Spaced learning enhances episodic memory by increasing neural pattern similarity across repetitions

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In a 543-727 ms cluster in the right frontal region, within-item STPS was greater for subsequently remembered items than forgotten items.

“This analysis revealed a 543-727 ms cluster in right frontal region (region 2) showing a significant subsequent memory by item-specificity interaction (F (1,32)max ϭ 12.84, F clustersum ϭ 391.75, p cluster ϭ 0.03; Fig. 2 B, C).”

• Also stated in: § Subsequently remembered items showed greater item-specific STPS · plain

  “Post hoc tests showed significantly greater WI STPS for remembered items than forgotten items (F (1,32) ϭ 10.98, p ϭ 0.002), but no difference in BI STPS (F (1,32) ϭ 0.34, p ϭ 0.56).”

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

There was a 676-710 ms time window showing a spacing (short-spaced vs long-spaced) by item specificity interaction, but it did not survive Bonferroni correction.

“We also found a 676 -710 ms time window that showed a spacing (SS vs LS) by item specificity interaction (F (1,32)max ϭ 9.54, F clustersum ϭ 70.16, p cluster ϭ 0.036), but it did not survive Bonferroni correction.”

May combine two claims.

There was no significant difference between short-spaced and long-spaced conditions in hit rate or discriminability (d').

“No significant difference between SS and LS was found for either hit rate (t (32) ϭ Ϫ1.18, p ϭ 0.25) or dЈ (t (32) ϭ Ϫ0.63, p ϭ 0.53).”

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

Subsequent memory performance was not significantly associated with reaction time or response consistency during encoding.

“Three-way (spacing condition, subsequent memory performance, and repetition) repeated-measures ANOVA revealed no significant main effect of subsequent memory (remembered vs forgotten) on reaction time (F (1,32) ϭ 0.21, p ϭ 0.65), nor its interactions with other two factors (all p Ͼ 0.066)”

• Also stated in: § Spaced learning reduced repetition priming and response consistency · plain

  “Results revealed a significant main effect of spacing condition (F (2,64) ϭ 25, p Ͻ 0.0001), but no effect of subsequent memory performance (F (1,32) ϭ 1.64, p ϭ 0.21) or the interaction between spacing condition and subsequent memory performance (F (2,64) ϭ 1.4, p ϭ 0.25).”

May combine two claims.

Compared with massed learning, short-spaced learning showed significantly greater within-item STPS in the right frontal cluster (606-652 ms), but comparable between-item STPS.

“Post hoc tests revealed that, compared with MA, SS showed significantly greater WI STPS (t (32) ϭ 2.43, p ϭ 0.02), but comparable BI STPS (t (32) ϭ 0.46, p ϭ 0.66) (Fig. 2F ).”

May combine two claims.

In that right frontal cluster, within-item STPS was greater than between-item STPS only for subsequently remembered items, not for forgotten items.

“In addition, significantly greater WI than BI STPS was only found for subsequently remembered items (F (1,32) ϭ 10.8, p ϭ 0.003), but not for forgotten items (F (1,32) ϭ 1.81, p ϭ 0.19) (Fig. 2D).”

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The LPC and item-specific STPS in the right frontal region occurred at a similar time window but with different topographic distributions.

“Interestingly, they occurred at a similar time window but with different topographic distributions.”

The quote only partly states this claim.

Within-item STPS in the right frontal region (606-652 ms) partially mediated the spacing effect on memory.

“Mediation analysis showed that the WI STPS partially mediated the spacing effect on memory (indirect effect ϭ 0.0047, 95% CI ϭ 0.001-0.0093)(Fig. 3).”

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The LPC representation contained no item-specific information but was associated with memory performance.

“Third, the LPC representation contained no item-specific information but was associated with memory performance.”

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Under the MA learning condition, there were significant primacy and recency effects; trials studied in the first and last quartiles of a run were remembered better than those studied in the middle.

“There were significant primacy and recency effects under the MA learning condition; that is, trials studied in the first and last quartiles of a run were remembered better than those studied in the middle (t (32) ϭ 2.33, p ϭ 0.026).”

