Liina Pylkkänen Department of Linguistics/ Center for Neuromagnetism New York University MEG, the Mental Lexicon and Morphology LP, Aug 03, Tateshina

Day 1 Lexical access 1: The M350 as an MEG index of lexical activation Day 2 Lexical access 2: The M350 and mechanisms of recognition Day 3 Morphology 1: The M350 as a tool for investigating similarity and identity Day 4 Morphology 2: Electrophysiological and behavioral evidence for early effects of morphology MEG, the Mental Lexicon and Morphology LP, Aug 03, Tateshina

Day 4 Morphology 2: Electrophysiological and behavioral evidence for early effects of morphology LP, Aug 03, Tateshina 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.

Day 4 Morphology 2: Electrophysiological and behavioral evidence for early effects of morphology LP, Aug 03, Tateshina 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 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 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 due to high cumulative root frequency

Cumulative root frequency effects for inflection 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 for derivation Family frequency magnet terror - ic –ize –ism - ist –ize -ism HIGH LOW Family frequency does not affect lexical decision times. Family size acid diary - ic –ity –ify –head –test –washed - ist HIGH LOW High family size speeds up lexical decision times. Schreuder & Baayen (1997): S&B: this is a late post-lexical effect. S&B: Therefore, no decomposition in derivation.

Alternative explanation for lack of cumulative root frequency effects in derivation root activationHigh morphological family frequency speeds up root activationBUT competition this facilitation is cancelled out by subsequent competition between the highly frequent morphological family members. Hypothesized affix-competition in priming (Marslen-Wilson, et al. 1994) : In crossmodal priming, NO PRIMING FOR government – governor ALTHOUGH ROBUST PRIMING FOR 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 root frequency effects in derivation root activationHigh morphological family frequency speeds up root activationBUT competition this facilitation is cancelled out by subsequent competition between the highly frequent morphological family members.  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-onset

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)

What happens in the brain when we read words? [msec] [fT] ms (M170) ms (M250) ms (M350) ms Pylkkänen and Marantz, Trends in Cognitive Sciences, in press. Letter string processing (Tarkiainen et al. 1999) Lexical activation (Pylkkänen et al. 2002)

What happens in the brain when we read words? ms (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 to 1.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, (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 th International Conference on Biomagnetism. Helsinki University of Technology, Espoo, Finland (c)Pylkkänen, L., Stringfellow, A. Marantz, A Inhibition and Competition in Word Recognition: MEG Evidence. Submitted. (d)Pylkkänen, L. Stringfellow, A., Gonnerman, L., Marantz, A Magnetoencephalographic indices of identity and similarity in lexical access. In preparation. (e)Pylkkänen, L., Stringfellow, A. Marantz, A Neuromagnetic evidence for the timing of lexical activation: an MEG component sensitive to phonotactic probability but not to neighborhood density. Brain and Language 81, (f) Stockall, L. Stringfellow, A. Marantz, A The precise time course of lexical activation: MEG measurements of the effects of frequency, probability and density in lexical decision, Submitted. Pylkkänen and Marantz, Trends in Cognitive Sciences, in press.

What happens in the brain when we read words? ms (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 to 1.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, (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 th International Conference on Biomagnetism. Helsinki University of Technology, Espoo, Finland (c)Pylkkänen, L., Stringfellow, A. Marantz, A Inhibition and Competition in Word Recognition: MEG Evidence. Submitted. (d)Pylkkänen, L. Stringfellow, A., Gonnerman, L., Marantz, A Magnetoencephalographic indices of identity and similarity in lexical access. In preparation. (e)Pylkkänen, L., Stringfellow, A. Marantz, A Neuromagnetic evidence for the timing of lexical activation: an MEG component sensitive to phonotactic probability but not to neighborhood density. Brain and Language 81, (f) Stockall, L. Stringfellow, A. Marantz, A The precise time course of lexical activation: MEG measurements of the effects of frequency, probability and density in lexical decision, Submitted. Pylkkänen and Marantz, Trends in Cognitive Sciences, in press.

n.s. * * * * (Pylkkänen, Stringfellow, Marantz, Brain and Language, 2002) Effect of probability/density (n=10)

(i) 1 st component sensitive to lexical factors (such as lexical frequency) (ii) not affected by competition time level of activation resting level Stimulus: TURN TURN TURNIP TURF TURTLEActivationSelection Competition M350

Effect of high phonotactic probability/ high neighborhood density: Hypothesis M350 RT - speed-up due to sublexical frequency - slow-down due to competition Effect of high morphological family frequency?M350 RT - speed-up due to cumulative root frequency - slow-down due to competition from highly frequent 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 (from Baayen, R. H., Lieber, R., & Schreuder, R. (1997). Linguistics 35, )

