The rate of glucose consumption by the neocortex is reduced by over 80% during anesthesia (Sibson et al. 1998), which disables the synapses (Richards 2002) that are supported by glial tissue (Engl and Attwell 2015). It is the synapses that provide the brain with its computational power (Hebb 1949). Disconnected (pig) neurons on life support (e.g., Sestan 2018)[1] have no ability to transfer information, and some might argue that such cells have been reduced to having a computational power below that of a single-cell organism, the amoeba (Saigusa et al. 2008), since they have been taken out of their ‘social’ environment for the expected programming between individual neural members. The organizational life of a multicellular organism is no trivial matter, requiring that each cell be subjected to some biological constraints (Albert et al. 2002) in exchange for the energy efficiency obtained per cell, which scales as the 3/4th power of an organism’s body mass (DeLong et al. 2010; Kleiber 1947; Wells 2007). This process has been shaped by 500 million years of evolution. We are a long way away from merely dumping a bunch of disconnected neurons into a dish that self-organize into a superorganism that supports consciousness, a well-studied topic by entomologist E.O. Wilson (Wilson 2012). Indeed, this calls for taking evolution seriously so that one day we might be able to really engineer a superorganism, which is not trivial (also see ‘converting rodents into humans’[2]).

Footnotes:

[1] The Yale researcher, Prof. Nenad Sestan, has managed to keep pig brains that were detached from the body and on life support (i.e. a warm blood supply mediated by pumps) alive for up to 36 hours (Regalado 2018). This result created quite a sensation at the National Institutes of Health with some even suggesting that this could yield the possibility of studying consciousness and the brain in the absence of the body. A notable observation was that the EEG activity of the pig brains was flat. What is clear from this is that a body is necessary to give the brain life through feedback (Tehovnik and Chen 2015). The challenge now is to determine how much of the body (or its prosthetic equivalent) is sufficient to provide function to a brain. A similar misthinking, as that which motivated Sestan (2018), has occurred by investigators who have hooked up two brains via wires to create the illusion that significant information can be transmitted between them (cf. Pais-Vieira et al. 2013 & Tehovnik and Teixeira e Silva 2014).

[2] Converting rodents into humans: Brain tissues from humans, called organoids, have been implanted into the brains of mice raising the possibility of having human brain cells incorporated into the rodent biostructure (Mansour et al. 2018). Some have speculated that this could endow rodents with an enhanced cognitive ability if the number of human cells were numerous enough (Begley 2017). Note that there are some 71 million neurons in a mouse brain, so this would require a significant addition of organized tissue. A fear persists amongst bioethicists that such implants might give rodents some degree of humanness: i.e., augmented consciousness. But injections of neural tissue into a foreign body are riddled with incompatibilities such as problems with blood supply, immunity, and functional connectivity.

The bird brain, unlike the human brain, regularly injects itself with new neurons via neurogenesis, and therefore it might provide clues about the challenges of adding new neurons into another’s nervous system (Barnea and Pravosudov 2011). Cell proliferation, cell migration via glia, and cell replacement are some of the steps that make up neurogenesis. Riding the brain of old cells is also part of the process (as anyone who has ever received chemotherapy understands). To add, this process is tightly regulated. For example, in the canary, neural augmentation occurs in the vocal control nuclei during periods of song and mating (Goldman and Nottebohm 1983). The point behind emphasizing this detail is to show that for the new neurons to contribute, one might need to reprogram the existing tissues—neurons, glia, epithelia—so that the new neurons are accepted and utilized effectively. At this point, injections of human neurons into a rodent brain may be more prone to producing cognitive deficits than cognitive enhancements.