Download HST:583 fMRI Acquisition Lab1 Susan Whitfield

Self Reference
Sensorimotor
HST:583
fMRI Acquisition Lab1
Susan Whitfield-Gabrieli
Sternberg
TASKS:
Self Reference
Sensorimotor
Breath holding
Sternberg
Breath holding
Self Reference Task
POLITE
Stimuli: Trait Adjectives
DARING
RUDE
DEPENDABLE
Cue:
“Does this word apply to you?” (self reference condition)
or
“Is this word positive?” (semantic condition)
Self reference task design
Stimuli: trait adjective words
Words were drawn from Anderson’s (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
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
Activation in CMS observed in imaging studies
during self related tasks in different domains.
Northoff Neuroimage 2006
Graphic representation of localizations of
clusters
2
1
Northoff Neuroimage 2006
Self Reference, Single Subject
(self-semantic)
Single subject
(4 sessions)
Single subject, one session only
Single Subject Data
Self reference, Group Analysis
Frontal regions are prone to susceptibility
artifact
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.
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)
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
You’ll see LEFT motor cortex (green), since the subject is
responding with the right hand, and you’ll 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).
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
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: 4:06
Breath holding calibration
•
The entire gray matter volume is activated in each subject by the breath-holding
task. This sample data is from Stanford’s 3T MRI shows the global response to
holding one’s breath for 15 seconds.
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 seconds*6 + 78 seconds+ 6 sec ddas = 360s
Total task time: 6:00min
Time frames: 180
Sternberg Task:
Group analysis (n=10)
HIGH (5) – LOW(1) Working Memory Load:
Green regions: ROIs of 3 working memory related areas (DLPFC, DLPMC, IPS) and
1 control region (MTG)
DLPMC
IPS
(dorsal lateral premotor
cortex)
(intraparietal
sulcus)
DLPFC
(dorsal lateral
prefrontal cortex)
MTG
(middle temp
gyrus)
Stuart Wallace,
MIND, BIRN