language experience shapes representation of pitch ... · pitch-tracking accuracy & periodicity...
TRANSCRIPT
Language experience shapes representation of pitch relevant neural activity in the human brainstem
Ananthanarayan (Ravi) Krishnan
Research supported by NIH Grant, 1R01DC008549
Auditory Electrophysiology Laboratory
FFR Workshop, May22-23 UCL, London
Why study Pitch?
Ø Pitch plays an important role in the percep1on of speech, language, and music.
Ø Therefore there is considerable interest in understanding: Ø (i) How pitch relevant informa2on is representa2on at both subcor2cal & cor2cal levels; Ø (ii) How long term language experience influences this experience-‐dependent; and
Ø (iii) The nature of interplay between cor2cal and subcor2cal components in the pitch processing hierarchy
Pitch processing-hierarchical-includes both cortical and sub-cortical stages of processing
Language experience shapes pitch processing
Pitch processing of lexical tones at the cortical level is influenced by language experience.
4
Present results from the brainstem that supports the view that language experience also influences representation of pitch relevant neural activity in the brainstem
Experimental Strategy: Cross-linguistic approach
Examine: 1. native & non-native contours
2. context (speech vs. non-speech) of contours 3. sensitivity to temporal regularity 4. relationship to behavioral measures 5. relationship between brainstem, cortical and
behavioral measures relevant to pitch Subjects: Chinese (Mandarin) & English subjects:
right handed, no music experience Mean age when Chinese started to learn English: 11 yrs Dependent Variables:
Pitch Tracking Accuracy Pitch strength (periodicity strength)
Methods: Chinese Subjects
Ø Normal hearing na-ve speakers of Mandarin Chinese Ø Closely matched in age (24.50 ± 3.53 years), years of formal educa1on (16.90 ± 2.88 years), and were strongly right handed (laterality index 93.10 ± 11.22%).
Ø All par-cipants were born and raised in mainland China.
Ø None had received formal instruc1on in English before the age of nine (12 ± 1.24 years).
Ø LiIle or no music experience
Krishnan et al. Hearing Research (2004); Cog. Br. Res (2005)
Clothing
aunt
chair
easy
Stimuli: Lexical Tones
Cross-linguistic approach: Native Mandarin vs non-native English Listeners Stimuli: lexical tones Note: Identical spectra with only pitch contour changing
1. Is brainstem neural activity relevant to pitch influenced by language experience?
3
Mandarin Tone 2 PITCH TRACKING
PERIODICITY STRENGTH
Encoding of pitch is sensitive to language experience
Krishnan, Xu, Gandour, & Cariani Cognitive Brain Research 2005
PT: crosscorrelation between Fo contours extracted from stimuli and FFRs PT: crosscorrelation between Fo contours extracted from stimuli and FFRs PT: crosscorrelation between Fo contours extracted from stimuli and FFRs PS: magnitude of normalized autocorrelation peak per time frame
Blue stripe shows the dominant interval for rising tone; 10 ms = 100 Hz; period is the inverse of frequency
Krishnan et al. Cognitive Brain Research 2005
Chinese English
More coherent phase-locking to F0 interval in the Chinese
FFRs preserved the pitch-relevant information of lexical tones in both native and non-native listeners
Summary
Stronger representation of in native listeners in terms of both tracking accuracy and periodicity strength
These results suggest long term language experience induced neural plasticity at the brainstem level may be enhancing or priming linguistically-relevant features of the speech input
3
Xu, Krishnan, & Gandour NeuroReport 2006; Krishnan et al., (2009)
Will linear & curvilinear variants of a higher degree polynomial still yield such results?
2. Is this language experience-dependent plasticity sensitive to shape of pitch contours?
Stimuli used by Krishnan et al. (2005) – curvilinear f0 contours that were modeled after Mandarin tones in natural speech.
If brainstem reorganization is induced by language experience, will deviations from prototypical f0 contour still produce an experience-dependent effect?
