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Cited by 198Memory and Neural MechanismsNeurotransmitter Receptor Influence on BehaviorNeuroscience and Neuropharmacology Research

Impaired Extinction Retention in Adolescent Rats: Effects of D-Cycloserine

Open access
McCallum, Jessica, Kim, Jee Hyun, Richardson, Rick·2010·Neuropsychopharmacology
DOI 10.1038/npp.2010.92PMC PMC3055297
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Abstract

The developmental trajectory of the prefrontal cortex (PFC) in both rats and humans is nonlinear, with a notable decline in synaptic density during adolescence, potentially creating a 'natural lesion' preparation at this age. Given that the PFC is critically involved in retention of extinction of learned fear in adult humans and rodents, the present study examined whether adolescent rats exhibit impaired extinction retention. The results of experiment 1 showed that adolescent rats were impaired in extinction retention, compared with both younger and older rats. The partial NMDA receptor agonist D-cycloserine (DCS) improved extinction retention in adolescent rats (experiment 2), but only if administered immediately after extinction training (experiment 3). In addition, providing extended extinction training improved extinction retention in adolescent rats in a manner similar to that of DCS (experiment 4). The results of this study show that adolescent rats exhibit impaired extinction retention, and that this can be reduced through either DCS or extended extinction training. These novel findings have potential implications for clinical treatments of fear and anxiety disorders in adolescent patients.

AI snapshot

Written from the paper’s full text.

TL;DR

Adolescent (35-day-old) rats showed poorer retention of fear extinction than younger or older rats, with nearly complete return of fear 24 h after extinction. Immediate post-extinction D-cycloserine or doubled extinction training reduced this impairment.

Key findings

  • In experiment 1, 35-day-old rats had significantly higher CS-elicited freezing at test than 24- or 70-day-old rats, F(2,37)=7.62, p<0.05; recovered fear was 105% in adolescents versus 45% and 57% in the younger and older groups.
  • In experiment 2, 15 mg/kg D-cycloserine given immediately after extinction reduced recovered fear to 64%, compared with 90% after saline; 5 mg/kg was ineffective at 95% recovery.
  • In experiment 3, immediate 15 mg/kg D-cycloserine reduced recovered fear to 43%, whereas saline produced 100% recovery and D-cycloserine given 4 h later produced 105% recovery.
  • In experiment 4, saline-treated adolescents showed 106% recovered fear, while immediate D-cycloserine and doubled extinction training (60 instead of 30 trials) produced 31% and 23% recovery, respectively, with no difference between those two treatments.

Methods

  • Male Sprague-Dawley rats were fear conditioned with a white-noise CS and a 0.6 mA, 1 s shock, then extinguished 24 h later with 30 CS presentations in experiments 1–3 or 30 versus 60 presentations in experiment 4; testing occurred 24 h after extinction.
  • Experiment 1 compared rats aged 24, 35, and 70 days at extinction; experiments 2–4 used 35-day-old rats and injected saline or D-cycloserine subcutaneously after extinction, with doses of 0, 5, or 15 mg/kg in experiment 2 and 15 mg/kg immediate versus 4 h delayed in experiment 3.
  • Freezing was scored by time sampling every 3 s, with a second blind observer for 30% of test data; analyses used mixed-model ANOVA with trial as repeated measure and age/group as between-subjects factor, plus Tukey HSD comparisons. Rats freezing below 30% in the first extinction block or identified as outliers were excluded; 15 of 139 rats failed the acquisition criterion and 2 were outliers.

Limitations

  • The paper states that the exact age at which impaired extinction retention emerges or disappears was not tested, that systemic D-cycloserine administration prevents conclusions about whether effects occur in prefrontal cortex, amygdala, or both, and that all animals were male, leaving female effects unknown.
  • The paper also states that extension to human adolescents remains to be tested.
  • Evident from the text: the adolescent group was defined only as 35 days old, so the findings may not capture the full adolescent period; the study did not directly measure neural activity, and the clinical implications are speculative.

Model-written summary. Check it against the paper before relying on it.

Integrity signals

Registry

Crossref · 10.1038/npp.2010.92

Cites

23 of 23 references verified0 citation errors · 0 not checkable

Statistics

Nothing to recompute.

Claims the paper makes

0 of 38 cited sources checked · 0 supported · 0 flagged

  • Findingown data

    In adolescent rats, 5 mg/kg D-cycloserine was ineffective at improving extinction retention.

