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1.  Tracking the Consequences of Morpho-Orthographic Decomposition Using ERPs 
Brain research  2013;1529:92-104.
We examined the effects of morpho-orthographic decomposition on complex word processing using a combination of masked priming and ERP recordings. The process of morpho-orthographic decomposition was primed by the prior presentation of complex non-words (formed by the combination a legal stem and legal affix, e.g. huntity, cornity, scanity) as prime stimuli. Targets were semantically transparent complex words (e.g. hunter), semantically opaque pseudocomplex words (e.g. corner), and simplex words (e.g. scandal) that contained the same stem as primes or a different stem (e.g., huntity-hunter vs. farmity-hunter). We found a large early (150–200 ms) priming effect for transparent complex words only, followed by widely distributed priming effects between 200 and 300 ms and more spatially focused N400 priming effects for all types of target. Furthermore, in the 150–200 ms time-window, the ERP waveforms generated by pseudocomplex words patterned with those of complex words, both of which generated less negative-going waveforms compared with simplex words. In the N400 time-window, on the other hand, complex words differed from both pseudocomplex and simplex words. The results provide further support for early morpho-orthographic segmentation processes that operate independently of semantic transparency, and suggest that the output of these processes only affects the subsequent processing of truly complex words.
PMCID: PMC3954534  PMID: 23872217
morphological processing; masked priming; event related potentials; visual word recognition; morpho-orthographic segmentation
2.  An electrophysiological study of cross-modal repetition priming 
Psychophysiology  2005;42(5):493-507.
Few studies have focused on language processing across modalities. Two experiments examined between-modality interactions across three prime–target intervals (0, 200, and 800 ms) in a cross-modal repetition priming paradigm. Event-related potentials were recorded to auditory targets following visual primes (Experiment 1) or visual targets following auditory primes (Experiment 2). In Experiment 1 robust repetition effects were found for auditory targets as early as 100 ms, and continued through the N400 epoch. Moreover, these visual–auditory repetition effects were large across all three prime–target intervals although they onset 200 ms later at the shortest interval. In Experiment 2 repetition effects to visual targets started later (at 200 ms), but also offset relatively later (∼1000 ms). These auditory–visual repetition effects were both smaller overall and absent for the two shortest prime–target intervals during the typical N400 window.
PMCID: PMC3582219  PMID: 16176372
ERPs; N400; Repetition priming; Word recognition
3.  An ERP Investigation of Visual Word Recognition in Syllabary Scripts 
The bi-modal interactive-activation model has been successfully applied to understanding the neuro-cognitive processes involved in reading words in alphabetic scripts, as reflected in the modulation of ERP components in masked repetition priming. In order to test the generalizability of this approach, the current study examined word recognition in a different writing system, the Japanese syllabary scripts Hiragana and Katakana. Native Japanese participants were presented with repeated or unrelated pairs of Japanese words where the prime and target words were both in the same script (within-script priming, Experiment 1) or were in the opposite script (cross-script priming, Experiment 2). As in previous studies with alphabetic scripts, in both experiments the N250 (sub-lexical processing) and N400 (lexical-semantic processing) components were modulated by priming, although the time-course was somewhat delayed. The earlier N/P150 effect (visual feature processing) was present only in Experiment 1 where prime and target words shared visual features. Overall, the results provide support for the hypothesis that visual word recognition involves a generalizable set of neuro-cognitive processes that operate in a similar manner across different writing systems and languages, as well as pointing to the viability of the bi-modal interactive activation framework for modeling such processes.
PMCID: PMC3650918  PMID: 23378278
erp; priming; lexical
4.  Effects of lexical status and morphological complexity in masked priming: An ERP study 
Language and cognitive processes  2010;26(4-6):558-599.
