Separating Processes within a Trial in Event-Related Functional MRI

Ollinger, John M.; Shulman, Gordon L.; Corbetta, Maurizio

doi:10.1006/nimg.2000.0710

Cited by 403 publications

(294 citation statements)

References 23 publications

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“…Task-related BOLD responses were analyzed in stages. First, we examined individual participant responses in each paradigm (Braille, auditory) by using the general linear model (20)(21)(22). Response strength was estimated by using a regressor obtained by convolution of the (six-frame) task plus control epochs with a standard hemodynamic response model (23).…”

Section: Methodsmentioning

confidence: 99%

Default brain functionality in blind people

Burton¹,

Snyder²,

Raichle³

2004

Proc. Natl. Acad. Sci. U.S.A.

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We studied whether default functionality of the human brain, as revealed by task-independent decreases in activity occurring during goal-directed behaviors, is functionally reorganized by blindness. Three groups of otherwise normal adults were studied: early blind, adventitiously blind, and normally sighted. They were imaged by using functional MRI during performance of a word association task (verb generation to nouns) administered by using auditory stimuli in all groups and Braille reading in blind participants. In sighted people, this task normally produces robust taskindependent decreases relative to a baseline of quiet wakefulness with eyes closed. Our functional MRI results indicate that taskindependent decreases are qualitatively similar across all participant groups in medial and dorsal prefrontal, lateral parietal, anterior precuneus, and posterior cingulate cortices. Similarities in task-independent decreases are consistent with the hypothesis that functional reorganization resulting from the absence of a particular sensory modality does not qualitatively affect default functionality as revealed by task-independent decreases. More generally, these results support the notion that the brain largely operates intrinsically, with sensory information modulating rather than determining system operations.M uch previous functional brain imaging work in normally sighted (NS) adult humans has documented activity decreases during performance of various goal-directed behaviors relative to a control state, such as quiet wakefulness with eyes closed, visual fixation, or a minimally demanding task (1-3). These activity decreases have a variable relationship to taskspecific activity increases. Some decreases appear to represent activity attenuation in sensory systems irrelevant to the task; these task-dependent decreases can occur in sensory cortex both within and separate from the modality engaged by the task (4-7).Other activity decreases appear to be independent of the performed task. With remarkable regularity, these taskindependent decreases occur in medial and lateral parietal cortices, posterior cingulate cortex, dorsal and ventral medial prefrontal cortex, and the amygdalae (reviewed in ref. 8). We propose that task-independent decreases represent suppression of default brain functionality (9) and have cited detailed circulatory and metabolic evidence showing that such decreases do not correspond to ''activations'' in the resting state, as has been suggested (3). Rather, task-independent decreases occur in areas that are functionally active but not physiologically ''activated.'' Default brain activity suggests spontaneous functions that are attenuated only when we reallocate resources to temporarily engage in goal-directed behaviors. Hence our designation of ''default'' functions (8, 9).Numerous studies show that blindness leads to cortical reorganization manifesting as increased visual cortex activity during performance of tasks involving tactile and auditory stimuli (reviewed in refs. 10 and 11). Of interest ...

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Section: Methodsmentioning

confidence: 99%

Default brain functionality in blind people

Burton¹,

Snyder²,

Raichle³

2004

Proc. Natl. Acad. Sci. U.S.A.

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“…Areas matching our anatomical criteria and lying closest to the corresponding reference cluster (resulting from the random-effects analysis for differential contrasts; p uncorrected \ 0.0001; T = 6.4) were considered as their appropriate equivalents on the single subject level. Time series of the mean voxel value, within a 4-mm-radius sphere around the local peak of the areas of interest, was calculated and extracted from our eventrelated sessions using finite impulse response (FIR) models (Ollinger et al 2001). The convolution of a reference hemodynamic response function with boxcars, representing the onsets and durations of the experimental conditions, was used to define the regressors for a general linear model analysis of the data.…”

Section: Imaging Parameters and Data Analysismentioning

confidence: 99%

Neural correlates of after-effects caused by adaptation to multiple face displays

et al. 2012

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Adaptation to a given face leads to face-related, specific after-effects. Recently, this topic has attracted a lot of attention because it clearly shows that adaptation occurs even at the higher stages of visual cortical processing. However, during our every-day life, faces do not appear in isolation, rather they are usually surrounded by other stimuli. Here, we used psychophysical and fMRI adaptation methods to test whether humans adapt to the gender properties of a composite multiple face stimulus as well. As adaptors we used stimuli composed of eight different individual faces, positioned peripherally in a ring around a fixation mark. We found that the gender discrimination of a subsequent centrally presented target face is significantly biased as a result of long-term adaptation to either male or female multiple face stimuli. Similar to our previous results with single-face adaptors (Kovács et al. in Neuroimage 43(1):156-164, 2008), a concurrent functional magnetic resonance imaging adaptation experiment revealed the strongest blood oxygen level-dependent signal adaptation bilaterally in the fusiform face area. Our results suggest that humans extract the statistical features of the multiple face stimulus and this process occurs at the level of occipito-temporal face processing.

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“…Images were smoothed using a Gaussian filter with a FWHM of 1.2 voxels. We used the general linear model to estimate the finite impulse response (FIR; Ollinger et al, 2001) associated with each stimulus event. For each stimulus event, a stimulus convolution matrix (SCM) was defined, i.e., a matrix operator representation of the time-discretized convolution with the event sequence (Ollinger et al, 2001).…”

Section: Fmri Analysismentioning

confidence: 99%

“…We used the general linear model to estimate the finite impulse response (FIR; Ollinger et al, 2001) associated with each stimulus event. For each stimulus event, a stimulus convolution matrix (SCM) was defined, i.e., a matrix operator representation of the time-discretized convolution with the event sequence (Ollinger et al, 2001). This was accomplished by placing a 1 in the row, corresponding to the time at which each image was acquired, and in the column, corresponding to the appropriate point of the hemodynamic response.…”

Section: Fmri Analysismentioning

confidence: 99%