Effect of Luminance Contrast on BOLD fMRI Response in Human Primary Visual Areas

1998 ◽  
Vol 79 (4) ◽  
pp. 2204-2207 ◽  
Author(s):  
Bradley G. Goodyear ◽  
Ravi S. Menon
Keyword(s):  
Luminance Contrast ◽  
Blood Oxygenation ◽  
Planar Imaging ◽  
Bold Fmri ◽  
Activation Level ◽  
Red Led ◽  
Visual Areas ◽  
Oxygenation Level ◽  
Fmri Response ◽  
Image Pixels

Goodyear, Bradley G. and Ravi S. Menon. Effect of luminance contrast on BOLD fMRI response in human primary visual areas. J. Neurophysiol. 79: 2204–2207, 1998. In this study, we examined the effect of stimulus luminance contrast on blood-oxygenation-level-dependent (BOLD) functional magnetic resonance imaging within human visual cortex (V1 and extrastriate). Between experiments, the calibrated luminance of a single red LED covering 2° of the subject's visual field was changed relative to a constant background luminance. This stimulus provided a different foveal luminance contrast for each experiment. We used an echo planar imaging sequence to collect blood-oxygenation-sensitive images during and in the absence of the presented stimulus. Our results showed that within V1 there was an increase in the spatial extent of activation with increasing stimulus contrast, but no trend was seen within extrastriate. In both V1 and extrastriate, the local mean activation level for all activated image pixels remained constant with increasing luminance contrast. However, when we investigated activated pixels common to all luminance contrast levels, we found that there was an increase in the mean activation level within V1, but not within extrastriate. These results suggest that there is an increase in the activity of cells in V1 with increasing luminance contrast.

BOLD fMRI Response of Early Visual Areas to Perceived Contrast in Human Amblyopia

2000 ◽  
Vol 84 (4) ◽  
pp. 1907-1913 ◽  
Author(s):  
Bradley G. Goodyear ◽  
David A. Nicolle ◽  
G. Keith Humphrey ◽  
Ravi S. Menon
Keyword(s):  
Spatial Frequency ◽  
Neuronal Response ◽  
Blood Oxygenation ◽  
Normal Vision ◽  
Staircase Method ◽  
Visual Areas ◽  
Oxygenation Level ◽  
Fmri Response ◽  
Visual Cortical ◽  
Contrast Thresholds

In this study, we used a temporal two-alternative forced choice psychophysical procedure to measure the observer's perception of a 22% physical contrast grating for each eye as a function of spatial frequency in four subjects with unilateral amblyopia and in six subjects with normal vision. Contrast thresholds were also measured using a standard staircase method. Additionally, blood-oxygenation-level–dependent (BOLD) functional magnetic resonance imaging (fMRI) was used to measure the neuronal response within early visual cortical areas to monocular presentations of the same 22% physical contrast gratings as a function of spatial frequency. For all six subjects with normal vision and for three subjects with amblyopia, the psychophysically measured perception of 22% contrast as a function of spatial frequency was the same for both eyes. Threshold contrast, however, was elevated for the amblyopic eye for all subjects, as expected. The magnitude of the fMRI response to 22% physical contrast within “activated” voxels was the same for each eye as a function of spatial frequency, regardless of the presence of amblyopia. However, there were always fewer “activated” fMRI voxels during amblyopic stimulation than during normal eye stimulation. These results are consistent with the hypotheses that contrast thresholds are elevated in amblyopia because fewer neurons are responsive during amblyopic stimulation, and that the average firing rate of the responsive neurons, which reflects the perception of contrast, is unaffected in amblyopia.

scholarly journals Perception affects the brain's metabolic response to sensory stimulation

2021 ◽  
Author(s):  
Mauro DiNuzzo ◽  
Silvia Mangia ◽  
Marta Moraschi ◽  
Daniele Mascali ◽  
Gisela E. Hagberg ◽  
...  
Keyword(s):  
Metabolic Response ◽  
Visual Stimulation ◽  
Aerobic Glycolysis ◽  
Sensory Stimulation ◽  
Blood Oxygenation ◽  
Bold Fmri ◽  
Physiological Variables ◽  
Fmri Signal ◽  
Oxygenation Level ◽  
Neurochemical Profile

Processing of incoming sensory stimulation triggers an increase of cerebral perfusion and blood oxygenation (neurovascular response) as well as an alteration of the metabolic neurochemical profile (neurometabolic response). Here we show that perceived and unperceived isoluminant chromatic flickering stimuli designed to have similar neurovascular responses as measured by blood oxygenation level dependent functional MRI (BOLD-fMRI) in primary visual cortex (V1) have markedly different neurometabolic responses as measured by functional MRS. In particular, a significant regional buildup of lactate, an index of aerobic glycolysis, and glutamate, an index of malate-aspartate shuttle, occurred in V1 only when the flickering is perceived, without any relation with behavioral or physiological variables. Wheras the BOLD-fMRI signal in V1, a proxy for input to V1, was insensitive to flickering perception by design, the BOLD-fMRI signal in secondary visual areas was larger during perceived than unperceived flickering indicating increased output from V1. These results indicate that the upregulation of energy metabolism induced by visual stimulation depends on the type of information processing taking place in V1, and that 1H-fMRS provides unique information about local input/output balance that is not measured by BOLD-fMRI.

