What we observe in early life teaches our brain how to see
Passive visual experiences were found to play an important role in the development and function of neurons that are central to the vision system.
According to the researchers, what we passively observe happening around us in early life teaches our brain “how to see.”
The findings are providing new insight into the learning mechanisms that affect neural development.
Even during gestation, we are exposed to continuous visual stimuli that become more intense and structured after birth. These stimuli feed into the learning mechanisms that are necessary for the development of vision.
Lead researcher Davide Zoccolan is the director of the Visual Neuroscience Lab at SISSA. He explained that there are two types of learning: supervised, which is guided by a teacher, or unsupervised, which is influenced by exposure to the surrounding environment.
“The first is the one we can all associate with our parents or teachers, who direct us to the recognition of an object. The second one happens spontaneously, passively, when we move around the world observing what happens around us.”
In some theoretical models that describe biological learning processes mathematically, spontaneous visual experience is considered fundamental to the development of the visual system.
To test this theory, the team designed an experiment that would expose two groups of young rodents to different visual environments. The researchers were particularly focused on the role of the temporal continuity of visual stimuli in training the brain to see.
“We played a series of videos, in either their original version or after randomly shuffling the single frames (or images), thus destroying the temporal continuity of visual experience,” said the study authors.
“In the subjects exposed to this discontinuous visual flow we observed the impairment of the maturation of some cells of the visual cortex called ‘complex.'”
“These neurons play a key role in visual processing: they allow recognizing the orientation of the contour of an object regardless of its exact position in the visual field, a perceptual ability that only recently has been implemented in artificial vision systems.”
“Having shown that their maturation is highly sensitive to the degree of continuity of visual experience is the first direct experimental confirmation of the theoretical prediction.”
The findings highlight the importance of passive visual experience for the development of the visual system.
Zoccolan noted that the study has important implications for clinical and technological applications.
“In some developing countries, there are children suffering from congenital cataract, who, after the surgery to remove it, have to develop substantially from scratch their visual recognition skills ” said Zoccolan.
“Already today, some rehabilitative approaches exploit the temporal continuity of specific visual stimuli (for example, geometric shapes in motion) to teach these patients to distinguish visual objects.”
“Our results confirm the validity of these approaches, revealing the neuronal mechanisms behind it and suggesting possible improvements and simplifications.”
Zoccolan pointed out that artificial visual systems use mainly “supervised” learning techniques, which require millions of images.
“Our results suggest that these methods should be complemented by ‘unsupervised’ learning algorithms that mimic the processes at work in the brain, to make training faster and more efficient.”
The study is published in the journal Science Advances.