Touch and sight are linked before birth

by time news

A new study from the laboratory of Dr. Guillermina López- Bendito, published today Sciencedemonstrates in mice that the circuits of the touch and of the vista they are not independent in the embryo, but are intermingled. It is at birth that these circuits separate and responses to sensory stimuli become independent.

In a previous study, López-Bendito’s lab showed that tactile stimuli they activate the brain circuits designed to process this type of information before birth: “We had discovered, at a local level, that at the moment of the embryo’s birth, the sense of touch is already developed and now we have been able to develop it on a large scale”, explains to ABC, Teresa Guillamón-Vivancos, first author of the work.

“But we wanted to determine if they do this independently or if there is a temporary overlap with other senses. This new study yields fascinating data on how senses they segregate in the first days of life» points out Guillermina López-Bendito, who has led the research. “This study has important implications because it was not known that the senses are segregated by default,” says Guillamón-Vivancos.

In this work they have been able to verify for the first time live in mice that, during the embryonic developmenta tactile stimulus not only elicits the expected response in the primary somatosensory cortex (one of the areas of the brain that deals with the sense of touch) but surprisingly also elicits a response in the primary visual cortex of both hemispheres.

The study has been developing for four years and although for now it has not been tested in people, due to the ethical debate of gene manipulation, they affirm that «it can be assumed that this information can be shared with other mammals».

“Is multimodal response (ie spanning more than one direction) was observed in mouse embryos tested on the last day of gestation, but disappeared at birth. Next, we tested whether the disappearance of this multimodal response could be related to the arrival of signals from the retina to the cerebral cortex and other brain structures. Our data show that the somatosensory and visual circuits do not segregate by default, but rather require the arrival of waves of activity from the retina to do so”, explains Teresa Guillamón Vivancos. «We have discovered with a blind mouse that, since it does not have the waves of the retina, it does have this multimodality. Thus, we notice that these retinal waves arrive before“Guillamón points out.

Track separation

This fundamental process of separating sensory circuits occurs during a window of time close to birth and in a brain structure called superior colliculus. Making a railway simile, at birth, in this structure the senses separate following different routes. The change of track is facilitated by waves of activity from the retinawhich act as railways that direct the stimuli of each sensory modality to the corresponding cortex, so that we can perceive them separately.

In fact, blockade of these retinal waves prolongs the multimodal (intermingled) configuration of the senses in life after birth, so that the superior colliculus retains a mixed tactile-visual identity and defects in the spatial organization of the system arise. visual.

This work extends the understanding of the wave function of retinal activity by revealing its decisive role in the acquisition of sensory modality specificity, which goes beyond the already known classical role in the postnatal refinement of visual circuits.

https://www.youtube.com/watch?v=b2IT1JCvJxc

Another important contribution of this work is to have verified the existence of a limited temporal window for the segregation of the visual systems from the somatosensory ones. So any delay in this segregation will cause lasting changes in the organization of the visual circuits.

“Our results highlight the ontogenetic perspective, where the superior colliculus exerts master control during the early stages of the organism’s development over the cortical specification and configuration of visual circuits. Therefore, we believe that a deeper understanding of the functional development of phylogenetically ancient structures is crucial to understand how is the cerebral cortex formed and their functional areas are specified”, highlights Dr. López-Bendito.

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