Two masked priming experiments examined behavioural and event-related potential responses to simplex target words (e.g., flex) preceded by briefly presented, masked, derived word primes (flexible-flex), complex nonword primes formed by an illegal combination of the target word and a real suffix (flexify-flex), and simplex nonword primes formed by adding a nonsuffix word ending to the target (flexint-flex). Subjects performed a lexical decision task. Behavioural results showed that all prime types significantly facilitated target recognition. Priming effects were reflected in the electrophysiological data by reduced N250 and N400 amplitudes, and these priming effects were statistically equivalent for the three types of prime. The strong priming effects found with simplex primes in the present study, compared with prior research, are thought to be due to the combination of targets always being completely embedded in prime stimuli plus the reduced lexical inhibition that arises with nonword primes. In line with prior behavioural research, however, there was evidence for differential priming effects as a function of prime type in the N400 ERP component in Experiment 2, with greater priming effects for derived and pseudocomplex primes relative to simplex primes at lateral posterior electrode sites.
PMCID: PMC3998725  PMID: 24771954
Evoked potentials; Morphology (language); Priming; Word recognition
5.  Masked priming and ERPs dissociate maturation of orthographic and semantic components of visual word recognition in children 
Psychophysiology  2013;51(2):136-141.
This study examined the time-course of reading single words in children and adults using masked repetition priming and the recording of event-related potentials. The N250 and N400 repetition priming effects were used to characterize form- and meaning-level processing, respectively. Children had larger amplitude N250 effects than adults for both shorter and longer duration primes. Children did not differ from adults on the N400 effect. The difference on the N250 suggests that automaticity for form processing is still maturing in children relative to adults, while the lack of differentiation on the N400 effect suggests that meaning processing is relatively mature by late childhood. The overall similarity in the children’s repetition priming effects to adults’ effects is in line with theories of reading acquisition, according to which children rapidly transition to an orthographic strategy for fast access to semantic information from print.
PMCID: PMC3996759  PMID: 24313638
Reading development; N250; N400; Event-related potentials (ERPs); Masked priming
6.  The real-time link between person perception and action: Brain potential evidence for dynamic continuity 
Social neuroscience  2010;6(2):139-155.
Using event-related potentials, we investigated how the brain extracts information from another’s face and translates it into relevant action in real-time. In Study 1, participants made between-hand sex categorizations of sex-typical and sex-atypical faces. Sex-atypical faces evoked negativity between 250-550 ms (N300/N400 effects), reflecting the integration of accumulating sex-category knowledge into a coherent sex-category interpretation. Additionally, the lateralized readiness potential (LRP) revealed that the motor cortex began preparing for a correct hand response while social category knowledge was still gradually evolving in parallel. In Study 2, participants made between-hand eye-color categorizations as part of go/no-go trials that were contingent on a target’s sex. On no-go trials, although the hand did not actually move, information about eye color partially prepared the motor cortex to move the hand before perception of sex had finalized. Together, these findings demonstrate the dynamic continuity between person perception and action, such that ongoing results from face processing are immediately and continuously cascaded into the motor system over time. The preparation of action begins based on tentative perceptions of another’s face before perceivers have finished interpreting what they just saw.
PMCID: PMC3047598  PMID: 20602284
person perception; action; face perception; social categorization; motor processes; ERPs
7.  The Impact of Visual Acuity on Age-Related Differences in Neural Markers of Early Visual Processing 
NeuroImage  2012;67:127-136.
The extent to which age-related differences in neural markers of visual processing are influenced by changes in visual acuity has not been systematically investigated. Studies often indicate that their subjects had normal or corrected-to-normal vision, but the assessment of visual acuity seems to most frequently be based only on self-report. Consistent with prior research, to be included in the current study, subjects had to report normal or corrected-to-normal vision. Additionally, visual acuity was formally tested using a Snellen eye chart. Event-related potentials (ERPs) were studied in young adults (18–32 years old), young-old adults (65–79 years old), and old-old adults (80+ years old) while they performed a visual processing task involving selective attention to color. Age-related differences in the latency and amplitude of ERP markers of early visual processing, the posterior P1 and N1 components, were examined. All results were then re-analyzed after controlling for visual acuity. We found that visual acuity declined as a function of age. Accounting for visual acuity had an impact on whether older and younger adults differed significantly in the size and latency of the posterior P1 and N1 components. After controlling for visual acuity, age-related increases in P1 and N1 latency did not remain significant, and older adults were found to have a larger P1 amplitude than young adults. Our results suggest that until the relationship between age-associated differences in visual acuity and early ERPs is clearly established, investigators should be cautious when interpreting the meaning of their findings. Self-reports about visual acuity may be inaccurate, necessitating formal measures. Additional investigation is needed to help establish guidelines for future research, especially of very old adults.
