FMRI and Reading Einar Mencl, Haskins Laboratories, New Haven, CT USA

fMRI and Reading

Einar Mencl, Haskins Laboratories, New Haven, CT USA

Koby finishes 49 in 12 minutes;Einar finishes 61 in…?

Collaborators

• Haskins Laboratories: Ken Pugh, Rebecca Sandak, Stephen Frost, Dina Moore, Stephanie Mason, Leonard Katz, Jay Rueckl, Donald Shankweiler, Annette Jenner, Jun Ren Lee, Carol Fowler, Ram Frost

• Yale Center for the Study of Learning and Attention: Bennett Shaywitz, Sally Shaywitz, Karen Marchione, John, Holahan, Jack Fletcher

• Yale University/Diagnostic Radiology: John Gore, Todd Constable, Robert Fulbright, Pawel Skudlarski, Cheryl Lacadie

Haskins - 270 Crown Street, New Haven CT

Haskins - 300 George Street, New Haven CT

Haskins - 300 George Street, New Haven CT

Haskins Folks (1)

Haskins Folks (2)

Behavioral Background

1) motor theory of speech perception; phonology 2) Evidence from fast priming: (Turvey, Lueketela, & Frost) a) toad - frog b) tode - frog c) towed - frog


1) motor theory of speech perception; phonology 2) Evidence from fast priming: (Turvey, Lueketela, & Frost) a) toad - frog b) tode - frog c) towed - frog

3) What is the best prime for a word? 1) fort - fort (identity)


1) motor theory of speech perception; phonology 2) Evidence from fast priming: a) toad - frog b) tode - frog c) towed - frog

3) What is the best prime for a word? 1) fort - fort 2) bowl - bowl?


1) motor theory of speech perception; phonology 2) Evidence from fast priming: a) toad - frog b) tode - frog c) towed - frog

3) What is the best prime for a word? 1) fort - fort 2) bowl - bowl? >>> boll - bowl (!) alternate pronounciations: howl, scowl

Slice Locations

Auditory versus Visual Sentence Task

Constable, Pugh et al., (NeuroImage 2004)

common print(red) speech(blue)

R - L

An Initial Neurobiological Reading Model

ANTERIORAreas:

inferior frontal gyrus (including Broca’s area)

One Hypothesized Function:Articulatory recoding

OCCIPITOTEMPORAL (VENTRAL)

Areas: occipitotemporal juncture, middle and inferior temporal gyriHypothesized Function: Linguistically structured memory- based fast word identification system (posterior aspect = “word-form” area)

TEMPOROPARIETAL(DORSAL)

Areas:supramarginal, angular, superior temporal (Wernicke’s) gyri

Hypothesized Function:Mapping of orthographic to phonological and semantic representations

(Pugh et al. 2000)

Auditory versus Visual Sentence Task

Constable, Pugh et al., (NeuroImage 2004)

common print(red) speech(blue)

R - L

temporoparietal

occipitotemporal

anterior

Case MixingExp. (design)

Subjects get 10 scan runs, each 5:40 long

Each run, they see 5 blocks of baseline trials:

//*\ or /\\/

and 4 blocks of lexical decision trials:1 high frequency unmixed case2 low frequency unmixed case3 high frequency mixed case4 low frequency unmixed case

charm or cHaRm

Case Mixing Exp. (design)

1 baseline /\*/2 HF unmixed case3 LF unmixed case4 HF mIxEd CaSe5 LF mIxEd CaSe

Case MixingExp. (1)

single-subjectwords - lines


Case MixingExp. (2)

single subjectmixed - unmixed


Case MixingExp. (12)

across subjecthigh frequency wordsmixed - unmixed


Case MixingExp. (13)

across subjectlow frequency wordsmixed - unmixed


Case Mixing (14): Time effects in IFG

Case Mixing (15): Time effects in OT

Event-Related Designs, Two Analyses

1) Using a priori predicted response functions a) long intertrial interval designs b) Reference waveform regression2) Estimating the actual response a) simple averaging b) delta function regression (FIR, finite impulse response)3) Some examples

Simulated Hemodynamic Response (1)

mean = 5000sd = 100effect size 0-1%, 0-50 pointsGamma function tau=1.08; n=3; delay=3

Simulated Hemodynamic Response (2)

