Schizophrenia Research 85 (2006) 1 – 11
Evidence for impaired mnemonic strategy use among patients with
schizophrenia using the part-list cuing paradigm
Bruce K. Christensen a,b,*, Todd A. Girard a,b, Aaron S. Benjamin c, Pierre Vidailhet d
a Neuropsychology Lab, Schizophrenia Program, Centre for Addiction and Mental Health, 250 College Street, Toronto, ON, Canada M5T 1R8
b Department of Psychiatry, University of Toronto, Canada
c Department of Psychology and Beckman Institute for Advanced Science and Technology, University of Illinois, Urbana-Champaign, USA
d INSERM Unite 405 Psychopathologie et Pharmacologie de la Cognition, Strasbourg, France
Received 3 March 2006; accepted 3 March 2006
Purpose: Strategic and mnemonic abilities of person with schizophrenia (SCZ) were studied using a part-list cuing (PLC) task. In this task, presentation of retrieval cues in the form of a subset of studied words typically impairs recall of the remainingitems. This impairment is thought to reflect a disruption of participants’ natural retrieval strategies. Methods: Participants with SCZ and healthy controls (ns = 28) studied word lists with three different levels of semanticorganization: (a) unrelated, (b) categorized, but presented in a random order, and (c) presented by category. For each type of list,participants recalled words under both free-recall and PLC conditions. Results: Consistent with SCZ-related impairment of strategic retrieval processes, the SCZ group was less disrupted by PLCinterference than controls in the unrelated-list condition. Comparison of free recall across lists also indicated a consistent deficitin SCZ despite varying levels of difficulty and retrieval contexts. Nonetheless, the SCZ group demonstrated parallelimprovement to the healthy group with increasing list organization. Conclusions: These results provide evidence of deficient retrieval processes in SCZ in a context placing maximal requirementsfor utilization of self-initiated, effortful, mnemonic strategies. Unlike most extant results demonstrating mnemonic impairmentin persons with SCZ, the present results cannot be accounted for by task difficulty; SCZ participants’ recall was less disruptedby PLC than was that of healthy participants. Results also demonstrated that SCZ participants could benefit, in terms of recalland strategy use, from list organization when this structure was explicitly provided at test. D 2006 Elsevier B.V. All rights reserved.
Keywords: Schizophrenia; Part-list cuing interference; Memory; Semantic organization; Mnemonic strategy
* Corresponding author. Neuropsychology Lab, Schizophrenia Program, Centre for Addiction and Mental Health—College Street Site, 250
College Street, Toronto, Ontario, Canada M5T 1R8. Tel.: +1 416 535 8501x6843; fax: +1 416 979 6936.
0920-9964/$ - see front matter D 2006 Elsevier B.V. All rights reserved.
B.K. Christensen et al. / Schizophrenia Research 85 (2006) 1–11
strategies aimed at free recall of the whole list to a lessefficient plan that is guided by the external, experi-
Deficits in declarative memory are particularly
menter-supplied cues. That PLC results in a tempo-
robust among persons with schizophrenia (SCZ;
rary disruption at retrieval is further supported by
observations that recall for bforgottenQ target items
and Zakzanis, 1998; Saykin et al., 1991, 1994; Weiss
returns if tested again under uncued conditions
and Heckers, 2001). However, the specific underlying
mechanisms of this impairment remain largely un-
and Milner, 1993). Although several theoretical
clear. One notable aspect of deficient memory in SCZ
is a reduction in the spontaneous application of
Aslan, 2004; Mueller and Watkins, 1977; Nickerson,
organizational strategies to aid recall, including
1984; Raaijmakers and Phaf, 1999; Raaijmakers and
Shiffrin, 1981; Rundus, 1973; Sloman et al., 1991),
the strategy disruption hypothesis remains a particu-
2004) organization of to-be-remembered material.
