The study investigates the neural basis of global resting-state fMRI activity in monkeys. It finds that spontaneous fluctuations in local field potential (LFP) measured from a single cortical site exhibit widespread positive correlations with fMRI signals over nearly the entire cerebral cortex. These correlations are particularly strong in the upper gamma frequency range (40–80 Hz), with a lag of 6–8 seconds between the neural and hemodynamic signals. Strong correlations are also observed in lower frequencies (2–15 Hz), though with a shorter lag. The coupling is dependent on the monkey's behavioral state, being stronger and more anticipatory when the animals' eyes are closed. These findings suggest that the global component of fMRI fluctuations during rest is tightly coupled with underlying neural activity, challenging the common practice of removing global signal fluctuations in resting-state fMRI studies. The study implications for understanding neurovascular coupling and the purpose of intrinsic brain activity are discussed.The study investigates the neural basis of global resting-state fMRI activity in monkeys. It finds that spontaneous fluctuations in local field potential (LFP) measured from a single cortical site exhibit widespread positive correlations with fMRI signals over nearly the entire cerebral cortex. These correlations are particularly strong in the upper gamma frequency range (40–80 Hz), with a lag of 6–8 seconds between the neural and hemodynamic signals. Strong correlations are also observed in lower frequencies (2–15 Hz), though with a shorter lag. The coupling is dependent on the monkey's behavioral state, being stronger and more anticipatory when the animals' eyes are closed. These findings suggest that the global component of fMRI fluctuations during rest is tightly coupled with underlying neural activity, challenging the common practice of removing global signal fluctuations in resting-state fMRI studies. The study implications for understanding neurovascular coupling and the purpose of intrinsic brain activity are discussed.