Sylvia Yuan October 13, 2005 Psych 593SG

1. N400-like semantic incongruity effect in 19-month-olds: Processing known words in picture contextsManuela Friedrich and Angela D. FriedericiJ. of cognitive neuroscience, 2004, 16:8, 1465-1477 Sylvia Yuan October 13, 2005 Psych 593SG

2. Goal • To investigate whether adult-like mechanisms of semantic integration, as indexed by N400, are present in 19-month-olds

3. N400 • An index of semantic processing in adults (e.g., Kutas & Hillyard, 1980)

4. N400 semantic incongruity effect • Semantically incongruous stimuli elicit greater N400 amplitudes than semantically congruous stimuli • This reflects a greater effort at semantic integration for unexpected than expected stimuli • Semantic priming prior to stimulus presentation can facilitate processes of semantic integration  a reduced N400

5. Adult-like N400 in children • Picture-matching • 7- to 10-year-olds, greater negative component at latency 400ms to non-matching pictures in picture pairs (Friedman et al., 1992) • Processing visually presented words and pictures • 10- and 11-year-olds, antN400 to word stimuli, dual anterior negativities (N350 & N430) to picture stimuli (Coch et al., 2002) • Processing sentences with semantic anomalies • Visually stimuli: 7- to 12-year-olds (Holcomb et al., 1992) • N400 decreased in both amplitude and latency with age • Auditory stimuli: 6- to 13-year-olds (Hahne et al., 2004) • N400 slightly delayed for 6- to 8-year-olds

6. What about younger children?(Molfese, Morse & Peters, 1990) • 14-month-olds • Trained on two novel words (“gibu” & “bidu”) for two objects • ERP responses on “mismatch” names: • An early negativity at 60ms • A positivity at 560ms • No N400-like incongruity effect

7. Why the focus on N400 in young children? • To learn about the neural mechanisms of early word learning • To evaluate the potential of using N400 to investigate other aspects of children’s cognitive development • Concepts, semantic memory

8. The present study • Goal: to investigate whether an N400-like response can be observed in 19-month-olds to words presented in contexts • Task: picture-word-matching • Congruous condition: picture-word match • Incongruous condition: picture-word mismatch • ERP recording • Comparisons of spatio-temporal distributions • Adults vs. children (19-month-olds) • Among children: high vs. low comprehenders

9. Stimuli • Pictures • Colored illustrations of single objects • 44 words • Basic-level words (mean item difficulty =78%) • Slowly spoken (mean word length: 1083 ms) • Each presented twice • Congruous context – with a matching picture • Incongruous context – with a non-matching picture

10. Procedure • Participants were seated in front of a computer screen • Session lasted 12 minutes

11. 0 ms 1000 ms 2000 ms 3000 ms 4000 ms Trial structure “ball” (congruous) “duck” (incongruous) “A…” Indef. article Picture onset Target word

12. Participants • 20 adults (mean age 23.7 years) • 55 19-month-old German-monolingual children • 25 additional children were tested but excluded for crying/excessive movement (13) and too many artifacts/too much non-looking (12) • On average, children were looking to the monitor about 85% of the session • Children were split into two groups by the median comprehended words (37): low vs. high comprehenders • To assess whether ERP effects are related to children’s comprehension of the presented words in the experiment

13. ERP recording • Reference electrodes: left and right mastoids • Trial exclusion: • Trials with a SD exceeding 40 μV (for adults) and 100 μV (children) in a 200ms time window were rejected • Mean number of trials accepted: 32 (out of 44)

14. Adults’ ERPs Figure 1

15. Adults’ spatial distribution of ERPs Figure 3

16. Spatial distribution of adults’ difference wave A prominent effect at central-parietal midline sites Figure 4

17. Adults’ condition main effects Table 1

18. Summary of adult ERPs • An early effect of condition at temporal sites • 100-250ms: Congruous words more (-) than Incong. words  Word-processing is affected by picture contexts early on • A broadly distributed long-lasting semantic incongruity effect • 300-1300ms: Incong. words more (-) than Congruous words • Most prominent at centro-parietal sites • Stronger & more extended in the right hemisphere • Anterior regions are also involved  This spatial distribution matches that of the typical N400 effect in semantic priming paradigms

