Neuralink & Technologies to Enhance Human Brains | Dr. Matthew MacDougall

Andrew Huberman opens by introducing Dr. Matthew MacDougall as the head neurosurgeon at Neuralink. He describes the company's goal as developing technologies to overcome specific clinical challenges of the brain and nervous system, and also to improve how brains currently function by augmenting memory and cognition and by improving communication between humans and between humans and machines. Huberman explains why he values a neurosurgeon's perspective: in his view, neurosurgeons are the astronauts of neuroscience, because they can watch how cognition, behavior and speech change as the brain is altered structurally and functionally. He previews several topics: which brain challenges Neuralink considers tractable now, devices in the peripheral nervous system, and the fact that MacDougall has a radio receiver implanted in his own body, as do members of his family. MacDougall trained in medicine at the University of California San Diego and at Stanford University School of Medicine.

Huberman asks how a surgeon conceptualizes the brain as an organ, noting that surgeons tend to see the world differently because they cut, fix and can add things to the brain. MacDougall says that when you see a small tumor eat away at one part of the brain and watch a very discrete function fail in isolation, a particular picture of the organ emerges.

the brain really is a collection of functional modules pinned together, duct taped together in this bone box attached to your head.

His most memorable example comes from early in his training at UC San Diego. A very young man had been in a car accident, and the team operated and saved his life, which MacDougall says may have come at the cost of quality of life. The patient woke with bilateral frontal lobe damage and essentially no impulse control. Soon after rounds, his 80-year-old recovery room nurse called the team back, and the patient pointed at her and said she would not have sex with him. MacDougall took this as evidence that the patient's frontal lobes were gone and that he would never again show reasonable human behavior, and he calls it one of the most tragic ways for a brain to malfunction. He then broadens the point: everything the brain does, from controlling hormone levels to vision, sensation and every kind of muscle movement, can go wrong, in part or entirely. He describes the work as very high stakes, but says that surgeons sometimes fix something that seems unfixable, and that "Lazarus-like miracles" happen "not too uncommonly."

Asked for one of the more satisfying experiences in neurosurgery, MacDougall describes a relatively new technique for small tumors deep in the brain. The traditional approach meant cutting through a lot of healthy brain and disrupting neurons and white matter, which he calls the wires connecting neurons. In the modern approach, the surgeon drills a two-millimeter hole in the skull, passes a small fiber optic cannula down to the tumor, attaches it to a laser, and heats the tumor while the patient is in an MRI scanner. Images are taken about every second, so the team can monitor the temperature and set it where it kills the tumor cells while barely harming the surrounding brain.

MacDougall confirms Huberman's summary that the technique gives better clinical outcomes with less collateral damage. He says it now helps even in cases once considered totally inoperable, such as tumors in the brain stem, primary motor cortex or primary verbal areas like Broca's area, where surgeons would previously have either not operated or caused catastrophic damage. He qualifies the claim: those patients "sometimes now are coming out unscathed."

Huberman questions the obvious reading of the frontal lobe case. Because the brain contains both excitatory and inhibitory neurons, acting as accelerators and brakes, damage to one region does not straightforwardly reveal what that region normally does. The frontal lobes might act as conductors that matter for impulsivity without being the immediate players. He asks what the frontal lobes do, given how much of this expanded real estate humans have compared with other animals, and more generally what damage tells us about the basic function of a tissue.

MacDougall says the answer varies from tissue to tissue. For the frontal lobes, he proposes that they act as a filter, selectively saying "Shh" back to the parts of the brain behind them. His example is an impulse to take something attractive out of a jewelry display case: the frontal lobes reply that you can if you pay for it first. In this picture they let the impulse through, but in a controlled way. He describes this as "very high level, very broad thinking about how the frontal lobes work." In his patient, the filter was missing, so "even the slightest inclination to want something came right up to the surface." He does not directly take up Huberman's alternative that the frontal lobes might be indirect conductors.

Huberman offers a personal parallel. As a graduate student he ran "acutes," neurophysiological experiments on anesthetized animals that ran for two or three days, with the animal terminated at the end. He apologizes to listeners uncomfortable with animal research and says the animal felt no pain throughout. The experimenters got only an hour of sleep here and there. After one such experiment, at a diner, he says it took every bit of self-control not to take food off a waitress's tray meant for another table. He did not do it, but he relates it to the "shh response" flickering in and out, and asks whether sleep deprivation limits forebrain activity in a similar way.

MacDougall declines to confirm a forebrain-specific effect. He says he does not know whether the effect is more pronounced in the forebrain than in other regions, but that sleep deprivation clearly has broad effects across the brain. People begin to see visual hallucinations, which points to the visual cortex at the back of the brain, and their motor coordination declines. If forced to give a definitive answer, he would guess that the entire brain is affected and that it is not clear any one part is affected more than another.

Huberman calls neuroplasticity the holy grail of the nervous system: its capacity to strengthen and weaken connections, and possibly add new neurons, though he thinks strengthening and weakening matter more. He mentions current excitement about classical psychedelics such as LSD and psilocybin, which seem to "open plasticity," among other effects, through neuromodulators like serotonin. He asks what is possible in adult brains, older than about 25, with and without machines.

MacDougall agrees that plasticity declines with age: older people find it harder to learn new things, change their behavior radically or break long-held habits. He then argues that implanted electrodes and computers are not necessarily the obvious answer to increasing plasticity. His reasoning is about scale and targeting. Plasticity involves the entire brain, altering "a trillion synapses" in a similar way, while an electrical stimulation target must be focused. It is also hard to know which brain area would be the most potent stimulation target. A device like Neuralink's might be able to steer current to multiple targets with some control, but he says no electrodes he can see coming in our lifetimes could cover the entire surface and depth of the brain the way a drug can.

And so I think plasticity research will bear the most fruit when it focuses on pharmacologic agents.

Huberman says he did not expect that answer from someone at Neuralink, and admits that outsiders, himself included, picture a chip giving people super memories but really do not know what the company is doing. He links this to the "mystique" around Elon Musk's ventures, such as SpaceX and Tesla, and to engineers taking on big problems. He then asks MacDougall to describe Neuralink's missions, to the extent he is allowed.