A new study has developed upon a new theory that the brain’s claustrum behaves less like the “seat of consciousness” as previously thought, and more like an internet router, receiving and broadcasting signals for complex cognitive tasks. The study is published in Trends in Cognitive Sciences.
Exploring the function of the claustrum
The claustrum is a region of the brain found underneath the cortex. It has long been thought to exchange signals with the cortex, itself an area responsible for coordinating higher processes such as reasoning, memory and complex thought.
Renowned scientist Francis Crick – made famous for his role in the discovery of the DNA double helix – suggested in a posthumously published article in 2005 that the claustrum is the “seat of consciousness”, theorizing its role in our awareness of the world and ourselves.
However, researchers from the University of Maryland School of Medicine (UMSOM) have proposed that Crick’s theory may have been incorrect. In this new study, they posit that the claustrum behaves more like a high-speed internet router than the seat of consciousness.
In this example, the claustrum receives direction and commands from the “boss”, i.e., from areas within the cortex. The claustrum then organizes and broadcasts these signals, much like a wireless router for an internet network. Together, the various networks are synchronized and allow us to carry out cognitively challenging tasks.
“The brain is the most complex system in the known universe. It is these data-driven theoretical advances that propel our knowledge forward toward harnessing that complexity for improving human life,” explained Dr. Brian Mathur, associate professor of pharmacology at UMSOM and senior author of the study. “As the most highly connected structure in the brain, the claustrum is a window into the enigma of the brain, the mind.”
Knowledge of the coordination of these networks between the cortex and the claustrum is important, as dysregulation of these systems is characteristic of many disorders including schizophrenia, addiction and Alzheimer’s disease. Insights into these networks and the mechanisms underpinning them may lead to more effective therapies for these disorders.
Evidence against Crick’s consciousness theory
Mathur and colleagues conducted a series of experiments on both animals and people to try and elucidate the exact role of the claustrum. Using a mouse model, the researchers first demonstrated that “turning off” the claustrum did not result in a loss of consciousness, and the mice continued their normal activity.
Next, the mice were given either a simple or a difficult task to complete. Under normal conditions, mice can successfully complete both simple and difficult tasks. However, the researchers found when they “turned off” the claustrum, the mice could not complete the difficult tasks.
To determine if these findings could extend to humans, Mathur set up a research study in collaboration with colleagues David Seminowicz, professor of neural and pain sciences at the UM School of Dentistry, and Fred Barrett, associate professor of psychiatry and behavioral sciences at Johns Hopkins University School of Medicine.
The study examined healthy volunteers undergoing functional MRI (fMRI) brain scans while completing either simple or complicated mental tasks. fMRI detects areas of activity within the brain by detecting changes in blood flow. This showed only the complicated tasks resulted in the claustrum “lighting up”, indicating increased activity. Additionally, this occurred alongside the activation of a network in the cortex that is associated with cognitive performance.
Together, these findings appear to dispel Crick’s consciousness theory. Nevertheless, Mathur explains that additional experiments are needed to support this new theory of claustrum function and understand how it can organize networks in the cortex to support cognition.
Reference: Madden MB, Stewart BW, White MG, et al. A role for the claustrum in cognitive control. TiCS. 2022;26(12):1133-1152. doi: 10.1016/j.tics.2022.09.006
This article is a rework of a press release issued by the University of Maryland. Material has been edited for length and content.