larly prominent, accepted, and tenable account (
Furthermore, persons with SCZ typically require a
den and Basden, 1995; MacLeod et al., 2003). This
more objective, salient, and/or explicit representation
hypothesis predicts that PLC will result in less
in order to benefit from any inherent organizational
disruption to individuals who are less able to utilize
techniques that enhance memory organization. In this
Interpretations of many SCZ memory findings are
regard, diminished interference in SCZ would signify
complicated, however, by a confounding of differen-
organizational memory deficits unencumbered by
tial deficit with task difficulty (e.g., less organized
lists are more difficult to recall). The challenge of
Importantly, several factors influence the magni-
equating tasks for difficulty in order to demonstrate a
tude and direction of PLC effects, which depend on
btrueQ differential deficit is non-trivial and
the compatibility of participants’ free (uncued) recall
and Chapman (1973) suggest an alternative solution:
strategies with the organization imposed by retrieval
use experimental manipulations where deficits actu-
cues and its relation to the remaining targets (
ally improve performance or disrupt it less compared
and Basden, 1995; Sloman et al., 1991). Of particular
relevance is the importance of list structure (
erson, 1984). Manipulations of list structure may be
In this regard, one promising approach for inves-
used to induce common output strategies between
tigating differential strategic mnemonic processes in
participants. For example, presenting category mem-
SCZ involves interference via part-list cuing (PLC).
bers consecutively encourages participants to encode
those items as exemplars of a common category.
evidenced when the provision of a subset of previ-
Consequently, when using organized lists, cues
ously studied words as retrieval cues interferes with
facilitate recall to the extent that they remind
recall of the remaining non-cued target items. In this
participants of super-ordinate categories. However,
vein, it is more appropriate to consider PLC as
increasing the proportion of cues from a given
providing a retrieval context than a recall aid
category increasingly impairs recall of remaining
1995; Bellezza and Hartwell, 1981; Lewis, 1971;
1977) have conceptualized PLC interference as a
Nickerson, 1984; Penney, 1988; Roediger, 1973,
retrieval strategy disruption. From this view, the
1974; Roediger et al., 1977; Rundus, 1973). This
structure of recall output is a reflection of an
result presumably arises because the presence of cues
organized retrieval plan that may be influenced by
encourages participants to switch from their bnaturalQ
retrieval order to a strategy by which they use cues to
1995; Slamecka, 1968; Sloman, 1991). In other
elicit memories for unpresented items.
words, PLC alters the retrieval environment and
In contrast to lists blocked by category, scrambled
prompts participants to switch from self-generated
presentation of exemplars from multiple categories
B.K. Christensen et al. / Schizophrenia Research 85 (2006) 1–11
may lead participants to form categories that are more
assessed performance across three levels of semantic
narrow or broad than intended by the experimenter
organization: (a) unrelated lists, whose recall relies
most on participant-generated strategy; (b) scrambled
zational strategies are even more expected with lists of
category lists; and (c) blocked category lists that
unrelated words, where the likelihood of congruency
explicitly define organizational structure. We pre-
between random/experimenter-selected cues with par-
dicted a Group x Cue x List type interaction such that
ticipant-generated strategies may reduce to chance
the SCZ group would demonstrate attenuated PLC
interference especially with unrelated lists, but show a
tion across these three list types–unrelated, scrambled,
similar effect of cuing when provided an organiza-
and blocked–should facilitate more homogenous
tional strategy in the blocked condition.
mnemonic strategy use across individuals. To theextent that persons with SCZ are similarly influencedby semantic organization, increased list structure
should produce more similar PLC profiles.
Although extensively investigated in healthy sam-
ples, application of PLC to clinical populations hasbeen rare (
Thirty persons with either SCZ or Schizoaffective
and Milner, 1993). Attenuated PLC interference in
Disorder were recruited via the Schizophrenia Regis-
SCZ was indirectly suggested by the multinomial
try for Research at the Centre for Addiction and
Mental Health (CAMH, Toronto, Canada), poster
separately demonstrated that (a) PLC in healthy
advertisement at the CAMH, and referrals from health
individuals affected only retrieval parameters and that
professionals; 30 healthy control (HC) participants
(b) performance of a SCZ group tested only on free
were recruited from the community via local news-
recall implicated reduced storage as well as greater
paper advertisements or word of mouth. However,
retrieval deficits. However, only one prior study has
data for two participants per group were excluded due
directly studied PLC in SCZ and concluded that
to technical problems during the PLC computer
similar PLC profiles to a healthy group bindicates
program; all results reported are based on the remai-
normal retrieval performance in SCZ patients under
Inclusion criteria included ability to provide
2005, p. 278). Visual inspection of these data,
informed consent, age between 18 and 60 years,
however, suggests that the study may have been
English as the primary language, and (corrected-to-)
underpowered to detect a subtle differential PLC
normal vision. Exclusion criteria consisted of a history
effect in SCZ. In fact, their power to detect even a
of neurological injury/disease (including brain injury
large interaction effect ( f = .40) was only .57 (al-
with loss of consciousness), lifetime history of any
(HC) or any non-psychotic (SCZ) Axis I psychiatric
weak grounds for concluding a null hypothesis, but
disorder (including alcohol/substance dependence or
significance hypothesis testing only allows for a
abuse—SCZ accepted if abuse N6 months prior), first-
dfailure to rejectT it. Alternatively, the scrambled
degree relative with a psychotic disorder (HC), recent
category lists used may not be sensitive to differential
(b2 weeks) use of psychotropic drugs (HC) or change
interference in SCZ. Clearly these results from this
in use of antipsychotic medication (SCZ), and
single study underscore the need for increased
prescribed medications with known deleterious cog-
research of the PLC phenomenon in SCZ.
