Autonomic Nervous System Identified as Key Driver of Global fMRI Brain Signal

Recent research has shed light on the intricate relationship between our body's autonomic nervous system and brain activity as measured by functional magnetic resonance imaging (fMRI). A study conducted by researchers from the University of California, Los Angeles (UCLA), and other institutions, has demonstrated that a widespread, repeating pattern in brain activity—known as the global signal—primarily originates from autonomic physiological processes. This pattern significantly correlates with systemic bodily functions such as heart rate, breathing, and other involuntary responses.

The global signal is a prominent feature seen in fMRI scans, characterized by a brain-wide surge in activity that appears suddenly and affects large parts of the brain simultaneously. Previously, the origin of this pattern was unclear, with some considering it a noise artifact. However, the current study clarifies that this global activity is heavily influenced by the body's autonomic system, which governs arousal and essential involuntary functions.

To reach these conclusions, the researchers analyzed extensive datasets of human fMRI data combined with detailed physiological recordings, including heart rate and respiration. They found a strong association between fluctuations in the global fMRI signal and various autonomic changes, such as cardiovascular and pulmonary activity. Additionally, they observed that manipulations influencing arousal—like deep breaths or auditory stimuli—induced similar co-fluctuations in brain and body activity. These findings extend to sleep, where spontaneous arousals also showed linked changes.

The study suggests that the global fMRI signal is not merely noise but a reflection of the autonomic nervous system’s activity, particularly related to arousal states. This insight opens new avenues to understand how brain and bodily systems coordinate during different states of wakefulness and sleep. Future research aims to explore the functional significance of this global signal, especially how it influences behaviors and neurological processes.

Overall, this research emphasizes the importance of considering systemic physiological factors in neuroimaging studies and highlights the integral role of the autonomic nervous system in shaping brain activity patterns. Understanding this connection better could lead to improved insights into brain health, consciousness, and disorders associated with arousal and autonomic regulation.

Source: Medical Xpress