Induced oscillatory brain responses under virtual reality conditions in the context of repetition priming.

In the human electroencephalogram (EEG), induced oscillatory responses in various frequency bands are regarded as valuable indices to examine the neural mechanisms underlying human memory. While the advent of virtual reality (VR) drives the investigation of mnemonic processing under more lifelike settings, the joint application of VR and EEG methods is still in its infancy (e.g., due to technical limitations impeding the signal acquisition). The objective of the present EEG study was twofold. First, we examined whether the investigation of induced oscillations under VR conditions yields equivalent results compared to standard paradigms. Second, we aimed at obtaining further insights into basic memory-related brain mechanisms in VR. To these ends, we relied on a standard implicit memory design, namely repetition priming, for which the to-be-expected effects are well-documented for conventional studies. Congruently, we replicated a suppression of the evoked potential after stimulus onset. Regarding the induced responses, we observed a modulation of induced alphaband in response to a repeated stimulus. Importantly, our results revealed a repetition-related suppression of the high-frequency induced gammaband response (>30 Hz), indicating the sharpening of a cortical object representation fostering behavioral priming effects. Noteworthy, the analysis of the induced gammaband responses required a number of measures to minimize the influence of external and internal sources of artefacts (i.e., the electrical shielding of the technical equipment and the control for miniature eye movements). In conclusion, joint VR-EEG studies with a particular focus on induced oscillatory responses offer a promising advanced understanding of mnemonic processing under lifelike conditions.

Dynamics of visual attention in exploration and exploitation for reward-guided adjustment tasks.

The learning process encompasses exploration and exploitation phases. While reinforcement learning models have revealed functional and neuroscientific distinctions between these phases, knowledge regarding how they affect visual attention while observing the external environment is limited. This study sought to elucidate the interplay between these learning phases and visual attention allocation using visual adjustment tasks combined with a two-armed bandit problem tailored to detect serial effects only when attention is dispersed across both arms. Per our findings, human participants exhibited a distinct serial effect only during the exploration phase, suggesting enhanced attention to the visual stimulus associated with the non-target arm. Remarkably, although rewards did not motivate attention dispersion in our task, during the exploration phase, individuals engaged in active observation and searched for targets to observe. This behavior highlights a unique information-seeking process in exploration that is distinct from exploitation.

Mechanisms of long-term repetition priming in recognising speech in noise.

Recognition of speech in noise is facilitated when spoken sentences are repeated a few minutes later, but the levels of representation involved in this effect have not been specified. Three experiments tested whether the effect would transfer across modalities and languages. In Experiment 1, participants listened to sets of high- and low-constraint sentences and read other sets in an encoding phase. At test, these sentences and new sentences were presented in noise, and participants attempted to report the final word of each sentence. Recognition was more accurate for repeated than for new sentences in both modalities. Experiment 2 was identical except for the implementation of an articulatory suppression task at encoding to reduce phonological recoding during reading. The cross-modal repetition priming effect persisted but was weaker than when the modality was the same at encoding and test. Experiment 3 showed that the repetition priming effect did not transfer across languages in bilinguals. Taken together, the results indicate that the facilitated recognition of repeated speech is based on a combination of modality-specific processes at the phonological word form level and modality-general processes at the lemma level of lexical representation, but the semantic level of representation is not involved.

Three Ways to Improve Arm Function in the Chronic Phase After Stroke by Robotic Priming Combined With Mirror Therapy, Arm Training, and Movement-Oriented Therapy.

