MRI of Functional Deactivation: Temporal and Spatial Characteristics of Oxygenation-Sensitive Responses in Human Visual Cortex

doi:10.1006/nimg.1999.0438

NeuroImage

Volume 9, Issue 6, June 1999, Pages 611-618

https://doi.org/10.1006/nimg.1999.0438 Get rights and content

Abstract

Magnetic resonance imaging (MRI) of neuronal “activation” relies on the elevation of blood flow and oxygenation and a related increase of the blood oxygenation level-dependent (BOLD) MRI signal. Because most cognitive paradigms involve both switches from a low degree of activity to a high degree of activity and vice versa, we have undertaken a baseline study of the temporal and spatial characteristics of positive and negative BOLD MRI responses in human visual cortex. Experiments were performed at 2.0 T using a multislice gradient-echo EPI sequence (TR = 1 s, mean TE = 54 ms, flip angle 50°) at 2 × 2-mm²spatial resolution. Activation and “deactivation” processes were accomplished by reversing the order of stimulus presentations in paradigms using homogeneous gray light and an alternating checkerboard as distinct functional states. For sustained stimulation (≥60 s) the two conditions resulted in markedly different steady-state BOLD MRI signal strengths. The transient responses to brief stimulation (≤18 s) differed insofar as activation processes temporally separate positive BOLD and negative undershoot effects by about 10 s, whereas negative BOLD effects and undershoot contributions overlap for deactivation processes. Apart from differences in stimulus features (e.g., motion) the used activation and deactivation protocols revealed similar maps of neuronal activity changes.

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¹: On leave from MR Research Center, Department of Clinical Neuroscience, Karolinska Institutet, Stockholm, Sweden.

²: To whom correspondence should be addressed. Fax: +49-551-201-1307. E-mail:[email protected].

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Regular ArticleMRI of Functional Deactivation: Temporal and Spatial Characteristics of Oxygenation-Sensitive Responses in Human Visual Cortex

Abstract

Processing strategies for time-course data sets in functional MRI of the human brain

Magn. Reson. Med.

Human brain language areas identified by functional magnetic resonance imaging

J. Neurosci.

Response and habituation of the human amygdala during visual processing of facial expression

Neuron

Spatial and temporal differentiation of fMRI BOLD response in primary visual cortex of human brain during sustained visual stimulation

Magn. Reson. Med.

Semantic encoding and retrieval in the left inferior prefrontal cortex: A functional MRI study of task difficulty and process specificity

J. Neurosci.

Temporal characteristics of oxygenation-sensitive MRI responses to visual activation in humans

Magn. Reson. Med.

Regular Article
MRI of Functional Deactivation: Temporal and Spatial Characteristics of Oxygenation-Sensitive Responses in Human Visual Cortex