex and the bilateral aPFC belong to separate networks,
associated with internally directed (i.e., self-referential) cognitive
processes and cognitive control processes (e.g., tracking performance
on detection tasks like our EM task), respectively (Vincent et al.,
2008). Our finding is also of interest in light of earlier studies
associating the medial prefrontal cortex with autobiographical
memory retrieval (Gilboa, 2004; Svoboda et al., 2006), retrieval of
self-referential episodes (Zysset et al., 2002), retrieval of selfgenerated versus externally presented words (Vinogradov et al.,
2008), and the self-reference effect of memory (Macrae et al., 2004).
These processes have in common that they involve self-referential
and memory components at the same time. Our data seem to suggest
that the self-referential component particularly contributes to medial
prefrontal activations observed in these studies.
Lateral parietal cortex
We find lateral parietal activations during both SRP and EMR. This is
in accordance with earlier studies, linking the lateral parietal and
adjacent temporal cortex to SRP (in particular, first-person perspective
Table 4
PPI: activations correlated with self-referential and retrieved seed region in the precuneus.
Anatomical region
k
t
Peak (x, y, z)
PPI self-referential seed region in anterior precuneus (peak: −4 − 60 36)
L dorsal ACC
33
L premotor cortex: superior frontal gyrus
6
L premotor cortex: medial frontal gyrus
6
R superior parietal lobule
7
R fusiform gyrus
37
BA
20
60
36
46
36
4.46
4.76
5.10
6.03
4.41
−8
−10
− 14
14
40
12
14
−8
−66
−54
26
60
58
56
−16
PPI retrieved seed region in posterior precuneus (peak: 20 −62 28)
L dorsal anterior paracingulate
32, 6
43
4.94
−4
34
36
Maximum t-values and peak voxel coordinates for activation clusters, uncorrected p = 0.001, k ≥ 20. BA=Brodmann Area, k=cluster size, t = t-value, L = Left, R = Right,
ACC = anterior cingulate cortex.
Please cite this article as: Sajonz, B., et al., Delineating self-referential processing from episodic memory retrieval: Common and dissociable
networks, NeuroImage (2010), doi:10.1016/j.neuroimage.2010.01.087
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Fig. 7. Schematic illustration of the three main dissociable findings in: (1) the medial parietal cortex, (2) the prefrontal cortex, and (3) the lateral parietal cortex. Top: Lateral surface
of the brain. Bottom: Mesial sagittal surface and axial slice at approximately z = 0 in MNI standard space. Networks associated with self-referential processing are depicted in red,
networks associated with episodic memory retrieval in blue, and overlapping networks in violet. (For interpretation of the references to colour in this figure legend, the reader is
referred to the web version of the article.)
taking (Vogeley and Fink, 2003)) and EMR success (Donaldson et al.,
2001; Konishi et al., 2000). Extending these findings, the present data
suggest functional dissociation within the lateral parietal and adjacent
temporal cortex: SRP is associated with activations in a posteroinferior division of the inferior parietal lobule and the adjacent
superior and middle temporal gyrus (temporo-parietal junction). In
contrast, EMR induces activations in an antero-superior division of the
inferior parietal lobule extending into the intraparietal sulcus and the
superior parietal lobule. This dissociation is, again, compatible with
data from functional connectivity studies (Vincent et al., 2008), linking
the posterior inferior parietal lobule to internally directed (i.e., selfreferential) cognitive processes, while associating the superior parietal
lobule and anterior inferior parietal lobule with attentional and
cognitive control processes, such as detecting targets and tracking
performance in our EMR task.
Our findings are also compatible with studies reporting dissociation of memory-related functions within the lateral parietal and
adjacent temporal cortex (Henson et al., 2005; Maguire and Mummery, 1999; Skinner and Fernandes, 2007; Vilberg and Rugg, 2009;
Wagner et al., 2005): the superior parietal lobule has been associated
with the relative salience of retrieval cues in memory tasks and the
intraparietal sulcus with retrieval success, consistent with our findings
during EMR success. The inferior parietal lobule, on the other hand, has
been implicated with the recollection of contextual information.
Although neither task in our study explicitly required such recollection, we cannot exclude that this accounts for the overlapping
activation observed in the inferior parietal lobule for SRP and EMR.
Independent of this interpretation, our findings suggest that the
postero-inferior division of the inferior parietal cortex and the
adjacent superior and middle temporal gyrus are particularly involved
in self-referential processes, possibly the retrieval of personally
relevant (contextual or non-contextual, cf. Maguire and Mummery,
1999) information.
Methodological considerations
Response times were longer for the SRP relative to the EMR task,
which may indicate that the SRP task was more demanding. However,
differences in task difficulty and related attentional processes should
not have affected the results reported here: The comparisons of our
experiments did not concern tasks (e.g., SRP task versus EMR task) but
stimulus qualities (e.g., self-referential/not retrieved versus non-selfreferential/successfully retrieved stimuli). Because subjects had to
perform both tasks in relation to each stimulus, we can assume that
the attention level during the picture perception period was similar
among conditions.