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The finding of greater item-specific STPS for remembered items replicates previous results from a study that used foreign characters as learning stimuli.

“This finding replicated previous results from a study that used foreign characters as learning stimuli (Lu et al., 2015).”

• cites Lu et al., 2015Not checked yet

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• AssumptionThe authors state this as an assumption: A greater within-item similarity than between-item similarity reflects item-specific encoding.

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Due to the temporal autocorrelation of the BOLD response, neural pattern similarity between two trials is affected by their temporal distance, which seriously confounds the spacing effect.

“First, due to the temporal autocorrelation of the BOLD response, the neural pattern similarity between two trials is affected by their temporal distance (Mumford et al., 2014), which seriously confounds the spacing effect.”

• cites Mumford et al., 2014Not checked yet

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Corrections for multiple comparisons were performed using nonparametric cluster-based permutation tests.

“Corrections for multiple comparisons were performed using a nonparametric statistical method based on cluster-level permutation tests implemented in Fieldtrip toolbox.”

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

Twelve additional faces were added at the beginning and end of study lists to minimize primacy and recency effects, but were not tested in the recognition task.

“To minimize the primacy and recency effects, 12 additional faces (four for each run) were added at the beginning and the end of the study lists, but were not tested in the recognition task.”

May combine two claims.

Spaced learning improves long-term memory by increasing retrieval effort and enhancing the pattern reinstatement of prior neural representations, which may be achieved by reducing the momentary retrieval strength as extended repetition lags might help eliminate the residual representation in working memory.

“These results suggest that spaced learning improves long-term memory by increasing retrieval effort and enhancing the pattern reinstatement of prior neural representations, which may be achieved by reducing the momentary retrieval strength as the extended repetition lags might help to eliminate the residual representation in working memory.”

• AssumptionThe authors state this as an assumption: A greater within-item similarity than between-item similarity reflects item-specific encoding.
• AssumptionRests on an assumption: Only condition differences in neural pattern similarity that are linked to successful memory encoding would explain the spacing effect in memory.

May combine two claims.

The LPC might not carry item-specific representations, but rather may reflect general memory-related cognitive processes.

“These results suggest that the LPC might not carry item-specific representations, but rather may reflect general memory-related cognitive processes.”

May combine two claims.

EEG provides higher temporal resolution to differentiate a 350-450 ms component reflecting retrieval strength and a 500-700 ms component containing the neural pattern similarity that supports later memory.

“Second, EEG provides higher temporal resolution to differentiate 350 -450 ms component reflecting retrieval strength (Rugg and Curran, 2007;Zhao et al., 2015), and the 500 -700 ms component containing the neural pattern similarity that supports later memory (Lu et al., 2015).”

• cites Rugg and Curran, 2007Not checked yet

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• cites Zhao et al., 2015Not checked yet

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• cites Lu et al., 2015Not checked yet

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Both the LPC that reflects general cognitive processing and the item-specific STPS in the right frontal region were associated with the spacing effect on memory.

“The above results suggest that both the LPC that reflects general cognitive processing and the item-specific STPS in the right frontal region were associated with the spacing effect on memory.”

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Pairwise comparisons between the three spacing conditions were further corrected for multiple comparisons using Bonferroni correction.

“When pairwise comparisons between the three spacing conditions were conducted, the cluster-level tests were further corrected for multiple comparisons using Bonferroni correction.”

Classified as probably not a substantial claim.

To determine whether within-item similarity reflected item-specific representations, between-item pairs were matched to within-item pairs on memory performance, spacing condition, number of repetitions, and inter-repetition interval.

“To determine whether the WI similarity reflected item-specific representations or common cognitive processes, we calculated the similarity for between-item (BI) pairs that matched the WI pairs in terms of their memory performance, spacing condition, number of repetitions (one or two), and IRI.”

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To determine whether key findings of pattern similarity were due to differences in univariate amplitude, linear mixed-effects models included EEG amplitude as a covariate.

