HST:583 fMRI Acquisition Lab1 Susan Whitfield-Gabrieli

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HST583fMRI Acquisition Lab1Susan
Whitfield-Gabrieli
Self Reference
Sternberg

• TASKS
• Self Reference
• Sensorimotor
• Breath holding
• Sternberg

Breath holding
Sensorimotor
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Self Reference Task
POLITE
DARING
Stimuli Trait Adjectives
RUDE
DEPENDABLE
Cue
Does this word apply to you? (self reference
condition) or Is this word positive?
(semantic condition)
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Self reference task design

• Stimuli trait adjective words
• Words were drawn from Andersons (1968) list of
  normed trait adjectives. The lists were
  counterbalanced for word valence, length and
  number of syllables.
• Presentation
• Words are presented in a blocked design. Each
  word is presented for 3 sec in blocks of ten and
  prior to each block onset subjects view a 2 sec
  cue describing their task for upcoming block.
  Each block is followed by 10 seconds of a rest
  condition. Each session has 2 blocks per self
  reference and 2 blocks per semantic conditions in
  the ABBA format.

Total task time 3min/session, 4 sessions or
12min
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Schematic illustration of cortical midline
structures (CMS)
MOPFC medial orbital prefrontal cortex (BA11,
BA12) VMPFC ventromedial prefrontal cortex
(BA10, 11) PACC pre and subgenual anterior
cingulate cortex (BA24, BA25, BA32) SACC
supragenual anterior cingulate cortex (BA24,
BA32) PCC posterior cingulate cortex (BA23)
Northoff Neuroimage 2006
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Activation in CMS observed in imaging studies
during self related tasks in different domains.
Northoff Neuroimage 2006
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Graphic representation of localizations of
clusters
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Northoff Neuroimage 2006
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Self Reference, Single Subject(self-semantic)
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Single subject(4 sessions)
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Single subject, one session only
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Single Subject Data
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Self reference, Group Analysis
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Frontal regions are prone to susceptibility
artifact
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Phase maps

• The field map is a 2D gradient echo sequence
  which acquires an image at 2 different echo
  times.  This sequence generates 2 types of
  images, a magnitude image and a phase map. 
• The phase map represents the phase differences
  of the spins which ultimately represent the local
  field inhomogeneities.  You can display this map
  to see which regions are prone to susceptibility
  artifacts.

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Sensorimotor Task
The task consists of a block design with block
durations of 16s on/off. When checkerboard
appears, subjects presses button using their
right index finger and the off-block is
fixation/no tapping. There are 15 total, 16s
blocks. (4 min)
On block parameters ISI ranges from 500-1000ms,
average ISI 762ms, std. dev 156ms. 21
checkerboard flashes per on block, each
checkerboard flash duration 200ms. The
sequence begins with an off block.Scanner
triggers the paradigm (after the dummy scans).
fBIRN ( functional biomedical informatics
research network)
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Motor and Visual Cortex
Motor cortex - BA4 shown in green Visual cortex
- BA 17,18,19 from rear view of brain BA 17 is
shown in red. BA 18 is orange BA 19 is yellow
Youll see LEFT motor cortex (green), since the
subject is responding with the right hand, and
youll see bilateral visual cortex.
Brain surface extracted from structural MRI
data (Wellcome Dept. Imaging Neuroscience, UCL,
UK). Brodmann Area data is based on information
from the online Talairach demon (electronic
version of Talairach and Tournoux, 1988).
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Example of Sensorimotor Task activation (with
visual, motor auditory)
Note This task has an additional auditory
component so you see temporal lobe activation as
well as motor and visual. In addition, the
subject is responding with both hands so you see
bilateral motor activation as opposed to only the
left hemisphere motor (contralateral to response
hand)
fBIRN ( functional biomedical informatics
research network) Gary Glover, Stanford
University
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Breath Holding Task

• This is a calibration task to measure subjects'
  global vascular reactivity.
• The task consists of a block design with
  alternating on/off blocks of 16-second periods of
  breath holding and normal breathing.
• During the off-block, the subject sees a green
  screen during which they are to breathe normally.
  During the last 2s of the off-block, the screen
  becomes yellow, signifying to the subject to take
  a deep breath in and hold. During the on-block
  (16s), the subject is shown a red screen, during
  which time they should hold their breath. The
  subject resumes breathing when they see a green
  colored screen.
• 15 total 16s blocks (4 min)
• Total task time 406

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Breath holding calibration

• The entire gray matter volume is activated in
  each subject by the breath-holding task. This
  sample data is from Stanfords 3T MRI shows the
  global response to holding ones breath for 15
  seconds.

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Sternberg Item Recognition Paradigm (SIRP) A
Working Memory Task

• Each block is composed of three epochs learn,
  encode, and probe
• 1.5 sec for the learn prompt followed by .5
  sec blank screen
• 6 sec to encode the target digits ( 1, 3, 5
  digit sets providing a range of task difficulty)
• 38 sec for the probe digits (sequential
  presentation of digits)
• This means each working memory set lasts a total
  of 46 seconds.
• A block of each set size occurs twice in random
  order within a single run and each working memory
  set is sandwiched between fixation blocks.
• The duration of the fixation blocks within a run
  is random
• Total time for all fixation blocks within a run
  78 seconds, (4,20)
• (min time 4 sec, max time 20 sec)
• Total scan time is thus 46 seconds6 78
  seconds 6 sec ddas 360s Total task time
  600min Time frames 180

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Sternberg Task Group analysis (n10)

• HIGH (5) LOW(1) Working Memory Load
• Green regions ROIs of 3 working memory
  related areas (DLPFC, DLPMC, IPS) and1 control
  region (MTG)

DLPMC (dorsal lateral premotor cortex)
IPS (intraparietal sulcus)
DLPFC (dorsal lateral prefrontal cortex)
MTG (middle temp gyrus)
Stuart Wallace, MIND, BIRN
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