liina pylkkänen department of linguistics/ center for

Liina PylkkänenLiina Pylkkänen

Department of Linguistics/ Center for NeuromagnetismDepartment of Linguistics/ Center for NeuromagnetismNew York UniversityNew York University

MEG, the Mental Lexicon and MEG, the Mental Lexicon and MorphologyMorphology

LP, Aug 03, Tateshina

Day 1Day 1 Lexical access 1: Lexical access 1: The M350 as an MEG index of lexical activationThe M350 as an MEG index of lexical activation

Day 2Day 2 Lexical access 2: Lexical access 2: The M350 and mechanisms of recognitionThe M350 and mechanisms of recognition

Day 3Day 3 Morphology 1: Morphology 1: The M350 as a tool for investigating similarity and identityThe M350 as a tool for investigating similarity and identity

Day 4Day 4 Morphology 2: Morphology 2: Electrophysiological and behavioral evidence for early Electrophysiological and behavioral evidence for early

effects of morphologyeffects of morphology

MEG, the Mental Lexicon and MEG, the Mental Lexicon and MorphologyMorphology


Day 4Day 4 Morphology 2: Morphology 2: Electrophysiological and Electrophysiological and behavioral evidence for early effects of behavioral evidence for early effects of morphologymorphology


I. Morphological family effects.II. Early effects of superficial morphology in masked

priming.III. Role of semantic transparency.IV. Early effects of morphology in ERPs.V. Grand summary of MEG results and comparison to

ERP literature.

Effect of lexical frequencyEffect of lexical frequency

• High frequency words are processed faster than low frequency words.

• Prediction of decompositional theories of morphology: cumulative root frequency effects.

magnet terror

Matched for surface frequency

- ic –ize –ism

Low frequency derivatives

- ist –ize -ism

High frequency derivatives

Same number of derivates

Effect of lexical frequencyEffect of lexical frequency

• High frequency words are processed faster than low frequency words.

• Prediction of decompositional theories of morphology: cumulative root frequency effects.

magnet terror

Matched for surface frequency

- ic –ize –ism

Low frequency derivatives

- ist –ize -ism

High frequency derivatives

Same number of derivates

Should be faster Should be faster due to high due to high cumulative root cumulative root frequencyfrequency

Cumulative root frequency effects for Cumulative root frequency effects for inflectioninflection• Response times to a noun depend on the cumulative frequency

of the singular and plural (Schreuder & Baayen, JML, 1997)

CAT CATS

But NO cumulative root frequency effects But NO cumulative root frequency effects for derivationfor derivation

• Family frequency

magnet terror - ic –ize –ism- ist –ize -ism

HIGH LOWFamily frequency does not Family frequency does not affect lexical decision times.affect lexical decision times.

• Family size

acid diary - ic –ity –ify –head –test –washed - ist

HIGH LOW High family High family sizesize speeds up speeds up lexical decision times.lexical decision times.

Schreuder & Baayen (1997):

S&B: this is a late post-lexical S&B: this is a late post-lexical effect.effect.

S&B: Therefore, no S&B: Therefore, no decomposition in derivation.decomposition in derivation.

Alternative explanation for lack of cumulative Alternative explanation for lack of cumulative root frequency effects in derivationroot frequency effects in derivation

• High morphological family frequency speeds up root activationroot activationBUTBUT this facilitation is cancelled out by subsequent competitioncompetition between the highly frequent morphological family members.

• Hypothesized affix-competition in priming (Marslen-Wilson, et al. 1994):In crossmodal priming,

NO PRIMING FOR governmentgovernment – – governorgovernor ALTHOUGH ROBUST PRIMING FOR government – govern government – govern

(Marslen-Wilson, W. D., Tyler, L., Waksler, R., & Older, L. (1994). Morphology and meaning in the English mental lexicon. Psychological Review 101, 3-33.)

Alternative explanation for lack of cumulative Alternative explanation for lack of cumulative root frequency effects in derivationroot frequency effects in derivation• High morphological family frequency speeds up root activationroot activation

BUTBUT this facilitation is cancelled out by subsequent competitioncompetition between the highly frequent morphological family members.

