GoKawiilThe workings of the brain are often compared to those of a computer. Some researchers are testing this analogy to its limits, attempting to build computers containing laboratory-grown cultures of brain cells. In doing so, they hope to circumvent the physical limitations of the silicon-based computing hardware used for today’s artificial intelligence1,2.
The promise is there. Brain tissue combines memory and computation in the same substrate, requiring fewer components than conventional computers do. Theories of neural networks, based on neurons and synapses, have inspired AI algorithms. Brains consume much less energy than AI machines do3 and don’t require vast cooling systems.
Human neuroscience is entering a new era — it mustn’t forget its human dimension
Such biocomputing does have distinct ethical challenges. Discussions have raged over the morality of using lab-grown brain tissue and the potential for consciousness4. Yet one key issue has been absent from debates so far: the lack of explicit consent for the use of human neural tissue in biocomputing.
Research in biocomputing relies on voluntary donations of cells, often from people undergoing medical procedures who give them altruistically to aid biomedical and basic biological research. Yet, consent forms don’t ask donors what sort of research they would like their cells to be used for in the future — or, more importantly, all the possible ways that they wouldn’t like them to be used. Donors who want to support the development of cancer treatments might not imagine that their tissues could be used to create biocomputers, possibly with commercial uses.
A more explicit and nuanced approach to donor consent is needed for biocomputing research that uses lab-grown brain tissue. In our view, researchers should avoid using cell lines for which consent was given only for biomedical research. A system must be established for seeking consent retrospectively, or for reviewing the ethics of projects when obtaining consent again (known as re-consent) is not possible.
Using brain cells to compute
Brain-based biocomputing relies on human cortical neurons because they are larger and form more complex circuits than do those from rodents or other primates. These features are thought to contribute to the remarkable information-processing capabilities of the human brain5,6, from recognizing a face to performing abstract reasoning.
Biocomputers are built using ‘pluripotent’ stem cells, which have the potential to develop into most of the body’s other cell types. Such cells can come either from donated embryos left over after in vitro fertilization or from engineered adult cells gifted by volunteers, including people undergoing medical treatment.
In the lab, pluripotent stem cells can be coaxed into becoming brain organoids — small 3D clusters that mimic the structure, function and organization of various regions of the brain. Information can be encoded in neural stimulation, providing ‘computational inputs’ that are processed by the neurons in the organoid, leading to neural outputs that can be recorded through microelectronic array systems (see ‘Brain-based biocomputing’). It has already been shown that this set-up can be used for some simple computational processes that are the basis by which hardware-based AI models identify patterns and make predictions7.
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