19. Children’s ERPs Figure 2

20. Children’s spatial distribution of ERPs Figure 3

21. Spatial distribution of children’s difference wave Negativity effect mostly in the left parietal & frontal areas Figure 4

22. Children’s condition main effects Table 2

23. Summary of child ERPs • An early effect of condition at lateral front sites • 150 – 400ms: Congruous words more (-) than Incong. words  Word-processing is affected by picture contexts early on • A broadly distributed long-lasting semantic incongruity effect • 700-1400ms: Incong. words more (-) than Congruous words • At centro-parietal & frontal sites • Possibly more contribution from the left hemisphere  The spatio-temporal distribution of the semantic incongruity in 19-month-olds differs from that in adults.

24. Comprehension groups • Median for comprehended words: 37 (out of 44) • Children were divided into two groups by the median: • High-comp. (N=27): group median 42, range 38-44 • Low-comp. (N=28): group median 33, range 6-37

25. Results: high- vs. low-comprehenders • Early context effect did not change between groups • For the later negative incongruity effect, there were group differences: • High comprehenders: • Earlier (starting 300ms) & in right hemisphere • More negative to incongruous words

26. ERPs of high & low comprehenders Figure 5

27. Main condition effects High comprehenders Adults Table 3 Table 1

28. Spatial distribution of ERPs More negativity in R hemisphere for high-comprehenders Figure 6

29. Summary of high- vs. low-comp. groups • Low-comprehension group • a small semantic incongruity effect in the left hemisphere that occurs much later (from 700ms) • High-comprehension group: • Much like adults: • a large semantic incongruity effect starting early (300-400ms) • stronger effect in right hemisphere • Unlike adults: • frontal areas are more involved

30. Discussion Auditory-evoked response • Adults: N1-P2 complex (adults) • Children: early positive-negative waveform Early context effect: greater negativity for congruous words • Earlier for adults (100-250ms vs. 150-400ms) • Not about better known vs. less known words (cf. Mills et al., 1993) • Possibly reflects top-down priming that facilitates early phonological-lexical processing • Known primed vs. unknown primed words

31. Later incongruity effect(greater negativity for incong. words) • First N400-like semantic incongruity effect in children under 2 years • Stronger involvement of frontal areas in children may reflect: • enhanced image-specific semantic processing, and/or • increased processing load

32. Later incongruity effect (cont’d) • Negative response in children to congruous words as well • stronger in low-comprehenders • may reflect child’s effort in accessing meaning of words • Effect stronger in high- than in low-comprehenders  Effect reflects different semantic processing w/ cong. & incong. words, representing a child N400!

33. Comprehension group differences • No difference in the early context effect • This suggests both groups were creating appropriate lexical expectations from picture • Differences between groups may lie in whether phono-lexical representations of presented words primed semantic representations (to be integrated) • Hemispheric differences in the incongruity effect • These may reflect processing differences as a function of the child’s general language abilities (e.g., Mills et al., 1993)

34. Comprehension group differences (cont’d) • High-comprehenders as fast as adults in incongruity effect • Possibly due to child-friendly stimuli or high-comprehenders’ knowing all (or most) word stimuli • Latency difference in low-comprehenders may reflect difficulties in perceptual & semantic processing

35. Conclusion • 19-month-olds show a child N400 in response to hearing words that do not match pictured objects • The strong involvement of anterior regions in children for the incongruity effect may reflect image-specific semantic processing. • Adult mechanisms of semantic integration of words are present early on. • Children’s comprehension abilities are reflected in strength, latency & hemispheric differences of the incongruity effect.

36. N400 in even younger children! • 14-month-olds (N=30) • Picture-word matching task, with words that one-year-olds already know Results: • Early context effect • 200 to 400ms • Congruous words more negative • Lateral front regions  Lexical expectations from pictures! • N400-like Incongruity effect • 400 to 1000ms, incong. words more negative • Mostly over central and parietal regions, some frontal  Semantic integration & influence of priming! (Friedrich & Friederici, 2005)

37. Questions • Is it really easier to go from pictures to lexical-phonological representations of words, than from representations of words to semantic representations? • What ERP components are observed for mismatch of grammatical gender of words to pictures? • If the incongruous word and its preceding article were additionally of mismatching gender (to the picture), would one expect to see stronger and/or faster N400 semantic incongruity effect?