University of Michigan researchers have built and tested neural probes that hold what are believed to be the smallest implantable LEDs ever made. The new probes control and record the activity of many individual neurons, measuring how changes in the activity of a single neuron can affect its neighbors. The team anticipates that the technologies could lead to breakthroughs in understanding and treating neurological diseases such as Alzheimer's.

Each probe array contains 12 LEDs and 32 electrodes. The micro LEDs are as small as a neuron's cell body, so they can turn single neurons on and off. Meanwhile, the microelectrodes measure activity at the single-neuron level.

"Using micro-LED probes, we may tease out how the signals propagate inside the neural circuitry so that we can understand how memories are formed, retrieved, and replaced," said Euisik Yoon, a professor of electrical engineering and computer science at U-M and project leader.

The proof-of-concept experiment found that superficial and deep neurons in the hippocampus produce different kinds of brain waves when stimulated. Future experiments will explore how these waves are related to memory.