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Abstract Grammatical Processing in Broca’s Area: Evidence from Human In-Vivo Electrophysiology and fMRI
Ned T. Sahin 1,2 Eric Halgren
2 Istvan Ulbert 2
Anders Dale 2 Don Schomer 3
Julian Wu 4 & Steven Pinker 1
© Ned T. Sahin • [email protected] • www.nedsahin.org
1 Harvard Psychology 2 MGH Martinos Center for Biomedical Imaging 3 Neurology & 4 Neurosurgery, Beth Isreal Deaconess Medical Center
Those are the ____.
+a child
+That is the ____.
+a ladder
+
+
a house
+
Noun Tasks
"Overt-Inflect"
"Zero-Inflect"
"Read"
repeat word: _____
Yesterday they ____.
+to walk
+Every day they ____.
+to teach
+
Verb Tasks
"Overt-Inflect"
"Zero-Inflect"
650 ms
1100 ms
250 ms
1500ms
}}}
}}}
}}}
repeat word: _____
+
to cancel
+
"Read"
Support: NIH HD 18381 (Pinker) • NIH NS 18741 (Halgren) • NCRR P41 RR14075 • MIND Institute
Task
Questions Results
fMRI
• 2x2x3 Design (CLASS, REGULARITY, INFLECTION) • 120 verbs (60 irregular) || 120 nouns (60 irreg) • 3 levels Inflection: Overt-Inflect, Zero-Inflect, Read• Covert production: "Silently produce; press button"• Controlled for (stem/form) freq, syllables, length• Particle (a/an or to) to prevent simple concatenation strategy for Zero-Inflect
t
Human In-Vivo Electrophysiology
• N = 18. (Healthy, RH, English-speaking, 18-26yo)• Random-Effects group analysis (p<0.005)• Gamma-fit analyses as well as FIR analyses• Spherical normalization; inflated brain visualization
• Rapid Event-Related fMRI; jittered, fully randomized• Siemens 3T whole-body scanner (Trio)• TR = 1.75s TER = 1.75s TE = 30ms Flip = 90• 25 3x3x5 mm slices, skip 0.5
2.3
3.04.05.0
2.3
3.04.05.0 2-
taile
d si
gnifi
canc
e -(
log(
p-va
lue)
)
Conclusions
3
3
2
12
5
2
6
9 8
7
1
4
89
10 11
1011
1
12
1213
13
14
14
15
15
16
16Anatomy Legend (on brain of study subject NV_Infl_01_X)
Overt-Inflect > Read
Overt-Inflect > Read
(Anatomicallabels as usedin fMRI group
averaging)
Overt-Inflect > Zero-Inflect
Zero-Inflect > Read
Left lateral medial
1. Inferior Frontal Gyrus, par opercularis (BA44)2. Inferior Frontal Gyrus, par triangularis (BA45)3. Inferior Frontal Gyrus, par orbitalis (BA47)4. Insula, Circular Sulcus, Superior5. Insula, Circular Sulcus, Anterior6. (Insula)7. Insula, Cicular Sulcus, Inferior8. Precentral Gyrus
9. Precentral Sulcus, Inferior10. Inferior Parietal - Supramarginal Gyrus11. Inferior Parietal - Angular Gyrus12. Superior Frontal Gyrus13. Cingulate Sulcus14. Cingulate Gyrus, Main15. Pericallosal Sulcus16. Corpus Callosum
18-subject group (random-efects) fMRI maps, p<0.005
44
44
44
444545
45
47
47
45
MFG
STGSTG
STGSTG
MTG
STG
4444
444445
4545
47
47
45STGSTG
STG
STGMTG
MTG
STG45
MTG
MFG
MFG
MFG
MFG PrCG
PrCG
PoCG
PoCG
PoCG
SMG
PrCG
PrCG
PrCG
PoCG
PoCG
SMGMFG
Group fMRI - 18 normal
Single patient, pre-surgical fMRI pre-surgical fMRI on anatomical MRI Post-implantation MRI with electrode trajectory
volta
ge (a
rbitr
ary
units
)
-1000 0 1000 2000 3000
0
-50
-100
50
100
150
Overt-Inflect trials
510 ms
255 ms
-1000 0 1000 2000 3000
0
-50
-100
50
100
150
Electrical Activity:Fixation trials
OF 1-2OF 2-3OF 3-4OF 4-5OF 5-6OF 6-7OF 7-8
Electrodechanels
ms
Contrast: Overt-Inflect vs Fixation
fMRI to Electrophysiology Direct Correspondence
criterion 1: task responsive/selective
criterion 2: probe-selective response
criteria 4 & 5: plausible cerebral location (Broca region, a priori selected) && Plausible neural time scale (200ms - 1000ms)
1.) What is the engram of Abstract grammar?
