Transcript Hemispheric Asymmetry in MRI Volumetric Amygdala

Age Group Comparisons in Category Member Generation Tasks: Effect of Stimulus Design
Keith M. McGregor1,3, Michelle L. Benjamin1,2, Yu-Ling Chang1,2, Zvinka Zlatar1,2, Colin Rackelman1,2,4,
Megan Gaiefsky1,2, Ilana Levy 1,2, Keith D. White1,3,4, and Bruce Crosson 1,2,4
Department of Veterans Affairs Rehabilitation Research and Development Brain Rehabilitation Research Center at the Malcom Randall VA Medical Center1
University of Florida Departments of Clinical and Health Psychology2, and Psychology3,and McKnight Brain Institute4, Gainesville, Florida
Presented at the February 2008 International Neuropsychological Society Conference, Waikoloa, Hawaii
This poster is available on the Web at http://www.BIRC.phhp.ufl.edu
INTRODUCTION
•Optimal stimulus presentation paradigms in functional magnetic resonance imaging
(fMRI) continues to be vital to experimental design particularly in the study of
language processes.
•Category member generation tasks have indicated a relationship between activation
between lateral inferior and medial frontal areas and the basal ganglia (Crosson et al.,
2003; Crosson et al., 2005), a finding with particular relevance to the imaging studies
of aging and stroke rehabilitation.
•The imaging of such word generation tasks for between group comparisons has been
reported using both block (Crosson et al., 2003) and event-related paradigms (Crosson
et al., 2005; Wierenga 2007), but we are not aware of research comparing the
sensitivity of different paradigm designs on group activation comparisons, particularly
in inferior frontal and subcortical areas.
•The present study compares age related differences in activation across event related
and block design fMRI during word retrieval (category member generation) tasks.
RESULTS
Age Group Comparison
Event-related
Block
L
R
L
R
METHODS
Subjects:
Twenty-two neurologically normal older adults at least 65 years of age and 22 young
adults between 18-35 years of age were recruited from the community and
participated in two fMRI category exemplar tasks (BLOCK & EVENT). Older
subjects were given a short mental status screening (MMSE) to screen for possible
dementia and Mild Cognitive Impairment; all older subjects scored > 27 on the
MMSE. See Table 1 for descriptive demographics.
Table 1. Group Demographics
Subject Group
(age range)
Mean Age
(SD)
Sex
(F:M)
Years Education
Mean (SD)
MMSE total
Mean (SD)
OLD
YOUNG
71.3 (6.2)
25.5 (4.5)
9:13
12:10
16.3 (3.2)
16.4 (2.3)
29.4 (0.9)
----
Talairach montage showing group activation comparisons @ p<.005:
Blue indicates Older > Younger; Orange indicates Younger > Older
fMRI Experimental Procedures:
•Baseline visual fixation task with simultaneous audio and visual presentation of
category exemplars and stop cue during active trials in both fMRI paradigms.
•60 total categories presented only once across BLOCK and EVENT conditions.
•EVENT Condition:
•Overt, single-item response, event-related fMRI of category-member generation
for 44 categories across 4 fMRI runs (e.g., “eagle” for “birds”).
•3.4 seconds/category for each active exemplar generation event.
•Resting blocks of 15.3, 17, 18.7, and 20.4 secs between active trials.
BLOCK Condition:
•Covert, multiple-response, block paradigm fMRI of category-member generation
for 16 total categories across 2 fMRI runs.
•17 seconds/category for each active exemplar generation block.
•Resting blocks of 10.2, 11.9, and 15.3 seconds between active blocks.
fMRI Acquisition: 3 T Siemens Allegra instrument, gradient echo planar images.
•Functional images: 240mm FOV, 64x64 matrix, 3.8mm x 3.8mm in-plane resolution,
TR=1700 ms, TE=25 ms, flip angle=70°. Whole-brain slice coverage using 32 5mm
thick slices (BLOCK=axial acquisition; EVENT=sagittal acqusition).
•High-resolution T1-weighted 3D MP-RAGE axial scan (TE = 4.13 ms; TR = 2000
ms; FOV = 240 mm; FA = 8°; matrix size = 256x192; 128 1.3mm slices).
fMRI Analyses: AFNI
•FWHM spatial-smoothing at 4mm.
•3dDeconvolve: Deconvolution analysis with response estimate (maxlag) of:
•EVENT: 12 images omitting the first two responses (minlag)
•BLOCK: 20 images
Left
Right
Left
Right
Inferior Frontal Gyrus (BA 47/11)
Dorsal Medial Thalamus
Superior Temporal Gyrus (BA 42)
Superior Parietal Lobule (BA 7)
Precentral Sulcus (BA 6)
Anterior Thalamus
Lingual/Fusiform Area (BA 19/37)
Lingual Gyrus (BA 19)
Precentral Gyrus (BA 4)
Putamen
Putamen
Middle Frontal Gyrus (BA 10)
Cerebellum
Precentral gyrus (BA 4)
Middle Frontal Gyrus (BA 47/11)
Supramarginal Gyrus (BA 40)
Capular projection of striatum
Angular Gyrus (BA 39)
Anterior Thalamus
Word Generation
Comparison to Baseline
L
Talairach
montage of
task-tobaseline
activation
comparisons:
conjunction
analysis of
Age at Block
(top) and
Eventrelated
(bottom)
comparisons
@ p<.0001:
Blue
indicates
Older
activation;
Yellow
indicates
Younger
activation;
Green
indicates
Both Older
and Younger
activation
R
Block
L
R
Eventrelated
Anterior Thalamus
CONCLUSIONS
•Acknowledging methodological differences in response production (i.e. – overt versus covert), the data indicate that
block paradigms with covert response may provide greater sensitivity to lateral frontal and basal ganglia activation in
healthy adults during category member generation tasks.
•However, event-related FMRI paradigms will continue to have relevance in studying certain patient populations in
which on-line task performance needs to be carefully monitored (e.g., language production in nonfluent aphasia;
Crosson et al, 2007).
•On-line task performance may be beneficial for neurologically normal populations, since different subsets of healthy
individuals may show different patterns of neural activation to complete a task. E.g., Wierenga et al (2007): “highfunctioning” old subjects showed a positive correlation between naming accuracy and right inferior frontal cortex
(IFC), whereas “low-functioning” old subjects and young subjects showed a negative correction in right IFC; all
groups showed positive correlations between accuracy and left IFC activity.
•Additionally, overt response monitoring within an event-related imaging paradigm may provide fruitful secondary
analysis strategies for a better understanding of language functions’ complex interactions and delineated task-related
contributions of specific brain areas (e.g., correct vs. error response comparisons). (Meinzer et al., 2006)
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Acknowledgements of support: VA RR&D Center of Excellence Grant #F2182C and Research Career Scientist Award (Crosson);
McKnight Brain Institute of University of Florida E. F. McKnight Grants.