How to measure timing of root activation, prior to any effect of competition?How to measure timing of root activation, prior to any effect of competition? M350, an magnetoencephalographic (MEG) response component elicited by word stimuli, peaking at ~350ms post word-onsetM350, an magnetoencephalographic (MEG) response component elicited by word stimuli, peaking at ~350ms post word-onset

Magnetoencephalography (MEG)Magnetoencephalography (MEG)

• Measures magnetic fields generated by large populations of neurons firing in synchrony.

• Millisecond temporal resolution.

• Millimeter spatial resolution (at least for cortical sources).

Magnetoencephalography (MEG)Magnetoencephalography (MEG)

What happens in the brain when we read words?

-100 0 100 200 300 400 500 600 700 [msec]

0

200

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[fT]

150-200ms (M170) 200-300ms (M250) 300-400ms (M350) 400-500ms

Pylkkänen and Marantz, Trends in Cognitive Sciences, in press.

Letter string processing

(Tarkiainen et al. 1999)

Lexical activation

(Pylkkänen et al. 2002)


300-400ms (M350)

Lexical activation

(Pylkkänen et al. 2002)The M350 is sensitive to

1. Lexical frequency (a)2. Repetition (b)3. Phonological similarity (c)4. Semantic similarity (d)5. Sublexical frequency (e, f)

The M350 is NOT sensitive to1. Interlexical competition (e)

(a) Embick, D., Hackl, M., Schaeffer, J., Kelepir, M. & Marantz, A. (2001). A magnetoencephalographic component whose latency reflects lexical frequency. Cognitive Brain Research 10:3, 345-348.

(b) Pylkkänen, L., Stringfellow, A., Flagg, E., Marantz, A. (2001). A Neural Response Sensitive to Repetition and Phonotactic Probability: MEG Investigations of Lexical Access. Proceedings of Biomag 2000. 12th International Conference on Biomagnetism. Helsinki University of Technology, Espoo, Finland. 363-367.

(c) Pylkkänen, L., Stringfellow, A. Marantz, A. 2002. Inhibition and Competition in Word Recognition: MEG Evidence. Submitted. (d) Pylkkänen, L. Stringfellow, A., Gonnerman, L., Marantz, A. 2002. Magnetoencephalographic indices of identity and similarity in lexical access. In preparation. (e) Pylkkänen, L., Stringfellow, A. Marantz, A. 2002. Neuromagnetic evidence for the timing of lexical activation: an MEG component sensitive to phonotactic probability but not

to neighborhood density. Brain and Language 81, 666-678. (f) Stockall, L. Stringfellow, A. Marantz, A. 2003. The precise time course of lexical activation: MEG measurements of the effects of frequency, probability and density in

lexical decision, Submitted.



300-400ms (M350)

Lexical activation

(Pylkkänen et al. 2002)The M350 is sensitive to

1. Lexical frequency (a)2. Repetition (b)3. Phonological similarity (c)4. Semantic similarity (d)5. Sublexical frequency (e, f)

The M350 is NOT sensitive to1. Interlexical competition (e)

(a) Embick, D., Hackl, M., Schaeffer, J., Kelepir, M. & Marantz, A. (2001). A magnetoencephalographic component whose latency reflects lexical frequency. Cognitive Brain Research 10:3, 345-348.

(b) Pylkkänen, L., Stringfellow, A., Flagg, E., Marantz, A. (2001). A Neural Response Sensitive to Repetition and Phonotactic Probability: MEG Investigations of Lexical Access. Proceedings of Biomag 2000. 12th International Conference on Biomagnetism. Helsinki University of Technology, Espoo, Finland. 363-367.

(c) Pylkkänen, L., Stringfellow, A. Marantz, A. 2002. Inhibition and Competition in Word Recognition: MEG Evidence. Submitted. (d) Pylkkänen, L. Stringfellow, A., Gonnerman, L., Marantz, A. 2002. Magnetoencephalographic indices of identity and similarity in lexical access. In preparation. (e) Pylkkänen, L., Stringfellow, A. Marantz, A. 2002. Neuromagnetic evidence for the timing of lexical activation: an MEG component sensitive to phonotactic

probability but not to neighborhood density. Brain and Language 81, 666-678. (f) Stockall, L. Stringfellow, A. Marantz, A. 2003. The precise time course of lexical activation: MEG measurements of the effects of frequency, probability and density in

lexical decision, Submitted.