OBJECTIVE: To examine the effects of bilateral robotic priming combined with mirror therapy (R-mirr) vs bilateral robotic priming combined with bilateral arm training (R-bilat), relative to the control approach of bilateral robotic priming combined with movement-oriented training (R-mov) in patients with stroke. DESIGN: A single-blind, preliminary, randomized controlled trial. SETTING: Four outpatient rehabilitation settings. PARTICIPANTS: Outpatients with stroke and mild to moderate motor impairment (N=63). INTERVENTIONS: Patients received 6 weeks of clinic-based R-mirr, R-bilat, or R-mov for 90 min/d, 3 d/wk, plus a transfer package at home for 5 d/wk. MAIN OUTCOME MEASURES: Fugl-Meyer Assessment Upper Extremity subscale (FMA-UE), ABILHAND, and Stroke Impact Scale v3.0 scores before, immediately after, and 3 months after treatment as well as lateral pinch strength and accelerometry before and immediately after treatment. RESULTS: The posttest results favored R-mirr over R-bilat and R-mov on the FMA-UE score (P<.05). Follow-up analysis revealed that significant improvement in FMA-UE score was retained at the 3-month follow-up in the R-mirr over R-bilat or R-mov (P<.05). Significant improvements were not observed in the R-mirr over R-bilat and R-mov on other outcomes. CONCLUSIONS: Between-group differences were only detected for the primary outcome, FMA-UE. R-mirr was more effective at enhancing upper limb motor improvement, and the effect has the potential to be maintained at 3 months of follow-up.

Effects of syntactic structure on the processing of lexical repetition during sentence reading.

Previous research has demonstrated that the ease or difficulty of processing complex semantic expressions depends on sentence structure: Processing difficulty emerges when the constituents that create the complex meaning appear in the same clause, whereas difficulty is reduced when the constituents appear in separate clauses. The goal of the current eye-tracking-while-reading experiments was to determine how changes to sentence structure affect the processing of lexical repetition, as this manipulation enabled us to isolate processes involved in word recognition (repetition priming) from those involved in sentence interpretation (felicity of the repetition). When repetition of the target word was felicitous (Experiment 1), we observed robust effects of repetition priming with some evidence that these effects were weaker when repetition occurred within a clause versus across a clause boundary. In contrast, when repetition of the target word was infelicitous (Experiment 2), readers experienced an immediate repetition cost when repetition occurred within a clause, but this cost was eliminated entirely when repetition occurred across clause boundaries. The results have implications for word recognition during reading, processes of semantic integration, and the role of sentence structure in guiding these linguistic representations.

Repetition Priming in Individuals with Amnestic Mild Cognitive Impairment and Alzheimer's Dementia: a Systematic Review and Meta-Analysis.

The literature on repetition priming in Alzheimer's disease (AD) is inconsistent, with some findings supporting spared priming while others do not. Several factors may explain these inconsistencies, including AD severity (e.g., dementia vs. Mild Cognitive Impairment; MCI) and priming paradigm-related characteristics. This systematic review and meta-analysis provides a quantitative summary of repetition priming in AD. We examined the between-group standard mean difference comparing repetition priming in AD dementia or amnestic MCI (aMCI; presumably due to AD) to controls. Thirty-two studies were selected, including 590 individuals with AD dementia, 267 individuals with amnestic MCI, and 703 controls. Our results indicated that both individuals with aMCI and AD dementia perform worse on repetition priming tasks than cognitively older adults. Paradigm-related moderators suggested that the effect size between studies comparing the combined aMCI or AD dementia group to cognitively healthy older adults was the highest for paradigms that required participants to produce, rather than identify, primes during the test phase. Our results further suggested that priming in AD is impaired for both conceptual and perceptual priming tasks. Lastly, while our results suggested that priming in AD is impaired for priming tasks that require deep processing, we were unable to draw firm conclusions about whether priming is less impaired in aMCI or AD dementia for paradigms that require shallow processing.

Comprehension exposures to words in sentence contexts impact spoken word production.

Comprehension or production of isolated words and production of words embedded in sentence contexts facilitated later production in previous research. The present study examined the extent to which contextualized comprehension exposures would impact later production. Two repetition priming experiments were conducted with Spanish-English bilingual participants. In Experiment 1 (N = 112), all encoding stimuli were presented visually, and in Experiment 2 (N = 112), all encoding stimuli were presented auditorily. After reading/listening or translating isolated words or words embedded in sentences at encoding, pictures corresponding to each target word were named aloud. Repetition priming relative to new items was measured in RT and accuracy. Relative to isolated encoding, sentence encoding reduced RT priming but not accuracy priming. In reading/listening encoding conditions, both isolated and embedded words elicited accuracy priming in picture naming, but only isolated words elicited RT priming. In translation encoding conditions, repetition priming effects in RT (but not accuracy) were stronger for lower-frequency words and with lower proficiency in the picture-naming response language. RT priming was strongest when the translation response at encoding was produced in the same language as final picture naming. In contrast, accuracy priming was strongest when the translation stimulus at encoding was comprehended in the same language as final picture naming. Thus, comprehension at encoding increased the rate of successful retrieval, whereas production at encoding speeded later production. Practice of comprehension may serve to gradually move less well-learned words from receptive to productive vocabulary.