Please cite this article as: Sajonz, B., et al., Delineating self-referential processing from episodic memory retrieval: Common and dissociable
networks, NeuroImage (2010), doi:10.1016/j.neuroimage.2010.01.087
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We cannot exclude that the emotional valence of our pictorial
stimuli has influenced both SRP (cf. Northoff et al., 2009) and EMR (cf.
Kensinger, 2004). Although one may consider valence an intrinsic
element of self-referential processing (Moran et al., 2006; Phan et al.,
2004), we attempted to reduce valence effects on SRP and EMR
findings in our experiment: we kept the variance of the normative
valence scores across the picture set to a minimum when we selected
IAPS pictures for our study. In addition, we included the individual
valence ratings as a covariate in our fMRI data analysis.
It is acknowledged that different tasks could have been chosen to
address our research question: Instead of episodic memory, we could
have used semantic or autobiographical memory tasks as control
conditions. Instead of self-referential picture judgment, we could have
used a self-referential trait (Kelley et al., 2002) or color (Johnson et al.,
2005) judgment task. At this point, one can only speculate on how
different task demands would have influenced our findings. In general,
potential alternative tasks could have increased the functional overlap
(e.g., autobiographical memory task introducing a stronger selfreferential component in the memory task) or the functional dissociation (e.g., self-referential task in relation to colors minimizing the
memory component) between SRP and memory retrieval. Our results
demonstrate that the standard tasks chosen here were able to explore
both functional overlap and dissociation for both processes. Notably,
the implicit involvement of SRP in the EMR condition and of EMR in the
SRP condition did not affect our search for specific networks, because
the direct comparison between self-referential/not retrieved versus
non-self-referential/successfully retrieved stimuli was used to cancel
out the potentially confounding processes.
Behavioral studies on trait judgments have suggested that selfreferential processing may involve semantic besides episodic memory
retrieval (Klein et al., 1996; Tulving, 1989, 1993; Klein et al., 2002).
Semantic personal memories can be regarded as summary representations of the personal past that have been generalized from episodic
memories. It has been proposed that semantic and episodic memory
systems function independently for some tasks but not others
(Kihlstrom and Klein, 1997; Klein et al., 2002). Because self-referential
trait and picture judgments involve similar brain regions (Northoff et
al., 2006), it seems plausible that the present self-referential task also
involved both memory systems: Subjects may have made selfreferential picture judgments based on general knowledge of the
circumstances of their lives in some cases and on episodic (or both
semantic and episodic) memories in others. Semantic memory
retrieval could be reflected in left middle temporal gyrus (BA 21)
activation during SRP (Svoboda et al., 2006). However, the present
study does not allow directly examining the relation between
semantic memory retrieval and SRP, because we did not include a
semantic memory task as a control.
Based on resting state (Greicius and Menon, 2004), tract tracing
studies in the macaque (e.g., Kobayashi and Amaral, 2007), functional
connectivity MRI studies (Vincent et al., 2006), and functional
neuroimaging studies in EMR (Skinner and Fernandes, 2007), one
might have expected to find EMR-related activations also in the
hippocampus. Such effect was not observed in our study, possibly
because the hippocampus also activates to novel items (implicit
encoding, Stark and Okado, 2003) and is more engaged in explicit
contextual information processing than simple recognition (Dobbins
et al., 2003; Yonelinas et al., 2005). An alternative explanation is that
medial temporal activation is more linked to retrieval mode (retrieval
efforts) than to retrieval success (Donaldson et al., 2001).
Conclusion
SRP and EMR engage both overlapping and segregated activations
in a neural network including the medial parietal cortex, medial and
anterior prefrontal cortex, and lateral parietal cortex. In large parts
this network corresponds to the so-called default-mode network.
11
While the present study helps to qualify the function of this network
in SRP and EMR, further processes from different domains have been
associated with this network. They include resting state, inductive and
deductive reasoning, navigation, envisioning the future, evaluation of
rewards (Montague et al., 2006), social cognition, moral decision
making, imagery, and autobiographical memory (Buckner and Carroll,
2007; Buckner et al., 2008; Legrand and Ruby, 2009; Schilbach et al.,
2008; Spreng et al., 2009). Although these processes are often studied
as distinct and interpreted within their own domain, it has been
speculated that they rely on a common set of internally directed
processes by which past experiences are used adaptively to imagine
self-referential events beyond those that are perceived in the
immediate external environment. The present study demonstrates
that combining two of these processes in one fMRI paradigm can be a
useful approach to explore the functional relevance, subdivisions, and
specificity of the default-mode network. Further work is needed to
understand how SRP and EMR relate to other processes associated
with this network.
Conflict of interest
The authors of the study have no conflicts of interest to declare.
Acknowledgments
We would like to thank Matt Walker for helpful discussion of the
paradigm of the study.
This work was supported by grants from the German Federal
Ministry of Education (BMBF-01GWSO61 to F.B., BMBF-01GV0612 to
A.S., M.S., and A.W., BMBF-01GS08148 to A.H., BMBF-01GS08159 to
A.H.); German Research Foundation (DFG-SFB 779-A6 to G.N.);
Canada Research Chair (CRC to G.N.); and EJLB-Michael Smith
Foundation (to G.N.).
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