100

200

300

400

500

600

700

800

M170 M250 M350 RT

High probability word Low probability word

n.s.

n.s.

*

*

100

200

300

400

500

600

700

800

M170 M250 M350 RT

High probability nonword Low probability nonword

n.s.n.s.

*

*

(Pylkkänen, Stringfellow, Marantz, Brain and Language, 2002)

Effect of probability/density Effect of probability/density (n=10)(n=10)

(i) 1st component sensitive to lexical factors (such as lexical frequency)

(ii) not affected by competition

time

leve

l of a

ctiv

atio

n

resting level

Stimulus: TURN

TURN

TURNIP

TURFTURTLE

ActivationActivation SelectionSelectionCompetitionCompetition

M350

• Effect of high phonotactic probability/ high neighborhood density:

HypothesisHypothesis

M350M350 RTRT

- - speed-up due to speed-up due to sublexical frequencysublexical frequency

- - slow-down due to slow-down due to competitioncompetition

• Effect of high morphological family frequency?

M350M350 RTRT

- - speed-up due to speed-up due to cumulative root frequencycumulative root frequency

- - slow-down due to slow-down due to competition from highly competition from highly frequent family membersfrequent family members

• Contrast 1: Family frequency

• Contrast 2: Family size

• Four categories of visual words, all nouns

magnet (n=18)terror (n=18)

- ic –ize –ism- ist –ize -ism

HIGH LOW Matched for:Length Freq. of the sg, Cumulative freq. of the sg. & pl. forms Family size Mean bigram frequency

acid (n=21) diary (n=21)

- ic –ity –ify –head –test –washed - ist

HIGH LOW Matched for:Length Freq. of the sg, Cumulative freq. of the sg. & pl. forms • Family frequency (not perfectly) Mean bigram frequency

Materials Materials (from (from Baayen, R. H., Lieber, R., & Schreuder, R. (1997). Baayen, R. H., Lieber, R., & Schreuder, R. (1997). Linguistics Linguistics 35, 861-87735, 861-877))

BehaviorBehavior

*n.s.

Behavioral data (n=10)

550

600

650

700

750

800

850

High-Freq Low-Freq High-Size Low-Size

[mse

c] *n.s

.

(Pylkkänen, Feintuch, Hopkins & Marantz, Cognition, to appear)

M350 source analysisM350 source analysis

HBM 2003, poster 1345

• Equivalent current dipole analysis• Latencies and amplitudes measured at points where the

source amplitude reached 25%, 50%, 75% and 100% of the maximum source strength.

25%50%75%100%

MEG data, single subjectMEG data, single subject

(Pylkkänen, Feintuch, Hopkins & Marantz, Cognition, to appear)

Family frequency: M350 (S1)Family frequency: M350 (S1)


05

10152025303540

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[msec]

[nA

m]

High family frequency


05

10152025303540

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[msec]

[nA

m]

High family frequency



05

10152025303540

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[msec]

[nA

m]

High family frequency Low family frequency

Extra processing load at the M350

Morphological competition at the M350



Family frequency: M350 amplitude Family frequency: M350 amplitude (n=10)(n=10)

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[nA

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high family frequency low family frequency


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*

Family frequency: M350 amplitude Family frequency: M350 amplitude (n=10)(n=10)


Family frequency: M350 latency Family frequency: M350 latency (n=10)(n=10)

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100% 75%fall

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[mse

c]


all n.s.


Family size: M350 amplitude (n=10)Family size: M350 amplitude (n=10)

05

1015202530354045

25%rise

50%rise

75%rise

100% 75%fall

50%fall

25%fall

[nA

m]

high family size low family size

all n.s.P = 0.09


Family : M350 latency (n=10)Family : M350 latency (n=10)

200

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RT

[mse

c]

high family size low family size

** *

M170 M250 M350 RT

(lexical decision)

High sublexical frequency/neighborhood density

Smaller amplitude

Shorter latency

Longer RT

(competition)

High morphological family frequency

Larger amplitude

(competition)

High morphological family size

Shorter latency

Shorter RT

1. Difference in the time course of competition.

2. High family size has an early facilitory effect.

Why?