nitive effects (i.e., tricyclic antidepressants, anticholi-
In sum, this study’s purpose was to investigate
nergics). Three patients prescribed benzodiazepines
mnemonic strategy use in SCZ via PLC, for which
(bas neededQ) and who abstained from these for at
deficient organizational retrieval processes would lead
least 3 days prior testing were accepted, as were six
to less interference, a result not accounted for by a
patients prescribed serotonin specific re-uptake inhib-
difficulty confound. Given the importance of list
itors and one prescribed bupropion for depressive
structure for both general recall and PLC effects, we
symptoms. Confirmation of SCZ diagnoses and
B.K. Christensen et al. / Schizophrenia Research 85 (2006) 1–11
screening of HC participants were made via the
relative impairment of declarative memory, however,
Structured Clinical Interview for DSM-IV-TR Axis I
measures of verbal and visual memory were inferior
in SCZ. Nonetheless, both groups’ mean performance
was in the average range across these measures.
participants were provided compensation of $10.00/h.
Descriptive information for the SCZ group is
provided in As shown in the groupsdid not differ significantly with regards to sex, age, or
Three list types were constructed: (a) unrelated; (b)
education; but, expectedly, the SCZ group had lower
scrambled (semantically related words in random
levels of competitive employment. Symptom ratings
order, without replacement); and (c) blocked (clus-
confirmed that the SCZ group was clinically stable with
tered by category). The organized lists (b, c) were
respect to patient norms (but reported greater
derived from 24 of the taxonomic lists in
psychopathological symptomatology than HCs (
Montague (1969; median category potency, Md =
2). All HC participants were within normal limits on all
6.86). Eight words per category were selected,
symptom measures (save one scoring in the mildly
omitting the two highest frequency exemplars to
elevated range on the depression and stress scales).
reduce guessing biases. For each SCZ–HC pair, fourlists (designated Blocked sets A and B and Scrambled
sets A and B), comprised of eight words selectedrandomly from six categories (i.e., 48 words per list),
Assessment of general intelligence failed to reveal
were created. Unrelated sets A and B (48 words each)
were obtained from the MRC PsycholinguisticsDatabase (to match the psycholinguis-tic characteristics of the categorized lists (3–10 letters;
concreteness 426–645; imagability 461–640; written
Frequencies and medians (ranges) of SCZ patient characteristics
frequency b 203). The final 96 nouns randomly
selected from this pool further met requirements that
they could not be easily grouped into semantic
categories and did not belong to any categories used
in the organized lists. Each of the six sets was
presented twice in a row during the learning phase to
3 (loxapine, zuclopenthixol,perphenazine + methotrimeprazine)
aid encoding, but such that no two words followed
each other in both presentations, in order to negate the
use of serial order as a mnemonic strategy. Scrambled
lists also required that words from the same category
did not immediately follow each other. Additionally,
blocked lists were formed such that adjacent pairs of
categories differed between study presentations. All
Abbreviations: AIMS = Abnormal Involuntary Movement Scale
random-order procedures were conducted on an
individual SCZ–HC pair-wise basis (i.e., 30 series of
Rating Scale; CPZe = Clorpromazine equivalents (
Butler and Jeffries, 2004); DDD = defined daily dose (
Sets A and B for each list type were counter-
2005); PANSS = Positive and Negative Symptom Scale (
balanced within groups to either the free (FR) or cued
a Two patients had been neuroleptic free for several weeks.
recall (QR) condition. Free recall sheets consisted of
b Includes one or both olanzapine and resperidone.
six columns of blank lines for participants’ responses.
c CPZe-values were unavailable for zuclopenthixol, perphenazine,
Sheets for the blocked and scrambled conditions
and methotrimeprazine; DDD was unavailable for methotrimepra-
provided category labels as column headings (in
zine; data include nil values from the two neuroleptic-free patients.
