In a recent study published on Cell Reports, researchers demonstrated that cortical organoids derived from pluripotent stem cells can exhibit goal-directed learning when interfaced with a closed-loop electrophysiology system. Using high-density microelectrode arrays, scientists recorded neural activity and delivered targeted electrical stimulation to organoids embedded in a simulated cartpole task, where the neural network controlled forces to balance a virtual pole.
The experiment followed three stages: mapping spontaneous neural activity, identifying stimulus-response connectivity, and applying adaptive training signals. Reinforcement-learning algorithms selected pairs of neurons to stimulate with high-frequency electrical pulses based on task performance. Organoids receiving these adaptive training signals improved significantly in balancing performance compared with random stimulation or no stimulation. Some organoids increased their balancing time from around 10 seconds to over 60 seconds during training cycles.
Analysis revealed that stimulus-evoked causal connectivity between neurons strongly predicted learning success. However, performance gains were short-lived and typically disappeared after 45-minute rest periods, suggesting the learning relied on short-term neural plasticity.
Pharmacological experiments confirmed the biological basis of this learning: blocking AMPA and NMDA glutamate receptors with NBQX and APV eliminated performance improvements, demonstrating that glutamatergic synaptic transmission is required.
Overall, the study shows that brain organoids can adapt their neural dynamics to perform goal-directed tasks, opening possibilities for studying learning mechanisms, developing neural therapies, and exploring hybrid biological–computational systems.
Research article: Cell Reports. Goal-directed learning in cortical organoids. Robbins, Ash et al.
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