1. Difference in the time course of competition1. Difference in the time course of competition

High frequency High frequency morphological familymorphological family

TERRORTERROR- ist –ize -ism

LINELINEloin

fine

pine

nine

lightlike

lie

lane

lime

High density phonological High density phonological neighborhood (frequency-weighted)neighborhood (frequency-weighted)

LINELINEloin

fine

pine

nine

lightlike

lie

lane

lime

TERRORTERRORterrorism

terrorize terrorist

DECOMPOSITIONDECOMPOSITION

NO NO DECOMPOSITIONDECOMPOSITION

Relationship between target and competitors qualitatively different: difference is due to morphology.

Difference is due to the different phonological and/or semantic properties of the competitors.


LINELINEloin

fine

pine

nine

lightlike

lie

lane

lime

TERRORTERRORterrorism

terrorize terroristNO NO DECOMPOSITIONDECOMPOSITION

Difference is due to the different phonological and/or semantic properties of the competitors.

Non-decompositional account also predicts interference effects in priming for pairs such as TERRORISM – TERROR.TERRORISM – TERROR.

BUT this is completely unsupported by data – effect is robustly BUT this is completely unsupported by data – effect is robustly facilitory (e.g. a-d)facilitory (e.g. a-d)..

(a) Marslen-Wilson, W. D., Tyler, L., Waksler, R., & Older, L. (1994). Morphology and meaning in the English mental lexicon. Psychological Review 101, 3-33.(b) Pylkkänen, L. Stringfellow, A., Gonnerman, L., Marantz, A. 2002. Magnetoencephalographic indices of identity and similarity in lexical access. In preparation. (c) Gonnerman, L. 1999, Morphology and the lexicon: exploring the semantics-phonology interface, PhD thesis, University of Southern California.(d) Rastle, K., Davis, M., Marslen

-Wilson, W., & Tyler, L.K. (2000). Morphological and semantic effects in visual word recognition: A time course study. Language and Cognitive Processes, 15, 507-538.

http://web.mit.edu/liina/Public/Neuroling_readings/RastleEtAl00.pdf






High frequency High frequency morphological familymorphological family

TERRORTERROR- ist –ize -ism

LINELINEloin

fine

pine

nine

lightlike

lie

lane

lime

High density phonological High density phonological neighborhood (frequency-weighted)neighborhood (frequency-weighted)

DECOMPOSITIONDECOMPOSITION

Competition between morphological family members appears to precede competition between phonological neighbors.

An account of the phenomenon needs to make a distinction between morphological and phonological competitors.

ConclusionConclusion


DecompositionDecompositionEarly morphological parsing/ segmentation Lexical access

Morphological competition effects

Phonological competition effects


Grammar happens early:Grammar happens early:

• Early determination of grammatical category in ERPs (Friederici, 2002).

• Early effects of morphology in masked priming (Rastle, Davis & New submitted)


2. High family size has an 2. High family size has an earlyearly facilitory effect facilitory effect

One possibility:• Effect is semantic in nature and is related to effects of polysemy.

• Heavily polysemous words (such as belt) are processed faster than words that only have few “senses” (such as ant).(Rodd, Gaskell & Marslen-Wilson (2002) Making Sense of Semantic Ambiguity: Semantic Competition in Lexical Access. Journal of Memory and Language 46, 245–266)


• Different morphological environments induce different senses of the root and therefore nouns with large morphological families have more senses than nouns with small morphological families.

•Prediction: semantically opaque morphological family members should contribute to the family size effect the most, as those would involve the most “sense-switching”.

•BUT: there is at least some evidence that the family size effect is in fact mostly carried by the semantically transparent members of the family.(De Jong NH, Feldman LB, Schreuder R, Pastizzo M, Baayen RH (2002) The processing and representation of Dutch and English compounds: peripheral morphological and central orthographic effects. Brain Lang 2002 Apr-Jun;81(1-3):555-67.)