Stimulus valence, episodic memory, and the priming of brain activation profiles in borderline personality disorder.

BACKGROUND: Borderline personality disorder (BPD) is characterized by instability in affective regulation that can result in a loss of cognitive control. Triggers may be neuronal responses to emotionally valenced context and/or stimuli. 'Neuronal priming' indexes the familiarity of stimuli, and may capture the obligatory effects of affective valence on the brain's processing system, and how such valence mediates responses to the repeated presentation of stimuli. We investigated the effects of affective valence of stimuli on neuronal priming (i.e. changes in activation to repeated presentation of stimuli), and if these effects distinguished BPD patients from controls. METHODS: Forty BPD subjects and 25 control subjects (age range: 18-44) participated in an episodic memory task during fMRI. Stimuli were presented in alternating epochs of encoding (six images of positive, negative, and neutral valence) and recognition (six images for 'old' v. 'new' recognition). Analyses focused on inter-group differences in the change in activation to repeated stimuli (presented during Encoding and Recognition). RESULTS: Relative to controls, BPD showed greater priming (generally greater decrease from encoding to recognition) for negatively valenced stimuli. Conversely, BPD showed less priming for positively valenced stimuli (generally greater increase from encoding to recognition). CONCLUSION: Plausibly, the relative familiarity of negative valence to patients with BPD exerts an influence on obligatory responses to repeated stimuli leading to repetition priming of neuronal profiles. The specific effects of valence on memory and/or attention, and consequently on priming can inform the understanding of mechanisms of altered salience for affective stimuli in BPD.

How word comprehension exposures facilitate later spoken production: implications for lexical processing and repetition priming.

Both comprehension and production exposures to words facilitate spoken production of the same words in picture-naming tasks performed several minutes later. Three experiments examined the mechanisms by which different types of comprehension exposures to words facilitate spoken production. Both overt and silent reading and listening tasks elicited substantial priming in picture naming at 10-minute but not 1-week retention intervals. Relative to silent conditions, encoding conditions that involved speaking the target word overtly elicited stronger priming effects in both RT and accuracy and larger frequency effects in RT. Frequency effects were not reliable in accuracy priming or silent-encoding RT priming. Articulatory suppression did not diminish priming effects relative to silent reading/listening, and priming effects did not depend on whether presentations at encoding were visual or auditory. Together, the results indicate that a common modality-general lemma representation is accessed in comprehension and production, that both lemma and phonological retrieval contribute to repetition priming in production, and that phonological retrieval is sensitive to word frequency. These results are consistent with a theory based on transfer-appropriate processing if word comprehension elicits top-down processing or feedback from the concept to the lemma.

Skill acquisition is enhanced by reducing trial-to-trial repetition.

Developing approaches to improve motor skill learning is of considerable interest across multiple disciplines. Previous research has typically shown that repeating the same action on consecutive trials enhances short-term performance but has detrimental effects on longer term skill acquisition. However, most prior research has contrasted the effects of repetition only at the block level; in the current study we examined the effects of repeating individual trials embedded in a larger randomized block, a feature that is often overlooked when random trial orders are generated in learning tasks. With 4 days of practice, a "Minimal Repeats" group, who rarely experienced repeating stimuli on consecutive trials during training, improved to a greater extent than a "Frequent Repeats" group, who were frequently presented with repeating stimuli on consecutive trials during training. Our results extend the previous finding of the beneficial effects of random compared with blocked practice on performance, showing that reduced trial-to-trial repetition during training is favorable with regard to skill learning. This research highlights that limiting the number of repeats on consecutive trials is a simple behavioral manipulation that can enhance the process of skill learning. Data/analysis code and Supplemental Material are available at https://osf.io/p3278/.NEW & NOTEWORTHY Numerous studies have shown that performing different subtasks across consecutive blocks of trials enhances learning. We examined whether the same effect would occur on a trial-to-trial level. Our Minimal Repeats group, who primarily responded to different stimuli on consecutive trials, learned more than our Frequent Repeats group, who frequently responded to the same stimulus on consecutive trials. This shows that minimizing trial-to-trial repetition is a simple and easily applicable manipulation that can enhance learning.

