Title: Neural mechanisms of spoken word recognition: Onsets and inhibition
1 Neural mechanisms of spoken word
recognition Onsets and inhibition
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- Liina Pylkkänen Alec Marantz
- KIT/MIT MEG Laboratory
- Dept. of Linguistics and Philosophy, MIT
2Problem of recognition
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- How does a single mental representation get
selected as the optimal match to a stimulus?
Stimulus TURN
3Behavioral inhibition
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- Words are often harder to recognize when they are
preceded by similar sounding words (e.g. Rastle
et al. 2000)
slower when preceded by
SPINACH
SPIN
than when preceded by
MUFFLER
4Behavioral inhibition
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- Words are often harder to recognize when they are
preceded by similar sounding words (e.g. Rastle
et al. 2000)
slower when preceded by
SPINACH
SPIN
5Inhibited activation
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activation level
time
time
RT
SPIN
s p i n a c h
PRIME
TARGET
6Alternative Inhibited recognition
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activation level
time
RT
SPIN
s p i n a c h
PRIME
TARGET
7Mechanisms of recognition
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- Inhibited activation
- Mismatching candidates are suppressed below their
resting level - Inhibited recognition
- Mismatching candidates are rejected simply
because they receive less excitation from the
input - BUT Both predict delayed RTs.
- Difficult to distinguish behaviorally
8Timing of activation
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INHIBITED ACTIVATION
INHIBITED RECOGNITION
9Previously
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- Magnetoencephalographic component at 350ms
post-stimulus onset which indexes initial
excitation of lexical entries - ? M350
- (Embick et al. Cognitive Brain Research 2001,
Pylkkänen et al. Brain and Language, 2001)
10Magnetoencephalography (MEG)
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http//www.ctf.com/Pages/page33.html
http//www.ctf.com/Pages/page33.html
11M350 a particular magnetic field distribution
at 300-400ms post onset of a visual word
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12M350 the 1st MEG component sensitive to lexical
factors
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- Frequency (Embick et al 2001)
- Frequent word elicit shorter M350 latencies than
infrequent words - Repetition (Pylkkänen et al 2001a)
- Repeated words elicit shorter M350 latencies than
nonrepeated words
13M350 NOT modulated by factors affecting the
speed of recognition
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- Pylkkänen et al. (2001b)
- Would stimuli that invoke fast activation but
late recognition elicit shortened or lengthened
M350 latencies? - M350 latencies are shortened while lexical
decision times are delayed - M350 indexes initial activation of lexical
entries
14M350 a tool for investigating inhibitory
mechanisms in word recognition
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INHIBITED ACTIVATION
INHIBITED RECOGNITION
15Materials
- Crossmodal priming paradigm
- SOA Duration of prime
- Task Lexical decision
16Materials
- Two types of phonological similarity (embedded in
a larger experiment)
1. ONSET-MATCHING
2. NON-ONSET-MATCHING
17Role of onsets in recognition?
- The Cohort model (Marslen-Wilson Welsh 1986)
- Activation purely onset-driven
- TRACE (McClelland and Elman)
- Activation is continuous
- Today
- abundant evidence for continuous activation but
also for the special role of onsets - How are onsets special?
18Materials
AUDITORY PRIME
s p i n a ch
1. ONSET-MATCHING
REACH
t e a c h e r
1. NON-ONSET-MATCHING
19Materials
AUDITORY PRIME
- Would the M350 show inhibition or priming?
- If inhibition, activation is inhibited.
- If priming, RT inhibition originates in
competition.
s p i n a ch
1. ONSET-MATCHING
REACH
t e a c h e r
1. NON-ONSET-MATCHING
20Materials
VISUAL TARGET
AUDITORY PRIME
SPIN
s p i n a ch
1. ONSET-MATCHING
SPIN
m u ff l e r
REACH
t e a c h e r
1. NON-ONSET-MATCHING
REACH
21Results
22Results
23Results
24Results
25spinach-spin inhibited activation?
onset-matching competitors are suppressed
26teacher-reach inhibited recognition?
non-onset-matching competitors NOT suppressed
27Same behavior but different neurophysiological
effects
- Cognitive level of similarity induced inhibition
depends on the type of phonological similarity
between the competitor entries - The speech recognition system has a mechanism of
complete deactivation that targets onset-matching
incorrect entries. - Non-onset-matching entries are activated, but not
suppressed
28Asymmetry predicted by the suppression mechanism
- Isel and Bacri 1999
- trombone RIB PRIMING (via BONE)
-
- cargo BUS NO PRIMING (via CAR)
29Onsets in acoustics and phonology
- Resist neutralization and are perceptually
salient. - If word onsets play a special role in word
recognition, the mechanisms of the speech
perception system can potentially shed light on
the distribution of these phonetic and
phonological processes (Gow, Melvold, Manuel,
1994 Frisch, 2001)
30Results compatible with
- Marslen-Wilson (1993)
- non-onsetmatching representations get activated,
but only for repair purposes - i.e. the mispronunciation shigarette activates
cigarette but not to a degree sufficient for word
recognition
31Acknowledgments
- Andrew Stringfellow, MIT
- - Lab manager
- Laura Gonnerman, USC
- - Majority of crossmodal materials
-