    “A lower dose of DCS (5 mg/kg) was ineffective (95% recovery).”
    Quote in the paperSubstantial claim
  • Findingown data

    In experiment 1, 35-day-old rats had significantly higher CS-elicited freezing at test than 24-day-old or 70-day-old rats.

    “35-day-old rats had significantly higher levels of CS-elicited freezing than did 24-day-old rats (po0.01) or 70-day-old rats (po0.05).”
    Quote in the paperSubstantial claim
  • Findingown data

    In adolescent rats, D-cycloserine administered 4 h after extinction training did not improve extinction retention.

    “Injecting DCS 4 h after extinction did not reduced the amount of fear recovery at test the following day (105% recovery).”
    Quote in the paperSubstantial claim
  • Findingown data

    A lower dose of DCS (5 mg/kg) was ineffective in alleviating impaired extinction retention in adolescent rats.

    “a lower dose of DCS (5 mg/kg) was ineffective.”
    Quote in the paperSubstantial claim
  • Findingown data

    In experiment 3, there were no group differences in pre-CS freezing at test.

    “There were no group differences in pre-CS freezing levels, F (2, 27) ¼ 1.11, p40.1; see Table 1.”
    Quote in the paperNot a substantial claim
  • May combine two claims. 25
  • Classified as probably not a substantial claim. 14
  • The quote only partly states this claim. 1

  • May combine two claims.

    Findingown data

    In experiment 2, there were no group differences in pre-CS freezing at extinction or test.

    “The groups did not differ in levels of pre-CS freezing, Fo1; see Table 1.”
    • Also stated in: § Conditioning. · plain
      “The groups did not differ in levels of pre-CS freezing, Fo1.0; see Table 1.”
    Quote in the paperNot a substantial claim

  • May combine two claims.

    Findingown data

    Across experiments 1-4, adolescent rats failed to retain extinction memory over 24 hours, exhibiting essentially complete recovery of fear at test (105, 90, 100, and 106 percent of the first extinction block).

    “The results of experiments 1-4 consistently show that adolescent rats fail to retain an extinction memory over a 24-h period.”
    • Also stated in: § DISCUSSION · plain
      “exhibited a comparable and essentially complete recovery of fear at test the following day (ie, 105, 90, 100, and 106% recovery of fear, as compared with the first block of extinction trials, in experiments 1-4, respectively).”
    Quote in the paperSubstantial claim

  • May combine two claims.

    Findingown data

    In experiment 4, extinction was successful, with freezing decreasing across blocks, and no effect of group or group-by-block interaction.

    “All groups showed high levels of CS-elicited freezing in the first block and substantially less freezing by the fifth block, F (4, 104) ¼ 63.42, po0.001; see Figure 4c.The effect of group, and the group-by-block interaction, was not significant, Fso1.”
    Quote in the paperNot a substantial claim

  • May combine two claims.

    Findingown data

    In experiment 2, extinction was successful, with freezing decreasing across blocks, and no effect of group or group-by-block interaction.

    “all groups exhibited high levels of CS-elicited freezing in the first block of extinction, which decreased substantially by the last block.Analysis of variance revealed a significant effect of block, F (4, 132) ¼ 46.49, po0.001.The effect of group, and the group-by-block interaction, was not significant (Fso1).”
    Quote in the paperNot a substantial claim

  • May combine two claims.

    Findingown data

    In experiment 3, conditioning was successful, with freezing increasing across trials, and no effect of group or group-by-trial interaction.

    “conditioning was successful.Statistical analysis confirmed that there was a significant effect of trial, with levels of freezing increasing across trials, F (2, 54) ¼ 70.39, po0.001.The effect of group, and the group-by-trial interaction, was not significant, (Fso1).”
    Quote in the paperNot a substantial claim

  • Probably not a substantial claim: may not pass S1 (asserted), S3 (load-bearing), S4 (based).

    Findingown data

    In experiment 4, rats given D-cycloserine and rats given double extinction training did not differ in CS-elicited freezing at test.

    “the latter two groups did not differ (p40.1).”
    Quote in the paperNot a substantial claim

  • May combine two claims.

    Findingown data

    In experiment 1, adolescent rats showed complete recovery of fear (105%), while 24-day-old and 70-day-old rats showed 45% and 57% recovery, respectively.

