Temporal and spatial nonlinearities in FMRI BOLD response in human primary visual cortex
Author(s)
Advisor
Date
2019-08Publisher
Bilkent University
Language
English
Type
ThesisItem Usage Stats
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Abstract
It is generally assumed that fMRI BOLD response (i.e., functional magnetic resonance
imaging blood-oxygen-level-dependent signal) is linear and time-invariant.
In this study, we investigated spatial and temporal nonlinearities in fMRI BOLD
response at different flickering durations (nearly instantaneous and 1 s). We
presented participants two successive flickering checkerboard wedge stimuli with
stimulus onset asynchrony (SOA) of 0 s, 0.5 s, 1.5 s, and 6 s. The spatial locations
of the stimuli were categorized as the same location in the same hemifield,
adjacent locations in the same hemifield, and between hemifields. We demonstrated
that fMRI BOLD response behaves nonlinearly when the successive stimuli
spatially and temporally were close to each other for both flickering durations.
Nonlinearity between the successive stimuli was the highest for the same location
in the same hemifield, higher in adjacent locations in the same hemifield, and the
lowest in between hemifields. In addition, nonlinearity at the shorter SOAs (0 s,
0.5 s, and 1.5 s) was found to be higher than nonlinearity at SOA 6.
Keywords
Spatial nonlinearitySpatial summation
Temporal nonlinearity
Temporal summation
fMRI BOLD
Primary visual cortex