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Negative functional MRI response correlates with decreases in neuronal activity in monkey visual area V1
Amir Shmuel1, Mark Augath, Axel Oeltermann
1Max Planck Institute for Biological Cybernetics, Spemannstr. 38, 72076 Tuebingen, Germany. Amir.Shmuel@tuebingen.mpg.de
Nature Neuroscience
|March 21, 2006
Summary
Negative BOLD responses (NBRs) in brain imaging are linked to decreased neuronal activity, not just increased blood flow. This study shows NBRs reflect reduced neural function below baseline levels, offering new insights into brain activity monitoring.
Area of Science:
- Neuroscience
- Cognitive Neuroscience
- Neuroimaging
Background:
- Functional brain imaging commonly infers neural activity from hemodynamic responses.
- Sustained negative BOLD responses (NBRs) are frequently observed but their neural origins are unclear.
Purpose of the Study:
- To investigate the neural basis of negative BOLD responses (NBRs) in the visual cortex.
- To determine if NBRs are associated with decreases in neuronal activity.
Main Methods:
- Simultaneous functional magnetic resonance imaging (fMRI) and electrophysiological recordings (local field potentials and multiunit activity) were employed.
- The study examined responses in the visual cortex during a functional imaging task.
Main Results:
- A negative BOLD response (NBR) was detected beyond stimulated regions, correlating with decreased neuronal activity below spontaneous levels.
- This NBR was spatially separated from positive BOLD responses and showed tight trial-by-trial coupling with neuronal activity decreases.
- Electrophysiological data confirmed that NBRs corresponded to reductions in both local field potentials and multiunit activity.
Conclusions:
- A significant portion of the negative BOLD response (NBR) originates from decreases in neuronal activity.
- This finding clarifies the neural underpinnings of NBRs, improving the interpretation of functional brain imaging data.