PMCID: PMC3545036  PMID: 23153966
Aging; Visual Processing; Visual Acuity; ERPs
8.  Cognitive Status Impacts Age-Related Changes in Attention to Novel and Target Events in Normal Adults 
Neuropsychology  2007;21(3):291-300.
This study investigated the relationship between the cognitive status of normal adults and age-related changes in attention to novel and target events. Old, middle-aged, and young subjects, divided into cognitively high and cognitively average performing groups, viewed repetitive standard stimuli, infrequent target stimuli, and unique novel visual stimuli. Subjects controlled viewing duration by a button press that led to the onset of the next stimulus. They also responded to targets by pressing a foot pedal. The amount of time spent looking at different kinds of stimuli served as a measure of visual attention and exploratory activity. Cognitively high performers spent more time viewing novel stimuli than cognitively average performers. The magnitude of the difference between cognitively high and cognitively average performing groups was largest among old subjects. Cognitively average performers had slower and less accurate responses to targets than cognitively high performers. Our results provide strong evidence that the link between engagement by novelty and higher cognitive performance increases with age. Moreover, it supports the notion of there being different patterns of normal cognitive aging and the need to identify the factors that influence them.
PMCID: PMC3045751  PMID: 17484592
cognitive aging; cognitive performance; novelty; attention
9.  Conscious intention to speak proactively facilitates lexical access during overt object naming 
Journal of memory and language  2012;65(4):345-362.
The present study explored when and how the top-down intention to speak influences the language production process. We did so by comparing the brain’s electrical response for a variable known to affect lexical access, namely word frequency, during overt object naming and non-verbal object categorization. We found that during naming, the event-related brain potentials elicited for objects with low frequency names started to diverge from those with high frequency names as early as 152 ms after stimulus onset, while during non-verbal categorization the same frequency comparison appeared 200 ms later eliciting a qualitatively different brain response. Thus, only when participants had the conscious intention to name an object the brain rapidly engaged in lexical access. The data offer evidence that top-down intention to speak proactively facilitates the activation of words related to perceived objects.
PMCID: PMC3770451  PMID: 24039339
Language production; Lexical access; Task intention; ERPs; Top-down processing
10.  Masked repetition priming of letter-in-string identification: An ERP investigation 
Brain research  2012;1472:74-88.
In a post-cued letter identification task, participants were presented with 7-letter nonword target stimuli that were formed of a random string of consonants (DCMFPLR) or a pronounceable sequence of consonants and vowels (DAMOPUR). Targets were preceded by briefly presented pattern-masked primes that could be the same sequence of letters as the target, composed of seven different letters, or sharing either the first or last five letters of the target. There was some evidence for repetition priming effects that were independent of target type in an early component, the N/P150, thought to reflect the mapping of visual features onto letter representations, and that is insensitive to orthographic structure. Following this, pronounceable nonwords showed significantly greater repetition priming effects than consonant strings, in line with the behavioral results. Initial versus final overlap only started to influence target processing at around 200–250 ms post-target onset, at about the same time as the effects of target type emerged. The results are in line with a model where the initial parallel mapping of visual features onto a location-specific orthographic code is followed by the subsequent activation of location-invariant orthographic and phonological codes.
PMCID: PMC3641898  PMID: 22824333
Pseudoword superiority effect; ERPs; Nonword processing; Masked priming
11.  (Pea)nuts and bolts of visual narrative: Structure and meaning in sequential image comprehension 
Cognitive Psychology  2012;65(1):1-38.
