Semantic priming modulates the N400, N300, and N400RP

https://doi.org/10.1016/j.clinph.2007.01.012Get rights and content

Abstract

Objective

To determine whether ERP components can differentiate between the semantic priming mechanisms of automatic spreading activation, expectancy, and semantic matching.

Methods

The present study manipulated two factors known to differentiate semantic priming mechanisms: associations between words (forward, backward, and symmetrical) and prime-target stimulus onset asynchrony (SOA). Twenty-six participants were tested in each SOA condition while high-density 128-channel data were collected. Principal components analysis was applied to separate the ERP components.

Results

Priming was observed for all conditions. Three semantic components were present: (1) the standard N400 effect for symmetric and forward priming pairs at both short and long SOAs, (2) an N300 for the long SOA symmetric priming pairs, and (3) a right-lateralized posterior N400RP for long SOA backward priming pairs.

Conclusions

Results suggest that the N300 reflects expectancy, but only for categorical and/or semantic similarity priming. Results further suggest that the N400RP is a replicable ERP component that responds to semantic matching. There is also some evidence that the N400 indirectly responds to both ASA and expectancy, perhaps as part of a post-lexical updating process and that backward priming at short SOAs is different from that at long SOAs.

Significance

Improved understanding of the semantic properties of the N400 and related ERP components may increase their utility for understanding language processes and for diagnostic purposes.

Introduction

Semantic priming is the facilitated processing of a target word when it is preceded by a semantically/associatively related prime word, relative to when it is preceded by a totally unrelated prime word (McNamara, 2005, Neely, 1991). Cognitive psychologists have used semantic priming to gain insight into how people use semantic context to access a word’s meaning and to shed light on how semantic memory is organized and accessed (Meyer and Schvaneveldt, 1976). A three process model of priming, consisting of automatic spreading activation (ASA), expectancy, and post-lexical semantic integration, has been used to account for the wide array of effects seen in semantic priming experiments (Neely and Keefe, 1989).

One method for isolating these three processes is the manipulation of the direction of association between the prime and the target. In forward associative priming, there is an association from the prime to target, but not the other way around (e.g., prime-FRUIT, target-FLY; prime-STORK, target-BABY). Forward priming is presumably produced by ASA at short SOAs and expectancy at longer SOAs. Backward associative priming (Koriat, 1981) occurs as a result of a strong associative link from target to prime but not the other way around (e.g., prime-FLY, target-FRUIT; prime-BABY, target-STORK). Because there is a backward association from the target fruit to the prime fly, the semantic matching mechanism could detect this target-prime relation, whose presence and absence is correlated with the target being a word or a nonword, thereby producing a priming effect in the lexical decision task.

Event-related potentials (ERPs) have been a useful tool in examining processes involved in priming. Of particular interest is the N400, an ERP component that appears to be sensitive to the congruity of a stimulus with the current semantic context (Kutas and Van Petten, 1994). Opinions regarding what the N400 reflects vary widely. Some argue that the N400 reflects controlled processes and not ASA (e.g., Chwilla et al., 1998) whereas others argue that it reflects both (e.g., Deacon et al., 1999). Overall, evidence suggests that the N400 reflects all three priming mechanisms, ASA (Deacon et al., 2004, Deacon et al., 2000, Kiefer, 2002, Kiefer and Spitzer, 2000, Kutas and Hillyard, 1989), expectancy (Kutas et al., 1984, Silva-Pereyra et al., 1999), and semantic matching (Chwilla et al., 1998, Holcomb, 1993), although the case for expectancy priming is not as strong. Although the relatively late time course of the N400 with respect to the presumed time course of semantic analysis (Sereno et al., 1998) might seem to tilt the evidence towards N400 being a manifestation of post-lexical semantic matching and/or integration, the P300 literature provides a clear precedent for a late acting component to index an expectancy process.

