Thalamus may guide timing of brain development and plasticity

The brain is known to develop gradually throughout the human lifespan, following a hierarchical pattern. First, it adapts to support basic functions, such as movement and sensory perception, then it moves onto more advanced human abilities, such as decision-making.

Researchers at the University of Pennsylvania and other institutes, led by Principal Investigator Dr. Theodore Satterthwaite, recently carried out a study aimed at better understanding how the thalamus, a structure deep within the brain known to be involved in the processing and routing of sensory information, could contribute to the brain’s development over time.

Their findings, published in Nature Neuroscience, suggest that the thalamus is more than a relay station for sensory and motor signals, and also plays a role in regulating the hierarchical pattern and timeline of brain development.

“Our research team had been studying how different regions of the human cortex (i.e., the outermost layer of the brain) exhibit different time windows of neuroplasticity during childhood and adolescence,” Dr. Valerie J. Sydnor, first author of the paper, told Medical Xpress.

“We’d shown that reductions in plasticity progress across cortical regions following a hierarchical, sensorimotor-to-association developmental sequence. This sequence results in an earlier reduction in plasticity in sensorimotor brain regions that support vision, hearing, and action during childhood—but allows for plasticity to extend into adolescence in association regions supporting complex cognitive, social, and emotional processing.

After unveiling the sequence that characterizes the brain’s development, Sydnor and her colleagues set out to identify the processes through which the brain orchestrates variations in the timing with which different cortical regions develop. To do this, they built on earlier neuroscience studies focusing on different animals.

“Studies done with rodents had uncovered that the thalamus, a sub-cortical brain region, can both promote and limit plasticity in cortical regions during development by communicating with the cortex through structural axonal connections,” said Sydnor. “However, the thalamus’s potential role in regulating the expression of neuroplasticity had not been tested in the human brain.”

Inspired by the findings of these earlier studies focusing on rodents, the researchers tried to uncover the neural mechanisms that regulate the brain’s adaptability during youth. They specifically examined structural connections between the thalamus and cortical brain regions, to determine whether these were linked to the timing of adaptations observed in the brains of children and adolescents.

To perform their experiments, they used a non-invasive and safe neuroimaging technique known as diffusion magnetic resonance imaging (MRI). This is a method to measure the movement of water molecules in brain tissues, which in turn allows neuroscientists to map the fiber tracts connecting different brain regions.

“Diffusion MRI is a remarkable method that allows us to identify large-scale neuronal connections in the brain based on how water molecules move (or diffuse) along them,” explained Satterthwaite.

“We analyzed diffusion MRI data that had been collected from children and adolescents aged 8–23 years old as part of three large samples: 1) a community-representative sample of youth from Philadelphia (N = 1,145), 2) a typically developing sample of youth from Minnesota, Massachusetts, California, and Missouri (N = 572), and 3) a sample of youth experiencing significant mental health symptoms from New York City (N = 959).”

To perform their analyses, the researchers had to create a new atlas of human thalamocortical structural connectivity, in other words, an anatomical map of connections between the thalamus and parts of the cortex. This map allowed them to locate over 200 connections between the thalamus and various cortical regions in the brain of each study participant.

“The thalamus has long been conceptualized as a simple ‘relay station’ in the brain that passes information from peripheral organs that process our environments to the cortex,” said Sydnor.

“Our data indicate that the thalamus likely plays a more active role in determining when cortical regions are plastic, and therefore when they exhibit both adaptability and vulnerability to our environments.”

Interestingly, Sydnor and her colleagues observed that the maturation of structural connections between the human thalamus and cortex followed a sensorimotor-to-association sequence. This suggests that the development of cortical regions in children and adolescents is aligned with changes in the strength of connections with the thalamus. Thus, the thalamus might serve as a “timekeeper” of cortical maturation.

“This is important given that the pace of cortical maturation is linked to cognitive and psychological outcomes,” explained Sydnor.

“Moreover, we discovered that cortical regions with thalamic connections that develop for longer show structural, functional, and neurochemical signatures of prolonged plasticity through the adolescent period. This indicates that developmental strengthening of thalamocortical structural connectivity promotes extended plasticity in brain regions linked to cognitive, social, and emotional processing.

“It also raises the question of how we may potentially leverage thalamocortical connectivity to enhance cortical plasticity in development, or even adulthood!”

Finally, the researchers observed that thalamocortical structural connections to association-related brain regions that develop over longer periods of time were more influenced by environmental factors. This suggests that the continuous development and plasticity of the brain is linked to prolonged environmental sensitivity.

In the future, the team’s findings could guide the development of interventions designed to support the healthy development of children and adolescents by enriching their surrounding environments. These interventions could support the strengthening of connections between the thalamus and cortical regions, promoting the acquisition of advanced mental capabilities.

“We’d now like to continue identifying mechanistic regulators of plasticity in association regions and understand their impact on developmental trajectories,” added Sydnor.

“We are also interested in identifying specific aspects of youth’s environments that can facilitate continued developmental strengthening of thalamocortical connectivity to promote cortical plasticity and adaptability. Future research in these domains will continue to provide insight into our primary research question: how can youth’s environments be leveraged to promote resiliency during child and adolescent windows of heightened cortical plasticity?”

