As prominent artificial intelligence (AI) researchers eye limits to the current phase of the technology, a different approach is gaining attention: using living human brain cells as computational hardware. These "biocomputers" are still in their early days. They can play simple games such as Pong, and perform basic speech recognition.

        But the excitement is fueled by three converging trends. First, venture capital is flowing into anything adjacent to AI, making speculative ideas suddenly fundable. Second, techniques for growing brain tissue outside the body have matured, with the pharmaceutical industry jumping on board. Third, rapid advances in brain‒computer interfaces have seen growing acceptance of technologies that blur the line between biology and machines.

        Nevertheless, plenty of questions remain. Are we witnessing genuine breakthroughs, or another round of tech-driven hype? And what ethical questions arise when human brain tissue becomes a computational component? For almost 50 years, neuroscientists have grown neurons on arrays of tiny electrodes to study how they fire under controlled conditions.

        By the early 2000s, researchers attempted rudimentary two-way communication between neurons and electrodes, planting the first seeds of a bio-hybrid computer. But progress stalled until another strand of research took off: brain organoids.

        In 2013, scientists demonstrated that stem cells could self-organise into three-dimensional brain-like structures. These organoids spread rapidly through biomedical research, increasingly aided by “organ-on-a-chip” devices designed to mimic aspects of human physiology outside the body.

        Today, using stem-cell-derived neural tissue is commonplace ⸺ from drug testing to developmental research. Yet the neural activity in these models remains primitive, far from the organised firing patterns that underpin cognition or consciousness in a real brain. While complex network behaviour is beginning to emerge even without much external stimulation, experts generally agree that current organoids are not conscious, nor close to it.

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