“To determine whether our key findings of pattern similarity were due to differences in univariate amplitude, we constructed linear mixed-effects models to examine the subsequent memory effect and spacing effect, by including the amplitude as covariate.”

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Participants were not told about the subsequent memory task during the encoding phase.

“They were not told about the subsequent memory task.”

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All faces used in the study were unfamiliar to the subjects.

“All faces were unfamiliar to the subjects and were drawn from the CAS-PEAL face database (Gao et al., 2008).”

• cites Gao et al., 2008Not checked yet

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A fixed intertrial interval of 4000 ms was used in the recognition phase so that total duration was not affected by participants' response time.

“We used a fixed intertrial interval (ITI) of 4000 ms in the recognition phase so that the total duration of this phase was not affected by participants' response time, which could help to discourage the participants from making hasty responses.”

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The materials used in the three spacing conditions were fully counterbalanced across participants.

“The materials used in the three conditions were fully counterbalanced across participants.”

May combine two claims.

N400 increases with repetitions and reflects momentary retrieval strength.

“our results are consistent with previous studies showing that the N400 increased with repetitions (Henson et al., 2003;Schweinberger and Neumann, 2016) and reflected the momentary retrieval strength (Zhao et al., 2015).”

• cites Henson et al., 2003Not checked yet

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• cites Schweinberger and Neumann, 2016Not checked yet

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• cites Zhao et al., 2015Not checked yet

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Item-specific representation in visual cortex is only found during perception, whereas during memory retrieval it is found in the inferior parietal lobule and is more abstract and aligned to current goals.

“Item-specific representation in the visual cortex was only found during perception, whereas item-specific representation during memory retrieval was found in the inferior parietal lobule (Xiao et al., 2017;Favila et al., 2018) and its representation was more abstract (Jeong and Xu, 2016;Ye et al., 2016) and more aligned to current goals (Favila et al., 2018).”

• cites Xiao et al., 2017Not checked yet

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• cites Favila et al., 2018Not checked yet

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• cites Jeong and Xu, 2016Not checked yet

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LPC is related to recollection, particularly the retrieval of complex information about prior events.

“Previous studies have shown that LPC is related to recollection (Rugg and Yonelinas, 2003;Rugg and Curran, 2007;Kappenman and Luck, 2012), in particular, the retrieval of complex information about prior events.”

• cites Rugg and Yonelinas, 2003Not checked yet

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• cites Rugg and Curran, 2007Not checked yet

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• cites Kappenman and Luck, 2012Not checked yet

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Early time window representations correspond to early visual cortex; later time window representations correspond to higher-order visual cortex.

“A recent study combining MEG and fMRI suggests that, whereas the representation in the early time window corresponded to the repre-sentations in the early visual cortex, the representations in the later time window corresponded to the representations in the higher-order visual cortex (Cichy et al., 2014).”

• cites Cichy et al., 2014Not checked yet

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Representations in early and late time windows might carry distinct information and have a differential effect on long-term memory formation.

“These results also suggest that the representations in early and late time windows might carry distinct information and have a differential effect on long-term memory formation.”

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According to the new theory of disuse, an item in memory can be characterized by two strengths: storage strength and retrieval strength.

“According to the new theory of disuse (Bjork and Bjork, 1992;Bjork, 1999), an item in memory can be characterized by two”

• cites Bjork and Bjork, 1992Not checked yet

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• cites Bjork, 1999Not checked yet

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N400 supports familiarity judgment.

“previous studies also suggested that the N400 supported the familiarity judgment (Curran and Cleary, 2003;Rugg and Curran, 2007;Kutas and Federmeier, 2011).”

• cites Curran and Cleary, 2003Not checked yet

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• cites Rugg and Curran, 2007Not checked yet

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• cites Kutas and Federmeier, 2011Not checked yet

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As the memory trace is updated, its similarity to other items decreases and becomes more distinguishable during retrieval.

“As the memory trace is updated, its similarity to other items decreases and becomes more distinguishable during retrieval.”

