Article summary with The role of the visual association cortex in scaffolding prefrontal cortex development: A novel mechanism linking socioeconomic status and executive function by Rosen a.o. - 2019

What is the role of the prefrontal cortex in executive function?

The prefrontal cortex (PFC) is involved in multiple forms of higher-order cognition, such as working memory, inhibitory control, conflict monitoring, and shifting between rule sets. These cognitive processes are referred to as executive functions. They allow the formation and execution of future-oriented plans as well as the inhibition of behaviors that do not serve those plans. It provides the foundation for decision-making and self-regulation.

How do environmental influences affect executive function and PFC development?

Environmental experiences shape developmental processes through:

• Experience-expectant processes. The neural circuits that process sensory information are sculpted by specific environmental inputs during sensitive periods in early development. Think of the sensory system development and the processing of light and sound.
• Experience-dependent processes. These reflect emergent connections between neuronal populations in a way that reflects each person´s unique environmental experiences. Think of long-term memory and home stimulus exposure.

Recent research indicates that there is unlikely to be one set of specific environmental experiences for optimal PFC development, but instead, that PFC development reflect adaptation to the child´s changing environment.

How is socioeconomic status thought to influence executive function development?

A variety of mechanisms operating at multiple levels of influence have been suggested. Children in poverty lack rules, structure, and routines, and their environments are more chaotic, unstable, and disorganized. This is thought to produce poor executive function. Also, exposure to high levels of stress has adverse effects on PFC function and executive function development. However, these explanations are limited in their ability to explain the types of environmental influences that are required for healthy PFC and executive function development.

How can cognitive stimulation be a mechanism linking socioeconomic status and executive function?

Cognitive stimulation is characterized by access to a complex environment with developmentally appropriate learning materials, a complex linguistic environment, a rich variety of experiences, and the presence of a caregiver who interacts with the child consistently and uses strategies that promote learning. This cognitive stimulation supports development of the feed-forward and feedback loops between sensory processing regions and the PFC, laying the groundwork for executive function development.

How do caregiver interactions and linguistic experience shape early PFC development?

Two pathways have been identified:

• Attention Regulation Pathway. In environments with limited caregiver interactions, children receive less guidance to attention regulation and have less experience involving competition between sensory inputs for attention that needs to be resolved. Combined with reduced access to sensory complexity this may result in limited organized feed-forward information from the ventral visual stream to the PFC.
• Linguistic Pathway. As children learn language, which facilitates object recognition and semantic knowledge, the PFC is continually engaged in conflict resolution and performing computations that are necessary for engagement in more complex forms of competition resolution that are considered in the domain of executive function.

How does socioeconomic status influence cognitive stimulation in a child’s household?

Environmental complexity varies as a function of socioeconomic status. Children growing up in low socioeconomic status households tend to experience lower levels of cognitive stimulation, including language exposure, environmental complexity, and caregiver interactions. Children growing up in higher socioeconomic status household tend to experience more cognitively stimulation environments, through enriching experiences (such as daytrips, museums), educational information (e.g. books), greater visual complexity of the home, and greater parental involvement in learning.

How can cognitive stimulation support executive function development?

Research shows that cognitive stimulation is associated with individual differences in working memory, cognitive flexibility, and inhibitory control. Caregiver involvement plays an important role in this relationship. Parental scaffolding and a rich linguistic environment support a child´s language ability and brain systems. Finally, cognitive stimulation has been linked to the structure and function of the ventral visual stream and the PFC. Specifically, a lack of cognitive stimulation appears to influence the cortical structure and function of the ventral visual stream regions, as well as the connectivity between those regions. 

How does socioeconomic status affect the ventral and dorsal visual streams?

Variation in environmental experience is associated with development of the ventral visual stream and associated functions. Socioeconomic status appears to influence ventral visual stream-dependent processes, but not dorsal visual stream dependent processes. Several research results support this idea:

• Socioeconomic status is positively associated with feature-based attention for color and object-based attention (ventral visual stream processes).
• Socioeconomic status is not associated with attention to motion (dorsal visual stream processes).
• Cognitive stimulation in early development predicts differences in cortical thickness in the PFC and ventral visual stream, but not the dorsal stream.

Does development of the ventral visual stream scaffold PFC development and executive function?

There is no direct evidence to support this relationship, but there are research results that are consistent with this hypothesis:

• Functional changes in the ventral visual stream across development play an important role in the development of higher order cognitive function among children.
• Structural maturation of the PFC is protracted and occipital, temporal, and parietal cortex maturation precede that of the PFC.

Earlier development of more posterior regions, including the ventral and dorsal visual streams, may help support the development of the PFC by feeding the PFC information about the environment.