A single system account of enhanced recognition memory in synaesthesia.

Researchers often adjudicate between models of memory according to the models' ability to explain impaired patterns of performance (e.g., in amnesia). In contrast, evidence from special groups with enhanced memory is very rarely considered. Here, we explored how people with unusual perceptual experiences (synaesthesia) perform on various measures of memory and test how computational models of memory may account for their enhanced performance. We contrasted direct and indirect measures of memory (i.e., recognition memory, repetition priming, and fluency) in grapheme-colour synaesthetes and controls using a continuous identification with recognition (CID-R) paradigm. Synaesthetes outperformed controls on recognition memory and showed a different reaction-time pattern for identification. The data were most parsimoniously accounted for by a single-system computational model of the relationship between recognition and identification. Overall, the findings speak in favour of enhanced processing as an explanation for the memory advantage in synaesthesia. In general, our results show how synaesthesia can be used as an effective tool to study how individual differences in perception affect cognitive functions.

Study-test congruence of response levels in item stimulus-response priming.

We investigated stimulus-response (S-R) memory links during object priming using a binary associative size judgement paradigm. At study, participants decided which of two objects was bigger in real life and, at test, made the same or the reverse judgement. We examined the effects of response congruence on item S-R priming in the associative paradigm. In Experiment 1, a task reversal manipulation had minimal impact on RT priming when classifications were congruent for both recombined objects between study and test. Experiment 2 found that RT priming was more disrupted by classification incongruence of the selected than of the nonselected item alone, with incongruence of the nonselected object having no effect on RTs. Experiment 3, however, found that classification incongruence of both items eliminated RT priming, indicating that a significant effect of classification incongruence for the nonselected item is only evident if both items are classification-incongruent. Finally, across all experiments, we found that accuracy was more sensitive than RTs to decision/action incongruence. We interpret these findings in light of a two-stream account of S-R priming, and suggest a few extensions to account for interactions between S-R links of recombined items.

Influence of lag length on repetition priming in emotional stimuli: ERP evidence.

BACKGROUND: Previous studies have demonstrated both behavioral and neural evidence for the potential mediations of lag length and pre-existing memory representation on repetition priming. However, such mediations on emotional stimuli have not been described. METHODS: The current experiment intended to disentangle lag length from pre-existing memory representation. A lexical decision task was performed, in which different emotional characters (either normal or transposed) were re-presented either immediately or delayed. RESULTS: In immediate repetition, one early and two late (ie, N400 and late positive complex) repetition-related event-related potential (ERP) effects were elicited, but these were not sensitive to pre-existing memory representation. The delayed repetition case merely observed the N400. CONCLUSION: These results suggest that the repetition-related priming effect is neutrally sensitive to lag length. Emotional information potentially exerts early and later influences in the processing underlying stimuli memory.

The elimination of positive priming with increasing prime duration reflects a transition from perceptual fluency to disfluency rather than bias against primed words.

With immediate repetition priming of forced choice perceptual identification, short prime durations produce positive priming (i.e., priming the target leads to higher accuracy, while priming the foil leads to lower accuracy). Many theories explain positive priming following short duration primes as reflecting increased perceptual fluency for the primed target (i.e., decreased identification latency). However, most studies only examine either accuracy or response times, rather than considering the joint constraints of response times and accuracy to properly address the role of decision biases and response caution. This is a critical oversight because several theories propose that the transition to negative priming following a long duration prime reflects a decision strategy to compensate for the effect of increased perceptual fluency. In contrast, the nROUSE model of Huber and O'Reilly (2003) explains this transition as reflecting perceptual habituation, and thus a change to perceptual disfluency. We confirmed this prediction by applying a sequential sampling model (the diffusion race model) to accuracy and response time distributions from a new single item same-different version of the priming task. In this way, we measured strategic biases and perceptual fluency in each condition for each subject. The nROUSE model was only applied to accuracy from the original forced-choice version of the priming task. This application of nROUSE produced separate predictions for each subject regarding the degree of fluency and disfluency in each condition, and these predictions were confirmed by the drift rate parameters (i.e., fluency) from the response time model in contrast to the threshold parameters (i.e., bias).