Class Information Predicts Activation by Object Fragments in Human Object Areas

2008 ◽  
Vol 20 (7) ◽  
pp. 1189-1206 ◽  
Author(s):  
Yulia Lerner ◽  
Boris Epshtein ◽  
Shimon Ullman ◽  
Rafael Malach
Keyword(s):  
Classification Performance ◽  
Blood Oxygenation ◽  
Imaging Studies ◽  
Behavioral Studies ◽  
Visual Areas ◽  
Human Object ◽  
Oxygenation Level ◽  
Class Information ◽  
High Level ◽  
Object Features

Object-related areas in the ventral visual system in humans are known from imaging studies to be preferentially activated by object images compared with noise or texture patterns. It is unknown, however, which features of the object images are extracted and represented in these areas. Here we tested the extent to which the representation of visual classes used object fragments selected by maximizing the information delivered about the class. We tested functional magnetic resonance imaging blood oxygenation level-dependent activation of highly informative object features in low- and high-level visual areas, compared with noninformative object features matched for low-level image properties. Activation in V1 was similar, but in the lateral occipital area and in the posterior fusiform gyrus, activation by “informative” fragments was significantly higher for three object classes. Behavioral studies also revealed high correlation between performance and fragments information. The results show that an objective class-information measure can predict classification performance and activation in human object-related areas.

scholarly journals Functional Activities Detected in the Olfactory Bulb and Associated Olfactory Regions in the Human Brain Using T2-Prepared BOLD Functional MRI at 7T

2021 ◽  
Vol 15 ◽  
Author(s):  
Xinyuan Miao ◽  
Adrian G. Paez ◽  
Suraj Rajan ◽  
Di Cao ◽  
Dapeng Liu ◽  
...  
Keyword(s):  
Olfactory Bulb ◽  
Orbitofrontal Cortex ◽  
Brain Regions ◽  
Vital Role ◽  
Blood Oxygenation ◽  
Olfactory Stimulation ◽  
Planar Imaging ◽  
Susceptibility Artifacts ◽  
Bold Fmri ◽  
Susceptibility Effects

Olfaction is a fundamental sense that plays a vital role in daily life in humans, and can be altered in neuropsychiatric and neurodegenerative diseases. Blood oxygenation level-dependent (BOLD) functional magnetic resonance imaging (fMRI) using conventional echo-planar-imaging (EPI) based sequences can be challenging in brain regions important for olfactory processing, such as the olfactory bulb (OB) and orbitofrontal cortex, mainly due to the signal dropout and distortion artifacts caused by large susceptibility effects from the sinonasal cavity and temporal bone. To date, few studies have demonstrated successful fMRI in the OB in humans. T2-prepared (T2prep) BOLD fMRI is an alternative approach developed especially for performing fMRI in regions affected by large susceptibility artifacts. The purpose of this technical study is to evaluate T2prep BOLD fMRI for olfactory functional experiments in humans. Olfactory fMRI scans were performed on 7T in 14 healthy participants. T2prep BOLD showed greater sensitivity than GRE EPI BOLD in the OB, orbitofrontal cortex and the temporal pole. Functional activation was detected using T2prep BOLD in the OB and associated olfactory regions. Habituation effects and a bi-phasic pattern of fMRI signal changes during olfactory stimulation were observed in all regions. Both positively and negatively activated regions were observed during olfactory stimulation. These signal characteristics are generally consistent with literature and showed a good intra-subject reproducibility comparable to previous human BOLD fMRI studies. In conclusion, the methodology demonstrated in this study holds promise for future olfactory fMRI studies in the OB and other brain regions that suffer from large susceptibility artifacts.

scholarly journals Separating vascular and neuronal effects of age on fMRI BOLD signals

2020 ◽  
Vol 376 (1815) ◽  
pp. 20190631 ◽  
Author(s):  
Kamen A. Tsvetanov ◽  
Richard N. A. Henson ◽  
James B. Rowe
Keyword(s):  
Neuronal Activity ◽  
Functional Neuroimaging ◽  
Well Being ◽  
Blood Oxygenation ◽  
Vascular Effects ◽  
Accurate Identification ◽  
Form Complex ◽  
Bold Fmri ◽  
Oxygenation Level ◽  
Neurovascular Interactions

Accurate identification of brain function is necessary to understand the neurobiology of cognitive ageing, and thereby promote well-being across the lifespan. A common tool used to investigate neurocognitive ageing is functional magnetic resonance imaging (fMRI). However, although fMRI data are often interpreted in terms of neuronal activity, the blood oxygenation level-dependent (BOLD) signal measured by fMRI includes contributions of both vascular and neuronal factors, which change differentially with age. While some studies investigate vascular ageing factors, the results of these studies are not well known within the field of neurocognitive ageing and therefore vascular confounds in neurocognitive fMRI studies are common. Despite over 10 000 BOLD-fMRI papers on ageing, fewer than 20 have applied techniques to correct for vascular effects. However, neurovascular ageing is not only a confound in fMRI, but an important feature in its own right, to be assessed alongside measures of neuronal ageing. We review current approaches to dissociate neuronal and vascular components of BOLD-fMRI of regional activity and functional connectivity. We highlight emerging evidence that vascular mechanisms in the brain do not simply control blood flow to support the metabolic needs of neurons, but form complex neurovascular interactions that influence neuronal function in health and disease. This article is part of the theme issue ‘Key relationships between non-invasive functional neuroimaging and the underlying neuronal activity’.

scholarly journals Is the Blood Oxygenation Level-Dependent fMRI Response to Motor Tasks Altered in Children After Neonatal Stroke?

2020 ◽  
Vol 14 ◽  
Author(s):  
Mariam Al Harrach ◽  
François Rousseau ◽  
Samuel Groeschel ◽  
Stéphane Chabrier ◽  
Lucie Hertz-Pannier ◽  
...  
Keyword(s):  
Blood Oxygenation Level Dependent ◽  
Blood Oxygenation ◽  
Motor Tasks ◽  
Neonatal Stroke ◽  
Blood Oxygenation Level ◽  
Oxygenation Level ◽  
Fmri Response
Sign in / Sign up

Export Citation Format

Share Document