To summarize: At the embryonic stage, tactile information activates both tactile and optic neural pathways. After birth, these pathways separate and reorganize to allow separate processing of visual and tactile information.
At the embryonic stage, tactile stimulation activates both tactile and optic neural pathways. Soon after birth, both pathways reorganize to allow for the separate processing of touch and vision.According to the UMH-CSIC Neuroscience Institute published today in science.
This separation occurs in a brain structure called the superior colliculus, which acts as a distributor of neural circuits or pathways. Any delay in the development of this dissociation leads to incorrect organization of the visual circuits that are maintained in adult life.
New research from Ph.D.’s lab. Guillermina López-Bendito, published today in science, showed in mice that the tactile and visual circuits are not independent but intermingled in the embryo. It is at birth when these circuits separate and their responses to sensory stimuli become independent.
In a previous study, López-Bendito’s lab showed that tactile stimulation activates brain circuits designed to process such information before birth.
“But we wanted to determine whether they did this independently or with a temporary overlap with other senses. This new study provides fascinating data on how the senses are separated during the first few days of life,” said Guillermo, who led the study. Mina Lopez-Bendito said.
In this work, led by Teresa Guillamón-Vivancos, they demonstrated for the first time in mice that during embryonic development, tactile stimulation not only triggers the expected response in the primary somatosensory cortex, one of the brain regions. processes touch), but surprisingly, it also elicits responses in the primary visual cortex in both hemispheres.
“This multimodal (i.e. containing more than one sensory) response was observed in mouse embryos tested on the last day of gestation, but disappeared with birth. We then tested whether the disappearance of this multimodal response was associated with signals from the retina Reaching the cerebral cortex is associated with other brain structures.
“Our data suggest that somatosensory and visual circuits are not secreted by default, but require waves of activity from the retina to do so,” explains Teresa Guillamón-Vivancos.
The fundamental process of this separation of sensory circuits occurs in a time window close to birth, in a brain structure called the superior colliculus. Take the railway, for example, at birth, the senses are separated in the superior colliculus, following different tracks.
The pathway changes are facilitated by retinal activity waves that act as switches to direct stimuli for each sensory modality to the corresponding cortex so that we can perceive them separately.
Indeed, blocking these retinal waves prolongs the postnatal multimodal (mixed) configuration of the senses, resulting in the preservation of mixed tactile-visual properties of the superior colliculus and deficits in the spatial organization of the visual system.
This work extends the classical role known in postnatal refined visual circuits by revealing the decisive role of retinal activity waves in acquiring sensory modality specificity, furthering the understanding of retinal activity wave function.
Another important contribution of this work is the discovery of a limited time window for decoupling visual from somatosensory systems. Therefore, any delay in this dissociation leads to long-term changes in the organization of visual circuits.
“Our findings highlight the ontogeny perspective that the superior colliculus exerts primary control over cortical specification and configuration of visual circuits during early stages of an organism’s development.
“We therefore believe that a deeper understanding of the functional development of phylogenetically ancient structures is critical to understanding how the cerebral cortex forms and specifies its functional regions,” said Dr. Lopez-Bendito.
About this Neurodevelopmental Research News
author: News office
touch: Press Office – CSIC
picture: Image credit to Instituto de Neurociencias (IN, CSIC-UMH)
Original research: closed access.
“Input-dependent segregation of visual and somatosensory circuits in the mouse superior colliculus” by Teresa Guillamón-Vivancos et al. science
Input-dependent segregation of visual and somatosensory circuits in the mouse superior colliculus
While sensory perception relies on specialized sensory pathways, it is unclear whether these pathways originate from pattern-specific circuits.
We demonstrate that the somatosensory and visual circuits are not separated by default, but require the earliest retinal activity to do so. In the embryo, somatosensory and visual circuits are intertwined in the superior colliculus, resulting in a multimodal cortical response to whisker pad stimulation.
At birth, these circuits separate and the response switches to a single peak. Blocking phase I retinal waves prolongs the multimodal configuration into postnatal life, and the superior colliculus preserves the mixed stereoscopic molecular identity and deficits seen in the spatial organization of the visual system.
Thus, the superior colliculus mediates temporal separation of sensory modalities in an input-dependent manner, directing specific sensory cues to their appropriate sensory pathways.