© 2025 Science X Network

The brain is known to develop gradually throughout the human lifespan, following a hierarchical pattern. First, it adapts to support basic functions, such as movement and sensory perception, then it moves onto more advanced human abilities, such as decision-making.

Researchers at the University of Pennsylvania and other institutes, led by Principal Investigator Dr. Theodore Satterthwaite, recently carried out a study aimed at better understanding how the thalamus, a structure deep within the brain known to be involved in the processing and routing of sensory information, could contribute to the brain’s development over time.

Their findings, published in Nature Neuroscience, suggest that the thalamus is more than a relay station for sensory and motor signals, and also plays a role in regulating the hierarchical pattern and timeline of brain development.

“Our research team had been studying how different regions of the human cortex (i.e., the outermost layer of the brain) exhibit different time windows of neuroplasticity during childhood and adolescence,” Dr. Valerie J. Sydnor, first author of the paper, told Medical Xpress.

“We’d shown that reductions in plasticity progress across cortical regions following a hierarchical, sensorimotor-to-association developmental sequence. This sequence results in an earlier reduction in plasticity in sensorimotor brain regions that support vision, hearing, and action during childhood—but allows for plasticity to extend into adolescence in association regions supporting complex cognitive, social, and emotional processing.

After unveiling the sequence that characterizes the brain’s development, Sydnor and her colleagues set out to identify the processes through which the brain orchestrates variations in the timing with which different cortical regions develop. To do this, they built on earlier neuroscience studies focusing on different animals.

“Studies done with rodents had uncovered that the thalamus, a sub-cortical brain region, can both promote and limit plasticity in cortical regions during development by communicating with the cortex through structural axonal connections,” said Sydnor. “However, the thalamus’s potential role in regulating the expression of neuroplasticity had not been tested in the human brain.”

Inspired by the findings of these earlier studies focusing on rodents, the researchers tried to uncover the neural mechanisms that regulate the brain’s adaptability during youth. They specifically examined structural connections between the thalamus and cortical brain regions, to determine whether these were linked to the timing of adaptations observed in the brains of children and adolescents.

To perform their experiments, they used a non-invasive and safe neuroimaging technique known as diffusion magnetic resonance imaging (MRI). This is a method to measure the movement of water molecules in brain tissues, which in turn allows neuroscientists to map the fiber tracts connecting different brain regions.

“Diffusion MRI is a remarkable method that allows us to identify large-scale neuronal connections in the brain based on how water molecules move (or diffuse) along them,” explained Satterthwaite.

“We analyzed diffusion MRI data that had been collected from children and adolescents aged 8–23 years old as part of three large samples: 1) a community-representative sample of youth from Philadelphia (N = 1,145), 2) a typically developing sample of youth from Minnesota, Massachusetts, California, and Missouri (N = 572), and 3) a sample of youth experiencing significant mental health symptoms from New York City (N = 959).”

To perform their analyses, the researchers had to create a new atlas of human thalamocortical structural connectivity, in other words, an anatomical map of connections between the thalamus and parts of the cortex. This map allowed them to locate over 200 connections between the thalamus and various cortical regions in the brain of each study participant.

“The thalamus has long been conceptualized as a simple ‘relay station’ in the brain that passes information from peripheral organs that process our environments to the cortex,” said Sydnor.

“Our data indicate that the thalamus likely plays a more active role in determining when cortical regions are plastic, and therefore when they exhibit both adaptability and vulnerability to our environments.”

Interestingly, Sydnor and her colleagues observed that the maturation of structural connections between the human thalamus and cortex followed a sensorimotor-to-association sequence. This suggests that the development of cortical regions in children and adolescents is aligned with changes in the strength of connections with the thalamus. Thus, the thalamus might serve as a “timekeeper” of cortical maturation.

“This is important given that the pace of cortical maturation is linked to cognitive and psychological outcomes,” explained Sydnor.

“Moreover, we discovered that cortical regions with thalamic connections that develop for longer show structural, functional, and neurochemical signatures of prolonged plasticity through the adolescent period. This indicates that developmental strengthening of thalamocortical structural connectivity promotes extended plasticity in brain regions linked to cognitive, social, and emotional processing.

“It also raises the question of how we may potentially leverage thalamocortical connectivity to enhance cortical plasticity in development, or even adulthood!”

Finally, the researchers observed that thalamocortical structural connections to association-related brain regions that develop over longer periods of time were more influenced by environmental factors. This suggests that the continuous development and plasticity of the brain is linked to prolonged environmental sensitivity.

In the future, the team’s findings could guide the development of interventions designed to support the healthy development of children and adolescents by enriching their surrounding environments. These interventions could support the strengthening of connections between the thalamus and cortical regions, promoting the acquisition of advanced mental capabilities.

“We’d now like to continue identifying mechanistic regulators of plasticity in association regions and understand their impact on developmental trajectories,” added Sydnor.

“We are also interested in identifying specific aspects of youth’s environments that can facilitate continued developmental strengthening of thalamocortical connectivity to promote cortical plasticity and adaptability. Future research in these domains will continue to provide insight into our primary research question: how can youth’s environments be leveraged to promote resiliency during child and adolescent windows of heightened cortical plasticity?”

© 2025 Science X Network