Some existing reports suggest the possibility that the different priming mechanisms are indexed by different ERP components. One such paper (Hill et al., 2002) conducted a lexical decision task with both short (150 ms) and long (700 ms) SOAs. In addition to the conventional centro-parietal N400 effect, there was a frontal negativity at about 300 ms that was sensitive to semantic incongruity only at the short SOA, as might be expected for an effect that responds to ASA. Such a frontal effect has been proposed elsewhere as potentially indexing ASA (Pritchard et al., 1991). Hill and colleagues (2002) also reported a right posterolateral N400 effect that was significant only at the long SOA, mirroring an ERP component in another study (Dien et al., 2006) that responded to both backward and forward associative priming and was therefore proposed to reflect semantic matching.

The first goal of this study was to try to provide more information on how the N400 (and other related components) relates to ASA, expectancy, and semantic matching. To isolate the operation of these mechanisms, this study manipulated SOA and direction of association. The empirical question to be answered is whether the four combinations of short vs. long SOA and forward vs. backward priming will be differentially associated with the N400. A long, 500-ms prime-target SOA and asymmetrically associated word pairs were used to isolate semantic matching, through backward priming, and expectancy, through forward priming. In addition, conventional symmetrically associated prime pairs were included for purposes of comparison.

A short, 150-ms SOA was also utilized to investigate whether ASA-based priming modulates the N400. This 150-ms SOA also permits us to observe the operation of a fourth potential priming mechanism that accounts for backward priming at short SOAs. It is speculated that there might be differences in the N400 effects seen for backward priming at the long and short SOAs based on behavioral evidence for different mechanisms of backward priming at short and long SOAs (Kahan et al., 1999).

An earlier study by Chwilla and colleagues (Chwilla et al., 1998) had much in common with the present study, including examining backward priming at both short and long interstimulus intervals (ISI) of 0 and 500 ms each, but using auditory stimuli. Reaction time and N400 priming effects occurred at both SOAs and were interpreted as supporting the position that the N400 reflects semantic matching/integration and possibly expectancy.

Although the study by Chwilla and colleagues (1998) was an important step towards better characterizing the N400, it left some issues unresolved. The present report provides new information beyond Chwilla and colleagues’ (1998) original report in the following ways: (1) because visual stimuli have a discrete onset time, the present study had stronger control over SOA timing issues; (2) the present study used a high-density recording montage that could detect potentially new semantic effects; (3) the high-density montage might make it possible to separate out P300 effects.

A potential issue with the experimental design is that the lexical decision task is likely to superimpose a P300 on the resulting waveforms. The study by Chwilla and colleagues (1998) sought to minimize the presence of the P300 by replicating the experiment with the instruction to press a button to nonwords only. However, the P300 responds primarily to stimulus probability rather than target status (Donchin, 1981) so simply designating the non-words as being the target will not eliminate the P300 from the word targets, although it will reduce it. In order to maximize comparability with the published behavioral priming literature this study attempted the strategy of capitalizing on a combination of high-density topographical information and principal components analysis (PCA) to separate the P300 and the N400, an approach that has been previously reported to work (Polich, 1985).

In summary, our procedures allow us the opportunity to achieve both psychophysiological and cognitive goals. The first psychophysiological goal is to try to better characterize the N400 with respect to the three priming mechanisms, separate from the P300. The second psychophysiological goal is to identify and characterize other semantic effects, especially the frontal effect and the right posterolateral effect. The cognitive goal is to obtain further information about whether backward priming at short SOAs is mediated by the same priming mechanism that produces backward priming at long SOAs.

Section snippets

Participants

Fifty-two, right-handed, native English speaking, Tulane University introductory-level psychology students, without neurological history or psychotropic medications, participated in the study for course credit. An additional 59 participants participated at the University of Kansas. Decisions were made prior to data analysis to exclude from analysis a participant’s data when they were likely to be unreliable and/or invalid, due to too many trials in which there were measurement problems due to

Behavioral results

As seen in Table 1 and Fig. 2, in the 2 (SOA) × 5 (Priming) factorial design, there was a borderline trend for the RTs to be faster for the long than for the short SOA (TWJt/c[1, 41.95] = 3.86, p = .055). There was also a significant main effect for priming (TWJt/c[4, 32.32] = 22.62, p < .0001) and a significant priming × SOA interaction (TWJt/c[4, 32.32] = 2.99, p = .030). However, contrasts of backward, forward, and symmetrical priming interactions with SOA were not at all significant, with all p-values > .33.