Just as syntax differentiates coherent sentences from scrambled word strings, the comprehension of sequential images must also use a cognitive system to distinguish coherent narrative sequences from random strings of images. We conducted experiments analogous to two classic studies of language processing to examine the contributions of narrative structure and semantic relatedness to processing sequential images. We compared four types of comic strips: 1) Normal sequences with both structure and meaning, 2) Semantic Only sequences (in which the panels were related to a common semantic theme, but had no narrative structure), 3) Structural Only sequences (narrative structure but no semantic relatedness), and 4) Scrambled sequences of randomly-ordered panels. In Experiment 1, participants monitored for target panels in sequences presented panel-by-panel. Reaction times were slowest to panels in Scrambled sequences, intermediate in both Structural Only and Semantic Only sequences, and fastest in Normal sequences. This suggests that both semantic relatedness and narrative structure offer advantages to processing. Experiment 2 measured ERPs to all panels across the whole sequence. The N300/N400 was largest to panels in both the Scrambled and Structural Only sequences, intermediate in Semantic Only sequences and smallest in the Normal sequences. This implies that a combination of narrative structure and semantic relatedness can facilitate semantic processing of upcoming panels (as reflected by the N300/N400). Also, panels in the Scrambled sequences evoked a larger left-lateralized anterior negativity than panels in the Structural Only sequences. This localized effect was distinct from the N300/N400, and appeared despite the fact that these two sequence types were matched on local semantic relatedness between individual panels. These findings suggest that sequential image comprehension uses a narrative structure that may be independent of semantic relatedness. Altogether, we argue that the comprehension of visual narrative is guided by an interaction between structure and meaning.
PMCID: PMC3331971  PMID: 22387723
Coherence; Comics; Discourse; ERPs; Event-related Potentials; Film; Image Sequence; LAN; N300; N400; Narrative; Pictures; Structure; Visual Language
12.  The “Electrophysiological Sandwich”: A Method for Amplifying ERP Priming Effects 
Psychophysiology  2012;49(8):1114-1124.
We describe the results of a study that combines ERP recordings and sandwich priming, a variant of masked priming that provides a brief preview of the target prior to prime presentation (Lupker & Davis, 2009). This has been shown to increase the size of masked priming effects seen in behavioral responses. We found the same increase in sensitivity to ERP priming effects in an orthographic priming experiment manipulating the position of overlap of letters shared by primes and targets. Targets were 6-letter words and primes were formed of the 1st, 3rd, 4th, and 6th letters of targets in the related condition. Primes could be concatenated or hyphenated and could be centered on fixation or displaced by two letter spaces to the left or right. Priming effects with concatenated and/or displaced primes only started to emerge at 250ms post-target onset, whereas priming effects from centrally located hyphenated primes emerged about 100ms earlier.
PMCID: PMC3399980  PMID: 22681238
sandwich priming; ERPs; orthographic priming; relative-position priming; location invariance
13.  Exploring the Temporal Dynamics of Visual Word Recognition in the Masked Repetition Priming Paradigm using Event-Related Potentials 
Brain research  2007;1180:39-58.
The present study used event-related potentials (ERPs) to examine the time-course of visual word recognition using a masked repetition priming paradigm. In two experiments participants monitored a stream of words for occasional animal names, and ERPs were recorded to non-animal critical target items that were either repetitions or were unrelated to the immediately preceding masked prime word. In Experiment 1 the onset interval between the prime and target (stimulus-onset-asynchrony – SOA) was manipulated across four levels (60, 180, 300 and 420 ms) and the duration of primes was held constant at 40 ms. In Experiment 2 the SOA between the prime and target was held constant at 60 ms and the prime duration was manipulated across four levels (10, 20 30 and 40 ms). Both manipulations were found to have distinct effects on the N250 and N400 ERP components. The results provide converging evidence that the N250 reflects processing at the level of form representations (orthography and phonology) while the N400 reflects processing at the level of meaning.
PMCID: PMC2151932  PMID: 17950262
Visual word processing; word recognition; N400; N250; masked priming
Journal of cognitive neuroscience  2012;25(3):484-502.
When a word is preceded by a supportive context such as a semantically associated word or a strongly constraining sentence frame, the N400 component of the ERP is reduced in amplitude. An ongoing debate is the degree to which this reduction reflects a passive spread of activation across long-term semantic memory representations as opposed to specific predictions about upcoming input. We addressed this question by embedding semantically associated prime-target pairs within an experimental context that encouraged prediction to a greater or lesser degree. The proportion of related items was used to manipulate the predictive validity of the prime for the target while holding semantic association constant. A semantic category probe detection task was used to encourage semantic processing and to preclude the need for a motor response on the trials of interest. A larger N400 reduction to associated targets was observed in the high than the low relatedness proportion condition, consistent with the hypothesis that predictions about upcoming stimuli make a substantial contribution to the N400 effect. We also observed an earlier priming effect (205–240 ms) in the high proportion condition, which may reflect facilitation due to form-based prediction. In sum, the results suggest that predictability modulates N400 amplitude to a greater degree than the semantic content of the context.