Fluency misattribution and auditory hindsight bias.

We conducted three experiments to test the fluency-misattribution account of auditory hindsight bias. According to this account, prior exposure to a clearly presented auditory stimulus produces fluent (improved) processing of a distorted version of that stimulus, which results in participants mistakenly rating that item as easy to identify. In all experiments, participants in an exposure phase heard clearly spoken words zero, one, three, or six times. In the test phase, we examined auditory hindsight bias by manipulating whether participants heard a clear version of a target word just prior to hearing the distorted version of that word. Participants then estimated the ability of naïve peers to identify the distorted word. Auditory hindsight bias and the number of priming presentations during the exposure phase interacted underadditively in their prediction of participants' estimates: When no clear version of the target word appeared prior to the distorted version of that word in the test phase, participants identified target words more often the more frequently they heard the clear word in the exposure phase. Conversely, hearing a clear version of the target word at test produced similar estimates, regardless of the number of times participants heard clear versions of those words during the exposure phase. As per Roberts and Sternberg's (Attention and Performance XIV, pp. 611-653, 1993) additive factors logic, this finding suggests that both auditory hindsight bias and repetition priming contribute to a common process, which we propose involves a misattribution of processing fluency. We conclude that misattribution of fluency accounts for auditory hindsight bias.

The future is now: the impact of present fluency in judgments about the future.

Recent research has emphasised the role of episodic memory in both remembering past events and in envisaging future events. On the other hand, it has been repeatedly shown that judgments about past events are affected by the fluency with which retrieval cues are processed. In this paper we investigate whether perceptual fluency also plays a role in judgments about future events. For this purpose we conducted four experiments. The first experiment replicated recent findings showing that stimuli that are processed fluently tend to be wrongly recognised as having been encountered in the past outside the laboratory walls [Brown, A. S., & Marsh, E. J. (2009). Creating illusions of past encounter through brief exposure. Psychological Science, 20, 534-538. doi: 10.1111/j.1467-9280.2009.02337.x ]. Two follow-up experiments using Brown and Marsh's [(2009). Creating illusions of past encounter through brief exposure. Psychological Science, 20, 534-538. doi: 10.1111/j.1467-9280.2009.02337 ] task tested the influence of perceptual fluency on future judgments. The fourth and last experiment was designed to rule out a potential confounding factor in the two previous experiments. Across experiments, we found that people rely on fluency when making judgments about events that are yet to come. These results suggest that fluency is an equally valid cue for past and future judgments.

Processing Lexical and Speaker Information in Repetition and Semantic/Associative Priming.

The purpose of this study is to investigate the interaction between processing lexical and speaker-specific information in spoken word recognition. The specific question is whether repetition and semantic/associative priming is reduced when the prime and target are produced by different speakers. In Experiment 1, the prime and target were repeated (e.g., queen-queen) or unrelated (e.g., bell-queen). In Experiment 2, the prime and target were semantically/associatively related (e.g., king-queen) or unrelated (e.g., bell-queen). In both experiments, the prime and target were either produced by the same male speaker or two different male speakers. Two interstimulus intervals between the prime and target were used to examine the time course of processing speaker information. The tasks for the participants included judging the lexical status of the target (lexical decision), followed by judging whether the prime and target were produced by the same speaker or different speakers (speaker discrimination). The results showed that both lexical decision and speaker discrimination were facilitated to a smaller extent when the prime and target were produced by different speakers, indicating reduced repetition priming by speaker variability. In contrast, semantic/associative priming was not affected by speaker variability. The ISI between the prime and target did not affect either type of priming. In conclusion, speaker variability affects accessing a word's form but not its meaning, suggesting that speaker-specific information is processed at a relatively shallow level.

