Purpose

1
Functional MRI Study Metaphor Irony Processing
in High-Functioning Autism D.L. Williams1,2 R.K.
Kana2 V.L. Cherkassky2 T. A. Keller2 N. J.
Minshew3, M.A. Just2 1Duquesne University
2Center for Cognitive Brain Imaging, Carnegie
Mellon University 3University of Pittsburgh
School of Medicine
Purpose
Results
Design
Correlation Between Brain Activation and Verbal IQ

• This functional magnetic resonance imaging (fMRI)
  study investigated the neural basis of
  comprehending literal, metaphoric, and ironic
  meaning in adults with high-functioning autism
  compared to typical control participants during a
  discourse comprehension task.

• The experiment was an event-related design. Data
  were collected for three conditions literal,
  metaphor, and irony. 9 stories of each condition
  plus 1 practice were presented.
• A 24-second fixation condition was presented 4
  times during the experiment to provide a baseline
  measure of brain activation with which to compare
  each experimental condition.
• Each participant practiced the task before going
  into the scanner. The practice consisted of two
  stories and questions of each condition.

Behavioral Data

• Areas positively correlated with VIQ in Irony
  Fixation and Metaphor Fixation contrasts for
  the autism group (no such areas for the control
  group).

• The participants with autism performed similarly
  to the controls on the literal sentences, but had
  more difficulty than the controls on
  comprehension of the ironic sentences.
• The autism group made reliably more errors in
  answering the comprehension question when the
  critical utterance was ironic (21.2 for autism
  vs. 5.5 for controls). There were no significant
  differences between the reaction times of the two
  groups

Introduction

• Behavioral studies indicate that individuals with
  autism exhibit difficulty with interpretation of
  figurative language such as irony and metaphor
  (Jolliffe Baron-Cohen, 1999 Happé, 1993
  Ozonoff Miller, 1996).
• These two language forms are experimentally
  interesting because, although both are nonliteral
  figurative language, only comprehension of irony
  requires common ground between speaker and
  addressee in the form of shared beliefs and
  knowledge.
• To interpret irony, the reader must recognize
  that the speakers mental state differs from the
  literal interpretation of the statement he makes.
  This is a process that may rely on theory of
  mind (Happé, 1993).
• Neurally, this demands the integration of regions
  associated with language processing and social
  cognition.

fMRI Presentation
Functional Connectivity

• Group differences in frontal-parietal and
  frontal-temporal functional connectivities in the
  3 experimental conditions.

fMRI Data
Brain Activation During Processing of CUs
Method
Scanner Procedure

• Within-group brain activation in the 3
  experimental conditions vs. fixation. Green
  ellipses indicate right temporal activation in
  autism group (but not in control group) in
  literal, irony, and (to a lesser extent) metaphor
  task.

Participants

• Participants were run on a 3.0T Siemens Allegra
  scanner using a Circularly Polarized (CP)
  transmit/receive head coil at the Brain Imaging
  Research Center, University of Pittsburgh/Carnegie
  Mellon University
• The experimental stimuli were rear projected onto
  a translucent plastic screen attached to the roof
  of the scanner bore. Participants viewed the
  screen through a pair of mirrors.
• A sixteen slice oblique axial prescription
  (approximately 25 angle) was set to maximize
  brain coverage.
• The onset of each trial was synchronized with the
  beginning of the acquisition of the superior most
  slice
• Cerebral activation was measured using BOLD
  contrast (Kwong et al., 1992 Ogawa et al., 1990)
• An EPI pulse sequence was used where the
  acquisition parameters for 16 oblique axial
  slices were TR 1000 ms, TE 30 ms, flip angle
  60º, 5mm thickness, 1mm gap, a 200 X 200 cm FOV,
  64x64 matrix, resulting in in-plane resolution of
  3.125 X 3.125 mm.

Conclusions

• As expected, participants with autism showed
  significantly more errors than control
  participants while comprehending the meaning of
  ironic utterances.
• Activation in bilateral IFG (during processing of
  irony and metaphor) was positively correlated
  with VIQ in the autism group but not the control
  group.
• The functional connectivity was consistently
  lower for the group with autism, relative to the
  controls, in all experimental conditions, but
  most prominently when processing the utterances
  involving irony.
• Functional connectivity was positively correlated
  with VIQ for the autism group only in the irony
  task (Autism r .76 Control r .22).
• Our data establish a task-dependent link between
  functional connectivity and individual
  differences in VIQ during processing of irony in
  autism.

1Participants with autism met diagnostic criteria
on the Autism Diagnostic Interview-Revised, on
the Autism Diagnostic Observation Schedule, and
by expert clinical judgment.
Experimental Paradigm
Stimuli
Brain Activation Difference Irony Literal
Data Analysis

• Irony Literal differences in activation. Both
  groups show additional activation in the medial
  frontal area (green ellipse). The group with
  autism additionally activates left inferior
  frontal and left posterior temporal areas.

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• The data were analyzed by using SPM99. Images
  were corrected for slice acquisition timing,
  motion-corrected, normalized to the Montreal
  Neurological Institute (MNI) template, resampled
  to a 2 x 2 x 2 mm voxels, and smoothed with an
  8mm Gaussian kernel to decrease spatial noise.
• Statistical analysis was performed on individual
  and group data by using the general linear model
  and Gaussian random field theory in SPM99
  (Friston et al., 1995).
• Group analysis were performed using a
  random-effects model. Statistical maps were
  superimposed on normalized T1-weighted images.
• An uncorrected height threshold of p 0.0001 and
  an extent threshold of six 8-mm3 voxels were used.

• Participants responded by pressing buttons in
  their right or left hand depending on whether the
  sentence was true or false.

For further information contact Diane L. Williams
at williamsd2139_at_duq.edu