Effect of task difficulty on blood-oxygen-level-dependent signal: A functional magnetic resonance imaging study in a motion discrimination task

There is much evidence that neural activity in the human brain is modulated by task difficulty, particularly in visual, frontal, and parietal cortices. However, some basic psychophysical tasks in visual perception do not give rise to this expected effect, at least not in the visual cortex. In the cu...

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Bibliographic Details
Published in:PloS one 2018-06, Vol.13 (6), p.e0199440-e0199440
Main Authors: Na, Ren, Bi, Taiyong, Tjan, Bosco S, Liu, Zili, Fang, Fang
Format: Article
Language:English
Subjects:
BASIC (programming language)
Behavior
Biology and Life Sciences
Blood
Blood gases
Brain
Brain mapping
Brain research
Cerebral circulation
Cortex (frontal)
Cortex (parietal)
Decision making
Discrimination (Psychology)
Female
Frontal lobe
Functional magnetic resonance imaging
Hierarchies
Humans
Laboratories
Life sciences
Magnetic resonance
Magnetic Resonance Imaging
Male
Medicine and Health Sciences
Mental health
Modulation
Motion
Motion perception
Multivariate Analysis
Neuroimaging
Neurological research
Neurophysiology
Neurosciences
NMR
Nuclear magnetic resonance
Oxygen
Oxygen - blood
Pattern Recognition, Visual
Peripheral vision
Photic Stimulation
Physiological aspects
Psychological aspects
Psychophysics
Psychophysiology
Quantitative psychology
Reactive oxygen species
Research and Analysis Methods
Resonance
Social Sciences
Studies
Task Performance and Analysis
Visual cortex
Visual Cortex - physiology
Visual discrimination
Visual fields
Visual perception
Visual tasks
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Summary:There is much evidence that neural activity in the human brain is modulated by task difficulty, particularly in visual, frontal, and parietal cortices. However, some basic psychophysical tasks in visual perception do not give rise to this expected effect, at least not in the visual cortex. In the current study, we used functional magnetic resonance imaging (fMRI) to record brain activity while systematically manipulating task difficulty in a motion discrimination task, by varying the angular difference between the motion direction of random dots and a reference direction. We used both a blocked and an event-related design, and presented stimuli in both central and peripheral vision. The behavioral psychometric function, across angular differences of 3°, 9°, 15°, or 80°, spanned the full response range, as expected. The mean blood oxygen level dependent (BOLD) signals were also correlated within-participants between the blocked and event-related designs, across all brain areas tested. Within the visual cortex, the voxel response patterns correlated more within-conditions (e.g., 3° and 3°) than between-conditions (e.g., 3° and 9°), in both designs, further attesting to the reasonable quality of the BOLD data. Nevertheless, the BOLD-o-metric functions (i.e., BOLD activity as a function of task difficulty) were flat in the whole-brain and region-of-interest (ROI) analyses, including in the visual cortex, the parietal cortex, in both designs, and in foveal and peripheral visual fields alike. Indeed, there was little difference between BOLD activity during the 3° and 80° conditions. Some suggestive evidence of difficulty modulation was revealed only in the superior and inferior frontal gyri for the blocked design. We conclude that, in motion discrimination, there is no systematic BOLD modulation that accompanies the standard psychometric function across different hierarchies of cortical areas, except for the frontal lobe of the brain.
ISSN:1932-6203
1932-6203
DOI:10.1371/journal.pone.0199440