3
Xu, Krishnan, & Gandour NeuroReport 2006
Sensitivity to shape of pitch contours: linear and non-linear contours in speech context
• No crosslanguage differences in periodicity strength or tracking accuracy for linear contours
3
LINEAR
CURVILINEAR
T2L
T4
T4L
T2 • Representation of pitch-relevant information appears to dependent on specific fine-grained features of pitch contours that occur in natural speech
• PT & PS: Chinese > English for T2 only • English = Chinese for curvilinear (T2i) and linear (T2 l, T2tl) variants of T2
Time (sec) 0.005 0.045 0.085 0.125 0.165 0.205 0.245
Freq
uenc
y (H
z)
100
105
110
115
120
125
130
135
Sensitivity to shape of pitch contours: linear and non-linear contours in a nonspeech context
Krishnan, Gandour, Bidelman, & Swaminathan NeuroReport (2009)
T2
T2i
T2l
T2tl
Summary
Brainstem representation of pitch relevant information in the Chinese appear to be acutely sensitive to dynamic changes in trajectory throughout the duration of a pitch contour
Conclude that long-term experience-dependent influence on brainstem representation of pitch relevant information is specific to contours that are part of their experience.
Conclusions 3. Is this language experience-dependent plasticity specific to speech context ?
Typically used non speech stimuli (rotated, sine wave, speech in noise etc) has some speech characteristics to it.
To answer this question the pitch contours have to presented in a non-speech context
We used dynamic curvilinear iterated rippled noise (IRN) stimuli to remove any potential lexical-semantic confound
3
15 Input, x(t)
Pitch contours in a non-‐speech context: IRN s1muli
T ime (sec )
0 0.25
Fund
amen
tal f
requ
ency
(Hz)
80
150
80
90
100
1 1 0
120
130
140
150
0 0.05 0.10 0.15 0.20 0.25
NON-SPEECH (IRN; N=32)
T1
T2
T3
T4
SPEECH
IRN block diagram
Delay d
Gain g
+ Delay d
Gain g +
Output, y(t)
Swaminathan et al, IEEE (2008)
D
T1
Krishnan, Swaminathan, & Gandour Journal of Cognitive Neuroscience (2008)
FFR: Mandarin tone; nonspeech; curvilinear; native/nonnative
1
T2
T3
T4
PITCH STRENGTH
Periodicity Strength (segmental analysis)
2 Swaminathan, Krishnan & Gandour Neuroreport (2008)
C > E on linguistic tones for both S & NS- particularly in segments showing rapid changes in pitch
18
Are language effects dependent on context? PITCH STRENGTH
C > E on linguistic tones both S & NS contexts and particularly in sections with rapid pitch changes
Swaminathan et al, NeuroReport (2008)
For both groups, pitch strength for speech greater than for non-speech
Pitch Strength: Speech > Non-Speech
In native listeners, representation of dynamic IRN stimuli were superior in terms of both tracking accuracy and pitch strength
3
These findings suggest that the experience-dependent enhancement of pitch relevant information is not specific to speech domain; and shows particular sensitivity to the dynamic portions of native pitch contours.
Summary
Segmental evaluation suggested better sensitivity in the native listeners to rate of change of pitch
Iteration steps (n) n = 4 n = 2 n = 8 n = 12 n = 16 n = 32
PITCH CONTOUR PITCH STRENGTH
4. Is this experience-dependent enhancement in pitch representation sensitive to changes in temporal regularity?
Krishnan, Bidelman, & Gandour Hearing Research (Brain Res., 2009; Hear Res., 2010;) 6
Pitch relevant informa1on appears to emerge at a lower itera1on number in Chinese listeners
Pitch tracking accuracy better in Chinese and at a smaller iteration step
Pitch Strength grows more rapidly with iteration steps for Chinese listeners
Summary
Pitch-tracking accuracy & periodicity strength shows greater sensitivity to pitch salience in the native tone language group (Chinese)
Periodicity strength emerges 2–3 times faster in the Chinese group with increasing pitch salience
These results suggest that long term language experience enhances the representation of pitch relevant neural activity in the brainstem that may underlie pitch salience.
