At Rise of AI 2019 in Berlin, Wagner Steuer Costa, a data scientist working in neuroscience and biochemistry, presents research on the nematode C. elegans, a one-millimeter worm with exactly 302 neurons, as a model for decision-making mechanisms that current AI systems lack. Using optogenetics, proteins controlled by light, his lab activates specific neurons and observes behavior and synaptic ultrastructure changes, showing that faster neural signaling increases both the release probability and the size, or information content, of synaptic vesicles. He describes a single neuron that decides whether the animal flees or freezes based on conflicting signals from head and tail, and shows that a distinct sleep neuron stays active for extended periods while the animal is unresponsive, only ceasing when the worm is woken by an oxygen pulse. He argues that neuromodulators, slower-acting chemicals like neuropeptides, help maintain the neural network in a state of criticality that allows fast, accurate responses to changing conditions. Steuer Costa closes by arguing that current AI approaches lack compartmentalized processing, sleep-like memory consolidation and, most provocatively, death, which he argues could be a necessary driver of intelligence through evolutionary pressure across many AI iterations.
Key takeaways
- Wagner Steuer Costa studies C. elegans, a worm with exactly 302 neurons, as a minimal model for decision-making circuits missing from current AI.
- Optogenetically speeding up neural signaling increases both vesicle release probability and vesicle size, showing modulation works by changing signal content, not just frequency.
- A single neuron integrates conflicting head and tail signals to decide whether the worm flees or freezes when threatened.
- A dedicated sleep neuron stays active for long periods during unresponsiveness and deactivates when the animal is woken by an oxygen pulse.
- Steuer Costa argues AI should be built to die, proposing mortality across iterations as an evolutionary driver of genuine intelligence.
Detailed notes
C. elegans as a minimal model for decision-making
Steuer Costa studies C. elegans, a one-millimeter hermaphroditic worm with exactly 302 neurons whose position is identical across individual animals, making it a tractable, genetically modifiable model organism. His lab works with optogenetics, using light-sensitive proteins to activate specific neurons, and the animal's roughly 7,000 synapses form a connectome comparable in relative scale to a small region of the human brain.
Optogenetics reveals how faster signaling changes synaptic vesicles
By photoactivating neurons to speed up the animal's swimming by about 30%, his team found faster movement came with more errors, and examined synaptic ultrastructure by electron microscopy. Faster signaling increased both the probability that synaptic vesicles release their contents and, unexpectedly, the size of dense-core vesicles carrying neuromodulators, meaning the modulation partly works by changing how much signal each vesicle carries, not just how often it fires.
A single neuron that decides whether to flee or freeze
He shows video data of a single neuron that determines whether the worm flees or waits when threatened, for example by a predator worm. The neuron activates briefly before a reversal in movement; if it also receives a hyperpolarizing signal from the tail indicating a threat from behind, the animal freezes instead of fleeing forward. He calls this the animal's decision-making circuit, tuned to be fast and highly specific because an error in either direction can be fatal.
A dedicated sleep neuron and network criticality
A different neuron stays active for long stretches while the animal is behaviorally unresponsive, a state Steuer Costa identifies as sleep; when the worm is stimulated by a pulse of oxygen, the neuron deactivates and the animal responds quickly. He argues this kind of rapid responsiveness depends on keeping the neural network in a state of criticality, and that neuromodulators, including more than 100 different neuropeptides and over 1,000 receptors identified so far, likely help maintain that state, though this has not yet been proven directly in C. elegans.
Population-level behavior: mating and individual variation
At the population level, he describes how harsh conditions increase the proportion of male worms, which mate to increase genetic variation and can live up to seven days versus the animal's normal three-day lifespan, and how males that fail to mate release neuromodulators that make younger males chase their own tails. Despite being genetically identical from the same mother, individual worms show large behavioral variation; about 40% of synaptic connections are consistent across animals, while roughly 10% are unique to a given individual, for reasons not yet understood.
What AI is still missing: compartmentalization, sleep and death
Steuer Costa argues current AI architectures already use some biological ideas, such as network topology, but lack the fine-grained compartmentalization seen in biological neurons, where different regions of a single cell process information differently; he cites an insect neuron with about 1,400 distinct compartments as an extreme example. He also argues AI systems lack a sleep-like mechanism for consolidating memory and, most provocatively, argues AI should be built to die, since mortality across many iterations of an AI population could be the evolutionary pressure needed to drive genuine intelligence.
Quotes
The moment where an artificial intelligence is capable of dying, it will be the point where we will truly achieve intelligence.
Wagner Steuer Costa
Questions answered in this talk
Why does Wagner Steuer Costa study a worm to understand AI decision-making?
At Rise of AI 2019, Steuer Costa explains that C. elegans has only 302 neurons in fixed positions across individuals, making it possible to trace exactly how a single neuron drives a decision, such as fleeing or freezing, in ways current AI models do not replicate.
What did the sleep-neuron experiment show?
Steuer Costa describes a neuron that stays active for long stretches while the worm is behaviorally unresponsive, a sleep-like state, and deactivates when the animal is woken with a pulse of oxygen, suggesting sleep exists outside mammals.
Why does Steuer Costa argue AI should be capable of dying?
He argues that mortality, tested across many iterations of an AI population in an evolutionary process, could be the mechanism that drives genuine intelligence, comparing it to how death has shaped efficiency in biological evolution.