lower-case) in a pseudo-randomized order to limit the
One individual taking double the conventional dose of
antipsychotics scored 10 on the AIMS; the next highest value was 3.
experimental manipulation to word (as opposed to
B.K. Christensen et al. / Schizophrenia Research 85 (2006) 1–11
Table 2Demographic and clinical characteristics of the HC and SCZ groups
a,b Use of (a) meansF standard deviations (M F S.D.) or (b) medians (range) reflect normal or non-normal distributions of data, respectively, ineither group; t-test results are reported for both as these paralleled non-parametric results. c Employment status: unemployed/student/employed/retired; significant 2
reflects more (z N 2) unemployed SCZ and student HC participants.
d e data excludes four SCZ participants with incomplete ratings. Abbreviations: DASS-21 = 21-item version of the Depression, Anxiety and Stress Scale (1995); PAI = Personality Assessment Inventory (WAIS-III FSIQe = estimated full-scale intelligence quotient derived from theMatrix Reasoning and Information subtests of the Wechsler Adult Intelligence Scale—Third Edition (1997a); WMS-III = Wechsler Memory Scale—Third Edition (WRAT-3 = Wide Range Achievement Test—Third Edition(
stone, 1966); the order for blocked lists did not matchthat at study. Cued recall sheets included 30 studied
Unrelated lists were presented first, followed by
words (cues) in capital letters and 18 blanks to be
the blocked and scrambled lists in a counterbalanced
filled in with the respective target words. Cues and
order. Within each list condition, FR preceded QR. At
blanks were presented pseudo-randomly such that
encoding, participants made pleasantness judgements
adjacent words differed from their presentation at
(bLikeQ, bDislikeQ) to single words presented on a
study and no more than three cues or two blanks
computer monitor for 2 s each (ISI = 1 s). Study words
were presented consecutively; for organized lists, five
were presented in uppercase type and lowercase labels
exemplars per category were cues and three were
preceded each category in the blocked condition.
deemed targets. Three random assortments defining
Participants were also instructed to remember the
targets and cues were created for each of the
words. After each list was shown twice, a 90-s buffer
unrelated sets and the category lists and these
consisting of recall instructions plus a symbol
configurations were assigned haphazardly among
cancellation task was inserted to avoid any differential
B.K. Christensen et al. / Schizophrenia Research 85 (2006) 1–11
Slamecka, 1969). Recall of each list was then limited
ance, or sphericity. Deviation from normality was
to 7 min. For blocked and scrambled conditions this
was divided into 1-min per category (remaining
parametric results reported did not differ from trans-
categories covered), plus a seventh for any additional
recall. On QR trials, participants were instructed to
Results were evaluated at an alpha-level of .05 with
read the cues and consider them as aids.
The primary measure of interest was the number of
correctly recalled target words, equating FR and QR
measures to a score out of 18. Two additionalmeasures provided validity checks: (a) percent correct
of available words to recall (FR/48, QR/18), where
revealed main effects of all factors on target recall,
comparable results indicate appropriate randomization
Group (SCZ b HC), F(1, 54) = 6.77, p = .012, f = 0.35,
List (Unrelated b Scrambled b Blocked), F(2, 108) =
difference as a percent of total correct (QR + FR),
254.60, p b .001, f = 2.17, and Cue (QR b FR), F(1,
given the potential for general ability to influence
54) = 33.44, p b .001, f = 0.79. Importantly however,
these effects were qualified by their three-way
Chapman, 1988, 1989, 2001), including PLC con-
interaction, F(2, 108) = 4.69, p = .011, f = 0.29 (see
These analyses yielded parallel results to those with
List type revealed a two-way interaction only with
raw targets and thus, we present only the latter more
Unrelated lists, F(1, 54) = 10.77, p = .002, f = 0.45.
conventional data. For clarity, the remaining word
This finding reflected that the SCZ group was
types are termed bcuesQ (QR) or bnon-targetsQ (FR)
impaired in FR, t(54) = À 2.88, p = .006, d = À 0.77,
depending solely on the cuing condition under which
but that a greater interference effect among HCs
resulted in equivalent Unrelated-QR performances,
Target recall revealed no significant outliers or
t(54) = À 0.07, p = .944, d = À 0.02. Similar analyses of
violations regarding normality, homogeneity of vari-
Scrambled and Blocked Lists revealed only main
Fig. 1. Mean recall of target words (+ S.E.) in HC and SCZ groups during free recall (FR) and cued recall (QR) conditions at each of the threelevels of semantic organization. Note the attenuated interference of part-list cues in SCZ for the most difficult unrelated-list condition.