PMCID: PMC3657387  PMID: 23163410
15.  Masked repetition priming and event-related brain potentials: A new approach for tracking the time-course of object perception 
Psychophysiology  2006;43(6):564-568.
This study reports a new approach to studying the time-course of the perceptual processing of objects by combining for the first time the masked repetition priming technique with the recording of event-related potentials (ERPs). In a semantic categorization task ERPs were recorded to repeated and unrelated target pictures of common objects that were immediately preceded by briefly presented pattern masked prime objects. Three sequential ERP effects were found between 100 and 650 ms post-target onset. These effects included an early posterior positivity/anterior negativity (N/P190) that was suggested to reflect early feature processing in visual cortex. This early effect was followed by an anterior negativity (N300) that was suggested to reflect processing of object-specific representations and finally by a widely distributed negativity (N400) that was argued to reflect more domain general semantic processing.
PMCID: PMC1857300  PMID: 17076812
ERP; N400; N300; Masked priming; Object recognition
16.  On the Time Course of Visual Word Recognition: An Event-related Potential Investigation using Masked Repetition Priming 
Journal of cognitive neuroscience  2006;18(10):1631-1643.
The present study used event-related potentials (ERPs) to examine the time course of visual word recognition using a masked repetition priming paradigm. Participants monitored target words for occasional animal names, and ERPs were recorded to nonanimal critical items that were full repetitions, partial repetitions, or unrelated to the immediately preceding masked prime word. The results showed a strong modulation of the N400 and three earlier ERP components (P150, N250, and the P325) that we propose reflect sequential overlapping steps in the processing of printed words.
PMCID: PMC1808538  PMID: 17014368
17.  How Word Frequency Modulates Masked Repetition Priming: An ERP Investigation 
Psychophysiology  2012;49(5):604-616.
The present study used ERPs to provide precise temporal information about the modulation of masked repetition priming effects by word frequency during the course of target word recognition. Contrary to the pattern seen with behavioral response times in prior research, we predicted that high-frequency words should generate larger and earlier peaking repetition priming effects than low-frequency words in the N400 time window. This prediction was supported by the results of two experiments. Furthermore, repetition priming effects in the N250 time window were found for low-frequency words in both experiments, whereas for high-frequency words these effects were only seen at the shorter (50 ms) SOA used in Experiment 2, and not in Experiment 1 (70 ms SOA). We explain this pattern as resulting from reset mechanisms operating on the form representations activated by prime stimuli when primes and targets are processed as separate perceptual events.
PMCID: PMC3323680  PMID: 22221077
masked priming; ERPs; word frequency; repetition; sigmoid activation function
18.  A funny thing happened on the way to articulation: N400 attenuation despite behavioral interference in picture naming 
Cognition  2012;123(1):84-99.
We measured Event-Related Potentials (ERPs) and naming times to picture targets preceded by masked words (stimulus onset asynchrony: 80 ms) that shared one of three different types of relationship with the names of the pictures: (1) Identity related, in which the prime was the name of the picture (“socks” – ), (2) Phonemic Onset related, in which the initial segment of the prime was the same as the name of the picture (“log” – ), and (3) Semantically related in which the prime was a co–category exemplar and associated with the name of the picture (“cake” – ). Each type of related picture target was contrasted with an Unrelated picture target, resulting in a 3 × 2 design that crossed Relationship Type between the word and the target picture (Identity, Phonemic Onset and Semantic) with Relatedness (Related and Unrelated). Modulation of the N400 component to related (versus unrelated) pictures was taken to reflect semantic processing at the interface between the picture's conceptual features and its lemma, while naming times reflected the end product of all stages of processing. Both attenuation of the N400 and shorter naming times were observed to pictures preceded by Identity related (versus Unrelated) words. No ERP effects within 600 ms, but shorter naming times, were observed to pictures preceded by Phonemic Onset related (versus Unrelated) words. An attenuated N400 (electrophysiological semantic priming) but longer naming times (behavioral semantic interference) were observed to pictures preceded by Semantically related (versus Unrelated) words. These dissociations between ERP modulation and naming times suggest that (a) phonemic onset priming occurred late, during encoding of the articulatory response, and (b) semantic behavioral interference was not driven by competition at the lemma level of representation, but rather occurred at a later stage of production.
