Our success in understanding how early socio-emotional relationships impact on subsequent brain-behavioral development will depend to a great degree on our assessment tools. To this end a second major effort of this initiative is focused on the development of tools that permit one to forge a linkage between brain and behavior.
It is our intent to develop a class of tools that range from molecular to molar, and that are geared to particular study groups, for example, normally developing children, children with disabilities (e.g., autism), rodents, non-human primates, and so forth.
At the molecular level, our studies focus on animals and perhaps human autopsy specimens that have been equated for age and developmental history. Here the latest advances in the tools of molecular biology prove indispensable (e.g., gene knockouts; high density arrays for gene sequencing; use of viruses to perturb normal patterns of gene and protein expression).
A number of studies in non-human primates have suggested that the amygdala is essential for the normal production and interpretation of social signals. Network researchers conducted a study in rhesus monkeys that challenges this long-held belief. Adult monkeys with amygdala lesions appear to demonstrate normal social behavior, while infant monkeys with amygdala lesions in previous studies have demonstrated impairments in social behavior.
However, these abnormalities may not have been attributable to the absence of the amygdala, but may rather have been attributable to abnormal rearing conditions (isolation or peer-rearing) or to additional damage to structures surrounding the amygdala due to less sophisticated lesioning methods than are currently available. This study found that infant rhesus monkeys with very precise lesions of the amygdala who were reared with their mothers did develop species-appropriate social behaviors, indicating that the amygdala is not necessary for normal social development.
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 individuals ability to associate rewards with certain behaviors. Finally, the amygdala is critically involved in the recognition and interpretation of …
The Network has conducted several related studies in Rhesus monkeys that address how early social deprivation affects brain and behavioral development. Monkeys who were removed from their mothers at either 1 week of age or 4 weeks of age developed strikingly abnormal behaviors compared both to each other and to normal monkeys who left their mothers at 6 months, the usual time for maternal separation. Neuroanatomical studies of these monkeys have shown distinct differences in some areas related to social functioning. Other studies involve introducing monkeys separated at 1 week of age (who appear to lack any social drive after the separation) to a supermom (a female monkey known to adopt infants). These studies are showing that, while the behavioral abnormalities seen in these separated monkeys can be remediated by the introduction of a substitute mother, there appears to be a narrow window of opportunity for the reintroduction of maternal …