Liina Pylkk

1
LP, Aug 03, Tateshina
MEG, the Mental Lexicon and Morphology

• Liina Pylkkänen
• Department of Linguistics/ Center for
  Neuromagnetism
• New York University

2
LP, Aug 03, Tateshina
MEG, the Mental Lexicon and Morphology

• 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

3
LP, Aug 03, Tateshina
Day 4 Morphology 2 Electrophysiological and
behavioral evidence for early effects of
morphology

• Morphological family effects.
• Early effects of superficial morphology in masked
  priming.
• Role of semantic transparency.
• Early effects of morphology in ERPs.
• Grand summary of MEG results and comparison to
  ERP literature.

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

• Morphological family effects.
• Early effects of superficial morphology in masked
  priming.
• Role of semantic transparency.
• Early effects of morphology in ERPs.
• Grand summary of MEG results and comparison to
  ERP literature.

5
Effect of lexical frequency

• High frequency words are processed faster than
  low frequency words.
• Prediction of decompositional theories of
  morphology cumulative root frequency effects.

6
Effect of lexical frequency

• High frequency words are processed faster than
  low frequency words.
• Prediction of decompositional theories of
  morphology cumulative root frequency effects.

Same number of derivates
High frequency derivatives
Low frequency derivatives
- ist ize -ism
- ic ize ism
terror
magnet
Matched for surface frequency
7
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

8
But NO cumulative root frequency effects for
derivation
Schreuder Baayen (1997)

• Family frequency

HIGH
LOW
Family frequency does not affect lexical decision
times.
- ic ize ism
- ist ize -ism
terror
SB Therefore, no decomposition in derivation.
magnet
High family size speeds up lexical decision times.
SB this is a late post-lexical effect.
9
Alternative explanation for lack of cumulative
root frequency effects in derivation

• High morphological family frequency speeds up
  root activation
• BUT
• 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.)

10
Alternative explanation for lack of cumulative
root frequency effects in derivation

• High morphological family frequency speeds up
  root activation
• BUT
• 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

11
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).

12
Magnetoencephalography (MEG)
13
What happens in the brain when we read words?
Letter string processing (Tarkiainen et al. 1999)
Lexical activation (Pylkkänen et al. 2002)
14
What happens in the brain when we read words?
Lexical activation (Pylkkänen et al. 2002)

• The M350 is sensitive to
• Lexical frequency (a)
• Repetition (b)
• Phonological similarity (c)
• Semantic similarity (d)
• Sublexical frequency (e, f)
• The M350 is NOT sensitive to
• Interlexical competition (e)

300-400ms (M350)

• Embick, D., Hackl, M., Schaeffer, J., Kelepir, M.
  Marantz, A. (2001). A magnetoencephalographic
  component whose latency reflects lexical
  frequency. Cognitive Brain Research 103,
  345-348.
• 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.
• 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.

Pylkkänen and Marantz, Trends in Cognitive
Sciences, in press.
15
What happens in the brain when we read words?
Lexical activation (Pylkkänen et al. 2002)

• The M350 is sensitive to
• Lexical frequency (a)
• Repetition (b)
• Phonological similarity (c)
• Semantic similarity (d)
• Sublexical frequency (e, f)
• The M350 is NOT sensitive to
• Interlexical competition (e)

300-400ms (M350)

• Embick, D., Hackl, M., Schaeffer, J., Kelepir, M.
  Marantz, A. (2001). A magnetoencephalographic
  component whose latency reflects lexical
  frequency. Cognitive Brain Research 103,
  345-348.
• 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.
• 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.

Pylkkänen and Marantz, Trends in Cognitive
Sciences, in press.
16
Effect of probability/density (n10)
(Pylkkänen, Stringfellow, Marantz, Brain and
Language, 2002)
17
M350
(i) 1st component sensitive to
lexical factors (such as lexical frequency)
(ii) not affected by competition
18
Hypothesis

• Effect of high phonotactic probability/ high
  neighborhood density

M350
RT
- slow-down due to competition
- speed-up due to sublexical frequency
19
Materials (from Baayen, R. H., Lieber, R.,
Schreuder, R. (1997). Linguistics 35, 861-877)

• Four categories of visual words, all nouns

• Contrast 1 Family frequency

HIGH
LOW

• Matched for
• Length
• Freq. of the sg,
• Cumulative freq. of the sg. pl. forms
• Family size
• Mean bigram frequency

- ic ize ism
- ist ize -ism
terror (n18)
magnet (n18)

• Contrast 2 Family size

LOW

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

HIGH
- ic ity ify head test washed
- ist
acid (n21)
diary (n21)
20
Behavior
(Pylkkänen, Feintuch, Hopkins Marantz,
Cognition, to appear)
21
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.