2.) Is morphological processing alone sufficient to activate Broca's area?
3.) Are Verbs & Nouns inflected by different brain circuits/regions, or by a single one?
4.) Correspondence of neuronal electrical and metabolic signals?
5.) How to combine intra-cranial electrophysiology and fMRI for cognitive research?
criterion 3: task-varying by inflection
• Morphological processing is sufficient to activate Broca's Area• Known (though debated) syntax area subserves morphosyntax• Isolated from working memory (WM) manipulations, syntactic movement• Covert production - no motor output• Constrained frontal circuit beyond Broca
• Broca's, BA47, anterior insula, medial SMA revealed on inflated cortex as significantly task-responsive circuit• Higher visual areas respond to Read task• Pattern similar across Nouns / Verbs• Constrained Broca-centered circuit for task
• Controlling frames further: morpho- logical processing including overt phonology activates Broca's, 47, SMA, anterior insula
• Abstract grammatical computation only Broca's, and BA47• Phonological manipulation brings online computation in insula (c.f. Dronkers)• Read condition includes unique processing, perhaps extra-linguistic; (c.f Raichle default-mode work); Failure of pure insertion.
• Task-responsive: significant electrophysiological activity to task.• Task-selective: no activity for Fixation events.• Signal inversions yield localization.• Peaks at 255ms and ~500ms in same Broca-region voxels activated in fMRI experiment (within-subject)• Nearby channels peak 250, 380, 500
• Neuronal evidence that fMRI driven by 2nd part of task (core morphological task) -- not the frame.• This probe-selectivity specific to response at ~500ms, and near Broca• Temporal and spatial profile of one electrophysiological activity for abstract grammar processing.
• The greater inflectional demand, the greater the amplitude in 500ms peak.• Earlier response non-task-varying, or inverse response pattern.• Corroborates 500ms response as grammar-related
• Specific fMRI-convergent response from Broca-region neurons at 500ms.
• Broca's-centered computation includes pure Grammar not just working memory / general processes.• Broca's Area is central to a system for processing word Morphology, for both Nouns and Verbs.• Grammatical inflection becomes a tractable Model System for studying Abstract grammar.• Read task activates separate pathways: belies pure insertion and questions Read as sole baseline. • IFG regions show Electrophysiological and BOLD response, selectively to word inflectional processing.• Neuronal response at ~500ms sensitive to type and degree of grammatical processing. • In-vivo electrophysiology & fMRI combine to reveal time and location, and to validate cognitive fMRI.
"MF" array:MFG --> CC genu
-
-1000 0 1000 2000 3000
0
-50
-100
50
100
MF 2-3MF 3-4MF 4-5MF 5-6255
350
500
"OF" Macro-electrode array: IFG -> OF
ms-1000 0 1000 2000 3000
0
-50
-100
50
100
Channels:255 ms
500435
355
OF 3-4OF 4-5OF 5-6
-1000 0 1000 2000 3000 4000 5000
ContextFrame
TargetWord
ContextFrame
TargetWord
-1000 0 1000 2000 3000 4000 5000
OF 3-4OF 4-5OF 5-6
MF 2-3MF 3-4MF 4-5MF 5-6
ReadZero-InflectOvert-Inflect
ReadZero-InflectOvert-Inflect
255
250
500 ms
***
*** ******
**
}
500
355
355
-1000 0 1000 2000 3000
0
-50
-100
50
100
Chan
nel M
F 3-
4 re
spon
se b
y ta
sk c
ondi
tion
Chan
nel M
F5-
6 re
spon
se b
y ta
sk c
ondi
tion
-1000 0 1000 2000 3000
0
-50
-100
-150
50
100
150
0
-50
-100
-150
50
100
150
435ms
255
-1000 0 1000 2000 3000
0
-50
50
Task Conditions:
ReadZero-InflectOvert-Inflect
Channel OF5-6 response by task condition
Poster presented at the Organization for Human Brain Mapping Annual Meeting, June 14-18, 2004, Budapest, Hungary. Poster number MO 144: Monday, June 14.Poster presented at the Organization for Human Brain Mapping Annual Meeting, June 14-18, 2004, Budapest, Hungary. Poster number MO 144: Monday, June 14.Poster presented at the Organization for Human Brain Mapping Annual Meeting, June 14-18, 2004, Budapest, Hungary. Poster number MO 144: Monday, June 14.