PMCID: PMC3634574  PMID: 22245030
Semantic interference; Lexical selection; Response selection; Speech production; ERP; N400
19.  The effects of prime visibility on ERP measures of masked priming 
In two experiments, the effect of the duration (40, 80 and 120 ms) of pattern masked prime words on subsequent target word processing was measured using event-related potentials. In Experiment 1, target words were either repetitions of the prior masked prime (car-CAR) or were another unrelated word (job-CAR). In Experiment 2, primes and targets were either semantically related (cap-HAT) or were unrelated (car-HAT). Unrelated target words produced larger N400s than did repeated (Exp 1) or semantically related (Exp 2) words across the different prime durations and these N400 priming effects tended to be smaller overall for semantic than repetition priming. Moreover, there was only a modest decline in the size of N400 repetition priming at the shortest prime durations, and there was no relationship between this N400 effect and a measure of prime categorization performance. However, the size of semantic priming at the shortest durations was relatively smaller than at longer durations and was correlated with prime categorization performance. The findings are discussed in the context of the functional significance of the N400 as well as a model that argues for different mechanisms during masked repetition and semantic priming.
PMCID: PMC3587782  PMID: 15922167
ERPs; N400; Masked priming; Semantic priming; Repetition priming
20.  An electrophysiological investigation of the effects of coreference on word repetition and synonymy ☆ 
Brain and language  2005;94(2):200-216.
In two experiments the effects of word repetition, synonymy, and coreference on event-related brain potentials during text processing were studied. Participants read one (Experiment 1) or two sentence (Experiment 2) texts in which critical nouns were preceded by the definite (the) or indefinite (a) articles. Experiment 1 was run as a control to verify that differences in article processing in the second sentences of Experiment 2 would not contaminate the ERPs to critical noun items. They did not. In Experiment 2, an initial sentence was used to set up a context and contained either a first presentation or synonym of the critical word from the second sentence. N400 (but not Late Positive Component; LPC) priming effects were found for repetitions and synonyms (larger for repetitions) in second sentences. This extends observations of priming in word lists and single sentences to two-sentence texts. There was also a greater left anterior negativity or “LAN” for coreferential critical nouns (those following the article “The”) compared to non-coreferential critical nouns (those following the article “A”) suggesting that ERPs are sensitive to working memory processes engaged during referential assignment. In response to the articles themselves, there was a greater N400-700 elicited by the article “A” vs. “The.” Finally, there was a greater N400-like negativity to the final words of non-coreferential sentences implying that the meanings of these sentences were difficult to integrate with the discourse level representation established by the prior sentence.
PMCID: PMC3581343  PMID: 15896394
N400; LAN; ERPs; Coreference; Anaphoric processing; Sentence processing
21.  The face-sensitive N170 encodes social category information 
Neuroreport  2010;21(1):24-28.
Prominent models of face perception posit that the encoding of social categories begins after initial structural encoding has completed. In contrast, we hypothesized that social category encoding may occur simultaneously with structural encoding. While event-related potentials were recorded, participants categorized the sex of sex-typical and sex-atypical faces. Results indicated that the face-sensitive right N170, a component involved in structural encoding, was larger for sex-typical relative to sex-atypical faces. Moreover, its amplitude predicted the efficiency of sex-category judgments. The right P1 component also peaked earlier for sex-typical faces. These findings show that social category encoding and the extraction of lower-level face information operate in parallel, suggesting that they may be accomplished by a single dynamic process rather than two separate mechanisms.
PMCID: PMC3576572  PMID: 19864961
face perception; N170; P1; person perception; social categorization; visual encoding
22.  Does modulation of selective attention to features reflect enhancement or suppression of neural activity? 
Biological Psychology  2011;89(2):398-407.