Brain regions that show repetition suppression and enhancement: A meta-analysis of 137 neuroimaging experiments.

Repetition suppression and enhancement refer to the reduction and increase in the neural responses for repeated rather than novel stimuli, respectively. This study provides a meta-analysis of the effects of repetition suppression and enhancement, restricting the data used to that involving fMRI/PET, visual stimulus presentation, and healthy participants. The major findings were as follows. First, the global topography of the repetition suppression effects was strikingly similar to that of the "subsequent memory" effects, indicating that the mechanism for repetition suppression is the reduced engagement of an encoding system. The lateral frontal cortex effects involved the frontoparietal control network regions anteriorly and the dorsal attention network regions posteriorly. The left fusiform cortex effects predominantly involved the dorsal attention network regions, whereas the right fusiform cortex effects mainly involved the visual network regions. Second, the category-specific meta-analyses and their comparisons indicated that most parts of the alleged category-specific regions showed repetition suppression for more than one stimulus category. In this regard, these regions may not be "dedicated cortical modules," but are more likely parts of multiple overlapping large-scale maps of simple features. Finally, the global topography of the repetition enhancement effects was similar to that of the "retrieval success" effects, suggesting that the mechanism for repetition enhancement is voluntary or involuntary explicit retrieval during an implicit memory task. Taken together, these results clarify the network affiliations of the regions showing reliable repetition suppression and enhancement effects and contribute to the theoretical interpretations of the local and global topography of these two effects. Hum Brain Mapp 38:1894-1913, 2017. © 2017 Wiley Periodicals, Inc.

Comparing different kinds of words and word-word relations to test an habituation model of priming.

Huber and O'Reilly (2003) proposed that neural habituation exists to solve a temporal parsing problem, minimizing blending between one word and the next when words are visually presented in rapid succession. They developed a neural dynamics habituation model, explaining the finding that short duration primes produce positive priming whereas long duration primes produce negative repetition priming. The model contains three layers of processing, including a visual input layer, an orthographic layer, and a lexical-semantic layer. The predicted effect of prime duration depends both on this assumed representational hierarchy and the assumption that synaptic depression underlies habituation. The current study tested these assumptions by comparing different kinds of words (e.g., words versus non-words) and different kinds of word-word relations (e.g., associative versus repetition). For each experiment, the predictions of the original model were compared to an alternative model with different representational assumptions. Experiment 1 confirmed the prediction that non-words and inverted words require longer prime durations to eliminate positive repetition priming (i.e., a slower transition from positive to negative priming). Experiment 2 confirmed the prediction that associative priming increases and then decreases with increasing prime duration, but remains positive even with long duration primes. Experiment 3 replicated the effects of repetition and associative priming using a within-subjects design and combined these effects by examining target words that were expected to repeat (e.g., viewing the target word 'BACK' after the prime phrase 'back to'). These results support the originally assumed representational hierarchy and more generally the role of habituation in temporal parsing and priming.

Early response activation in repetition priming: an LRP study.

According to recent interpretations of repetition priming, response codes are automatically bound to a stimulus and retrieved during successive presentations of the stimulus, hence, affecting its current processing. Despite a solid corpus of behavioural evidence in line with this interpretation, electrophysiological studies have reported contrasting results regarding the nature and the timing of response code retrieval. The present experiment aims to establish at which stage of information processing decision and action codes are retrieved in repetition priming. To this end, the lateralized readiness potential (LRP) was analysed for primed faces to monitor motor cortex activity related to response preparation. Congruent and incongruent responses were obtained by having identical or reversed tasks between study and test. Primed stimuli presented LRP activations with opposite polarities for the two congruency conditions in the time-window 250-300 ms, indicating response-related motor cortex activity resulting from the retrieval of correct and incorrect decision/action codes for congruent and incongruent trials, respectively. This result indicates that decision and action codes bound to a primed stimulus are retrieved at early stages of stimulus processing and that these codes are transmitted to the motor cortex.