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Introducing variance in the massed repetitions could reduce the momentary retrieval strength, enhance the retrieval of later abstract representations, and improve memory.

“Introducing variance in the massed repetitions could reduce the momentary retrieval strength, enhance the retrieval of later abstract representations, and improve memory.”

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

Some behavioral studies found that the spacing effect could be effective in terms of days or months.

“Some behavioral studies found that the spacing effect could be effective in terms of days or months (Cepeda et al., 2008).”

• cites Cepeda et al., 2008Not checked yet

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When study-phase retrieval fails, recall depends on the new trace and performance is impaired.

“Therefore, the probability of recalling the item mostly depended on the new trace and the performance is thus impaired (Raaijmakers, 2003).”

• cites Raaijmakers, 2003Not checked yet

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The long-spaced interval might not be long enough to bend the curve.

“It seems that this long-spaced interval might not be long enough to bend the curve.”

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According to the differentiation model of memory, repeated exposure to an item results in the storage of additional information in the single memory trace established during the first exposure.

“According to the differentiation model of memory (Kılıc ¸et al., 2017), repeated exposure to an item results in the storage of additional information in the single memory trace established during the first exposure.”

• cites Kılıç et al., 2017Not checked yet

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The design results in an imbalance in the temporal distributions of repetitions under different spacing conditions, which might have some effect on memory performance.

“In addition, this design unavoidably results in an imbalance in the temporal distributions of repetitions under different spacing conditions, which might have some effect on memory performance.”

May combine two claims.

Early pattern similarity might reflect more sensory information that did not predict later memory, whereas later item-specific pattern similarity might reflect more abstract information and contribute to long-term memory.

“Because perceptual details might decay more rapidly than more abstract information such as semantics (Craik and Tulving, 1975), the early pattern similarity might reflect more sensory information that did not predict later memory, whereas the later item-specific pattern similarity might reflect more abstract information and contribute to long-term memory.”

• cites Craik and Tulving, 1975Not checked yet

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Introducing variance under the spaced condition could increase the chance of retrieval failure, in which case a new trace might be formed.

“However, introducing variance under the spaced condition could increase the chance of retrieval failure (Verkoeijen et al., 2005;Cepeda et al., 2006), in which case a new trace might be formed.”

• cites Verkoeijen et al., 2005Not checked yet

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• cites Cepeda et al., 2006Not checked yet

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The optimal interval varies in different learning tasks, different repetition intervals, and different retention lags.

“In addition, the optimal interval also varied in different learning tasks, different repetition intervals, and different retention lags (Cepeda et al., 2006;Pashler et al., 2009;Toppino and Gerbier, 2014).”

• cites Cepeda et al., 2006Not checked yet

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• cites Pashler et al., 2009Not checked yet

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• cites Toppino and Gerbier, 2014Not checked yet

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The mechanism accounts for the inverted U-shaped relationship between lag and memory, as too long a lag could result in retrieval failure.

“This mechanism could also account for the inverted U-shaped relationship between lag and memory (Verkoeijen et al., 2005;Cepeda et al., 2006), as too long a lag could also result in retrieval failure.”

• cites Verkoeijen et al., 2005Not checked yet

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• cites Cepeda et al., 2006Not checked yet

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

Serial position and spacing might interact to affect memory performance, which could potentially confound the result.

“This sug-gests that the serial position and spacing might interact to affect memory performance, which could potentially confound the result.”

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

Repetition priming might be a result of residual working memory representation, which might hinder later pattern reinstatement and impair memory.

“Although our results suggest that repetition priming might be a result of residual working memory representation, which might hinder later pattern reinstatement and impair memory”

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The results highlight the complex interactions of multiple memory processes and representations in determining memory performance.

“These results highlight the complex interactions of multiple memory processes and representations in determining memory performance.”

May combine two claims.

Better memory was associated with greater STPS that occurred at a late time window and spacing enhanced memory by increasing the STPS.

“Contrary to the encoding variability hypothesis, better memory was associated with greater STPS that occurred at a late time window and spacing enhanced memory by increasing the STPS.”