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Early effects of morphological complexity on visual evoked fields in MEG. Eytan Zweig & Liina Pylkkänen New York University. 80 th Annual LSA meeting, January 7, 2006. Morphological decomposition - Two questions. Do all affixed words decompose? Does semantic opacity play a role? - PowerPoint PPT Presentation
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Early effects of morphological complexity on visual evoked
fields in MEG
Eytan Zweig & Liina PylkkänenNew York University
80th Annual LSA meeting, January 7, 2006
Morphological decomposition -Two questions
• Do all affixed words decompose? Does semantic opacity play a role?
• What is the timing of lexical decomposition?
Semantic opacity• Transparent words generally taken to decompose
• Competing hypotheses about opaque words
“Farmer” Farm + -er
“Folder”Fold + -er
Folder ?
1. Opaque words decompose (Rastle & Davis, 2003; Davis et al., 2004)
2. Opaque words do not decompose (Marslen-Wilson et al., 1994)
Semantic opacity
• Previous experiments have produced contradictory results (as reviewed by Feldman et al., 2004).
Timing of decomposition
Decomposition Lexical access
1. Early decomposition (Taft & Forster, 1975; Rastle & Davis, 2003; Davis et al., 2004)
3. Race (Baayen, 1992)
Lexical access Decomposition
2. Late decomposition (Feldman et al., 2004)
farm + -er farm, -er
farmer farm + -er
Decomposition Lexical access
Lexical access
farm + -er farm, -er
farmer
ERP evidence for early decomposition in sentence processing
• Word category violations elicit an early left anterior negativity (ELAN) (Friederici, 2000; Friederici et al., 2002).
• Category is determined through morphological cues.
• Indirectly supports an early effect of morphology.
This study
• Takes advantage of the millisecond temporal resolution of MEG.
• Simple lexical decision task without priming.
Magnetoencephalography (MEG)
http://www.ctf.com/Pages/page33.html
EEGEEGMEGMEG
MEG analysis
MEG analysis
MEG analysis
MEG analysis
Typical MEG response to visual words
Experiment 1Suffixed words
Experiment 1 Stimuli
No SuffixNo Suffix Orth. -er
Opaque Suffix
Transparent
Suffix
SWITCH WINTER FOLDER FARMER
34 words per condition
Conditions were controlled for matched for length, surface frequency, orthographic neighborhood density and frequency, and syntactic category.
Suffixed conditions were further controlled for stem frequency and orthographic regularity.
Testing for pre-lexical effects
• M350 is the first component to show effects of lexical factors (Embick et al., 2001;
Pylkkänen & Marantz, 2003).
• Fiorentino & Poeppel (2003) found that the M350 is sensitive to constituent frequency in compounds. – Decomposition likely to happen before M350.
Prediction - Timing
• If decomposition is pre-lexical, we should find effects before the M350.
M170
• The first component that has been found to be sensitive to the presence of letter strings (Tarkiainen et al., 1999).
• Most research has found that the M170 is not sensitive to lexical factors such as frequency.
M170
• Fusiform gyri have been found to be the primary generators of M170 activity.
Fusiform Gyri
• Functional asymmetry between hemispheres (Tarkiainen et al., 2002) :
– The left fusiform gyrus sensitive to letter strings (Cohen et al., 2000; Dehaene et al., 2002).
• “Visual Word Form Area”
– The right fusiform gyrus primarily sensitive to faces.
Prediction – Semantic opacity
• If opaque words decompose, they will pattern with transparent words.
• If they do not, they will pattern with orthographic controls.
-15
-10
-5
0
5
10
15
20
25
30
-50 -16 18 51 85 119 153 187 220 254 288 322 356 390
Suffixed
Not Suffixed
M170 - Left Hemisphere Grandaveraged waveform
n=16 no effect
Time
nAm
10
12
14
16
18
20
22
24
26
28
30
No Suffix No Suffix, Orth. Match Opaque Suffix Transparent Suffix
M170 - Left Hemisphere Amplitudes
SWITCH WINTER FOLDER FARMER
nAm
-15
-10
-5
0
5
10
15
20
25
30
-50 -16 18 51 85 119 153 187 220 254 288 322 356 390
Suffixed
Not Suffixed
M170 - Right Hemisphere Grandaveraged waveform
n=16 p < 0.001
Time
nAm
M170 - Right Hemisphere Amplitudes
10
12
14
16
18
20
22
24
26
28
30
No Suffix No Suffix, Orth. Match Opaque Suffix Transparent Suffix
SWITCH WINTER FOLDER FARMER
nAm
Other measures
• No M100 effects.
• No M350 effects.
• No response time effect.
Conclusions
• M170 activity is influenced by the presence of derivational suffixes.• Early lexical decompositon.
• No effect of opacity• All affixed words decompose.
Conclusions
• The right lateralization of the effect is surprising.
• Early visual word processing may be bilateral, with distinct functional roles for the left and the right hemispheres.
• However, there is a second hypothesis.
Why the right hemisphere?F
AR
ME
R
FA
RM
ER
FA
RM
ER
Experiment 2Prefixed words
Experiment 2 Stimuli
No Prefix No Prefix Orth. re-
Prefix
ROTATE RESUME REFILL
32 words per condition
Conditions were controlled for matched for length, surface frequency, orthographic neighborhood density and frequency, and syntactic category.
Prefixed condition was further controlled for stem frequency and orthographic regularity.
M170 - Right Hemisphere Grandaveraged Waveform
-10
-5
0
5
10
15
20
25
30
35
-50 -16 18 51 85 119 153 187 220 254 288 322 356 390
Prefixed
No Prefix, Ortho re-
No Prefix
Time
nAm
n=10 p < 0.02
M170 - Left Hemisphere Grandaveraged Waveform
-10
-5
0
5
10
15
20
25
30
35
-50 -16 18 51 85 119 153 187 220 254 288 322 356 390
Prefixed
No Prefix, Ortho re-
No Prefix
n=10 p < 0.02
Time
nAm
Other measures
• No M100 effects.
• No M350 effects.
• No response time effect.
Conclusions
• Experiment 1 replicated.
• Stem lexicality cannot be the sole reason for the RH effect in Experiment 1.
• Possibly a combined effect of morphological complexity and stem lexicality.
/ta-ba-ko/
KanaKanji
smoke-weed
Nakamura et. al (2005)
FMRI activity in fusiform gyri
Conclusions
• Morphological decomposition is a pre-lexical effect, and is not sensitive to semantic opacity.
• The RH M170 source is sensitive to morphological complexity irrespective of the linear ordering between a stem and an affix. • A crucial role for the right hemisphere in early
word processing.