One of the most fascinating mysteries in science is the origin of consciousness. The Nobel Laureate and Oxford mathematician Roger Penrose, and Stuart Hammeroff, an anesthesiologist, suggested a solution. They attributed consciousness to quantum computations in brains. This hinges on the idea that gravity might play a role when quantum effects disappear or "collapse". However, a series of experiments carried out in an Italian laboratory deep beneath the Gran Sasso Mountains failed to support a gravity-related model of quantum collapse, which undermines the possibility of this explanation of consciousness. The journal Physics of Life Reviews reports the results.
Catalina Curceanu is a member the Foundational Questions Institute (FQXi) and the lead physicist for the INFN experiments in Frascati, Italy. There are many competing ideas but few that can be experimentally tested.
Quantum physics has long taught us that cats can live and die simultaneously, at least theoretically. In practice, however, we don't see felines trapped in this unfortunate limbo state. The "wavefunction" of a system, its quantum character that allows it to exist in two contradictory states simultaneously, is a reason why it is less likely to "collapse" or die. This is due to the fact that it is either dead or alive at once. Penrose and Hammeroff used this model of collapse to explain gravity's effect on heavy objects such as cats when they developed their model of consciousness in the 1990s, "Orch OR theory" (the Orchestrated Objective Reduction Theory).
Quantum computations in brain
Curceanu was first interested in Orch OR theory after she met Penrose at a conference a few years back. Because quantum effects are fragile and hard to sustain even in controlled conditions, consciousness is not often associated with them. It was long assumed that quantum effects would not survive in a warm and humid environment like the brain. Penrose and Hammeroff discovered microtubules in neurons within the brain, which could sustain quantum effects for short periods of time. This is just enough to allow quantum computations to be performed. Orch OR theory attributes consciousness and quantum computations orchestrated ("Orch") through electrical oscillations within these microtubules. Curceanu says, "What I loved most about this theory is that it can be tested in principle and I decided that I would search for evidence to support it."
"I loved the fact that this theory could be tested in principle, so I set out to find evidence to support it."
The theory's core idea is that gravity is linked to quantum wavefunction collapsing and that this happens faster in systems with greater mass. In the 1980s, physicists developed a variety of models to illustrate this concept. Lajos Diasi, at Wigner Research Center for Physics, and at Eotvos Lorand University, Budapest, Hungary, was one of these physicists and co-authored the paper. He is also affiliated with Curceanu, Maaneli Darakhshani from Rutgers University, New Jersey, Matthias Laubenstein, also at INFN, as well as Kristian Piscicchia, CREF, and INFN. This idea was first proposed by Penrose a few years later, and became the basis of his consciousness theory together with Hammeroff.
Both theories are commonly referred to as the "Diosi–Penrose theory." Curceanu notes that there is a crucial difference behind the common name. Diosi's method predicts that collapse will be accompanied with the spontaneous emission of small amounts of radiation. This is just enough to detect by cutting-edge experiments.
Going underground
Curceanu's underground laboratory is located within the Gran Sasso National Laboratory. It is situated 1.4km under the Gran Sasso Italian Mountains. The lab is located on the one-side of the 10-km long highway tunnel that crosses the Gran Sasso mountain, connecting Teramo and L'Aquila. Curceanu says that the location was chosen as it is free from any cosmic-ray radiation sources above ground. This could potentially interfere with the experiment. This experiment employs a highly sensitive cylindrical detector made of pure germanium, which is smaller than a cup. To protect it from radiation from rocks, shielding is provided by layers of ultra-pure copper and lead. The experiment was run for two months and the team failed to detect any spontaneous radiation signals. This limited the possibility of gravity-related collapsing. Nature Physics reported that the team's negative results had allowed them to rule out the simplest Diosi–Penrose model in 2020.
Their new paper examines the implications of their findings for Penrose's Orch OR theory and Hammeroff’s Orch OR theory. They were able to reexamine the most plausible scenarios that Hammeroff and Penrose had presented, taking into account their experimental constraints on quantum collapsing, and came up with almost no plausible scenarios. Curceanu says, "This is the first experimental study of gravity-related quantum collapsing pillar of Orch OR consciousness model. We hope that many other researchers will follow our lead." Curceanu said, "I am extremely proud of our accomplishment."
Interdisciplinarity
Partly funded by the Foundational Questions Institute (FQXi), are the experiments and analysis. Curceanu says, "Without it it wouldn't have been possible to achieve that outcome." It is difficult to get funding for projects like this without it, due to its interdisciplinarity.
"It is really exciting to connect what you can do in the laboratory to perhaps the biggest mystery in the universe--consciousness."
Curceanu adds that Orch Or is not done yet. "Actually the real work is only at the beginning." She says. Penrose's original model of collapse, which was not like Diosi, didn't predict spontaneous radiation so it has not been ruled out. This paper briefly discusses how gravity-related collapse models might be modified. Curceanu states that such a revised model (which we are currently working on in the FQXi-financed project) could open the door for Orch OR theory.
The team is currently testing these new collapsible models to see if they can be used in the Orch OR model. "It is really exciting to connect what you can do in the laboratory to perhaps the biggest mystery in the universe--consciousness," says Curceanu.