Alternatively:The family size effect is not a facilitory effect of high family size, but an inhibitory effect stemming from more potent competitors in the low family size condition.

acid diary

-ic -ity -ify -head -test -washed -Ø

-st -ø

Keeping family frequency constant but lowering family size creates more potent competitors.(See Perea and Rosa (2000) for a review of studies indicating that the important neighborhood variable in visual word recognition is not the number of neighbors per se, but the frequency of a word's neighbors relative to its own frequency. Perea M. and E. Rosa (2000) Psicologica, 21, 327-340)


• Evidence for decomposition (although somewhat indirect).

• Evidence for the existence of morphological competition (cf. Marslen-Wilson 1994).

• Identification of a neural correlate of the morphological family size effect.

Thanks to:

Sophie Feintuch & Emily Hopkins (Portsmouth High School, NH)



I. Morphological family effects.II. Early effects of superficial morphology in masked


ERP literature.

Rastle, Davis & New (2003)Rastle, Davis & New (2003)

• Masked priming – eliminates semantic effects.• 500ms forward mask, 43ms prime.

TRANSPARENT: cleaner – CLEAN OPAQUE: corner – CORN

ORTHOGRAPHIC: brothel - BROTH



• Result:


EQUAL PRIMING

NO PRIMING

TRANSPARENT: cleaner – CLEAN OPAQUE: corner – CORN

ORTHOGRAPHIC: brothel - BROTH


Conclusion:There is an early processing stage of pre-

lexical morphological segmentation which is based only on the formal properties of the input.


If morphological parsing occurs early, one would expect morphological competition to occur early as well, which is what the family frequency results suggest.



I. Morphological family effects.II. Early superficial effects of morphology in masked


ERP literature.

Zweig et al.: Does morphological decomposition Zweig et al.: Does morphological decomposition require semantic transparency?require semantic transparency?

• If semantically opaque forms aren’t decomposed, processing a form such as UNIVERSITY would involve

i. access to the lexical representation UNIVERSITY

(Zweig, van Rijsingen & Pylkkänen, in progress)

Does morphological decomposition require Does morphological decomposition require semantic transparency?semantic transparency?

• If semantically opaque forms are decomposed, processing a form such as UNIVERSITY would involve

i. access to UNIVERSE and ITYii. combining UNIVERSE and ITYiii. access to the special meaning that is associated with

this complex structure

• Processing semantically transparent morphology would not involve step (iii).



• Decomposition hypothesis: Semantically opaque morphology should be HARDER than semantically transparent morphology.

• Storage hypothesis: Semantically opaque morphology should be easier EASIER than semantically transparent morphology.



• Most research on the effects of morphological transparency has used a priming paradigm.

• However, it’s unclear what the decomposition account would predict the effect of step (iii) (= access to a special meaning) to be in a priming paradigm – could be a complicated combination of priming and inhibition.

• The basic, contrasting, predictions of the Storage and Decomposition hypotheses can be tested in single-word lexical decision.



MaterialsMaterials

• 5 bins of 16 affixed or “pseudoaffixed” forms organized according to subjective ratings of “connectivity” between the base and the affixed form

• Affixes used: -ity, -ment, -er, and –en.

“Connectivity” to the base increases

Transparent

Pseudoaffixed

Opaque

• Bins matched for length, base frequency, frequency of the affixed form and difference in frequency between the base and the affixed form.

Bin 1: CORNERBin 2: RUBBERBin 3: SNEAKERBin 4: HEADERBin 5: CONSUMER



MaterialsMaterials

• 5 bins of 16 affixed or “pseudoaffixed” forms organized according to subjective ratings of “connectivity” between the base and the affixed form

• Affixes used: -ity, -ment, -er, and –en.

“Connectivity” to the base increases

Transparent

Pseudoaffixed

Opaque

Bin 1: CORNERBin 2: RUBBERBin 3: SNEAKERBin 4: HEADERBin 5: CONSUMER

• + 16 length and surface frequency matched non-affixed forms (e.g. PAINT).