B.K. Christensen et al. / Schizophrenia Research 85 (2006) 1–11
effects of Cue and Group; that is, although overall
represented the degree to which each participant’s
recall was reduced in SCZ, similar PLC interference
QR performance deviated from that predicted from
was observed in the context of organized lists.
his/her FR score. The mean zQR for the HC group is
In addition to within-list effects, it was of interest
thus zero and the z-scores for SCZ participants
to examine the effects of list organization. Main
indicate their deviation from the HC expected values.
effects of Group and List were maintained in separate
Regression of HC QR on FR scores confirmed
significant, positive, and medium to large associa-
organization aided FR of both groups similarly, F(2,
tions, Unrelated R2 = .27, p = .005, f 2 = 0.37, Scram-
108) = 0.07, p = .934, f = 0.03. In contrast, a Group x
bled R2 = .67, p b .001, f 2 = 2.03, Blocked R2 = .17,
List interaction, F(2, 108) = 6.01, p = .003, f = 0.33,
p = .028, f 2 = 0.20. A two-way ANOVA of zQR-scores
reflected a SCZ deficit in QR only with organized
revealed identical effects of List and Group x List
interaction, both Fs(2, 108) = 3.91, ps = .023. Thisinteraction supported the previous raw target analyses
and indicated better QR performance in SCZ thanexpected from the HC regression line in the Unrelated
There was no overall difference in error production
condition, t(27) = 2.52, p = .018, d = 0.48. Inter-corre-
between the SCZ (Md = 6.00, range: 0–23) and HC
lations further supported a division between Unrelated
groups (Md = 6.50, range: 0–39), t(54) = 0.34, p = .733,
and organized PLC interference: there was no relation
d = 0.09. Moreover, the groups did not differ signif-
between Unrelated and Scrambled, HC, r(28) b .01,
icantly in their rates of any specific error types and
p = .996, SCZ, r(28) = À .25, p = .209, or Blocked
thus, these are primarily of task-related interest. Most
zQR’s, HC, r(28) = .01, p = .957, SCZ, r(28) = .16,
common were semantic intrusions in organized-list
p = .408. In contrast, correlations between the orga-
recall (170 by 86% of HC, 124 by 75% of SCZ),
nized lists were significant, positive, and large, HC,
which proved sensitive to PLC interference (FR N QR),
r(28) = .51, p = .005, SCZ, r(28) = .50, p = .006.
F(1, 54) = 4.30, p = .043, f = 0.28. Intrusions of irrele-
Correlations among the PLC zQR scores with
vant/unrelated words were also common (48 and 62 by
demographic, diagnostic, symptom, medication, and
61% of both HC and SCZ, respectively), the majority
cognitive measures only revealed notable relations
(88%) occurring with Unrelated lists. Thus, a majority
between increased ratings of depression, anxiety, and
of participants produced intrusions in recall that may
1995) with greater PLC interference (lower zQR’s)
among HC participants on the organized lists
also somewhat frequent (13 by 32% of HC, 23 by 43%
(r’s b À.40). It is not immediately clear how to
of SCZ), indicating that participants wrote down cue
interpret these relations or why they were only found
words that were printed in front of them. Other types of
in the HC group; replication of these observations
may prove interesting for future study.
3.3. Individual differences and correlational analyses
Last, it was of interest to assess individual differ-
ences in PLC effects and their correlations with other
Strategic and mnemonic abilities in SCZ were
sample characteristics. The FR–QR interference effect
investigated using PLC at three levels of semantic
was of most interest in this regard. Because of
organization. Cuing at retrieval and increasing within-
problems with raw difference scores, we instead used
list semantic structure were successful in interfering
standardized residualized scores as suggested by
and facilitating recall output, respectively. An overall
deficit in SCZ across PLC and neuropsychological
mance of HC participants was first regressed on their
measures of memory was also expected. Most
FR scores, then these results were used to compute
importantly, the three-way interaction reflected a
standardized residuals (zQR) for both groups that
differential PLC effect in the unrelated-list condition
B.K. Christensen et al. / Schizophrenia Research 85 (2006) 1–11
only. In the context of maximal requirements for
hypothesis that persons with SCZ are particularly less
effortful, self-initiated, strategic organization, the SCZ
apt to self-generate and employ effortful organized
group demonstrated impaired FR but equivalent
retrieval strategies. That is, the SCZ results indicate
performance to the HC group in the more difficult
use of an initially less efficient and less organized
QR condition. That is, the SCZ group was less
strategy during FR, which only reduces to an equally
disrupted by PLC interference, consistent with hy-
inefficient strategy as the HC group during QR (see
pothesized deficits in the aforementioned abilities. In
In sum, the current results are consistent with
contrast, the SCZ group showed a similar ability to
previous findings and strategy disruption accounts of
that of HC participants to benefit from the semantic
organization provided by scrambled and blocked lists,
suggest that increased organization according to pre-
and furthermore, showed a similar PLC effect under
existing semantic representations allows for increased
these conditions. In contrast to the parallel improve-
flexibility and automaticity at the item (word) level,
yet within a more consistent hierarchical (categorical)
from unrelated to scrambled recall in SCZ. A key
framework both work to dprotectT from interference.
