Optogenetic astrocyte activation evokes BOLD fMRI response with oxygen consumption without neuronal activity...

Area of Science:

• Neuroscience
• Neuroimaging
• Cellular Biology

Background:

• Functional magnetic resonance imaging (fMRI) relies on the blood oxygenation-level-dependent (BOLD) signal to map brain activity.
• Previous interpretations assumed BOLD signals exclusively reflect neuronal activation.

Purpose of the Study:

• To investigate the cellular source of BOLD signal generation.
• To determine if non-neuronal cells, such as astrocytes, contribute to the BOLD signal.

Main Methods:

• Optogenetic activation of astrocytes and neurons in mice.
• fMRI in awake mice.
• Electrophysiological recordings and histochemical analysis.
• Imaging mass spectrometry.

Main Results:

• Astrocytic activation alone evoked a BOLD signal response.
• Astrocyte-induced BOLD signals involved oxygen consumption without altering neuronal activity.
• Acetyl-carnitine synthesis via glucose metabolism was identified at astrocyte-activated sites.

Conclusions:

• Astrocytes represent an independent cellular source of the BOLD signal.
• The findings necessitate a reconsideration of the interpretation of fMRI BOLD signals.
• Astrocytic activity should be considered in neuroimaging studies.