Previous research had suggested the existence of such cells, but Shin and team demonstrate conclusively that they are not isolated anomalies—they represent a clearly defined, functionally significant subpopulation. “What we were unaware of is that these neurons facilitate local pattern completion within the primary visual cortex,” remarks Shin. “We have shown that these cells are causally linked to the pattern completion process which we hypothesize plays a role in the perceptual experience of illusory contours,” adds Adesnik.
Upcoming behavioral assessments
This doesn’t imply the mice “perceived” the illusory contours when the neurons were stimulated artificially. “We didn’t actually assess behavior in this research,” states Adesnik. “It was focused on the neural representation.” At this point, we can only assert that the IC-encoders were able to elicit neural activity patterns consistent with imaging results during typical perception of illusory contours.
“It’s conceivable that the mice weren’t perceiving them,” concedes Shin, “as the technique has utilized a relatively limited number of neurons due to technical constraints. However, in future endeavors, one could increase the number of neurons and also implement behavioral assessments.”
That represents the next challenge, according to Adesnik: “Our plan is to photo-stimulate these neurons to determine if we can elicit an animal’s behavioral reaction even in the absence of any stimulus displayed on the screen.” Currently, optogenetics can stimulate only a limited number of neurons, and IC-encoders are quite uncommon and dispersed. “Presently, we have only activated a small subset of these detectors, mainly due to technical constraints. IC-encoders are an infrequent population, likely spread throughout the layers [of the visual system], but we could envision an experiment where we engage three, four, five, or even ten times more neurons,” he explains. “In such circumstances, I believe we could start to observe behavioral responses. We are certainly very eager to conduct this test.”
Nature Neuroscience, 2025. DOI: 10.1038/s41593-025-02055-5
Federica Sgorbissa is a science journalist; she covers neuroscience and cognitive science for both Italian and international publications.