• 40 non-words formed by attaching affixes to real words (STUPIDMENT).• 40 non-words formed by attaching affixed to non-words (LIFFMENT).• 74 non-affixed real words (stimuli for a different experiment).• 90 non-affixed non-words (stimuli for a different experiment).


600620640660680700720740760780

0 1 2 3 4 5PAINT CORNER RUBBER SNEAKER HEADER CONSUMER

[msec]

Pseudoaffixed Opaque TransparentNon-affixed

Results (n = 14)Results (n = 14)




600620640660680700720740760780


[msec]

Pseudoaffixed Opaque TransparentNon-affixed(Zweig, van Rijsingen & Pylkkänen, in progress)



600620640660680700720740760780


[msec]

Pseudoaffixed Opaque TransparentNon-affixed

All affixation is costly.

Semantically opaque “real” morphology is the most costly.

Cannot be accounted for by the Storage hypothesis.







ERP literature.

Category, first-pass parsing, ELANCategory, first-pass parsing, ELAN

• The Rastle, Davis et al. proposal about fast semantics-free segmentation should connect to models of sentence processing where first-pass parsing occurs purely on the basis of word category information (Frazier, Friederici).

• Earliness of morphological segmentation:In ERP’s, violating a word category expectation has been reported to lead to an Early Left Anterior Negativity (ELAN).

NP required but participle occurs:

Der Freund wurde im besucht‘The friend was in-the visited.’


ELAN, how early?ELAN, how early?

• Auditory:• As early as 50ms after word uniqueness point:

The holiday is being shortened/shortening.

• Visual:• Usually a LAN – around 400ms.






ERP literature.

Stimulus factors affecting the M350Stimulus factors affecting the M350

• Lexical frequency in visual and auditory modality• Repetition• Phonotactic probability (likely a secondary effect)

• Phonological similarity in priming• Semantic similarity in priming• Regular morphological relatedness in priming

• regular AND irregular • Constituent frequency in compounds• Morphological family frequency• Morphological family size


Representation:Representation:• There is a modality There is a modality

independent lexicon.independent lexicon.

• Lexical entries connect Lexical entries connect sound and meaning – single sound and meaning – single lexicon.lexicon.

• All word formation is All word formation is syntactic. syntactic.

Revisiting: Assumptions/hypotheses that drive, Revisiting: Assumptions/hypotheses that drive, and are tested by, the present researchand are tested by, the present research


Processing:Processing:• Timing of lexical access Timing of lexical access

depends on the activation level depends on the activation level of lexical entries at stimulus of lexical entries at stimulus presentation.presentation.

• The activation level of lexical The activation level of lexical entries depends onentries depends on

• FrequencyFrequency

• Preceding context (priming)Preceding context (priming)

• Phonological and semantic Phonological and semantic relatedness should affect the relatedness should affect the same neural activity.same neural activity.

NB: All of these assumptions are more or less controversial so we’ll continually keep evaluating how they succeed in explaining the data.

N400 ERPN400 ERPLP, Aug 03, Tateshina

N =12

_ _ _ He spread the warm bread with SOCKS

____ He spread the warm bread with BUTTER (Kutas and Hillyard, 1980)

• Discovered in a semantic anomaly manipulation.

• But today we know that every word in a sentence elicits an N400. Not a “violation-component”

M350 = N400?M350 = N400?


Polarity Polarity

• A typical M350 source should generate a negativity at the top of the head.

• N400 usually largest at central/midline electrodes.

_

+

Polarity Polarity

• NB: The M350 is often bilateral. • Both the LH and RL

M350 sources contribute to the midline negativity.

• N400 sums over both hemispheres.

_

+

Localization of the N400 using MEGLocalization of the N400 using MEG

• Helenius et al 1999:• Classic N400 paradigm in MEG.• Source of the N400 localizes where the M350

localizes: in the vicinity of the left auditory cortex.

