Findings point to brain areas where planning, purpose, physiology, behavior, and movement are integrated.
The practitioners of mindfulness say that a calm body leads to a calm mind. A new study conducted by researchers at Washington University School of Medicine in St. Louis indicates that the concept of the inseparable connection between the body and mind goes beyond being just an abstraction. It is shown in the study that networks involved in thinking, planning, and control of involuntary bodily functions like blood pressure and heartbeat are connected to parts of the brain that control movement. In essence, the body and mind are literally linked within the brain’s structure.
The research, which was published on April 19 in the journal Nature, could provide an explanation for certain perplexing phenomena. For instance, it could shed light on why anxiety drives some individuals to engage in pacing; why the stimulation of the vagus nerve, responsible for regulating internal organ functions like digestion and heart rate, might alleviate depression; and why individuals who exercise regularly report a more positive perspective on life.
“It has been observed by individuals who meditate that by calming the body through practices like breathing exercises, the mind also becomes calm,”
stated first author Evan M. Gordon, PhD, an assistant professor of radiology at the School of Medicine’s Mallinckrodt Institute of Radiology.
“Such practices can be incredibly beneficial for individuals with anxiety, for instance. However, the scientific evidence supporting their mechanisms has been limited. Nonetheless, we have now identified a connection. We have discovered the region where the highly active and goal-oriented part of the mind is linked to the brain regions that regulate breathing and heart rate. Calming one aspect should indeed have reciprocal effects on the other.”
The aim of Gordon and senior author Nico Dosenbach, MD, PhD, an associate professor of neurology, was not to delve into age-old philosophical inquiries about the relationship between the body and the mind. Instead, they sought to confirm the established brain map of movement control areas, employing modern brain-imaging techniques.
In the 1930s, neurosurgeon Wilder Penfield, MD, conducted mappings of motor areas in the brain by applying small electrical jolts to exposed brains during surgical procedures and observing the resulting responses. His findings revealed that stimulating a narrow strip of tissue on each hemisphere of the brain causes specific body parts to twitch. Furthermore, these control areas in the brain are arranged in a corresponding order to the body parts they govern, with the toes located at one end of each strip and the face at the other. Penfield’s depiction of the motor regions of the brain, known as the homunculus or “little man,” has since become a fundamental element in neuroscience textbooks.
Gordon, Dosenbach, and their colleagues embarked on the replication of Penfield’s work using functional magnetic resonance imaging (fMRI). A total of seven healthy adults were recruited to undergo extensive fMRI brain scanning while either at rest or engaged in tasks. Utilizing this comprehensive dataset, individualized brain maps were constructed for each participant. Subsequently, their findings were validated by utilizing three large publicly available fMRI datasets—the Human Connectome Project, the Adolescent Brain Cognitive Development Study, and the UK Biobank—which collectively encompass brain scans from approximately 50,000 individuals.
To their surprise, it was discovered that Penfield’s map was not entirely accurate. While control of the feet, hands, and face aligned with Penfield’s identifications, there were three additional areas interspersed among these key regions that did not appear to be directly associated with movement, despite their location within the brain’s motor area.
Furthermore, the non-movement areas exhibited distinct characteristics compared to the movement areas. They appeared to be thinner and exhibited strong connections with one another and with other brain regions involved in processes such as thinking, planning, mental arousal, pain, and regulation of internal organs and functions like blood pressure and heart rate. Additional imaging experiments demonstrated that although the non-movement areas did not show activation during movement, they did become active when individuals contemplated movement.
“All of these connections can be understood when considering the true purpose of the brain,”
commented Dosenbach.
“The brain serves the function of enabling successful behavior in the environment, allowing us to achieve our goals without causing harm or endangering ourselves. Our body movements serve specific purposes. It is only logical that the motor areas are connected to executive function and the regulation of fundamental bodily processes, such as blood pressure and pain. Pain serves as a potent feedback mechanism, doesn’t it? When we engage in an action that causes pain, we instinctively think, ‘I won’t do that again.'”
The newly identified network, discovered by Dosenbach and Gordon, has been named the Somato-Cognitive Action Network, or SCAN. To comprehend the development and evolution of this network, they conducted brain scans on a newborn, a 1-year-old, and a 9-year-old. Additionally, they analyzed previously collected data from nine monkeys. The network was not evident in the newborn but became clearly observable in the 1-year-old and displayed near-adult-like characteristics in the 9-year-old. The monkeys exhibited a smaller and more rudimentary system with fewer extensive connections compared to humans.
“It is possible that this system initially evolved as a simpler mechanism to integrate movement with physiology, ensuring that we don’t faint, for instance, when we stand up,”
explained Gordon.
“However, as we evolved into organisms capable of much more intricate thinking and planning, the system underwent upgrades to incorporate numerous complex cognitive elements.”
Evidence pointing to the existence of a mind-body network has been present for a considerable period, scattered across various isolated papers and unexplained observations.
“Penfield possessed remarkable brilliance, and his ideas have remained dominant for 90 years, creating a blind spot within the field,”
remarked Dosenbach, who holds positions as an associate professor of biomedical engineering, pediatrics, occupational therapy, radiology, and psychological & brain sciences.
“Once we initiated a search for it, we encountered numerous published data that didn’t quite align with his concepts, as well as overlooked alternative interpretations. By collating diverse sets of data, including our own observations, and adopting a broader perspective to synthesize it, we arrived at a fresh approach to understand the interconnectedness of the body and mind.”
DOI: 10.1038/s41586-023-05964-2
Abstract
Motor cortex (M1) has been thought to form a continuous somatotopic homunculus extending down the precentral gyrus from foot to face representations1,2, despite evidence for concentric functional zones3 and maps of complex actions4. Here, using precision functional magnetic resonance imaging (fMRI) methods, we find that the classic homunculus is interrupted by regions with distinct connectivity, structure and function, alternating with effector-specific (foot, hand and mouth) areas. These inter-effector regions exhibit decreased cortical thickness and strong functional connectivity to each other, as well as to the cingulo-opercular network (CON), critical for action5 and physiological control6, arousal7, errors8 and pain9. This interdigitation of action control-linked and motor effector regions was verified in the three largest fMRI datasets. Macaque and pediatric (newborn, infant and child) precision fMRI suggested cross-species homologues and developmental precursors of the inter-effector system. A battery of motor and action fMRI tasks documented concentric effector somatotopies, separated by the CON-linked inter-effector regions. The inter-effectors lacked movement specificity and co-activated during action planning (coordination of hands and feet) and axial body movement (such as of the abdomen or eyebrows). These results, together with previous studies demonstrating stimulation-evoked complex actions4 and connectivity to internal organs10 such as the adrenal medulla, suggest that M1 is punctuated by a system for whole-body action planning, the somato-cognitive action network (SCAN). In M1, two parallel systems intertwine, forming an integrate–isolate pattern: effector-specific regions (foot, hand and mouth) for isolating fine motor control and the SCAN for integrating goals, physiology and body movement.