    “adolescent rats exhibited complete recovery, (105% recovered fear), whereas the other groups exhibited more modest and comparable levels of fear recovery (45% recovery for the 24-day-old rats and 57% recovery for the 70-day-old rats).”
    Quote in the paperSubstantial claim

  • May combine two claims.

    Findingown data

    DCS at 15 mg/kg injected immediately after extinction enhances extinction retention, reducing freezing at test, in adolescent rats.

    “Experiment 2 then showed that this impairment in extinction retention in adolescent rats could be alleviated by injecting 15 mg/kg of DCS immediately after the extinction session”
    • Also stated in: § DISCLOSURE · plain
      “Immediate injection of DCS resulted in significantly less freezing at test compared with the saline control group in adolescent rats.”
    • Also stated in: § DISCLOSURE · plain
      “Adolescent rats in the saline control group exhibited significantly higher levels of freezing at test compared with rats given DCS after extinction”
    Quote in the paperSubstantial claim

  • May combine two claims. The quote only partly states this claim.

    Findingown data

    In experiment 4, there were no group differences in pre-CS freezing at extinction or test.

    “There were no group differences in pre-CS levels of freezing, F (2, 26) ¼ 2.15, p40.1; see Table 1.”
    Quote in the paperNot a substantial claim

  • May combine two claims.

    Findingown data

    In experiment 2, rats given the low dose of D-cycloserine did not differ from saline-treated rats or from rats given the high dose.

    “The rats given the low dose of DCS did not differ from rats given saline (p40.1) or from those given the high dose of DCS (p40.05).”
    Quote in the paperSubstantial claim

  • Probably not a substantial claim: may not pass S1 (asserted), S3 (load-bearing), S4 (based).

    Findingnone given

    In experiment 4, the effect of extended extinction training on extinction retention did not differ from that of D-cycloserine.

    “the latter two groups did not differ (p40.1).”
    Quote in the paperNot a substantial claim

  • May combine two claims.

    Findingown data

    In experiment 2, conditioning was successful, with freezing increasing across trials, and no effect of group or group-by-trial interaction.

    “conditioning was successful.Statistical analysis confirmed that there was a significant effect of trial, with levels of freezing increasing across trials, F (2, 66) ¼ 52.49, po0.001.The effect of group, and the group-by-trial interaction, was not significant, (Fso1).”
    Quote in the paperNot a substantial claim

  • May combine two claims.

    Findingown data

    In experiment 3, extinction was successful, with freezing decreasing across blocks, and no effect of group or group-by-block interaction.

    “all groups exhibited high levels of CS-elicited freezing in the first block and substantially less freezing by the last block, F (4, 104) ¼ 48.44, po0.001.The effect of group, and the group-by-block interaction, was not significant (Fso1).”
    Quote in the paperSubstantial claim

  • May combine two claims.

    Findingown data

    In experiment 4, conditioning was successful, with freezing increasing across trials, and no effect of group or group-by-trial interaction.

    “conditioning was successful.Statistical analysis confirmed that there was a significant effect of trial, with levels of freezing increasing across trials, F (2, 56) ¼ 51.69, po0.001.The effect of group, and the group-by-trial interaction, was not significant, (Fso1).”
    Quote in the paperNot a substantial claim

  • May combine two claims.

    Premisecitation

    Depression of prefrontal cortex synaptic efficacy does not affect acquisition of fear or within-session extinction.

    “depression of PFC synaptic efficacy has no effect on either acquisition of fear or within-session extinction (ie, the decrease in fear across the repeated presentations of the fear-eliciting stimulus)”
    Quote in the paperSubstantial claim0 of 1 sources checked
    • cites Herry and Garcia, 2003

      Not checked in the free run.

  • May combine two claims.

    Premisecitation

    The developmental trajectory of the prefrontal cortex in rats and humans is nonlinear, with a decline in synaptic density or volume during adolescence.

    “The developmental trajectory of the prefrontal cortex (PFC) in both rats and humans is nonlinear, with a notable decline in synaptic density during adolescence, potentially creating a 'natural lesion' preparation at this age.”
    • Also stated in: § Abstract · plain
      “the developmental trajectory of PFC in both rats and humans is largely nonlinear (Geidd, 2004;Gogtay et al, 2004;Shaw et al, 2008), with a decline in volume during adolescence.”
    Quote in the paperSubstantial claim0 of 3 sources checked
    • cites Geidd, 2004 source

      Not checked in the free run.