(Helenius, P, Salmelin, E, et al. 1998. Distinct time courses of word and context comprehension in the left temporal cortex. Brain, 121, 1133-1142. )

http://web.mit.edu/liina/Public/Neuroling_readings/helen_N400_Brain.pdf




Timing: N400 Timing: N400

N =12

_ _ _ He spread the warm bread with SOCKS

____ He spread the warm bread with BUTTER (Kutas and Hillyard, 1980)

• Onset: ~250ms.• Peak: ~400ms• Offset: ~550-600ms.

M350 distribution

Timing: M350 Timing: M350

• Important:• The M350 is defined

as the first peak of the M350 distribution.

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[fT]

• But the M350 field pattern often peaks twice.

• Most of our M350 effects hold of the first peak, not of the second.


• Important:• The M350 is defined

as the first peak of the M350 distribution.

-100 0 100 200 300 400 500 600 700 [msec]

0

200

200

[fT]

• But the M350 field pattern often peaks twice.

• Most of our M350 effects hold of the first peak, not of the second.

M350

NOT M350 although may have more or less the same source.


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M350


Timing of the M350 and timing of the M350 source are two separate questions.


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M350


• M350:From valley to valley, may as short as 50ms.

• M350 source:Onset: 300msPeak 1: ~350ms(Peak 2: ~450ms)Offset: ~500ms

Stimulus factors affecting the N400 (partial list)Stimulus factors affecting the N400 (partial list)LP, Aug 03, Tateshina

Also affects M350?

Same kind of effect?

Expectancy:Smaller N400 for highly expected words.

YES for M350 source(Helenius et al.)

YES

Repetition:Smaller N400 for repeated words.

YES NO (latency effect for M350)

Semantic similarity:Smaller N400 for semantically related words in priming.

YES YES (but w/M350, also latency)

Phonological similarity:Smaller N400 for phonologically related words in priming.

YES YES for rhyme, NO for onset-matching

Lexical frequency: Smaller N400 for frequent words.

YES NO (latency effect for M350)

Position in sentence:N400 gets smaller the further into the sentence it occurs

? ?

M350 M350 ≠≠ N400 N400

but the M350 is likely a but the M350 is likely a subcomponent of the N400 subcomponent of the N400 (the M250 might also be a (the M250 might also be a

subcomponent of the N400).subcomponent of the N400).


Possible reasons for differences in Possible reasons for differences in waveform morphology in MEG and ERPswaveform morphology in MEG and ERPs


1. EEG picks up more activity than MEG.

2. ERP data are usually grandaveraged.• Small latency differences may be lost.

3. Summation over hemispheres in ERPs.• Differences between hemispheres may be lost.

(Some) outstanding questions(Some) outstanding questions


Latency vs. amplitude effectsLatency vs. amplitude effectsLP, Aug 03, Tateshina

• Some stimulus factors affect M350 latencies (e.g. lexical frequency, morphological family size) while others affect amplitudes (e.g. morphological family frequency).

• General assumption in cognitive neuroscience: more processing load more activity.

• How should we understand the relationship between latency and amplitude effects?

Functional significance of the “M250”Functional significance of the “M250”LP, Aug 03, Tateshina

• Activity at 200-300ms difficult to manipulate.

• Lots of distributional variance across subjects.

• Not a single source and depends on the individual’s brain physiology which part of the activity is captured by MEG?

M350 in the right hemisphereM350 in the right hemisphereLP, Aug 03, Tateshina

• The M350 is bilateral roughly 60% of the time (impressionistic estimate).

• There has been no systematic investigation of RH M350 sources.

• The problem being that it’s still difficult to obtain enough RH sources within a single study to obtain statistical power.

What’s so special about the M350 peak What’s so special about the M350 peak (as opposed to other points on the waveform)?(as opposed to other points on the waveform)?


• One might expect activation of the lexicon to be indexed as a rise in activity in a source.

• Why do most of our effects only hold at the peak of the M350?

Post-M350 activity and neural Post-M350 activity and neural correlates of recognitioncorrelates of recognition


• The M350 is not sensitive to (phonologically-based) interlexical competition.

• What activity is? – We’ve identified no MEG activity that would appear

to index recognition (i.e. selection instead of activation).


Thank Thank you!you!

liina pylkkänen department of linguistics/ center for

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