Discussion

The behavioral results reveal significant RT priming effects for all conditions. The forward and backward priming RT priming effects were roughly numerically equivalent at the 500- and 150-ms SOAs. These data are similar to the significant effects found in a larger sample tested by Kahan and colleagues (1999) and allow an investigation of the ERPs with the knowledge that priming was indeed occurring in all conditions. As for the three goals, the effort to separate the N400 from the P300 appears

Acknowledgements

The research in this paper was done in partial fulfillment of the first author’s requirements for the M.S. degree at Tulane University. Portions of this research were presented at the Cognitive Neuroscience Society, April 2003, in New York City. We thank Kyle Malone for assistance with the behavioral data. We also thank the members of the first author’s thesis committee, Gary Dohanich, Paul Colombo, and Dave Corey, for their helpful comments and support throughout the study. The preparation of

References (61)

  • G.A. Frishkoff et al.

    Frontal and posterior sources of event-related potentials in semantic comprehension

    Cogn Brain Res

    (2004)
  • J.P. Hamm et al.

    Comparison of the N300 and N400 ERPs to picture stimuli in congruent and incongruent contexts

    Clin Neurophysiol

    (2002)
  • H. Hill et al.

    Automatic vs. controlled processes in semantic priming – differentiation by event-related potentials

    Int J Psychophysiol

    (2002)
  • M. Kiefer

    The N400 is modulated by unconsciously perceived masked words: further evidence for an automatic spreading activation account of N400 priming effects

    Cogn Brain Res

    (2002)
  • M. Kutas et al.

    Event-related potential asymmetries during the reading of sentences

    Electroencephalograph Clin Neurophysiol

    (1988)
  • J.H. Neely et al.

    Semantic context effects on visual word processing: a hybrid prospective/retrospective processing theory

  • J. Polich et al.

    Cognitive and biological determinants of P300: an integrative review

    Biol Psychol

    (1995)
  • J. Polich

    Semantic categorization and event-related potentials

    Brain Cogn

    (1985)
  • J. Silva-Pereyra et al.

    N400 and lexical decisions: automatic or controlled processing?

    Clin Neurophysiol

    (1999)
  • S.L. Thompson-Schill et al.

    Effects of semantic and associative relatedness on automatic priming

    J Mem Lang

    (1998)
  • J.E. Anderson et al.

    Auditory and visual semantic priming using different stimulus set asynchronies: an event-related brain potential study

    Psychophysiology

    (1995)
  • C.A. Becker

    Semantic context effects in visual word recognition: an analysis of semantic strategies

    Mem Cognit

    (1980)
  • D.J. Chwilla et al.

    The mechanism underlying backward priming in a lexical decision task: Spreading activation versus semantic matching

    Q J Exp Psychol

    (1998)
  • A.M.B. de Groot

    Word-context effects in word naming and lexical decision

    Q J Exp Psychol

    (1985)
  • J. Dien

    Addressing misallocation of variance in principal components analysis of event-related potentials

    Brain Topogr

    (1998)
  • J. Dien

    Issues in the application of the average reference: Review, critiques, and recommendations

    Behav Res Methods

    (1998)
  • Dien J. Looking both ways through time: the Janus model of lateralized cognition....
  • Dien J, Franklin MS, Michelson CA, Lemen LC, Adams CL, Kiehl KA. Localizing the N400 Semantic Cloze Effect: Parametric...
  • J. Dien et al.

    Parsing the Late Positive Complex: mental chronometry and the ERP components that inhabit the neighborhood of the P300

    Psychophysiology

    (2004)
  • E. Donchin

    Surprise, surprise

    Psychophysiology

    (1981)
  • Cited by (0)

    View full text