    • cites Gogtay et al, 2004 source

      Not checked in the free run.

    • cites Shaw et al, 2008 source

      Not checked in the free run.

  • Classified as probably not a substantial claim.

    Premisecitation

    Many anxiety disorders emerge during adolescence.

    “many anxiety disorders emerge during adolescence (Kessler et al, 2005)”
    Quote in the paperSubstantial claim0 of 1 sources checked
    • cites Kessler et al, 2005 source

      Not checked in the free run.

  • Probably not a substantial claim: may not pass S3 (load-bearing).

    Premisecitation

    NMDA is not involved in extinction in preweanling rats.

    “NMDA is not involved in extinction in preweanling rats (Langton et al, 2007)”
    Quote in the paperNot a substantial claim0 of 1 sources checked
    • cites Langton et al, 2007

      Not checked in the free run.

  • May combine two claims.

    Premisecitation

    Rats with prefrontal cortex lesions have impaired memory of extinction when tested the following day, with greater return of fear than controls.

    “lesioned rats have impaired memory of extinction when tested the following day; that is, their fear returns more than that observed in controls (Quirk et al, 2000).”
    Quote in the paperSubstantial claim0 of 1 sources checked
    • cites Quirk et al, 2000 source

      Not checked in the free run.

  • Probably not a substantial claim: may not pass S3 (load-bearing).

    Premisecitation

    The decline in prefrontal cortex volume during adolescence is due to reorganization of synaptic connections.

    “This decline in volume is due to a 'reorganization' of synaptic connections (Blakemore and Choudhury, 1999)”
    Quote in the paperNot a substantial claim0 of 1 sources checked
    • cites Blakemore and Choudhury, 1999 source

      Not checked in the free run.

  • May combine two claims.

    Premisecitation

    Preweanling rats do not show reinstatement or renewal of extinguished fear.

    “postnatal day 16 rats do not exhibit either reinstatement (Kim and Richardson, 2007a) or renewal of extinguished fear (Kim and Richardson, 2007b;Yap and Richardson, 2007).”
    Quote in the paperNot a substantial claim0 of 3 sources checked
    • cites Kim and Richardson, 2007a

      Not checked in the free run.

    • cites Kim and Richardson, 2007b

      Not checked in the free run.

    • cites Yap and Richardson, 2007

      Not checked in the free run.

  • May combine two claims.

    Premisecitation

    Lesions of the prefrontal cortex in rats do not affect the expression of learned fear or the within-session rate of extinction.

    “Lesions of PFC in rats affect neither the expression of learned fear nor the within-session rate of extinction (Lebron et al, 2004).”
    Quote in the paperSubstantial claim0 of 1 sources checked
    • cites Lebron et al, 2004

      Not checked in the free run.

  • Classified as probably not a substantial claim. May combine two claims.

    Premisecitation

    Adolescent mice exhibit more rapid fear conditioning than adult mice, but no age differences in extinction.

    “adolescent mice exhibited more rapid fear conditioning compared with adult mice, but no age differences were found for extinction (Hefner and Holmes, 2007).”
    Quote in the paperSubstantial claim0 of 1 sources checked
    • cites Hefner and Holmes, 2007

      Not checked in the free run.

  • Probably not a substantial claim: may not pass S3 (load-bearing).

    Study design and conductnone given

    All animals used in these experiments were male.

    “all the animals used in these experiments were male.”
    Quote in the paperNot a substantial claim

  • Probably not a substantial claim: may not pass S3 (load-bearing). May combine two claims.

    Study design and conductown data

    The study did not test the exact age at which impaired extinction retention first emerges or when it no longer occurs.

    “We did not test to determine the exact age that this impaired extinction retention first emerges or when it no longer occurs”
    Quote in the paperNot a substantial claim

  • Probably not a substantial claim: may not pass S3 (load-bearing). May combine two claims.

    Study design and conductown data

    DCS was given systemically in the present study, so conclusions about the neural bases of the observed effects are not possible.

    “In the present study, DCS was given systemically, so conclusions about the neural bases of the observed effects are not possible.”
    Quote in the paperNot a substantial claim

  • Probably not a substantial claim: may not pass S3 (load-bearing).

    Study design and conductown data

    In experiment 3, because of a significant group difference in pre-CS freezing at extinction, extinction data were analyzed with analysis of covariance using pre-CS freezing as the covariate.

