Gain control in the response of human visual cortex to plaids

2012 ◽  
Vol 107 (9) ◽  
pp. 2570-2580 ◽  
Author(s):  
J. Scott McDonald ◽  
Damien J. Mannion ◽  
Colin W. G. Clifford
Keyword(s):  
Visual Cortex ◽  
Tree Shrew ◽  
Gain Control ◽  
Imaging Study ◽  
Blood Oxygenation ◽  
Human Visual Cortex ◽  
Intrinsic Signal ◽  
Orientation Response ◽  
Oxygenation Level ◽  
The Individual

A recent intrinsic signal optical imaging study in tree shrew showed, surprisingly, that the population response of V1 to plaid patterns comprising grating components of equal contrast is predicted by the average of the responses to the individual components (MacEvoy SP, Tucker TR, Fitzpatrick D. Nat Neurosci 12: 637–645, 2009). This prompted us to compare responses to plaids and gratings in human visual cortex as a function of contrast and orientation. We found that the functional MRI (fMRI) blood oxygenation level-dependent (BOLD) responses of areas V1–V3 to a plaid comprising superposed grating components of equal contrast are significantly higher than the responses to a single component. Furthermore, the orientation response profile of a plaid is poorly predicted from a linear combination of the responses to its components. Together, these results indicate that the model of MacEvoy et al. (2009) cannot, without modification, account for the fMRI BOLD response to plaids in human visual cortex.

scholarly journals Eccentricity Mapping of the Human Visual Cortex to Evaluate Temporal Dynamics of Functional T1ρ Mapping

2015 ◽  
Vol 35 (7) ◽  
pp. 1213-1219 ◽  
Author(s):  
Hye-Young Heo ◽  
John A Wemmie ◽  
Casey P Johnson ◽  
Daniel R Thedens ◽  
Vincent A Magnotta
Keyword(s):  
Blood Flow ◽  
Visual Cortex ◽  
Temporal Dynamics ◽  
Occipital Cortex ◽  
Hemodynamic Response ◽  
Proton Exchange ◽  
Blood Oxygenation ◽  
Human Visual Cortex ◽  
Tissue Metabolism ◽  
Oxygenation Level

Recent experiments suggest that T1 relaxation in the rotating frame ( T1ρ) is sensitive to metabolism and can detect localized activity-dependent changes in the human visual cortex. Current functional magnetic resonance imaging (fMRI) methods have poor temporal resolution due to delays in the hemodynamic response resulting from neurovascular coupling. Because T1ρ is sensitive to factors that can be derived from tissue metabolism, such as pH and glucose concentration via proton exchange, we hypothesized that activity-evoked T1ρ changes in visual cortex may occur before the hemodynamic response measured by blood oxygenation level-dependent (BOLD) and arterial spin labeling (ASL) contrast. To test this hypothesis, functional imaging was performed using BOLD, and ASL in human participants viewing an expanding ring stimulus. We calculated eccentricity phase maps across the occipital cortex for each functional signal and compared the temporal dynamics of T1ρ versus BOLD and ASL. The results suggest that T1ρ changes precede changes in the two blood flow-dependent measures. These observations indicate that T1ρ detects a signal distinct from traditional fMRI contrast methods. In addition, these findings support previous evidence that T1ρ is sensitive to factors other than blood flow, volume, or oxygenation. Furthermore, they suggest that tissue metabolism may be driving activity-evoked T1ρ changes.

Blood oxygenation level-dependent (BOLD) total and extravascular signal changes and ΔR 2 * in human visual cortex at 1.5, 3.0 and 7.0 T

2010 ◽  
Vol 24 (1) ◽  
pp. 25-34 ◽  
Author(s):  
Manus J. Donahue ◽  
Hans Hoogduin ◽  
Peter C. M. van Zijl ◽  
Peter Jezzard ◽  
Peter R. Luijten ◽  
...  
Keyword(s):  
Visual Cortex ◽  
Blood Oxygenation Level Dependent ◽  
Blood Oxygenation ◽  
Human Visual Cortex ◽  
Blood Oxygenation Level ◽  
Oxygenation Level ◽  
Signal Changes

scholarly journals Neural Basis of the Sound-Symbolic Crossmodal Correspondence Between Auditory Pseudowords and Visual Shapes

2021 ◽  
pp. 1-50
Author(s):  
Kelly McCormick ◽  
Simon Lacey ◽  
Randall Stilla ◽  
Lynne C. Nygaard ◽  
K. Sathian
Keyword(s):  
Phonological Processing ◽  
Imaging Study ◽  
Blood Oxygenation ◽  
Sound Symbolism ◽  
Neural Basis ◽  
Oxygenation Level ◽  
Crossmodal Correspondence ◽  
Study Participants ◽  
The Brain ◽  
Left Middle