Behavior * n.s. * (Pylkkänen, Feintuch, Hopkins & Marantz, Cognition, to appear)

M350 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 subject (Pylkkänen, Feintuch, Hopkins & Marantz, Cognition, to appear)

Family frequency: M350 (S1) HBM 2003, poster 1345 High family frequency

HBM 2003, poster 1345 High family frequency Family frequency: M350 (S1)

HBM 2003, poster 1345 High family frequency Low family frequency Extra processing load at the M350  Morphological competition at the M350 Family frequency: M350 (S1)

HBM 2003, poster 1345 Family frequency: M350 amplitude (n=10)

HBM 2003, poster 1345 * Family frequency: M350 amplitude (n=10)

HBM 2003, poster 1345 Family frequency: M350 latency (n=10) all n.s.

HBM 2003, poster 1345 Family size: M350 amplitude (n=10) all n.s. P = 0.09

HBM 2003, poster 1345 Family : M350 latency (n=10) ** *

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 competition High frequency morphological family TERROR - ist –ize -ism LINE loin fine pine nine light like lie lane lime High density phonological neighborhood (frequency-weighted) LINE loin fine pine nine light like lie lane lime TERROR terrorism terrorize terrorist DECOMPOSITION NO DECOMPOSITION  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.

1. Difference in the time course of competition LINE loin fine pine nine light like lie lane lime TERROR terrorism terrorize terrorist NO DECOMPOSITION  Difference is due to the different phonological and/or semantic properties of the competitors. TERRORISM – TERROR.  Non-decompositional account also predicts interference effects in priming for pairs such as TERRORISM – TERROR.  BUT this is completely unsupported by data – effect is robustly 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, (b)Pylkkänen, L. Stringfellow, A., Gonnerman, L., Marantz, A 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, 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,

1. Difference in the time course of competition High frequency morphological family TERROR - ist –ize -ism LINE loin fine pine nine light like lie lane lime High density phonological neighborhood (frequency-weighted) DECOMPOSITION  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.

Conclusion HBM 2003, poster 1345 Decomposition Early morphological parsing/ segmentation Lexical access Morphological competition effects Phonological competition effects

HBM 2003, poster 1345 Grammar happens early: Early determination of grammatical category in ERPs (Friederici, 2002). Early effects of morphology in masked priming (Rastle, Davis & New submitted) Conclusion

2. High family size has an early 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)

2. High family size has an early facilitory effect 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): )

2. High family size has an early facilitory effect 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. aciddiary -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, )

Conclusion 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)

Day 4 Morphology 2: Electrophysiological and behavioral evidence for early effects of morphology LP, Aug 03, Tateshina 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.

Rastle, Davis & New (2003) Masked priming – eliminates semantic effects. 500ms forward mask, 43ms prime. TRANSPARENT: cleaner – CLEAN OPAQUE: corner – CORN ORTHOGRAPHIC:brothel - BROTH LP, Aug 03, Tateshina

Rastle, Davis & New (2003) Result: LP, Aug 03, Tateshina EQUAL PRIMING NO PRIMING TRANSPARENT: cleaner – CLEAN OPAQUE: corner – CORN ORTHOGRAPHIC:brothel - BROTH

Rastle, Davis & New (2003) Conclusion: There is an early processing stage of pre- lexical morphological segmentation which is based only on the formal properties of the input. LP, Aug 03, Tateshina  If morphological parsing occurs early, one would expect morphological competition to occur early as well, which is what the family frequency results suggest.

Day 4 Morphology 2: Electrophysiological and behavioral evidence for early effects of morphology LP, Aug 03, Tateshina I.Morphological family effects. II.Early superficial effects of 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.

Zweig et al.: Does morphological decomposition 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 semantic transparency? If semantically opaque forms are decomposed, processing a form such as UNIVERSITY would involve i.access to UNIVERSE and ITY ii.combining UNIVERSE and ITY iii.access to the special meaning that is associated with this complex structure Processing semantically transparent morphology would not involve step (iii). (Zweig, van Rijsingen & Pylkkänen, in progress)

Does morphological decomposition require semantic transparency? 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. (Zweig, van Rijsingen & Pylkkänen, in progress)

Does morphological decomposition require semantic transparency? 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. (Zweig, van Rijsingen & Pylkkänen, in progress) LP, Aug 03, Tateshina