    “Analysis of pre-CS freezing levels revealed a significant group difference, F (2, 27) ¼ 3.87, po0.05, because of the rats in the saline condition having higher baseline freezing levels than rats in the DCS-immediate condition (see Table 1).Because of these differences, extinction data were analyzed by analysis of covariance with pre-CS freezing as the covariant.”
    Quote in the paperNot a substantial claim

  • Probably not a substantial claim: may not pass S3 (load-bearing).

    Study design and conductcitation

    The conditioning, extinction, and test procedures were the same as those used in previous developmental studies on extinction of learned fear.

    “The conditioning, extinction, and test procedures are those that we have used in previous developmental studies on extinction of learned fear (eg, Kim and Richardson, 2007a, b).”
    Quote in the paperNot a substantial claim0 of 2 sources checked
    • cites Kim and Richardson, 2007a

      Not checked in the free run.

    • cites Kim and Richardson, 2007b

      Not checked in the free run.

  • May combine two claims.

    Premisecitation

    The prefrontal cortex undergoes substantial restructuring during adolescence, to the point that it might even be seen as a natural lesion.

    “and (2) undergoes substantial restructuring during adolescence (Blakemore and Choudhury, 1999), to the point that it might even be seen as a 'natural lesion'.”
    Quote in the paperSubstantial claim0 of 1 sources checked
    • cites Blakemore and Choudhury, 1999 source

      Not checked in the free run.

  • May combine two claims.

    Interpretationown data

    The poor retention of extinction in adolescent rats can be completely overcome by either doubling the amount of extinction training or by injecting DCS immediately after extinction.

    “Importantly, the results reported here also suggest that the poor retention of extinction in adolescent rats can be completely overcome by either doubling the amount of extinction training or by injecting the NMDA receptor partial agonist DCS immediately after extinction.”
    Quote in the paperSubstantial claim

  • Probably not a substantial claim: may not pass S3 (load-bearing). May combine two claims.

    Study design and conductown data

    In total, 15 of 139 rats failed to acquire the CS-US association and two were statistical outliers.

    “In all, 15 out of 139 rats failed to acquire the CS-US association and two were statistical outliers.”
    Quote in the paperNot a substantial claim

  • Classified as probably not a substantial claim. May combine two claims.

    Study design and conductreasoning

    Rats that failed to meet a learning criterion (mean freezing <30% during the first extinction block) or were statistical outliers (>2.5 SD from group mean) were excluded from analyses.

    “Any rat that had a mean freezing level o30% during the first block of extinction was excluded from all analyses.Further, any rats that were statistical outliers at test (performance more than 2.5 SDs away from the group mean) were excluded.”
    Quote in the paperSubstantial claim

  • Probably not a substantial claim: may not pass S3 (load-bearing). May combine two claims.

    Study design and conductown data

    A second observer, unaware of experimental condition, scored a random sample of 30% of test data, and interrater reliability was high in each experiment.

    “A second observer, unaware of the rat's experimental condition, scored a random sample of 30% of the test data.Interrater reliability was high in each experiment (rs40.94).”
    Quote in the paperNot a substantial claim
33 of 33

  • The authors state this as an assumption.

    The developmental decline in prefrontal cortex volume and synaptic density during adolescence produces functional impairment equivalent to a prefrontal cortex lesion.

    “This substantial decrease in PFC volume could have a significant impact on the extinction of fear.”
    “if the decreases in PFC volume during adolescence are akin to a 'natural lesion', then adolescent rats should exhibit impaired extinction retention relative to the other age groups.”

  • The paper relies on this without support.

    35-day-old rats are a valid model of human adolescence.

    “In experiment 1, rats were 24, 35, or 70 days of age (preadolescent, adolescent, and adult rats, respectively) at the time of fear extinction.”
2 of 2

Claims other papers make about this one

Each is checked against this paper’s own text: does it say what the citing paper says it does?

  • Under conditions of similar fear conditioning and within-session extinction, adolescents show impaired retention of extinction and spontaneously reinstate fear to CS presentation.

    “adolescents showed markedly impaired retention of the extinction, thereby spontaneously reinstating their fear to CS presentation (McCallum et al, 2010; Kim et al, 2011).”

    From Rewards, aversions and affect in adolescence: emerging convergences across laboratory animal and human data (2011) · cites this paper as McCallum et al, 2010

  • Recent research with rodents and humans has shown distinctive developmental profiles of blunted threat extinction recall in adolescents relative to children and adults.