Numerous studies have demonstrated that selective attention to color is associated with a larger neural response under attend than ignore conditions, but have not addressed whether this difference reflects enhanced activity under attend or suppressed activity under ignore. In this study, a color-neutral condition was included, which presented stimuli physically identical to those under attend and ignore conditions, but in which color was not task relevant. Attention to color did not modulate the early sensory-evoked P1 and N1 components. Traditional ERP markers of early selection (the anterior Selection Positivity and posterior Selection Negativity) did not differ between the attend and neutral conditions, arguing against a mechanism of enhanced activity. However, there were markedly reduced responses under the ignore relative to the neutral condition, consistent with the view that early selection mechanisms reflect suppression of neural activity under the ignore condition.
PMCID: PMC3272645  PMID: 22178708
23.  Invariance to Rotation in Depth Measured by Masked Repetition Priming is Dependent on Prime Duration 
Brain research  2011;1424:38-52.
The current experiment examined invariance to pictures of objects rotated in depth using event-related potentials (ERPs) and masked repetition priming. Specifically we rotated objects 30°, 60° or 150° from their canonical view and, across two experiments, varied the prime duration (50 or 90 milliseconds (ms)). We examined three ERP components, the P/N190, N300 and N400. In Experiment 1, only the 30° rotation condition produced repetition priming effects on the N/P190, N300 and N400. The other rotation conditions only showed repetition priming effects on the early perceptual component, the N/P190. Experiment 2 extended the prime duration to 90 ms to determine whether additional exposure to the prime may produce invariance on the N300 and N400 for the 60° and 150° rotation conditions. Repetition priming effects were found for all rotation conditions across the N/P190, N300 and N400 components. We interpret these results to suggest that whether or not view invariant priming effects are found depends partly on the extent to which representation of an object has been activated.
PMCID: PMC3218085  PMID: 22005687
masked priming; object recognition; event-related potentials; view-point invariance; view-point dependence
24.  Language Effects in Trilinguals: An ERP Study 
Event-related potentials were recorded during the visual presentation of words in the three languages of French-English-Spanish trilinguals. Participants monitored a mixed list of unrelated non-cognate words in the three languages while performing a semantic categorization task. Words in L1 generated earlier N400 peak amplitudes than both L2 and L3 words, which peaked together. On the other hand, L2 and L3 words did differ significantly in terms of N400 amplitude, with L3 words generating greater mean amplitudes compared with L2 words. We interpret the effects of peak N400 latency as reflecting the special status of the L1 relative to later acquired languages, rather than proficiency in that language per se. On the other hand, the mean amplitude difference between L2 and L3 is thought to reflect different levels of fluency in these two languages.
PMCID: PMC3490278  PMID: 23133428
language effects; trilingualism; visual word recognition; N400
25.  Mechanisms Underlying Age- and Performance-related Differences in Working Memory 
Journal of cognitive neuroscience  2010;23(6):1298-1314.
This study took advantage of the subsecond temporal resolution of ERPs to investigate mechanisms underlying age- and performance-related differences in working memory. Young and old subjects participated in a verbal n-back task with three levels of difficulty. Each group was divided into high and low performers based on accuracy under the 2-back condition. Both old subjects and low-performing young subjects exhibited impairments in preliminary mismatch/match detection operations (indexed by the anterior N2 component). This may have undermined the quality of information available for the subsequent decision-making process (indexed by the P3 component), necessitating the appropriation of more resources. Additional anterior and right hemisphere activity was recruited by old subjects. Neural efficiency and the capacity to allocate more resources to decision-making differed between high and low performers in both age groups. Under low demand conditions, high performers executed the task utilizing fewer resources than low performers (indexed by the P3 amplitude). As task requirements increased, high-performing young and old subjects were able to appropriate additional resources to decision-making, whereas their low-performing counterparts allocated fewer resources. Higher task demands increased utilization of processing capacity for operations other than decision-making (e.g., sustained attention) that depend upon a shared pool of limited resources. As demands increased, all groups allocated additional resources to the process of sustaining attention (indexed by the posterior slow wave). Demands appeared to have exceeded capacity in low performers, leading to a reduction of resources available to the decision-making process, which likely contributed to a decline in performance.
PMCID: PMC3076134  PMID: 20617886

Results 1-25 (66)