Information related to pitch salience emerges early along the auditory pathway in pre-attentive, sensory-level processing
Krishnan, Bidelman, & Gandour Hearing Research (2010) 2
Relationship between neural and behavioral measures
Rela-onship between brainstem, cor-cal, and behavioral measures relevant to pitch
The pitch Onset Response (POR)
Ø Human POR, as measured by MEG, reflects synchronized cor1cal neural ac1vity specific to pitch
Ø POR latency and magnitude,
for example, has been shown to depend on pitch salience.
Ø Anatomical Source: Lateral
Heschl’s Gyrus-‐the puta1ve site of pitch processing
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Seither-Preisler et al., 2004
EEG version of POR (CPR): IRN s1muli
Iteration steps 8 and 32
IRNo: no pitch
only slow spectro- temporal
fluctuations
Two segments 500 ms 250 ms
Krishnan et al., Neuropsychologia (2012)
Extrac1on of brainstem and cor1cal pitch response
0 20030 Hz
80 Hz
A
C
B
400 600 800
+
+
-
-
1000Time (ms)
0 200 400 1000Time (ms)
-5
0
5
500 550 600 650 700 750 800 850Time (ms)
600 800
Ampl
itude
(μV)
5 μV
0.4
μV
P1
N1
CPR Components
CORTICAL
BRAINSTEM
FFR
3-25 Hz
75-1500 Hz
CPR-Average: EEG down-sampled to 2048Hz; Analysis epoch: 1200 ms including 100 ms prestimulus; 1000 sweeps
Pitch Onset Response is sensi1ve to change in pitch salience
JJ
J
J
pIRNo nIRNo IRN8 IRN32
610
620
630
640
650
Late
ncy
(ms)
Stimulus
-6
-5
-4
-3
-2
-1
0
Am
plitu
de (u
V)
***
***
Since there are multiple transient components of the POR We chose to name our response as the Cortical Pitch Response (CPR)
Comparison between neural and behavioral data
FFR vs CPR; CPR vs F0 DL; and FFR vs F0 DL are correlated suggesting that behavioral pitch responses were well predicted by both neural responses. These results suggest smaller F0 DLs are associated with more robust encoding at brainstem and cortical levels
CPR: Experience-‐dependent enhancement
!2
0
2
500 600 650 750 800 850 900!2
0
2
500 550 600 650 700 750 800 850 900!2
!1
0
1
2
!2
0
2
2 µV
+
-100 100 300 500 700 900Time (ms)
0 100 200 300 400Time (ms)
T2_200
T2_250
T2_150
P1
N1
Pa
Na
Pb
Nb
Pc
Nc
Pa
Na
PbNb
Pc
Nc
Pa
Na
Pb
Nb
Pc
Nc
Pa
Na
Pb
Nb
Pc
Nc
C E
No systematic latency effects
For both Na-Pb & Pb-Nb, C>E
Lateraliza1on only at temporal electrode sites
500 550 600 650 700 750 800 850 900!1
!0.5
0
0.5
1
500 550 600 650 700 750 800 850 900!1
!0.5
0
0.5
1
0
1
500 550 600 650
700
750 800 850 900!1
!0.5
0
0.5
1
!1
0
1
500 550 600 650 700 750 800 850 900!1
!0.5
0
0.5
1
25.0
13.5
2.0
Fre
qu
en
cy
(H
z)
1.0
µV
T2_250
T2_200
T2_150
Chinese English
T7
T8
T8
T8
T7
T7
T8
T8
T8
(µV2/Hz)
0.006
0
Pa
Na
Pa
Na
Pb
Nb
Pc
Nc
Pa
Na
Pa
Pa
Na
Na
Pb
Pb
Nb
Nb
Nb
Pc
Pc
Nc
Nc
Time (ms)
100 300 400100400300
T7 T7
T7
2000 200 0 0 200 600 800 1100400 0 200 600 800 1100400
Pb
Pb
PbPa
Na
Nb
Nb
Pc
Pc
Pc
Nc