Materials 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:CORNER Bin 2:RUBBER Bin 3:SNEAKER Bin 4:HEADER Bin 5:CONSUMER (Zweig, van Rijsingen & Pylkkänen, in progress) LP, Aug 03, Tateshina

Materials 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:CORNER Bin 2:RUBBER Bin 3:SNEAKER Bin 4:HEADER Bin 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). LP, Aug 03, Tateshina

PAINT CORNER RUBBER SNEAKER HEADER CONSUMER [msec] Pseudoaffixed OpaqueTransparent Non-affixed Results (n = 14) (Zweig, van Rijsingen & Pylkkänen, in progress) LP, Aug 03, Tateshina

Results (n = 14) PAINT CORNER RUBBER SNEAKER HEADER CONSUMER [msec] Pseudoaffixed OpaqueTransparent Non-affixed (Zweig, van Rijsingen & Pylkkänen, in progress) LP, Aug 03, Tateshina

Results (n = 14) PAINT CORNER RUBBER SNEAKER HEADER CONSUMER [msec] Pseudoaffixed Opaque Transparent Non-affixed  All affixation is costly.  Semantically opaque “real” morphology is the most costly.  Cannot be accounted for by the Storage hypothesis. (Zweig, van Rijsingen & Pylkkänen, in progress) LP, Aug 03, Tateshina

Day 4 Morphology 2: Electrophysiological and behavioral evidence for early effects of morphology LP, Aug 03, Tateshina I.Morphological family effects. II.Early superficial effects of 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.

Category, 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.’ LP, Aug 03, Tateshina

ELAN, how early? Auditory: As early as 50ms after word uniqueness point: The holiday is being shortened/shortening. Visual: Usually a LAN – around 400ms. LP, Aug 03, Tateshina

Day 4 Morphology 2: Electrophysiological and behavioral evidence for early effects of morphology LP, Aug 03, Tateshina I.Morphological family effects. II.Early superficial effects of 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.

Stimulus 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 LP, Aug 03, Tateshina

Representation: There is a modality independent lexicon.There is a modality independent lexicon. Lexical entries connect sound and meaning – single lexicon.Lexical entries connect sound and meaning – single lexicon. All word formation is syntactic.All word formation is syntactic. Revisiting: Assumptions/hypotheses that drive, and are tested by, the present research LP, Aug 03, Tateshina Processing: Timing of lexical access depends on the activation level of lexical entries at stimulus presentation.Timing of lexical access depends on the activation level of lexical entries at stimulus presentation. The activation level of lexical entries depends onThe activation level of lexical entries depends on FrequencyFrequency Preceding context (priming)Preceding context (priming) Phonological and semantic relatedness should affect the same neural activity.Phonological and semantic relatedness should affect the 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 ERP LP, 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? LP, Aug 03, Tateshina

Polarity A typical M350 source should generate a negativity at the top of the head. N400 usually largest at central/midline electrodes. _ +

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

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: ~ ms.

M350 distribution Timing: M350 Important: The M350 is defined as the first peak of the M350 distribution [msec] [fT] But the M350 field pattern often peaks twice. Most of our M350 effects hold of the first peak, not of the second.

Timing: M350 Important: The M350 is defined as the first peak of the M350 distribution [msec] [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.

Timing: M [msec] [fT] M350 NOT M350 although may have more or less the same source.  Timing of the M350 and timing of the M350 source are two separate questions.

Timing: M [msec] [fT] M350 NOT M350 although may have more or less the same source. M350: From valley to valley, may as short as 50ms. M350 source: Onset: 300ms Peak 1: ~350ms (Peak 2: ~450ms) Offset: ~500ms

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. YESNO (latency effect for M350) Semantic similarity: Smaller N400 for semantically related words in priming. YESYES (but w/M350, also latency) Phonological similarity: Smaller N400 for phonologically related words in priming. YESYES for rhyme, NO for onset- matching Lexical frequency: Smaller N400 for frequent words. YESNO (latency effect for M350) Position in sentence: N400 gets smaller the further into the sentence it occurs ??

M350 ≠ N400 but the M350 is likely a subcomponent of the N400 (the M250 might also be a subcomponent of the N400). LP, Aug 03, Tateshina

Possible reasons for differences in waveform morphology in MEG and ERPs LP, Aug 03, Tateshina 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 LP, Aug 03, Tateshina

Latency vs. amplitude effects LP, 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” LP, Aug 03, Tateshina Activity at ms 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 hemisphere LP, 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 (as opposed to other points on the waveform)? LP, Aug 03, Tateshina 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 correlates of recognition LP, Aug 03, Tateshina 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).

LP, Aug 03, Tateshina Thank you!