Light stimulation of about 20 motor cortex cells triggered a learned movement in mice
Light stimulation of about 20 motor cortex cells triggered a learned movement in mice
On October 14, Nature published a study from Takaki Komiyama’s group in which researchers used light to activate cells that normally become active before a learned lever press. In some trials, mice made a similar movement, and other motor cortex cells reproduced the familiar activity pattern. The outcome depended on both the cells selected and the state of the cortex before stimulation.
On October 14, 2026, Nature published a study from Takaki Komiyama’s group. In 2014, the same laboratory observed a recurring sequence of neuronal activity during lever presses in trained mice. The new study tests whether a brief signal to these cells can trigger the familiar movement.
The researchers first trained mice for two weeks to press a lever in response to a sound. They then monitored hundreds of neurons in the upper layers of the primary motor cortex, a brain region involved in controlling movement, and selected about 20 cells that became active before the movement. Holographic optogenetics, a method that uses light to activate selected cells, allowed them to stimulate this group specifically. In randomly interspersed trials, they replaced the sound with a three-millisecond light pulse that activated all the selected cells simultaneously. Lever presses in these trials were not rewarded.
The full text of the study describes 17 sessions in 11 mice. In some trials, the animals pressed the lever along a trajectory similar to the one they had learned. About half of the evoked movements had a similarity coefficient above 0,5 relative to the learned trajectory. Cells that were not directly targeted by light also reproduced the activity pattern associated with the learned lever press.
As a control, the authors stimulated the same number of cells that normally became active after movement began. The movements evoked in these experiments were less similar to the learned movement: the median similarity coefficient was 0,229, compared with 0,455 when the early-active cells were stimulated. The number of cells was the same; what differed was when they normally became active within the sequence.
The same three-millisecond pulse produced different outcomes across trials. The authors measured cortical activity during the half-second before stimulation. The closer this activity was to the state preceding a normal learned lever press, the more closely the subsequent movement resembled the learned movement, and the more closely the activity of the other cells resembled the pattern associated with that press.