22
MEG data, single subject
(Pylkkänen, Feintuch, Hopkins Marantz,
Cognition, to appear)
23
Family frequency M350 (S1)
HBM 2003, poster 1345
24
HBM 2003, poster 1345
Family frequency M350 (S1)
25
HBM 2003, poster 1345
Family frequency M350 (S1)
Low family frequency

• Morphological competition at the M350

26
HBM 2003, poster 1345
Family frequency M350 amplitude (n10)
27
HBM 2003, poster 1345
Family frequency M350 amplitude (n10)

28
HBM 2003, poster 1345
Family frequency M350 latency (n10)
all n.s.
29
HBM 2003, poster 1345
Family size M350 amplitude (n10)
all n.s.
P 0.09
30
HBM 2003, poster 1345
Family M350 latency (n10)


31
Why?
32
1. Difference in the time course of competition
High frequency morphological family
High density phonological neighborhood
(frequency-weighted)

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

DECOMPOSITION

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

terrorism
TERROR
NO DECOMPOSITION
terrorist
terrorize
33
1. Difference in the time course of competition

• 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).

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

terrorism
TERROR
NO DECOMPOSITION
terrorist
terrorize

• (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.
• Gonnerman, L. 1999, Morphology and the lexicon
  exploring the semantics-phonology interface, PhD
  thesis, University of Southern California.
• 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.

34
1. Difference in the time course of competition
High frequency morphological family
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.

35
Conclusion
HBM 2003, poster 1345
Decomposition
Morphological competition effects
Phonological competition effects
36
Conclusion
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)

37
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, 245266)

38
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-Jun81(1-3)555-67.)

39
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.

• (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)

40
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)

41
LP, Aug 03, Tateshina
Day 4 Morphology 2 Electrophysiological and
behavioral evidence for early effects of
morphology

• Morphological family effects.
• Early effects of superficial morphology in masked
  priming.
• Role of semantic transparency.
• Early effects of morphology in ERPs.
• Grand summary of MEG results and comparison to
  ERP literature.

42
LP, Aug 03, Tateshina
Rastle, Davis New (2003)

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

TRANSPARENT cleaner CLEAN OPAQUE
corner CORN ORTHOGRAPHIC brothel - BROTH
43
LP, Aug 03, Tateshina
Rastle, Davis New (2003)

• Result

TRANSPARENT cleaner CLEAN OPAQUE
corner CORN ORTHOGRAPHIC brothel - BROTH
EQUAL PRIMING
NO PRIMING
44
LP, Aug 03, Tateshina
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.
? If morphological parsing occurs early, one
would expect morphological competition to occur
early as well, which is what the family frequency
results suggest.
45
LP, Aug 03, Tateshina
Day 4 Morphology 2 Electrophysiological and
behavioral evidence for early effects of
morphology

• Morphological family effects.
• Early superficial effects of morphology in masked
  priming.
• Role of semantic transparency.
• Early effects of morphology in ERPs.
• Grand summary of MEG results and comparison to
  ERP literature.

46
Zweig et al. Does morphological decomposition
require semantic transparency?

• If semantically opaque forms arent decomposed,
  processing a form such as UNIVERSITY would
  involve
• access to the lexical representation UNIVERSITY

(Zweig, van Rijsingen Pylkkänen, in progress)
47
Does morphological decomposition require semantic
transparency?

• If semantically opaque forms are decomposed,
  processing a form such as UNIVERSITY would
  involve
• access to UNIVERSE and ITY
• combining UNIVERSE and ITY
• 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)
48
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)
49
LP, Aug 03, Tateshina
Does morphological decomposition require semantic
transparency?

• Most research on the effects of morphological
  transparency has used a priming paradigm.
• However, its 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)
50
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.

Bin 1 CORNER Bin 2 RUBBER Bin
3 SNEAKER Bin 4 HEADER Bin 5 CONSUMER
Connectivity to the base increases
Transparent

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

(Zweig, van Rijsingen Pylkkänen, in progress)
51
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.

Bin 1 CORNER Bin 2 RUBBER Bin
3 SNEAKER Bin 4 HEADER Bin 5 CONSUMER
Connectivity to the base increases
Transparent

• 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).

52
LP, Aug 03, Tateshina
Results (n 14)
msec
PAINT CORNER RUBBER SNEAKER HEADER
CONSUMER
Pseudoaffixed
Opaque
Transparent
Non-affixed
(Zweig, van Rijsingen Pylkkänen, in progress)
53
LP, Aug 03, Tateshina
Results (n 14)
msec
PAINT CORNER RUBBER SNEAKER HEADER
CONSUMER
Pseudoaffixed
Opaque
Transparent
Non-affixed
(Zweig, van Rijsingen Pylkkänen, in progress)
54
LP, Aug 03, Tateshina
Results (n 14)

• 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)
55
LP, Aug 03, Tateshina
Day 4 Morphology 2 Electrophysiological and
behavioral evidence for early effects of
morphology

• Morphological family effects.
• Early superficial effects of morphology in masked
  priming.
• Role of semantic transparency.
• Early effects of morphology in ERPs.
• Grand summary of MEG results and comparison to
  ERP literature.