difference was our provision of labels and forced
As reviewed, study of PLC with special popula-
category recall, both known to facilitate FR (
tions and the underlying neural mechanisms is
et al., 1997; Incisa della Rocchetta and Milner, 1993;
limited. In contrast to enhanced interference in
Roediger, 1978; Tulving and Pearlstone, 1966).
Together these studies show that SCZ participants
can benefit from organization, but only when this
1993), a left-temporal/hippocampal group showed
structure is explicitly provided at test, and support a
utilization deficit in SCZ, where the cognitive
and Milner, 1993) with organized lists. Our SCZ
resources required to organize/maintain mnemonic
results are most consistent with the latter, but
particularly those from our unrelated condition.
Despite prefrontal and temporal contributions to
This study is unique in concurrently assessing PLC
across unrelated and categorized lists within one
2003; Weiss and Heckers, 2001), we replicated
experiment, let alone within participants. Interference
was most pronounced among HCs in recall of
differential interference with organized lists. The
unrelated compared to organized lists, consistent with
opposing effects of PLC suggested above may
account for this lack of overt difference given
man, 1991). The ability to form relational associations
combined frontal–temporal dysfunction in SCZ. An
alternative functional–anatomic distinction is that
between archicortical (e.g., dorsal–lateral prefrontal,
provide some descapeT from interference. The similar
hippocampus) and paleocortical (e.g., orbital–frontal,
effects across scrambled and blocked conditions
suggest that both groups employed similar categorical
where preferential archicortical dysfunction is sup-
representations to each other and to those intended.
The observed semantic intrusions, and their suscepti-
the archicortical trend is associated with controlled,
bility to interference, further demonstrate participants’
effortful, volitional, goal-directed behaviour as re-
quired for maximizing FR scores and susceptibility to
Marsh et al., 2004) and can be attributed to false
PLC interference in the unrelated condition. Con-
memories elicited by semantic processes at retrieval
versely, the paleocortical trend functions in a more
automatic fashion towards which the highly struc-
unrelated recall in HCs is consistent with their use of
tured, organized list conditions likely catered. This
more idiosyncratic strategies (e.g., imagery, forming
duality is consistent with dependence of PLC inter-
FR and PLC effect with unrelated lists support the
1991), lack of interference on more automatic tasks
B.K. Christensen et al. / Schizophrenia Research 85 (2006) 1–11
for their assistance with stimuli preparation, partici-
familiarity-based gist retrieval versus conscious rec-
pant recruitment/testing, and data management. Por-
tions of this research were presented at the biennial
meeting of the International Congress on Schizophre-
The impetus for the current investigation was to
nia Research, Savannah, GA, 2005. This research was
examine strategic retrieval deficits unencumbered by a
supported, in part, with a grant received from the
difficulty confound. As predicted, this result was
Canadian Psychiatric Research Foundation.
obtained specifically with unrelated lists, whereinterference in HCs was greatest and SCZ least (1). Comparing across lists also indicated a consistent
deficit in SCZ–FR, at the varying levels of difficultyand retrieval contexts, likely reflecting a more general
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• Copyright ᮊ by Walter de Gruyter • Berlin • New York. DOI 10.1515/JPM.2005.087 A clinical evaluation of controlled-release dinoprostone for cervical ripening – a review of current evidence in hospital and outpatient settings Werner Rath* many clinical circumstances, such as pregnancy-inducedhypertension, prelabor rupture of the membranes, sus-Department Obstetrics and Gynecology
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