Noise SD = 0

Noise SD = 10

Noise SD = 100


1) Using a priori predicted response functions a) long intertrial interval designs b) Reference waveform regression2) Estimating the actual response a) simple averaging b) Delta Function Regression3) Some examples

Long Intertrial Intervals, Single Conditioncf. Ni et al., (2000)

Event Regressor

Simulated Data

Long Intertrial Intervals, Multiple Conditions

Cond 1Cond 2

Cond 1Cond 2

Event Regressors

Simulated Data

Multiple Regression (3):Reference Waveform Regression

Friston et al. 1994 int C1 C2

Cond 1Cond 2

Variability of the HRFAguirre et al., 1998


1) Using a priori predicted response functions a) long intertrial interval designs b) reference waveform regression2) Estimating the actual response a) simple averaging b) delta function regression3) Some examples

Estimating the Response (1):Simple Averaging, No Overlap

Cond 1Cond 2

Estimating the Response (2):Simple Averaging, With Overlap

Cond 1Cond 2

Estimating the Response (3):Simple Subtraction with Overlap

Dale & Buckner, 1997

Delta Function Regression (1)

Meizin et al., 2000

Delta Function Regression (2)Cond 1Cond 2

EventRegressorsFor Cond 1

EventRegressorsFor Cond 2

-1 0

+1+2+3

.

.

.+15P

eris

timul

us

Tim

e

Delta Function Regression (3)

Cond 1 Cond 2___

Cond 1

Cond 2

Delta Function Regression (4):Evoked Responses

Estimated Response

Peristimulus Time

Imag

e In

tens

ity

Imag

e In

tens

ity

Delta Function Regression (5): Overlapping Responses

Cond 1Cond 2

Cond 1 Cond 2___

Estimated Response & Gamma Fits

Delta Function Regression (6):Gamma Fitting

Peristimulus Time

Imag

e In

tens

ity

Imag

e In

tens

ity

Estimated Response

Peristimulus Time

Imag

e In

tens

ity

Imag

e In

tens

ity

Baseline Timepoints[-1 to 0]

Activation Timepoints[+3 to +8]

Delta Function Regression (4):“Blocklet” Analysis

Compare & Contrast...

Reference Waveform Regression 1) most designs are analyzable 2) stronger power 3) biased when reference <> actual

Delta Function Regression 1) some designs not analyzable 2) weaker power 3) unbiased measure of temporal response

Primed Lexical Decision Experiment (intro)

5 trialtypes: orthographic phonological

prime target relationship relationship

1 O+P+ bribe TRIBE similar similar2 O+P- couch TOUCH similar dissimilar3 NWO+ bliss TRISS similar similar4 NW brick THILM dissimilar dissimilar5 UNRE lunch TRUNK dissimilar dissimilar

LD/Prime Exp. (intro)

1 bribe - TRIBE2 couch - TOUCH3 bliss - TRISS4 brick - THILM5 lunch - TRUNK

LD/PrimeExp. (1)

single subjectunrelated primelunch - TRUNK


LD/PrimeExp. (2)

raw time course


LD/PrimeExp. (4)

across subjects

bribe - TRIBE


LD/PrimeExp. (5)

across subjects

couch - TOUCH


LD/PrimeExp. (6)

across subjects

couch - TOUCH vsbribe - TRIBE


LD/PrimeExp. (6)

across subjects

couch - TOUCH vsbribe - TRIBE


LD/PrimeExp. (1)

across subjectregion timecourses


titration of stimulus duration

+

house

&&&&&

1000 msec

500/1500 msec

25/50/100 msec

1000 msec

titration of stimulus duration (2)

Interactivity: Phonology and Semantics

(Strain et al. 1999)

• RT faster for hi-imageability words

• Imageability modulates Cons x Freq

• Triangle model exhibits same pattern

• Does the brain…?

Design

Go/no-go naming in a block fMRI session

Stimuli:• Words (Consistency x Imageability x Frequency)• Pseudowords

IFG = Consistency

MTG =Imageability

Region of interest analysis

(Main effect)

(Main effect)

Frost, et al., 2005, Neuroreport

Cross-Linguistic Effects - Word Frequency

…and implications for developmental dyslexia…

Documents

FMRI and Reading Einar Mencl, Haskins Laboratories, New Haven, CT USA