Methods for Studying Brain-Behavior Relations – Part of the challenge of studying the effects of experience on the brain is the paucity of methods for examining the development of particular brain structures. These research projects focus on the development of methods that will allow us to look at how brain structures thought to be involved in particular aspects of behavioral development change with time and experience.
As interest in the brain increases among those studying behavioral development, the need for basic knowledge about brain development also grows. For those interested in emotional development and temperament, it is crucial to understand the development of the amygdala, a part of the brain that is believed to serve as the “seat” of emotion. The amygdala also plays a prominent role in regulating an individual’s ability to associate rewards with certain behaviors. Finally, the amygdala is critically involved in the recognition and interpretation of certain facial expressions that convey emotion.
In parallel, our understanding of the development of executive functions and how these functions impact the regulation of emotion require that we explore the developmental processes that shape the circuitry and function of the prefrontal cortex. It is in this context that our Network has undertaken a series of basic neuroscience projects, information from which will prove critical to understanding the development of both cognitive and emotional behaviors.
Analysis of Developing Amygdaloid Circuitry Using Transynaptic Passage of Pseudorabies Virus (PRV)
In one of our studies, Network researchers are using an innovative technique to examine the development of the circuits of neurons extending to and from the amygdala. Using this method, we have learned that the amygdala (in certain Mammalian species) has already developed connections to the autonomic nervous system in the first week of life. It is known from previous experiments that the development of this neural system is affected by experience, and now it is known that connections in this system are present very early in development. The findings of these experiments have great importance for advancing the Network’s mission of assessing the effects of experience upon brain development. In performing these studies, the investigators have developed the first and currently the only known method for tracking the assembly of a complex neuronal circuit during development.
Analysis of the Effects of Stress on Developmental Assembly of Central Nervous System (CNS) Circuitry
Following the success of the pseudorabies project, the Network initiated a follow-up project to study the effects of stress on the formation of neural connections from the forebrain to the brainstem (the vital core components of the brain controlling functions essential for survival, including respiration, heart rhythm, blood pressure, eating, drinking, and sleep).
This study will help to determine how different early experiences in rats cause changes in how early connections between the forebrain and brainstem are established – either in how the connections are organized, or when the connections are formed. This experiment will help to determine if the underlying biological mechanisms for handling stress as adult rats changes as a result of experiences (handling and separation) encountered as pups.
Amygdalo-cortical Development and the Emergence of Primate Social Behavior
Using similar techniques to the PRV experiment, another Network researcher is examining the development of connections between the temporal neocortex, the amygdala, and the frontal cortex. Thus far, we have been able to determine that connections between the amygdala, the temporal neocortex, and the frontal cortex are present by the second week of life in some primates.
We hope to apply the methods piloted in this study and in the PRV study to other studies to help determine how these developing circuits might play a role in the development of behavioral abnormalities as a result of early experience. The methods we have developed will enable us to examine alterations in neural connectivity that may result from early aberrant social experience.