    “Recent research with rodents and humans has shown distinctive developmental profiles of blunted threat extinction recall in adolescents6–11, relative to children and adults.”

    From Multimodal evidence for delayed threat extinction learning in adolescence and young adulthood (2019) · cites this paper as [6]

Self-check

Percentages, sums and reported differences re-computed from the paper’s own numbers.

  • Experiment 2 extinction degrees of freedom do not match group sizes

    Minor

    With 40 rats in three groups and five extinction blocks, the block-effect error degrees of freedom should be 4 × 37 = 148. The reported 132 instead implies fewer rats were analyzed, without a corresponding change to the stated group sizes.

    Reported 132 · recomputed 148

  • Experiment 4 conditioning degrees of freedom imply more rats than reported

    Minor

    The stated group sizes total 29 rats, giving 26 between-rat residual degrees of freedom. Across three conditioning trials, the trial-effect error degrees of freedom should be 52, not 56.

    Reported 56 · recomputed 52

2 of 2

Cites

Flagged first, then by citations

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  21. Milad MR, Wright CI, Orr SP, Pitman RK, Quirk GJ, Rauch SL (2007). Recall of fear extinction in humans activates the ventromedial prefrontal cortex and hippocampus in concert. Biol Psychiatry 62: 446–454. · DOI · Paper page
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Cited by

Sorted by citations

Authors
McCallum, J., Kim, J. H., & Richardson, R.
Affiliations
  • UNSW Sydney (AU)
  • University of Michigan (US)
Corresponding author
Richardson, Rick
ORCID
Venue
Neuropsychopharmacology
Publisher
Springer Science and Business Media LLC
Published
2010-06-30
Volume
35
Issue
10
Pages
2134-2142
ISSN
  • 0893-133X (ISSN-L)
  • 1740-634X
DOI
10.1038/npp.2010.92
PMC
PMC3055297
OpenAlex
W2052401494
Cited by
198
References
23
Citations by year
2026: 4 · 2025: 8 · 2024: 6 · 2023: 8 · 2022: 7 · 2021: 12 · 2020: 13 · 2019: 20 · 2018: 17 · 2017: 16 · 2016: 17 · 2015: 16 · 2014: 10 · 2013: 17 · 2012: 9
FWCI
8.51
Type
journal article
Language
en
Open access
Licence
www.springer.com/tdm (tdm)
Locations
  • Neuropsychopharmacology (publishedVersion)
  • Europe PMC (PubMed Central) (publishedVersion)
  • PubMed Central (publishedVersion)
  • PubMed (publishedVersion)
Funders
  • University of New South Wales
  • Australian Research Council (DP0985554)
Topics
  • Life Sciences › Neuroscience › Cognitive Neuroscience › Memory and Neural Mechanisms
  • Life Sciences › Neuroscience › Cellular and Molecular Neuroscience › Neurotransmitter Receptor Influence on Behavior
  • Life Sciences › Neuroscience › Cellular and Molecular Neuroscience › Neuroscience and Neuropharmacology Research
Keywords
extinction retention, fear extinction, adolescence, D-cycloserine, NMDA receptor, prefrontal cortex development, synaptic density, extinction training, anxiety disorders, fear disorders, rats
MeSH terms
Animals, Antimetabolites, Behavior, Animal, Conditioning, Classical, Cycloserine, Dose-Response Relationship, Drug, Extinction, Psychological, Fear, Learning Disabilities, Male, Rats, Sprague-Dawley, Rats

About these checks

Registry, retraction, Cites and statistics results are computed, not judged, with one exception: a printed reference that no index lists is read once by a model before it counts as a citation error. Claims are extracted by a model and kept only when their quote appears verbatim in the text; each cited source is then checked, with a model’s help, for whether it says what the claim relies on. Those verdicts can be wrong — read the claim’s quote and the cited source before relying on one.

Claims read by deepseek-v4.1-flash under definition version 3 (extract-v3) on 2026-10-06.

Classified by jev-1.13-20260917 (gold-guideline-v0.2) on 2026-10-06.

Statistics and arithmetic are recomputed, not judged.

Confidence bands are shown only for fields calibrated on our annotated test set. None is calibrated yet, so no band is shown.

What counts as a claim ›How we measure confidence ›How we check this ›

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