Nc
Nc
T7 C T8 C T7 E T8 E
Chinese English
500 550 600 650
700
750 800 850 900!1
!0.5
0
0.5
1
!1
0
1
500 550 600 650 700 750 800 850 900!1
!0.5
0
0.5
1
25.0
13.5
2.0
Freq
uen
cy (
Hz)
1.0
µV
T2_250
Chinese English
F3
F4
F4
F4
F3
F3
F4
F4
F4
(µV2/Hz)
0.006
0
Pa
Na
Pa
Na
Pb
Nb
Pc
Nc
Pa
Na
Pa
Pa
Na
Na
Pb
Pb
Nb
Nb
Nb
Pc
Pc
Nc
Nc
Time (ms)
100 300 400100400300
F3 F3
F3
2000 200 0 0 200 600 800 1100400 0 200 600 800 1100400
Pb
Pb
Pb
Pa
Na
Nb
Nb
Pc
Pc
Pc
Nc
Nc
Nc
F3 C F4 C F3 E F4 E
500 550 600 650 700 750 800 850 900!1
!0.5
0
0.5
1
0
1
500 550 600 650 700 750 800 850 900!1
!0.5
0
0.5
1
500 550 600 650 700 750 800 850!1
!0.5
0
0.5
1
500 550 600 650 700 750 800 850 900!1
!0.5
0
0.5
1
!1
0
1
T2_150
T2_200
Chinese English
F3/F4: No asymmetry for either group
T7/T8: Stimulus-dependent rightward asymmetry only for the Chinese
Stimulus-dependent rightward asymmetry for Chinese only for T2-200 and more robust effect for T2-250.
T2_250
0.0
0.5
1.0
1.5
2.0 T7 C T8 C T7 E T8 E
Response ComponentsNa-Pb Pb-Nb
Peak
to P
eak
Ampl
itude
(V)
0.0
0.5
1.0
1.5
2.0
F3 C F4 C F3 E F4 E
Isola1ng pitch related components from s1mulus offset component
On Hierarchical processing for pitch (PaIerson et al., 2002)
Ø Stage 1.Extrac-on of -me-‐interval informa-on from neural firing paQern in the AN and construc-on of interval histograms in the IC and Thalamus
Ø Stage 2. Determining the specific value of pitch and its salience from the interval histograms-‐ probably in lateral HG (creates summary histograms and locates the first peak)
Ø Stage 3. Determine con-nuous (tonal language) and
discrete (music) pitch changes and tracking them-‐beyond PAC in STG or PP. this is were asymmetries emerge!
Mechanisms: Corticofugal pathways in experience-dependent pitch encoding
Experience which engages cerebral cortex shapes subcortical circuitry via corticofugal (CF) modulation
Krishnan & Gandour Brain and Language (2009) 2
IC, inf. colliculus AC, auditory cortex MGB, medial geniculate body LE, left ear RE, right ear CFL, left corticofugal
Mechanisms: Local brainstem mechanisms underlying experience-dependent encoding of pitch-relevant information
Pitch is organized orthogonal to frequency in the IC neurons
English
Chinese Langner (1992,1997)
Temporal correlation analysis model
Krishnan & Gandour Brain and Language (2009)
Best modulation frequency neurons along the pitch axis extract pitch relevant periodicities
Pitc
h
Long-term experience could sharp tuning, improve coherence of neural-phase-locking, and increase synaptic efficiency
Ravi Krishnan Jack Gandour Jayaganesh
Swaminathan* Gavin Bidelman* Chris Smalt* Sharada
Ananthakrishnan* Jill Wendell Suresh Chandan * Students who have
graduated
Auditory Electrophysiology Lab
Our mantra for studying tones
Bob Dylan Rainy Day Women 1966 Everybody must get sTONED!