The primate brain has an organized set of a map for each of senses be it touch, sight or hearing. Researchers have known for a while that these maps are categorized into designated area that responds to different types of stimuli in each of the senses in adults. However, there has been a lot of ambiguity if this organization is innate or develops over time.
Through a study, the Harvard Medical School researchers Michael Arcaro and Margaret Livingstone tried to find the answer to it and their research seems to suggest that the answer could be both. The study was published recently in eLife and it says that a primitive blueprint of an organization is present in the brains of primates within few days of birth. With age and experience, it gradually gets filled in. The findings of the study explain some characteristics of neurodevelopmental disorders like autism, like avoidance of certain visual stimuli, and stress the importance of correcting visual deficits in infants early to ensure normal brain development.
Livingstone and Arcaro in their new study have tried to gain a better understanding of the organization of the visual system. As a part of their research, the brain activity of four 10 days young macaques was monitored with the aid of a functional magnetic resonance scanner as they viewed various images, including scenes and faces. But, there were some hindrances to their work. As the macaques were swaddled, they would doze off to sleep. So, the researchers were able to get only a small amount of data of the time when the monkeys were awake. A huge chunk of the data from the magnetic resonance scans was collected when they were asleep.
In order to ensure that the data from the sleeping time is not wasted, Arcaro, who is also a postdoctoral fellow in Livingstone’s lab, decided to analyze it anyway. His study of the data led to a surprising finding. He found that even when the animals were asleep with their eyes shut, many parts of the visual system would turn on in conjunction with each other. These findings point to a functional organization that connects all of these visual areas in the brain.
Over the next several years, the researchers continued to work on the same macaques. They carried out scans as the animals grew mature and stayed awake longer. Their research revealed that the primitive maps present at the time of birth were still there are very gradually filled in and became more sophisticated. It now had the ability to respond to specific stimuli that absent in their early days.
During the early days of the macaques, the visual system activity was already somewhat organized into ventral and dorsal streams. When the animals get older, these areas are key to object recognition and visually guided actions, respectively, But, there were certain things that were missing in the early days like – they lacked clusters of neurons in the fusiform gyrus, a structure linked to recognition. But, as they were about 200 days old, such neuronal selectivity arose.
Arcaro explained that the brain sets a system by creating a map this early into which more information can be added in set places with experience. Since the evidence of the organization is present even in the early dates, it is most likely that it is there from before birth.
Since humans and monkeys are quite linked genetically; the findings will have some implications for humans also. An inability of the maps to later incorporate and respond to stimuli such as faces as is seen in neurodevelopmental disorders can be explained by the theory that these maps do not evolve normally with experience Livingstone added.
While it is known that the earliest visual experiences are key to child’s perceptual development, the new findings of the study further reiterate the importance of promptly correcting any visual deficits present at birth, not just to prevent blindness but also for the proper development of higher visual and cognitive functions.