Abstract Sound symbolism refers to the association between the sounds of words and their meanings, often studied using the crossmodal correspondence between auditory pseudowords, e.g., ‘takete’ or ‘maluma’, and pointed or rounded visual shapes, respectively. In a functional magnetic resonance imaging study, participants were presented with pseudoword–shape pairs that were sound-symbolically congruent or incongruent. We found no significant congruency effects in the blood oxygenation level-dependent (BOLD) signal when participants were attending to visual shapes. During attention to auditory pseudowords, however, we observed greater BOLD activity for incongruent compared to congruent audiovisual pairs bilaterally in the intraparietal sulcus and supramarginal gyrus, and in the left middle frontal gyrus. We compared this activity to independent functional contrasts designed to test competing explanations of sound symbolism, but found no evidence for mediation via language, and only limited evidence for accounts based on multisensory integration and a general magnitude system. Instead, we suggest that the observed incongruency effects are likely to reflect phonological processing and/or multisensory attention. These findings advance our understanding of sound-to-meaning mapping in the brain.

scholarly journals Dynamic metabolic changes in human visual cortex in regions with positive and negative blood oxygenation level-dependent response

2018 ◽  
Vol 39 (11) ◽  
pp. 2295-2307 ◽  
Author(s):  
Miguel Martínez-Maestro ◽  
Christian Labadie ◽  
Harald E Möller
Keyword(s):  
Visual Cortex ◽  
Tricarboxylic Acid Cycle ◽  
Blood Oxygenation Level Dependent ◽  
Blood Oxygenation ◽  
Metabolic Changes ◽  
Resonance Spectroscopy ◽  
Bold Response ◽  
Full Field ◽  
Blood Oxygenation Level ◽  
Oxygenation Level

Dynamic metabolic changes were investigated by functional magnetic resonance spectroscopy (fMRS) during sustained stimulation of human primary visual cortex. Two established paradigms, consisting of either a full-field or a small-circle flickering checkerboard, were employed to generate wide-spread areas of positive or negative blood oxygenation level-dependent (BOLD) responses, respectively. Compared to baseline, the glutamate concentration increased by 5.3% ( p = 0.007) during activation and decreased by −3.8% ( p = 0.017) during deactivation. These changes were positively correlated with the amplitude of the BOLD response ( R = 0.60, p = 0.002) and probably reflect changes of tricarboxylic acid cycle activity. During deactivation, the glucose concentration decreased by −7.9% ( p = 0.025) presumably suggesting increased consumption or reduced glucose supply. Other findings included an increased concentration of glutathione (4.2%, p = 0.023) during deactivation and a negative correlation of glutathione and BOLD signal changes ( R = −0.49, p = 0.012) as well as positive correlations of aspartate ( R = 0.44, p = 0.035) and N-acetylaspartylglutamate ( R = 0.42, p = 0.035) baseline concentrations with the BOLD response. It remains to be shown in future work if the observed effects on glutamate and glucose levels deviate from the assumption of a direct link between glucose utilization and regulation of blood flow or support previous suggestions that the hemodynamic response is mainly driven by feedforward release of vasoactive messengers.

scholarly journals Neural Basis of the Sound-Symbolic Crossmodal Correspondence Between Auditory Pseudowords and Visual Shapes

2018 ◽  
Author(s):  
Kelly McCormick ◽  
Simon Lacey ◽  
Randall Stilla ◽  
Lynne C. Nygaard ◽  
K. Sathian
Keyword(s):  
Phonological Processing ◽  
Imaging Study ◽  
Blood Oxygenation ◽  
Sound Symbolism ◽  
Neural Basis ◽  
Oxygenation Level ◽  
Crossmodal Correspondence ◽  
Underlying Mechanisms ◽  
Study Participants ◽  
The Brain

ABSTRACTSound symbolism refers to the association between the sounds of words and their meanings, often studied using the crossmodal correspondence between auditory pseudowords, e.g. ‘takete’ or ‘maluma’, and pointed or rounded visual shapes, respectively. In a functional magnetic resonance imaging study, participants were presented with pseudoword-shape pairs that were sound-symbolically congruent or incongruent. We found no significant congruency effects in the blood oxygenation level-dependent (BOLD) signal when participants were attending to visual shapes. Rather, during attention to auditory pseudowords, we observed greater BOLD activity for incongruent compared to congruent audiovisual pairs bilaterally in the intraparietal sulcus and supramarginal gyrus, and in the left middle frontal gyrus. We compared this activity to independent functional contrasts designed to test potential underlying mechanisms, but found no evidence for semantic mediation, and only limited evidence for multisensory integration and magnitude estimation. Instead, we suggest that the observed incongruency effects are likely to reflect phonological processing and/or multisensory attention. These findings advance our understanding of sound-to-meaning mapping in the brain.

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