56
LP, Aug 03, Tateshina
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 ERPs, 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.

57
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.

58
LP, Aug 03, Tateshina
Day 4 Morphology 2 Electrophysiological and
behavioral evidence for early effects of
morphology

• Morphological family effects.
• Early superficial effects of morphology in masked
  priming.
• Role of semantic transparency.
• Early effects of morphology in ERPs.
• Grand summary of MEG results and comparison to
  ERP literature.

59
LP, Aug 03, Tateshina
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

60
LP, Aug 03, Tateshina
Revisiting Assumptions/hypotheses that drive,
and are tested by, the present research

• Representation
• There is a modality independent lexicon.
• Lexical entries connect sound and meaning
  single lexicon.
• All word formation is syntactic.

• Processing
• Timing of lexical access depends on the
  activation level of lexical entries at stimulus
  presentation.
• The activation level of lexical entries depends
  on
• Frequency
• Preceding context (priming)
• Phonological and semantic relatedness should
  affect the same neural activity.

NB All of these assumptions are more or less
controversial so well continually keep
evaluating how they succeed in explaining the
data.
61
LP, Aug 03, Tateshina
N400 ERP
N 12

• Discovered in a semantic anomaly manipulation.
• But today we know that every word in a sentence
  elicits an N400.
• Not a violation-component

_ _ _ He spread the warm bread with SOCKS ____ He
spread the warm bread with BUTTER
(Kutas and Hillyard, 1980)
62
LP, Aug 03, Tateshina
M350 N400?
63
Polarity

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

64
Polarity

• NB The M350 is often bilateral.
• Both the LH and RL M350 sources contribute to the
  midline negativity.
• N400 sums over both hemispheres.

65
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. 1998. Distinct
time courses of word and context comprehension in
the left temporal cortex. Brain, 121, 1133-1142. )
66
Timing N400
N 12

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

_ _ _ He spread the warm bread with SOCKS ____ He
spread the warm bread with BUTTER
(Kutas and Hillyard, 1980)
67
Timing M350

• Important
• The M350 is defined as the first peak of the M350
  distribution.

• But the M350 field pattern often peaks twice.

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

68
Timing M350

• Important
• The M350 is defined as the first peak of the M350
  distribution.

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

• But the M350 field pattern often peaks twice.

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

200
fT
0
200
-100 0 100 200 300 400
500 600 700


msec
69
Timing M350

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

NOT M350 although may have more or less the same
source.
M350
200
fT
0
200
-100 0 100 200 300 400
500 600 700


msec
70
Timing M350

• M350
• From valley to valley, may as short as 50ms.
• M350 source
• Onset 300ms
• Peak 1 350ms
• (Peak 2 450ms)
• Offset 500ms

NOT M350 although may have more or less the same
source.
M350
200
fT
0
200
-100 0 100 200 300 400
500 600 700


msec
71
LP, Aug 03, Tateshina
Stimulus factors affecting the N400 (partial list)
72
LP, Aug 03, Tateshina
M350 ? N400 but the M350 is likely a
subcomponent of the N400 (the M250 might also be
a subcomponent of the N400).
73
LP, Aug 03, Tateshina
Possible reasons for differences in waveform
morphology in MEG and ERPs

• EEG picks up more activity than MEG.
• ERP data are usually grandaveraged.
• Small latency differences may be lost.
• Summation over hemispheres in ERPs.
• Differences between hemispheres may be lost.

74
LP, Aug 03, Tateshina
(Some) outstanding questions
75
LP, Aug 03, Tateshina
Latency vs. amplitude effects

• 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?

76
LP, Aug 03, Tateshina
Functional significance of the M250

• Activity at 200-300ms difficult to manipulate.
• Lots of distributional variance across subjects.
• Not a single source and depends on the
  individuals brain physiology which part of the
  activity is captured by MEG?

77
LP, Aug 03, Tateshina
M350 in the right hemisphere

• 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 its still difficult to
  obtain enough RH sources within a single study to
  obtain statistical power.

78
LP, Aug 03, Tateshina
Whats so special about the M350 peak (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?

79
LP, Aug 03, Tateshina
Post-M350 activity and neural correlates of
recognition

• The M350 is not sensitive to (phonologically-based
  ) interlexical competition.
• What activity is?
• Weve identified no MEG activity that would
  appear to index recognition (i.e. selection
  instead of activation).

80
LP, Aug 03, Tateshina
Thank you!